WW 510 SEVERE TSTM KY TN VA WV 212210Z - 220500Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 510
NWS Storm Prediction Center Norman OK
510 PM CDT Tue Jul 21 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Southeast Kentucky
Northern Tennessee
Extreme Southwest Virginia
Southern West Virginia
* Effective this Tuesday afternoon from 510 PM until Midnight
CDT.
* Primary threats include...
Scattered damaging wind gusts to 70 mph likely
Isolated large hail events to 1.5 inches in diameter possible
A tornado or two possible
SUMMARY...A line of scattered intense thunderstorms over Kentucky
will sag southward into the watch area through the evening.
Damaging winds are the main concern, but hail and a tornado or two
are also possible.
The severe thunderstorm watch area is approximately along and 40
statute miles north and south of a line from Dyersburg TN to 110
miles east of Jackson KY. For a complete depiction of the watch see
the associated watch outline update (WOUS64 KWNS WOU0).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 506...WW 507...WW
508...WW 509...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
30025.
...Hart
WW 509 SEVERE TSTM DC DE MD NC VA WV CW 211845Z - 220200Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 509
NWS Storm Prediction Center Norman OK
245 PM EDT Tue Jul 21 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
District Of Columbia
Delaware
Maryland
Far Northwest North Carolina
Virginia
The Eastern West Virginia Panhandle
Coastal Waters
* Effective this Tuesday afternoon and evening from 245 PM until
1000 PM EDT.
* Primary threats include...
Scattered damaging wind gusts to 70 mph likely
Isolated large hail events to 1.5 inches in diameter possible
A tornado or two possible
SUMMARY...Multiple rounds of strong to severe thunderstorms are
expected across the region today and tonight, beginning with the
ongoing storms across central Virginia. Environmental conditions
support robust updrafts, with all severe hazards possible, including
damaging gusts and isolated hail. A low-probability tornado risk
exists with any afternoon development as well. Another round of
storms is possible along a cold front later tonight, with damaging
gusts as the primary risk. A low-probability, line-embedded tornado
risk exists with these more linear storms as well.
The severe thunderstorm watch area is approximately along and 105
statute miles east and west of a line from 30 miles north northeast
of Baltimore MD to 10 miles west of South Hill VA. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU9).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 506...WW 507...WW 508...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
26030.
...Mosier
WW 508 SEVERE TSTM IL IN KY 211820Z - 220200Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 508
NWS Storm Prediction Center Norman OK
120 PM CDT Tue Jul 21 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Far Southern Illinois
Far Southern Indiana
Kentucky
* Effective this Tuesday afternoon and evening from 120 PM until
900 PM CDT.
* Primary threats include...
Widespread damaging wind gusts to 70 mph likely
Scattered large hail events to 1.5 inches in diameter possible
A tornado or two possible
SUMMARY...Thunderstorms coverage and intensity is expected to
increase this afternoon along a cold front pushing southeastward
into the region. Very warm and moist conditions ahead of the front
will support robust buoyancy, with moderate vertical shear in place
as well. Initial supercells could produce all severe hazards,
including isolated large hail and potentially even a brief tornado.
A trend towards a more linear mode is anticipated with time, with
damaging gusts as the primary severe risk.
The severe thunderstorm watch area is approximately along and 60
statute miles north and south of a line from 30 miles east northeast
of Lexington KY to 30 miles north northwest of Paducah KY. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU8).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 506...WW 507...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
29030.
...Mosier
WW 507 TORNADO CT DE NJ NY PA CW 211805Z - 220100Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 507
NWS Storm Prediction Center Norman OK
205 PM EDT Tue Jul 21 2026
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
Western Connecticut
Northern Delaware
New Jersey
Central and Southern New York
Western Pennsylvania
Coastal Waters
* Effective this Tuesday afternoon and evening from 205 PM until
900 PM EDT.
* Primary threats include...
