RSS Mesoscale Discussions from Storm Prediction Center
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
Read more
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
Read more
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
Read more
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
Read more
WW 0509 Status Updates
STATUS REPORT ON WW 509
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..BENTLEY..07/21/26
ATTN...WFO...LWX...PHI...AKQ...RNK...
STATUS REPORT FOR WS 509
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
DEC001-005-212140-
DE
. DELAWARE COUNTIES INCLUDED ARE
KENT SUSSEX
DCC001-212140-
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-
033-035-037-039-041-043-045-047-510-212140-
MD
. MARYLAND COUNTIES INCLUDED ARE
ALLEGANY ANNE ARUNDEL BALTIMORE
CALVERT CAROLINE CARROLL
CECIL CHARLES DORCHESTER
FREDERICK GARRETT HARFORD
Read more
WW 0508 Status Updates
STATUS REPORT ON WW 508
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 5 WNW MDH TO
40 SE MVN TO 40 SW BMG.
FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 1693
..CHALMERS..07/21/26
ATTN...WFO...PAH...LMK...JKL...
STATUS REPORT FOR WS 508
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
ILC059-069-087-127-151-153-165-199-212040-
IL
. ILLINOIS COUNTIES INCLUDED ARE
GALLATIN HARDIN JOHNSON
MASSAC POPE PULASKI
SALINE WILLIAMSON
INC019-025-037-043-051-061-077-117-123-125-129-143-147-163-173-
175-212040-
IN
. INDIANA COUNTIES INCLUDED ARE
CLARK CRAWFORD DUBOIS
FLOYD GIBSON HARRISON
JEFFERSON ORANGE PERRY
PIKE POSEY SCOTT
SPENCER VANDERBURGH WARRICK
WASHINGTON
Read more
WW 0507 Status Updates
STATUS REPORT ON WW 507
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 30 NW AVP TO
30 SE BGM TO 50 N MSV TO 15 W ALB TO 5 NE GFL.
..BENTLEY..07/21/26
ATTN...WFO...OKX...ALY...PHI...BGM...CTP...
STATUS REPORT FOR WT 507
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
CTC001-005-009-212140-
CT
. CONNECTICUT COUNTIES INCLUDED ARE
FAIRFIELD LITCHFIELD NEW HAVEN
DEC003-212140-
DE
. DELAWARE COUNTIES INCLUDED ARE
NEW CASTLE
NJC001-003-005-007-009-011-013-015-017-019-021-023-025-027-029-
031-033-035-037-039-041-212140-
NJ
. NEW JERSEY COUNTIES INCLUDED ARE
ATLANTIC BERGEN BURLINGTON
CAMDEN CAPE MAY CUMBERLAND
ESSEX GLOUCESTER HUDSON
Read more
WW 0506 Status Updates
STATUS REPORT ON WW 506
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 55 NNE SDF
TO 20 NE LUK TO 30 SW CMH TO 35 SSE MFD.
FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 1693
..CHALMERS..07/21/26
ATTN...WFO...ILN...RLX...PBZ...
STATUS REPORT FOR WS 506
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
INC029-115-137-155-212040-
IN
. INDIANA COUNTIES INCLUDED ARE
DEARBORN OHIO RIPLEY
SWITZERLAND
KYC015-019-023-037-041-043-077-081-089-117-127-135-161-187-191-
201-212040-
KY
. KENTUCKY COUNTIES INCLUDED ARE
BOONE BOYD BRACKEN
CAMPBELL CARROLL CARTER
GALLATIN GRANT GREENUP
KENTON LAWRENCE LEWIS
MASON OWEN PENDLETON
ROBERTSON
Read more
MD 1697 CONCERNING SEVERE THUNDERSTORM WATCH 509... FOR EASTERN VIRGINIA INTO THE DELMARVA
Mesoscale Discussion 1697
NWS Storm Prediction Center Norman OK
0343 PM CDT Tue Jul 21 2026
Areas affected...eastern Virginia into the DelMarVa
Concerning...Severe Thunderstorm Watch 509...
Valid 212043Z - 212215Z
The severe weather threat for Severe Thunderstorm Watch 509
continues.
SUMMARY...The severe weather threat will continue through the
afternoon and into the evening.
DISCUSSION...Storms across Virginia and into the DelMarVa have
mostly lacked structure thus far with only occasional stronger
multi-cell storms. As height falls overspread the area this evening,
expect more robust convection with a greater damaging wind threat
and an eventual line of storms along or ahead of the cold front,
advances east. In addition, strengthening mid-level and low-level
flow will assist in storm organization, further supporting the
threat.
..Bentley.. 07/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...AKQ...LWX...RNK...
