WW 338 SEVERE TSTM IL IN MI OH LM 162010Z - 170300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 338
NWS Storm Prediction Center Norman OK
410 PM EDT Tue Jun 16 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
East Central Illinois
Northern and Central Indiana
Southern Lower Michigan
Northwest Ohio
Lake Michigan
* Effective this Tuesday afternoon and evening from 410 PM until
1100 PM EDT.
* Primary threats include...
Scattered damaging wind gusts to 70 mph possible
Scattered large hail events to 1.5 inches in diameter possible
A tornado or two possible
SUMMARY...Thunderstorms will form this afternoon along a cold front
and sweep eastward across the watch area. The strongest storms will
be capable of damaging winds and large hail. A tornado or two is
also possible.
The severe thunderstorm watch area is approximately along and 55
statute miles east and west of a line from 30 miles south of Terre
Haute IN to 30 miles east northeast of Grand Rapids MI. 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.
&&
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
24030.
...Hart
WW 0338 Status Updates
STATUS REPORT ON WW 338
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 E DEC TO
35 ENE LAF TO 30 WSW GRR TO 10 NW MKG.
FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 1157
..WEINMAN..06/16/26
ATTN...WFO...ILX...IWX...IND...LOT...GRR...
STATUS REPORT FOR WS 338
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
ILC023-025-029-033-035-041-045-049-079-101-139-159-173-170040-
IL
. ILLINOIS COUNTIES INCLUDED ARE
CLARK CLAY COLES
CRAWFORD CUMBERLAND DOUGLAS
EDGAR EFFINGHAM JASPER
LAWRENCE MOULTRIE RICHLAND
SHELBY
INC001-003-005-009-011-013-017-021-023-033-035-039-045-053-055-
057-059-063-065-067-069-075-081-085-087-095-097-103-105-107-109-
113-119-121-133-135-145-151-153-159-165-167-169-179-183-
170040-
IN
. INDIANA COUNTIES INCLUDED ARE
ADAMS ALLEN BARTHOLOMEW
BLACKFORD BOONE BROWN
CASS CLAY CLINTON
MD 1158 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR NORTHERN INTO NORTHEAST MT AND NORTHWEST ND
Mesoscale Discussion 1158
NWS Storm Prediction Center Norman OK
0525 PM CDT Tue Jun 16 2026
Areas affected...northern into northeast MT and northwest ND
Concerning...Severe potential...Watch unlikely
Valid 162225Z - 170030Z
Probability of Watch Issuance...20 percent
SUMMARY...The risk for isolated severe gusts and perhaps marginally
severe hail will develop as storms intensify during the next few
hours.
DISCUSSION...Widely scattered thunderstorms are developing ahead of
an amplifying upper trough over southern Alberta. GOES and
model-based upper flow fields show very strong westerly flow with
80+ kt flow at 8 km AGL per the Glasgow, MT WSR-88D VAD. Although
low-level moisture is modest (surface dewpoints ranging from 45-50
deg F), steepened 0-3 km lapse rates and cool mid levels are
supporting upwards of 500-1000 J/kg SBCAPE. Very long hodographs
will support storm organization mainly in the form of a couple of
supercells early during the convective life cycle before more storms
and coalescing cold pools promotes more of a multicell mode. The
greater risk for severe hail will accompany the supercells before
the risk for severe gusts also begins to increase owing to higher
storm coverage.
..Smith/Gleason.. 06/16/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BIS...GGW...TFX...
LAT...LON 48780942 48970824 48960393 48750161 48360088 47780094
47310121 47200232 47450518 47960798 48260907 48490943
48780942
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 PM CDT Tue Jun 16 2026
Valid 162000Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
EASTERN ILLINOIS...INDIANA AND LOWER MICHIGAN THROUGH THIS EVENING
AND IOWA TONIGHT...
...SUMMARY...
Severe thunderstorms remain possible this afternoon and tonight
across multiple parts of the Midwest, as well as on a more isolated
basis across the Gulf Coast, south-central Plains and northern
Plains.