A couple tornadoes possible
Scattered damaging wind gusts to 70 mph likely
Scattered large hail events to 1.5 inches in diameter possible
SUMMARY...Thunderstorm intensity has recently increased from central
New York across eastern Pennsylvania, in the vicinity of a warm
front moving northward/northeastward across the region. Deep-layer
shear is forecast to increase with some increase in low to mid-level
flow as well. This increased shear could support some more organized
storm structures capable of producing tornadoes as these storms
continue eastward. Damaging gusts are possible as well, particularly
as storms trend towards a more linear structure over time. Another
round of storms is possible later this evening, and some severe
threat will accompany these storms as well.
The tornado watch area is approximately along and 60 statute miles
east and west of a line from 30 miles northwest of Albany NY to 20
miles south southwest of Wilmington DE. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU7).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 506...
AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 1.5 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean
storm motion vector 27035.
...Mosier
WW 506 SEVERE TSTM IN KY OH PA WV 211710Z - 220000Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 506
NWS Storm Prediction Center Norman OK
110 PM EDT Tue Jul 21 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Far Southeast Indiana
Far Northern Kentucky
Central and Southern Ohio
Southwest Pennsylvania
West Virginia
* Effective this Tuesday afternoon and evening from 110 PM until
800 PM EDT.
* Primary threats include...
Scattered damaging wind gusts to 70 mph likely
Scattered large hail events to 1.5 inches in diameter possible
A tornado or two possible
SUMMARY...Thunderstorm coverage is expected to increase this
afternoon as a pre-frontal trough and associated cold front moves
through the region. Overall environmental conditions favor strong to
severe thunderstorms, with a linear convective mode favoring
damaging gusts as the primary risk. Low-level shear is also strong
enough to support a low-probability risk for a few brief,
line-embedded tornadoes as well.
The severe thunderstorm watch area is approximately along and 80
statute miles north and south of a line from 75 miles north
northeast of White Sulphur Springs WV to 50 miles west northwest of
Cincinnati OH. For a complete depiction of the watch see the
associated watch outline update (WOUS64 KWNS WOU6).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
27035.
...Mosier
WW 0510 Status Updates
STATUS FOR WATCH 0510 HAS NOT BEEN ISSUED YET
WW 0509 Status Updates
STATUS REPORT ON WW 509
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..LYONS..07/21/26
ATTN...WFO...LWX...PHI...AKQ...RNK...
STATUS REPORT FOR WS 509
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
DEC001-005-212340-
DE
. DELAWARE COUNTIES INCLUDED ARE
KENT SUSSEX
DCC001-212340-
DC
. DISTRICT OF COLUMBIA COUNTIES INCLUDED ARE
DISTRICT OF COLUMBIA
MDC001-003-005-009-011-013-015-017-019-021-023-025-027-029-031-
033-035-037-039-041-043-045-047-510-212340-
MD
. MARYLAND COUNTIES INCLUDED ARE
ALLEGANY ANNE ARUNDEL BALTIMORE
CALVERT CAROLINE CARROLL
CECIL CHARLES DORCHESTER
FREDERICK GARRETT HARFORD
WW 0508 Status Updates
STATUS REPORT ON WW 508
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 45 NW POF TO
10 SE LEX TO 55 E LUK.
FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 1699
..LYONS..07/21/26
ATTN...WFO...PAH...LMK...JKL...
STATUS REPORT FOR WS 508
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
ILC003-127-153-212340-
IL
. ILLINOIS COUNTIES INCLUDED ARE
ALEXANDER MASSAC PULASKI
KYC001-003-007-009-011-021-025-027-031-033-035-039-045-047-049-
051-053-055-057-059-061-063-065-069-075-079-083-085-087-093-099-
105-107-109-113-115-123-125-129-137-139-141-143-145-149-151-153-
155-157-165-167-169-171-173-175-177-179-181-183-189-197-199-203-
205-207-213-217-219-221-227-229-231-233-237-212340-
KY
. KENTUCKY COUNTIES INCLUDED ARE
ADAIR ALLEN BALLARD
BARREN BATH BOYLE
BREATHITT BRECKINRIDGE BUTLER
CALDWELL CALLOWAY CARLISLE
CASEY CHRISTIAN CLARK
CLAY CLINTON CRITTENDEN
WW 0507 Status Updates
STATUS REPORT ON WW 507
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 30 W ILG TO
5 WNW TTN TO 20 SSE MSV TO 15 SSW PSF TO 10 WNW BAF.
..LYONS..07/21/26
ATTN...WFO...OKX...ALY...PHI...BGM...CTP...