LAT...LON 36648039 37457909 38317774 38907701 39477640 39497553
39107487 38507479 37967507 37297548 36677596 36648039
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
Read more
MD 1696 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF THE EASTERN GREAT BASIN
Mesoscale Discussion 1696
NWS Storm Prediction Center Norman OK
0323 PM CDT Tue Jul 21 2026
Areas affected...portions of the eastern Great Basin
Concerning...Severe potential...Watch unlikely
Valid 212023Z - 212230Z
Probability of Watch Issuance...5 percent
SUMMARY...Scattered, high-based thunderstorms are expected this
afternoon and evening across much of the Great Basin. Isolated
damaging/severe wind gusts may occur with the strongest downdrafts.
DISCUSSION...18z observed soundings from GJT/SLC depicted dry,
increasingly well-mixed boundary layer profiles underlying steep
mid-level lapse rates. Amid enhanced mid-level moisture and ahead of
a weak mid-level perturbation along the western periphery of an
upper-level ridge, convective coverage is forecast to increase
through the afternoon as convective temperatures are breached.
Inverted-v thermodynamic profiles with LCLs of 2.5-3.0+ km will
promote efficient evaporative cooling and the potential for isolated
damaging/severe wind gusts with downdrafts. The best potential for
this risk may manifest from southeastern Utah/far western Colorado
into central Utah where marginally stronger low-to-mid level flow
(20-25 kts sampled by the GJX/ICX VWPs) and effective shear (20-25
kts per latest objective analysis) may promote a loosely organized
convective cluster or two. The threat for damaging/severe wind gusts
is forecast to remain too isolated to warrant watch issuance at this
time, however.
..Chalmers/Mosier.. 07/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GJT...SLC...LKN...
LAT...LON 37651219 38241325 39261416 40481446 41131416 41611339
41561219 41111100 40631010 40130941 39460876 38790857
37900872 37250932 37091006 37111048 37251135 37651219
MOST PROBABLE PEAK WIND GUST...55-70 MPH
Read more
MD 1695 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR NORTHEAST OHIO AND NORTHWEST PENNSYLVANIA AND WESTERN NEW YORK
Mesoscale Discussion 1695
NWS Storm Prediction Center Norman OK
0316 PM CDT Tue Jul 21 2026
Areas affected...northeast Ohio and northwest Pennsylvania and
western New York
Concerning...Severe potential...Watch possible
Valid 212016Z - 212145Z
Probability of Watch Issuance...40 percent
SUMMARY...Strong to severe storms are possible this afternoon and
evening.
DISCUSSION...Storms across southern Ontario will move eastward this
afternoon toward western New York this evening. This area has seen
cloud cover for most of the day, but as clouds are clearing, the
environment is destabilizing rapidly from northeast Ohio into
northwest Pennsylvania. It is unclear how far northeast the greater
instability (1500+ J/kg MLCAPE) will extend ahead of the ongoing
activity. However, if it can sufficiently destabilize, there may be
some severe weather threat this evening across western New York and
perhaps into northern Ohio with any additional development which may
occur along the cold front.
..Bentley/Mosier.. 07/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BUF...CTP...PBZ...CLE...
LAT...LON 40798318 41608221 42478071 43437878 43507801 42927799
42177845 41567906 40798015 40798318
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
Read more
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1118 AM CDT Tue Jul 21 2026
Valid 211630Z - 221200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE OHIO VALLEY TO MID-ATLANTIC STATES...
...SUMMARY...
Numerous severe thunderstorms are expected across a broad region
from the Tennessee and Ohio Valleys to the Mid-Atlantic and
Northeast States today into tonight. Swaths of damaging wind gusts
are expected to be the most common impact, but some tornadoes are
possible as well.
...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.
..Mosier/Chalmers.. 07/21/2026
Read more
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.
Read more
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1228 PM 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.
...Synopsis...
The pattern on D2/Wednesday will be characterized by upper-level
ridging across western US with a more progressive wave pattern
within a trough across the eastern US. A cold front will be located
roughly from the Mid-Atlantic south into the Carolinas and western
Tennessee. This will be the focus of thunderstorm development and
severe potential Wednesday afternoon.
...Mid-Atlantic into New England...
Morning cloud cover will extend across New England to the
Mid-Atlantic Wednesday morning, which will likely temper heating and
destabilization with northern extent into New England. More filtered
heating through broken cloud cover in combination with moist
southerly flow should yield moderate instability across portions of
the southern Mid-Atlantic. This in combination with strong mid-level
flow and resulting strong deep layer shear will support potential
for a few organized storms/clusters capable of producing damaging
winds and perhaps a tornado. Highest confidence in this potential
will extend from the Carolinas to southern Delaware, where strongest
heating is anticipated. Strong deep layer shear will extend
northward into New England, which may support isolated stronger
storms with potential for damaging wind though instability becomes
less favorable further north.
...Eastern Colorado...
High based thunderstorms are expected to develop across the high
terrain in eastern Colorado Wednesday afternoon. Marginally unstable
and deeply mixed profiles may support a few instances of strong to
severe wind. Overall, weak deep layer shear profiles will likely
keep this threat too limited for probabilities to be included at
this time.
..Thornton.. 07/21/2026
Read more
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
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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...
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