...20z Update Wisconsin and Michigan to Illinois and Indiana...
Beneath the cold core of the clipper, steep mid-level lapse rates
and weak buoyancy are supporting scattered thunderstorms. While
available MUCAPE is somewhat limited (500-750 J/kg) 500 mb temps
near -20C are supportive of marginally severe hail with the stronger
cores. This threat should end by evening as buoyancy declines with
the loss of diurnal heating. Have expanded the 5% hail across Lake
Michigan into the UP and eastern WI shores.
Southern portions of the Level 2 Slight risk were also expanded into
eastern IL where robust convection is expected along the cold front
this afternoon and evening. Hail, damaging gusts and a couple of
tornadoes remain possible.
...MT and northern Plains into the Midwest tonight...
Ahead of the strong belt of mid-level flow ahead of the upper trough
moving out of Canada, afternoon model guidance remains bullish on
several rounds of strong and occasionally severe storms late tonight
into early Wed. However, CAPE will be rather weak, which should
limit overall convective organization. Isolated severe gusts remain
possible.
The upstream convection will eventually intersect with a rapidly
moistening air mass across parts of IA and the Midwest. This will
likely result in a cluster of more robust severe storms near
daybreak across SD, IA and MN at the nose of a 50+ kt 850 mb jet.
Increasingly strong vertical shear from the upstream trough/jet will
support supercells or elevated bowing segments capable of hail and
severe wind gusts by 12z Wed. Have connected the MRGL areas over the
northern Plains into the Midwest.
...Southern and central Plains...
Strong heating along the stalled front initially over the southern
and central Plains could result in isolated to widely scattered
thunderstorms late this afternoon and early evening. Increasing
vertical shear and low-level moisture advection could favor some
risk for hail with supercells. However, warm temperatures aloft and
only modest large-scale forcing for ascent casts considerable
uncertainty on storm development/maintenance this evening. Should a
supercell or two become established, large hail and damaging gusts
would be possible before ending overnight.
..Lyons.. 06/16/2026
.PREV DISCUSSION... /ISSUED 1113 AM CDT Tue Jun 16 2026/
...IN/Lower MI...
Morning water vapor loop shows a strong and progressive Clipper
system tracking southeastward across MN/WI. A band of clouds and
isolated thunderstorms precedes this system, extending from southern
Lower MI into central IL. While a few strong storms are possible to
develop in this band, the greater risk for severe storms appears to
be associated with a period of heating in the wake of these clouds.
Steep lapse rates and cold temperatures aloft will combine with
dewpoints around 60F to result in sufficient afternoon/evening CAPE
for widely scattered strong/severe storm development. Large hail
will be the initial main concern, along with some risk of a tornado
or two. By early evening, damaging winds will be the main concern.
...IA Overnight...
The next in a series of fast-moving upper-level features will move
across the Dakotas tonight, with large-scale forcing for ascent
spreading into parts of MN/IA before 12z. This ascent will begin
interacting with a plume of returning moisture, leading to scattered
thunderstorm development in the pre-dawn hours. Elevated supercells
capable of large hail will be the main risk through 12z.
...MT/ND...
The aforementioned upper feature will affect northeast MT and the
Dakotas this afternoon and evening. A deeply-mixed boundary layer
will develop over this area with temperatures in the 80s and 35-45F
t-td spreads. CAPE will be rather weak, which should limit overall
convective organization. Nevertheless, fast-moving high-based
showers and thunderstorms capable of gusty and occasionally severe
wind gusts are expected.
...Gulf Coast...
The tropical system (PTC 1) along the south TX coast is expected to
slowly organize today, with widespread showers and thunderstorms
from east TX into the central Gulf coast. Low-level winds are not
particularly strong and forecast hodographs are only marginally
favorable for updraft rotation. Nevertheless with such a broad area
of risk, a tornado or two is certainly possible this afternoon
through tonight.