STATUS REPORT FOR WT 507
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
CTC001-005-009-212340-
CT
. CONNECTICUT COUNTIES INCLUDED ARE
FAIRFIELD LITCHFIELD NEW HAVEN
DEC003-212340-
DE
. DELAWARE COUNTIES INCLUDED ARE
NEW CASTLE
NJC001-003-005-007-009-011-013-015-017-021-023-025-027-029-031-
033-035-039-212340-
NJ
. NEW JERSEY COUNTIES INCLUDED ARE
ATLANTIC BERGEN BURLINGTON
CAMDEN CAPE MAY CUMBERLAND
ESSEX GLOUCESTER HUDSON
WW 0506 Status Updates
STATUS REPORT ON WW 506
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 50 W HTS TO
30 WSW MGW TO 45 E MGW.
..LYONS..07/21/26
ATTN...WFO...ILN...RLX...PBZ...
STATUS REPORT FOR WS 506
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
KYC019-043-089-127-135-212340-
KY
. KENTUCKY COUNTIES INCLUDED ARE
BOYD CARTER GREENUP
LAWRENCE LEWIS
OHC087-212340-
OH
. OHIO COUNTIES INCLUDED ARE
LAWRENCE
WVC001-005-007-011-013-015-017-019-021-033-035-039-041-043-053-
067-075-077-079-083-085-087-091-093-097-099-101-105-212340-
WV
. WEST VIRGINIA COUNTIES INCLUDED ARE
BARBOUR BOONE BRAXTON
CABELL CALHOUN CLAY
MD 1701 CONCERNING SEVERE THUNDERSTORM WATCH 506... FOR WEST VIRGINIA...FAR SOUTHEAST OHIO...AND FAR NORTHEAST KENTUCKY
Mesoscale Discussion 1701
NWS Storm Prediction Center Norman OK
0602 PM CDT Tue Jul 21 2026
Areas affected...West Virginia...far southeast Ohio...and far
northeast Kentucky
Concerning...Severe Thunderstorm Watch 506...
Valid 212302Z - 220000Z
The severe weather threat for Severe Thunderstorm Watch 506
continues.
SUMMARY...The threat for damaging winds and perhaps a brief tornado
may persist beyond the 00Z watch expiration. A local watch extension
may be required.
DISCUSSION...As of 2255Z, KRLX radar imagery showed a
west-northwest- to east-southeast-oriented band of strong
thunderstorms across portions of Gilmer, Lewis, Upshur, and Randolph
Counties with a storm motion of 296/33 kt. Over time, the line of
storms has become increasingly aligned with the deep-layer shear
vectors, which may tend to limit the damaging wind potential to the
eastern end of the line. To the immediate west of Charleston, WV,
semi-discrete storm structures exhibiting periodic rotation are
embedded within a broader shield of weaker convection.
The KRLX VWP, which is sampling 0-1 km SRH of 200-250 m2/s2 and 0-6
km bulk shear of around 50 kt, is likely quite representative of
both regimes. However, widespread clouds, convectively processed
air, and resultant weak low-level lapse rates may offset the
otherwise favorable kinematic environment to some extent.
Nonetheless, at least an isolated severe weather threat may persist
beyond the scheduled watch expiration, mainly in the form of
damaging winds. As such, some counties may need to be either
extended in time or added to the more recently issued Severe
Thunderstorm Watch 510 prior to 00Z.
..Mead.. 07/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...RNK...PBZ...RLX...
LAT...LON 38028099 38078163 38088228 38188266 38968250 39498184
39408072 39107950 38617969 38377995 38368036 38028099
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
MD 1700 CONCERNING SEVERE THUNDERSTORM WATCH 509... FOR PARTS OF SOUTHEASTERN VIRGINIA
Mesoscale Discussion 1700
NWS Storm Prediction Center Norman OK
0527 PM CDT Tue Jul 21 2026
Areas affected...Parts of southeastern Virginia
Concerning...Severe Thunderstorm Watch 509...
