Storms

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1259 AM CDT Tue Jul 21 2026

Valid 211200Z - 221200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE UPPER OHIO VALLEY INTO THE MID-ATLANTIC...

...SUMMARY...
Numerous severe thunderstorms are expected across a broad region
from the Ohio Valley into the Mid-Atlantic and Northeast today. All
severe hazards are possible, but swaths of damaging wind gusts
should be the primary severe risk during the afternoon and early
evening hours.

...Ohio Valley into the Mid-Atlantic...
A broad area of 40-50-kt midlevel west-southwesterly flow will
overspread the OH Valley into the Mid-Atlantic as a large-scale
trough shifts across the northeastern CONUS. Scattered to numerous
thunderstorms are expected to develop ahead of an eastward-moving
cold front across the OH Valley and along a pre-frontal trough over
the Mid-Atlantic. In the base of the trough, a convectively
augmented midlevel impulse moving from the lower OH Valley into the
Mid-Atlantic may also serve as a focus for convective development. 

Diurnal heating within cloud breaks, combined with upper 60s to
lower 70s dewpoints, will support moderate surface-based instability
across the broad pre-frontal warm sector. The most favorable overlap
of this instability and 40-50 kt of effective shear is expected from
the lower OH Valley into the Mid-Atlantic, where a mix of organized
clusters and supercells should evolve and spread eastward through
the day. Swaths of damaging wind gusts will be the primary severe
hazard, though severe hail will also be possible with any sustained
supercells. Additionally, a gradually strengthening and expanding
30-kt low-level jet will contribute to clockwise-curved low-level
hodographs, and a few tornadoes may occur.

...Mid-South into the Tennessee Valley...
Greater instability is expected southwestward into portions of the
Mid-South and TN Valley, although somewhat weaker deep-layer shear
(around 30-40 kt of effective shear) may temper storm organization 
compared to ares farther northeast. Nevertheless, widely scattered
thunderstorms capable of organizing into multicell clusters and
occasional supercell structures will pose a risk of damaging wind
gusts and isolated severe hail ahead of the cold front during the
afternoon and early evening hours.

...Northeast...
Increasing midlevel height falls/forcing for ascent preceding the
upper trough will support scattered thunderstorm development near an
effective warm front moving northward across portions of the
Northeast. While poor midlevel lapse rates and weaker instability
should limit the overall severe risk compared to areas farther
south, around 40 kt of effective shear will still support organized
storm structures. Damaging wind gusts will be the primary concern,
though isolated severe hail and a tornado or two will also be
possible.

..Weinman/Jirak.. 07/21/2026

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1215 AM CDT Tue Jul 21 2026

Valid 221200Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHERN MID-ATLANTIC...

...SUMMARY...
Isolated severe thunderstorms will pose a risk for damaging wind
gusts across parts of the southern Mid-Atlantic. Additional
thunderstorms are expected northward across New England, some of
which could produce locally strong wind gusts.

...Mid-Atlantic into New England...

Several shortwave impulses are forecast to move through large-scale
upper troughing across the Northeast on Wednesday. Relatively strong
deep-layer winds for mid/late July are forecast, characterized by
500 mb southerly flow around 45-60 kt, 35-55 kt at 700 mb, and 25-35
kt at 850 mb. At the surface, low pressure will lift northeast
across Quebec, with a surface trough extending southward into the
Mid-Atlantic. A cold front is forecast to be located from eastern NY
to the central Appalachians and the TN Valley Wednesday morning. The
northern extent of the front will be rather progressive as it moves
across New England and the northern Mid-Atlantic through the
afternoon and evening. The southern extent of the front will more
slowly sag south/southeast across VA/NC. Ahead of the front,
southerly low-level flow will maintain a seasonally moist airmass
beneath the moderately strong deep-layer wind fields. 

While the boundary layer will be moist, strong heating will be
limited due to cloud cover and poor lapse rates. This will limit
instability, especially with northward extent into New England.
Nevertheless, sufficient instability coupled with the stronger
deep-layer flow will support organized clusters capable of wind
damage. The greatest risk will be focused across the southern
Mid-Atlantic where instability will be greatest (1000-1500 J/kg
MLCAPE).

