No watches are valid as of Fri Sep 18 18:56:01 UTC 2026.MD 2307 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR NORTHERN UTAH INTO FAR SOUTHWEST WYOMING
Mesoscale Discussion 2307
NWS Storm Prediction Center Norman OK
0153 PM CDT Fri Sep 18 2026
Areas affected...northern Utah into far southwest Wyoming
Concerning...Severe potential...Watch unlikely
Valid 181853Z - 182130Z
Probability of Watch Issuance...20 percent
SUMMARY...Storms over northern Utah may gradually strengthen, with
hail over 1.00" diameter and locally strong wind gusts expected.
DISCUSSION...An upper low with midlevel cooling continues to move
slowly across northern NV and into southern ID this afternoon.
Meanwhile, surface heating and boundary layer mixing continue within
the surface trough located over eastern NV into UT.
Radar trends indicate that the early day activity may be
transitioning/strengthening coincident with surface heating, with
stronger cores noted. The earlier elongated echoes also appear to be
consolidating into cells.
The steep lapse rate environment, ample moisture and elongated mid
to upper level hodographs should support sporadic severe hail later
this afternoon. Locally severe gusts may also occur as outflows
possibly aggregate and move across northern UT into southwest WY.
..Jewell/Mosier.. 09/18/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...RIW...SLC...PIH...
LAT...LON 40421077 39851176 39851296 39891359 40161377 40271377
41361311 41841198 42251085 42281022 42040995 41310995
40991006 40421077
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
MD 2306 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF NORTHERN GEORGIA INTO THE CAROLINA PIEDMONT
Mesoscale Discussion 2306
NWS Storm Prediction Center Norman OK
0113 PM CDT Fri Sep 18 2026
Areas affected...portions of northern Georgia into the Carolina
Piedmont
Concerning...Severe potential...Watch unlikely
Valid 181813Z - 182015Z
Probability of Watch Issuance...5 percent
SUMMARY...Widely scattered thunderstorms may bring some potential
for isolated damaging wind gusts through this evening. Watch
issuance is not anticipated.
DISCUSSION...Widely scattered to scattered thunderstorms have begun
to initiate across portions of the central Appalachians and Carolina
Piedmont as surface temperatures have risen into the low-90s F amid
continued insolation. Poor mid-level lapse rates and weak deep-layer
flow/shear will tend to limit overall convective intensity and
organization; however, MLCAPE of 1000-2000 J/kg coupled with steep
low-level lapse rates and PW around 1.75-2.00 inches (as supported
by a modified 12z GSO observed sounding and current objective
analysis) are supportive of at least some potential for isolated
damaging downburst wind gusts (with peak gust magnitudes likely in
the 45-55 mph range). Locally greater potential may exist across
portions of central North Carolina where the latest observational
trends and CAM guidance are suggestive of greater storm coverage.
Trends will continue to be monitored, but the overall severe threat
is likely to remain too isolated and limited in magnitude to warrant
watch issuance.
..Chalmers/Mosier.. 09/18/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...RAH...ILM...RNK...CAE...GSP...MRX...FFC...
LAT...LON 34878398 36088112 36557996 36717935 36717887 36657860
36497839 36107816 35717814 35347826 34897868 34377963
33928105 33578270 33518354 33588423 33788465 33978476
34328463 34658430 34878398
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1129 AM CDT Fri Sep 18 2026
Valid 181630Z - 191200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
CAROLINA PIEDMONT INTO NORTHERN GEORGIA...NORTHERN IOWA...PARTS OF
THE CENTRAL HIGH PLAINS...AND PARTS OF THE INTERMOUNTAIN WEST...
...SUMMARY...
An isolated severe risk is forecast later today into the evening for
the Carolinas into northern Georgia, northern Iowa, parts of the
central High Plains, and parts of the Intermountain West.
...Carolina Piedmont into Northern Georgia...
Recent surface analysis places a wavy stationary front from southern
IL through southern IN and southern OH into southwest PA. Decaying
showers and thunderstorms currently precede this boundary from
southern IL into northern KY. This boundary is forecast to shift
southward today in response to a modest surge of cooler air in the
wake of a shortwave trough moving through southern Quebec and the
Canadian Maritimes. This front will be relatively weak, but
thunderstorm development is still anticipated this afternoon as the
front interacts with the warm, moist, and diurnally destabilized
airmass across the Carolina Piedmont and northern GA. Vertical shear
will be weak and a largely outflow-dominant storm mode is expected.