Valid 212227Z - 220000Z
The severe weather threat for Severe Thunderstorm Watch 509
continues.
SUMMARY...A locally favorable corridor for damaging wind gusts and
possibly a brief tornado is evident in southeastern Virginia for the
next couple of hours.
DISCUSSION...Along the southern edge of ongoing convection, a
surface-based thunderstorm is evolving along an east/west-oriented
differential heating zone in southeastern VA. Ahead of this
activity, a warm/moist PBL (middle 70s dewpoints) is contributing to
moderate surface-based buoyancy. This, combined with around 40 kt of
0-6 km shear and a clockwise-curved low-level hodograph (sampled by
the AKQ VWP), is yielding a locally favorable corridor for organized
clusters and supercell structures. The primary concern continues to
be damaging wind gusts, though a brief tornado cannot be ruled out
given the aforementioned low-level shear.
..Weinman.. 07/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...
LAT...LON 36617670 36787735 37037759 37307743 37367725 37277670
36837592 36607608 36617670
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MD 1699 CONCERNING SEVERE THUNDERSTORM WATCH 508... FOR KENTUCKY INTO NORTHERN TENNESSEE AND FAR WESTERN VIRGINIA
Mesoscale Discussion 1699
NWS Storm Prediction Center Norman OK
0448 PM CDT Tue Jul 21 2026
Areas affected...Kentucky into northern Tennessee and far western
Virginia
Concerning...Severe Thunderstorm Watch 508...
Valid 212148Z - 212345Z
The severe weather threat for Severe Thunderstorm Watch 508
continues.
SUMMARY...The potential for damaging winds, large hail, and perhaps
a tornado or two is expected to spread south of the watch area
between 23Z and 00Z. A new watch will be required prior to that
time.
DISCUSSION...Regional radar imagery shows a mix of supercells and
bowing structures ongoing across eastern and central parts of the
watch area with more recent storm development present near the
confluence of the Mississippi and Ohio Rivers. The inflow air mass
to the storms is warm and quite moist with MLCAPE of 2500-3500+
J/kg, per recent objective analysis. However, considerable downshear
anvil blowoff has limited the potential for stronger insolation
across the warm sector, which in turn is resulting in relatively
poor low-level lapse rates. Kinematically, regional VWPs are
sampling seasonably strong mid- and high-level winds and resultant
deep-layer shear with the strongest low-level shear currently
analyzed from eastern KY into western WV.
Extrapolation of current storm motions takes the storms to the
southern edge of the watch area between 23Z and 00Z with latest CAM
guidance suggesting the storms will remain intense as they continue
into portions of TN and far western VA. That scenario appears
reasonable given the presence of the strong vertical shear. Expect
the continuation of supercell and bowing structures with the primary
hazards being damaging winds and large hail. The extent of the
longer-term tornado threat remains somewhat uncertain owing to the
weaker low-level lapse rates, which may limit near-ground parcel
accelerations. However, in the near-term, the greatest tornado risk
will extend from the tornadic supercell in Hart County KY, into
eastern KY where low-level shear is the strongest.
..Mead.. 07/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...RLX...MRX...JKL...ILN...LMK...OHX...PAH...MEG...
LAT...LON 36228986 36678976 37848656 38748303 38308240 37598192
36858211 36248375 35928569 36118836 36218938 36228986
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
MD 1698 CONCERNING TORNADO WATCH 507... FOR PARTS OF SOUTHERN NJ
Mesoscale Discussion 1698
NWS Storm Prediction Center Norman OK
0442 PM CDT Tue Jul 21 2026
Areas affected...Parts of southern NJ
Concerning...Tornado Watch 507...
Valid 212142Z - 212315Z
The severe weather threat for Tornado Watch 507 continues.
SUMMARY...A locally favorable corridor for damaging wind gusts is
evident in southern New Jersey for the next hour or two -- within
Tornado Watch 507.