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0232 PM CDT Tue Jun 16 2026
Valid 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM KENTUCKY AND
NORTHERN TENNESSEE INTO THE MID-ATLANTIC...
...SUMMARY...
Isolated to scattered severe thunderstorms will be possible from
Kentucky to the Mid-Atlantic. Damaging wind gusts will be the main
hazard with this activity.
...Synopsis...
An upper trough will move across southern Quebec on Thursday. A
trailing cold front from the Northeast into the southern Plains will
serve as a focus for convection. A remnant tropical system will also
promote scattered thunderstorms in the Southeast.
...Ohio Valley into the Northeast/Mid-Atlantic...
As the upper trough slowly moves through southern Quebec, a belt of
strong mid-level winds will be present across these regions.
Mid-level flow will rapidly diminish from south of the mid/lower
Ohio Valley latitude, however. Precipitation is expected to be
ongoing along at least parts of the cold front early in the day.
This will act to limit surface heating/destabilization into the
afternoon. Even with that limitation, the very moist airmass ahead
of the front will promote moderate (Mid-Atlantic/parts of Northeast)
to strong (mid/lower Ohio Valley) buoyancy. Given the strong
low/mid-level winds, potential exists for scattered damaging winds.
...Southern Plains into Mid-South...
Strong instability is forecast south of a sagging cold front. Though
these regions will be removed from the stronger mid-level winds,
sufficient effective shear will be in place to promote potential for
damaging downburst winds with the stronger storms/clusters that
develop during the afternoon.
...Southeast...
The remnants of Potential Tropical Cyclone 1 will continue to move
through the northern Gulf into the Southeast on Thursday. With 70+
dewpoints likely to be ahead of this feature, even muted surface
heating will promote moderate instability will develop. With locally
enhanced shear near the remnant low, isolated strong wind gusts and
perhaps a tornado or two will be possible. Should greater
destabilization occur, higher probabilities could be warranted.
..Wendt.. 06/16/2026
SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0450 PM CDT Tue Jun 16 2026
Valid 181200Z - 241200Z
...Synopsis...
On Day 3/Thursday, an upper low will slowly slide eastward over
southern Quebec as a belt of strong mid-level flow expands across
the Ohio Valley into the Northeast. Simultaneously, an upper ridge
will break down across the West owing to an approaching upper
trough. Some isolated dry thunderstorm potential alongside dry and
breezy conditions with above normal temperatures (and resultant dry
fuels) will support expansive fire concerns through Day 5/Saturday.
The trough will lose its amplitude as it traverses the Great Plains,
transitioning western CONUS to temporary zonal flow aloft. While
predictability is low, extended guidance exhibits increasing
potential for ridging to build back across the Pacific Northwest,
bringing warm and dry conditions back into the region early next
week.
...Day 3-5/Thursday-Saturday - Parts of the Pacific Northwest and
Great Basin...
As upper-level troughing moves onshore the West Coast, surging
mid-level moisture and synoptic scale lift will bring increasing
chances for thunderstorms. Given preceding days of warm and dry
conditions and coincident curing fuels, the isolated nature of
thunderstorm development could pose a threat for lightning ignitions
across a very dry environment -- possibly as early as Day 3/Thursday
evening. The potential for thunderstorm development on Day
3/Thursday will be reevaluated on the approaching Day 2 outlook
cycle as higher resolution guidance becomes available. Fast storm
motions, high cloud bases, and locally breezy conditions support 10%
Dry Thunderstorm probabilities on Day 4/Friday, and again on Day
5/Saturday as the trough shifts eastward. Spatial extent of the
aforementioned risk areas may fluctuate as guidance is better
resolved in future outlook cycles.
Increasing southerly to westerly flow across the Southwest will
transport very dry air and breezy conditions amid recently receptive
fuels, promoting continued fire concerns in the Great Basin through
the weekend. 40% Critical probabilities have been maintained on Days
4-5/Friday-Saturday to account for this threat.
..Elizalde-Garcia.. 06/16/2026
...Please see www.spc.noaa.gov/fire for graphic product...
|