..Leitman.. 07/21/2026

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0126 AM 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 into the northern Rockies.

...Central High Plains...

Scattered thunderstorms are expected to develop over higher terrain
in the central Rockies during the afternoon. Easterly low-level flow
across the adjacent High Plains will transport modest boundary layer
moisture westward across western KS and eastern CO. Meanwhile, a
weak surface boundary may develop south across the central High
Plains as convection moves off higher terrain into the High Plains.
Forecast soundings indicate generally weak midlevel lapse rates, but
steep low-level lapse rates within modest instability (MLCAPE up to
1000 J/kg). This could support gusty outflow winds with storms
across the Plains. However, effective shear values in the 20-25 kt
range and very weak flow below 500 mb suggests organized severe
convection is unlikely amid the weakly unstable airmass. 

...Northern Rockies...

Some enhancement to upper flow is forecast as a shortwave upper
trough moves across Alberta and Saskatchewan, and an upper low
persists off the Pacific Northwest coast. Forecast soundings show a
deeply-mixed boundary layer with steep 0-3 km lapse rates. Steep
midlevel lapse rates will be sufficient for weak destabilization,
and isolated thunderstorms are expected during the
afternoon/evening. Given weak vertical shear and limited
instability, organized severe potential is low, though gusty outflow
winds could occur.

..Leitman.. 07/21/2026

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0218 AM CDT Tue Jul 21 2026

Valid 241200Z - 291200Z

...DISCUSSION...
...Great Lakes/Midwest...

An amplified upper ridge will persist across the Plains and Rockies
through early next week. Periods of strengthening northwesterly
mid/upper flow are expected on the eastern periphery of the upper
ridge as a series of upper shortwave troughs move across the
Canadian Prairies and glance the Great Lakes vicinity, mainly Day
5-7/Sat-Mon. This could support areas of severe thunderstorm
potential across parts of the Upper Midwest to the Ohio Valley
vicinity during this time as stronger northwesterly flow overspreads
a seasonally moist and unstable airmass. However, both traditional
physics-based NWP and ML/AI NWP are inconsistent and/or show
relatively low/broad probability areas -- increasing uncertainty in
timing and spatial delineation of severe potential. Given the
proximity to the upper ridge, capping may be a concern. Trends will
be monitored and severe probabilities may become necessary is
confidence increases in subsequent outlooks.

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1245 AM CDT Tue Jul 21 2026

Valid 211200Z - 221200Z

...Synopsis...
...Northern California and west/central Oregon...
Along the northwestern periphery of a large-scale ridge encompassing
much of the central and western CONUS, ample mid-level moisture will
be in place atop a warm and dry airmass across parts of northern CA
into OR. Forecast soundings depict inverted-V profiles with weak
(albeit sufficient) buoyancy for high-based thunderstorms across the
area during the afternoon and evening hours. Cloud cover, smoke, and
warmer temperatures aloft will help limit thunderstorm
development/coverage across the IsoDryT area, but isolated
thunderstorms remain possible. While 0.8 to 1.2 inch PWATs may
promote a mix of wet/dry storms, relatively fast storm motions and
the dry boundary layer should limit precipitation efficiency. As a
result, isolated lightning-induced ignitions will be possible within
a very dry fuelscape. 

...South Carolina...
Progressive upper-level troughing will continue across the
northeastern U.S. as a closed low traverses northern Ontario,
sending a cold front through the Ohio Valley. Enhanced 850 mb
southwesterly flow ahead of the front will encourage gusty surface
winds amid minimum RH values of 30-40% in portions of South
Carolina. Locally elevated fire weather conditions are likely, as
ERCs generally range from the 80th-95th percentile across this area.

..Elizalde-Garcia.. 07/21/2026

...Please see www.spc.noaa.gov/fire for graphic product...

Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1250 AM CDT Tue Jul 21 2026

Valid 221200Z - 231200Z

...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.

..Elizalde-Garcia.. 07/21/2026

...Please see www.spc.noaa.gov/fire for graphic product...