DISCUSSION...Clusters of thunderstorms are tracking eastward across
far southwestern NJ, with some low/midlevel rotation evident in the
last 15 minutes or so. These storms are moving into a corridor of
strong heating/destabilization of a very moist PBL (upper 70s
dewpoints). This, combined with a long/mostly straight hodograph
(around 50 kt of 0-6 km shear per DIX VWP), will favor a continued
risk of organized clusters capable of producing damaging wind gusts
as they track eastward across southern NJ during the next hour or
two. While low-level shear is not particularly strong, the ample PBL
moisture could support a brief tornado with any embedded
mesovortex/supercell structures.
..Weinman.. 07/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...
LAT...LON 39647539 40107480 40197446 40127406 39967394 39217434
38867476 38907514 39357554 39647539
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0301 PM CDT Tue Jul 21 2026
Valid 212000Z - 221200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PORTIONS
OF THE NORTHEAST AND MID ATLANTIC TO THE OHIO VALLEY...
...SUMMARY...
Numerous severe thunderstorms are expected across a broad region
from the Tennessee and Ohio Valleys to the Mid-Atlantic and
Northeast States into tonight. Swaths of damaging wind gusts are
expected to be the most common impact, but some tornadoes and hail
are possible as well.
...20z Update Mid Atlantic and New England...
A complicated convective situation continues across the area with
numerous cluster of strong to severe storms ongoing from southern
NY/CT/MA to the DelMarVA. A diffuse warm frontal zone from the
Hudson valley to Long Island and the Atlantic coast has supported a
few instances of stronger rotating supercells and QLCS structures.
This focus may continue as additional more discrete storms approach
from northern NJ and eastern PA. Otherwise, clustering of storms
ahead of the cold front and across VA will pose a risk for damaging
gusts through this evening. The primary update to the outlook was to
lower probabilities behind the ongoing convection over NY and
northeast OH where the air mass has been partially overturned.
Isolated damaging gusts and some hail remain possible tonight.
...OH Valley...
A broken band of storms ahead of a cold front, extending into WV and
southwest PA should continue to track east/southeast through this
afternoon and into the evening hours. Strong northwesterly flow
aloft is supporting moderate deep-layer shear and a mixed mode of
supercells and clusters across southern IN/OH and into northern KY.
A primary risk for damaging winds is expected given upscale growth
as storm coverage increases. However, the large buoyancy (MLCAPE
3000-4000 J/kg) and some supercell structures could support large
hail. Some tornado potential will also exist with the semi-discreet
supercells and QLCS structures. This appears most likely near a
convective modified boundary from astern OH into WV and southwest
PA.
Storm coverage should continue to increase this afternoon across
western KY and the lower OH Valley. With a predominately linear
storm mode expected along the cold front, damaging winds are the
most likely hazard. The primary change to the probabilities was to
trim behind the front over OH/IN. See the prior outlook for more
information.
..Lyons.. 07/21/2026
.PREV DISCUSSION... /ISSUED 1118 AM CDT Tue Jul 21 2026/
...Tennessee/Ohio Valley into the Mid-Atlantic and Northeast...
Recent satellite imagery reveals a shortwave trough moving quickly
southeastward across the Upper Great Lakes region, embedded within
the upper troughing that covers much of eastern Canada and extends
down into the Ohio Valley. Moderate mid-level flow accompanies this
shortwave, with wind speeds greater than 50 kt sampled around 500 mb
on the 12Z ILX, DTX, ILN, and PIT soundings. The strongest flow was
sampled at ILX and DTX, and the expectation is for this stronger
flow to spread eastward today, moving in tandem with the progressive
shortwave.
Showers and thunderstorms are already ongoing downstream of this
shortwave, with the highest coverage along and near the pre-frontal
trough in Ohio. Recent surface analysis reveals a somewhat complex
boundary structure, with a wavy warm front, a diffuse pre-frontal
trough, and a cold front. Primary warm front appears to extend
west-to-east from southeast Ohio across southern Pennsylvania and
into northern New Jersey, far southern New York, and extreme
southwest Connecticut. The cold front arcs southwestward from
northern Lower Michigan through central Illinois and central
Michigan.