Even so, the strong buoyancy and ample moisture (i.e. PW values over
2 inches) will support the potential for occasionally strong
downbursts.
...Central High Plains...
Water-vapor imagery continues to show a convectively enhanced
vorticity maximum moving north-northeast from north-central NM into
southern CO. This vorticity max is forecast to continue
northeastward along the periphery of the upper ridging centered over
east TX, contributing to thunderstorm development from eastern WY
through eastern CO this afternoon/evening. Much of this activity
will occur in regions of cooler surface temperatures and/or more
limited low-level moisture. However, surface-based buoyancy could
exists in the CO/NE/KS border intersection vicinity, where a
combination of strong heating, and lingering post-frontal low-level
moisture will exist. Potential exists for initially isolated to
widely scattered storms to grow upscale into a small,
eastward-moving cluster this evening. Isolated severe gusts may
accompany the stronger outflow surges with this activity.
...Intermountain West...
Continued thunderstorm development is anticipated across the region
today, with overall coverage and intensity increasing as a shortwave
trough continues to move eastward into southern ID and northern UT.
Some moderate, filtered daytime heating is possible, but the overall
region is expected to remain relatively cool (i.e. high temperatures
ranging from the upper 60s across southern ID to the low to mid 70s
across northern UT). Even so, cold temperatures aloft will support
enough buoyancy, which will combine with strong deep-layer vertical
shear to support occasionally strong/organized updrafts. Strong to
severe gusts will be possible with any stronger, more persistent
storms. Some instances of small hail are possible as well.
...Northern Iowa into Far Southern MN...
Elevated thunderstorm development is still anticipated tonight,
supported by warm-air advection associated with a moderate low-level
jet that extends through the region. Highest storm coverage will
likely be displaced north and east of the strongest buoyancy. Even
so, a few of the southernmost storms could occur where moderate
vertical shear and buoyancy are in place, supporting the potential
for an isolated supercell or two. Primary risk with any stronger
storms is hail, but a strong gust or two is possible if any more
linear structures develop.
..Mosier/Chalmers.. 09/18/2026
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1226 PM CDT Fri Sep 18 2026
Valid 191200Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE SATURDAY
AFTERNOON/EVENING FROM NORTHWEST OKLAHOMA INTO EASTERN KANSAS...
...SUMMARY...
Scattered severe wind and hail producing storms are likely across
portions of the central Plains, with more isolated severe storms
possible across the central High Plains, central Rockies, and the
Midwest to Southeast states tomorrow.
...Central Plains to the OH Valley...
North of a weakening midlevel high over the south central CONUS, a
belt of midlevel westerlies will be maintained from a shortwave
trough crossing ID/UT/WY/CO eastward to the central Plains and OH
Valley. In associated with an embedded speed max, a weak surface
wave will develop eastward along a baroclinic zone from IA/IL to
northern OH by the end of the period. The trailing cold front will
move slowly southeastward across the central Plains. This front
will focus thunderstorm development Saturday afternoon/evening from
the eastern TX Panhandle across northwest OK into eastern KS.
Strong surface heating along and south of the front will drive
inverted-V profiles and moderate buoyancy (MLCAPE of 1500-2000
J/kg), which combined with ~30 kt midlevel flow will favor multicell
clusters with hybrid microbursts and occasional severe outflow
gusts. Isolated large hail will also be possible with any more
organized storms moving along the front in a narrow zone of somewhat
enhanced vertical shear.
Farther east into the Midwest/OH Valley, the amplitude of the
surface wave and any associated low-level mass response will depend
on the degree of prior convective enhancement/MCV development.
Confidence is low in diurnal storm clusters evolving from morning
convection, though such a scenario could warrant higher wind
probabilities in later updates if a storm corridor can be identified
with more confidence. Forecast confidence is low so will maintain
low severe probabilities to reflect the potential for isolated wind
damage with embedded storm clusters across the OH Valley. The
southern extent of the MRGL area (into AL) reflects the potential
for diurnal convection with isolated downbursts.
...Eastern CO/WY...
A weak low-level upslope flow regime and the approach of a midlevel
trough from the west will foster scattered thunderstorm development
Saturday afternoon near and immediately east of the higher terrain
from CO into WY. Buoyancy and deep-layer vertical shear will be
sufficient for organized clusters and possibly a couple of
supercells with an attendant threat for isolated large hail and
strong-severe outflow gusts. Convection will likely persist into
Saturday night while spreading toward western KS, though storms will
likely become slightly elevated and weaken with time.
..Thompson.. 09/18/2026
|