Highest overall coverage is anticipated along and ahead of the cold
front this afternoon through this evening, with additional
development expected farther east (from central Pennsylvania into
central Virginia) along the lee trough as well. Highest buoyancy is
expected along the western periphery of the cold front from central
into western Kentucky, where mid to upper 70s dewpoints are
anticipated amid temperatures in the upper 80s/low 90s. Strong
buoyancy is still anticipated across Ohio as well. Robust
thunderstorm development is expected along the front. Vertical shear
is robust enough for supercells, but linear forcing along the front
and strong downdraft production will likely lead to quick upscale
growth. In either convective mode, damaging gusts (with speeds from
55 to 70 mph) will be the primary risk, with brief tornadoes as a
secondary threat, and large hail tertiary.
Farther east, a similar convective environment exists, although with
slightly less buoyancy and deep-layer vertical shear. A more
outflow-dominant multicell mode is anticipated across the central
Virginia vicinity, with a trend towards a more organized mode
possible with northern extent. Primary risk will be damaging gusts,
including a few around 65 to 70 mph. A somewhat confined corridor of
greater tornado potential exists from the Hudson Valley vicinity
into western Massachusetts/Connecticut as the warm front lifts
northward. Here, enhanced vorticity along the boundary coupled with
stronger low-level southerly flow could support a few brief
tornadoes.
...Great Basin...
Scattered to numerous thunderstorms are expected across the Great
Basin today, supported by strong diurnal heating/mixing and moderate
mid-level moisture along the western periphery of the upper ridging
centered over the central Rockies. A few strong updrafts/downdrafts
are possible, with an attendant risk for strong to severe (i.e. 50
to 65 mph) wind gusts.
...Gulf Coast...
Tropical Storm Bertha is expected to continue to drift
west-northwestward over the northern Gulf tonight from off the coast
of the Florida Panhandle toward the southern Mississippi/southern
Alabama coast. Reference the National Hurricane Center for the
latest details.
A strong low-level wind field will approach these coastal areas
later today and tonight. However, as is typical for a westward
moving tropical cyclone, forecast SRH should remain relatively
modest inland. Given the marginal thermodynamic profiles (aside from
the rich boundary layer moisture) and limited SRH over land, any
Bertha-related mini-supercell potential is expected remain offshore.
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0224 PM CDT Tue Jul 21 2026
Valid 231200Z - 241200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorm potential appears low on Thursday. However,
locally gusty winds could occur with thunderstorms across the
central High Plains.
...Discussion...
The pattern on D3/Thursday will continue to favor high amplitude
ridging across the western US and troughing in the eastern US.
Surface high pressure will build in from the Midwest to the Ohio
Valley with a cold front extending from the Carolinas into the
Mid-South/northern Gulf states. Widely scattered thunderstorm
activity is expected along and south of this boundary. Moist and
moderately unstable conditions may support few strong storms with
water loaded downburst potential, but generally weak shear should
limit the overall severe potential.
Across the central High Plains, easterly upslope flow will promote
moisture advection into eastern Colorado/ Wyoming. A weak shortwave
will rotate through the flow with thunderstorm development expected
across the high terrain in eastern Colorado/Wyoming by the afternoon
with a gradual shift into the central Plains into the evening.
Initially, high based thunderstorms may pose some localized
potential for strong to severe wind. Deep layer shear across the
central Plains will strengthen, but increasing MLCIN with eastward
extent will likely temper severe potential. Overall, locally gusty
winds will be possible but organized severe potential appears too
low and localized for inclusion of probabilities.
..Thornton.. 07/21/2026
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0224 PM CDT Tue Jul 21 2026
Valid 221200Z - 231200Z
Thunderstorm coverage will likely exceed 50% across central into
southern Oregon and perhaps approach 80% in central Oregon. Given
PWAT values of 0.9-1.25" and southerly flow induced training of
storms, wetting rain is likely in portions of central Oregon. This
precludes an upgrade to a Scattered DryT area where the greater
coverage of thunderstorms is expected. However, given the dry fuels,
ongoing large wildfire activity, and expected dry and windy
conditions following this lightning, including isolated nocturnal
thunderstorms, new lightning ignited wildfires will emerge.
Additionally, thunderstorm outflow winds and potential deep
pyroconvection on active large wildfires are a concern.
..Nauslar.. 07/21/2026
.PREV DISCUSSION... /ISSUED 1250 AM CDT Tue Jul 21 2026/
...Synopsis...
Upper-level troughing will remain in place across the eastern U.S.
as a southward progressing cold front promotes widespread chances of
rainfall along the Eastern Seaboard on Day 2/Wednesday. Meanwhile,
the remnants of Post-Tropical Cyclone Elida will continue to
translate northward along the western periphery of a large-scale
ridge across the western CONUS. As high pressure shifts towards the
Four Corners, additional monsoonal moisture will advect into the
Pacific Northwest.
Despite being less than 48 hours from the forecast period, model
data (including high-resolution guidance) exhibits prominent
differences in the amplitude of the upper ridge; thus, disparity in
the strength and direction of upper/mid-level flow. While a mix of
wet/dry thunderstorms are still expected across the IsoDryT area, a
slightly more eastward progression of the Pacific upper low could
result in expasive thunderstorm coverage. Forecast PWAT values do
approach 0.9-1.25", but 20-30 kt storm motions should inhibit
precipitation efficiency, resulting in greater potential for
lightning ignitions. Given very receptive fuels and fire activity in
the area, a subsequent outlook upgrade to a Scattered Dry
Thunderstorm area may be warranted if the wetting rain footprint
remains relatively smaller to thunderstorm coverage.
...Please see www.spc.noaa.gov/fire for graphic product...
SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0439 PM CDT Tue Jul 21 2026
Valid 231200Z - 291200Z
Upper-level troughing will move into the Pacific Northwest with
stronger southwest to westerly flow aloft across the northwest US
starting Day 3/Thursday and continuing through the weekend. The
upper low will likely remain off the coast until this weekend, but
forecast guidance remains uncertain regarding its track and timing.
An upper high will remain in the vicinity of the Four Corners into
the weekend, with daily monsoonal thunderstorms likely continuing
across the region.
As upper-level troughing begins to move into the Northwest, isolated
to scattered mixed wet/dry thunderstorms are likely across
central/eastern Washington, eastern Oregon, and western/north Idaho
into northwest Montana Day 3/Thursday. Residual subtropical moisture
will maintain PWAT values of 0.75-1.1", but storm motions of 20-30
knots, a dry sub cloud layer, and receptive fuels will result in
lightning ignitions. Dry and breezy conditions will also develop
during the afternoon and evening from central/eastern Washington
extending south into northeast California and northwest Nevada as
the onshore pressure gradient tightens and stronger winds aloft
arrive that can mix to the surface.
With an onshore pressure gradient, surface pressure troughing
extending from eastern Washington to southwest Idaho, and 40-65 knot
mid-level flow, breezy west-southwest winds will develop across the
Inland Northwest, northwest Great Basin, and the northern Rockies
onto the northern Plains Day 4/Friday - Day 5/Saturday and possibly
Day 6/Sunday. Drier air will move across this region as well, with
elevated to locally critical conditions expected. These dry and
breezy conditions will follow lightning likely resulting in
holdovers and growth on existing wildfires, especially active large
wildfires.
Forecast guidance remains mixed on identifying corridors of critical
conditions, which precludes introducing 70% area(s) at this time.
Ensemble forecast guidance (GEFS, ECENS, and NBM) indicates that
critical winds/RH are likely to develop (> 50% probabilities), but
these corridors are somewhat narrow and tend to overlap some of the
areas that have less receptive fuels. However, given the forecast
pattern, BIs, and Hot-Dry-Windy-Index probabilities, critical
conditions will likely develop in portions of the 40% areas on Day
4/Friday - Day 5/Saturday.
..Nauslar.. 07/21/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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