MD 1537 CONCERNING SEVERE THUNDERSTORM WATCH 481... FOR MIDDLE ATLANTIC AND SOUTHERN NEW ENGLAND


Mesoscale Discussion 1537
NWS Storm Prediction Center Norman OK
0456 PM CDT Tue Jul 01 2025

Areas affected...Middle Atlantic and southern New England

Concerning...Severe Thunderstorm Watch 481...

Valid 012156Z - 020000Z

The severe weather threat for Severe Thunderstorm Watch 481
continues.

SUMMARY...Damaging wind threat continues with convection across the
Middle Atlantic into southern New England early this evening.

DISCUSSION...Weak disturbance that tracked along the OH River has
advanced into eastern PA, very near the NJ border. Organized
convection continues just ahead of this feature, and new scattered
robust updrafts are maturing across the southern Delmarva. Modest
southwesterly flow favors this activity propagating off the Middle
Atlantic Coast later this evening. Until then, a narrow corridor of
strong instability extends across the southern Delmarva toward
western Long Island, with moderate buoyancy into southern New
England where surface temperatures have warmed into the upper
80s/lower 90s. This zone of instability will prove favorable robust
updrafts capable of generating damaging winds.

..Darrow.. 07/01/2025

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

ATTN...WFO...BOX...OKX...ALY...PHI...BGM...AKQ...LWX...

LAT...LON   42517144 41907108 40527340 37827558 37437798 38197828
            39407619 41227492 42517144 

MOST PROBABLE PEAK WIND GUST...55-70 MPH

WW 481 SEVERE TSTM DC DE MD NJ PA VA WV CW 011655Z - 020100Z


URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 481
NWS Storm Prediction Center Norman OK
1255 PM EDT Tue Jul 1 2025

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  District Of Columbia
  Delaware
  Maryland
  New Jersey
  South-Central and Southeast Pennsylvania
  Northern and Central Virginia
  Eastern West Virginia Panhandle
  Coastal Waters

* Effective this Tuesday afternoon and evening from 1255 PM until
  900 PM EDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph possible

SUMMARY...Thunderstorm coverage is expected to increase across the
region over the next several hours ahead of a shortwave trough and
attendant cold front. The airmass across the region is moist and
unstable, with moderate to strong instability anticipated amid
continued daytime heating. Vertical shear is modest, with a
predominantly outflow-dominant storm mode anticipated. Given the
expected updraft strength and ample moisture, some strong
water-loaded downdrafts capable of producing wind damaging are
possible.

The severe thunderstorm watch area is approximately along and 110
statute miles east and west of a line from 40 miles south southeast
of Charlottesville VA to 40 miles northwest of Allentown PA. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU1).

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 inch. Extreme turbulence and surface wind gusts to 60 knots. A few
cumulonimbi with maximum tops to 500. Mean storm motion vector
24020.

...Mosier

WW 0481 Status Updates


STATUS REPORT ON WW 481

SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 S CHO TO
20 E BWI TO 20 W ACY.

..SPC..07/01/25

ATTN...WFO...LWX...PHI...AKQ...CTP...RNK...


STATUS REPORT FOR WS 481 

SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS 

DEC001-005-020040-

DE 
.    DELAWARE COUNTIES INCLUDED ARE

KENT                 SUSSEX              


MDC003-009-011-017-019-033-035-037-039-041-045-047-020040-

MD 
.    MARYLAND COUNTIES INCLUDED ARE

ANNE ARUNDEL         CALVERT             CAROLINE            
CHARLES              DORCHESTER          PRINCE GEORGES      
QUEEN ANNE'S         ST. MARYS           SOMERSET            
TALBOT               WICOMICO            WORCESTER           


NJC001-009-011-029-020040-

NJ 
.    NEW JERSEY COUNTIES INCLUDED ARE

ATLANTIC             CAPE MAY            CUMBERLAND

WW 0482 Status Updates


STATUS FOR WATCH 0482 HAS NOT BEEN ISSUED YET

WW 482 SEVERE TSTM NE SD WY 012205Z - 020500Z


URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 482
NWS Storm Prediction Center Norman OK
405 PM MDT Tue Jul 1 2025

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Western Nebraska
  Western South Dakota
  Northeast Wyoming

* Effective this Tuesday afternoon and evening from 405 PM until
  1100 PM MDT.

* Primary threats include...
  Scattered large hail and isolated very large hail events to 2
    inches in diameter possible
  Isolated damaging wind gusts to 70 mph possible

SUMMARY...Isolated to widely scattered severe storm development,
potentially including a couple of high-based supercells, is expected
regionally through early evening, with the possibility that a
loosely organized cluster could evolve later this evening.

The severe thunderstorm watch area is approximately along and 70
statute miles east and west of a line from 65 miles north of Rapid
City SD to 50 miles east of Sidney NE. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU2).

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 481...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 550. Mean storm motion vector
29025.

...Guyer

SPC Day 3-8 Fire Weather Outlook

Day 3-8 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0356 PM CDT Tue Jul 01 2025

Valid 031200Z - 091200Z

...Days 3-5/Thursday-Saturday...
An upper-level ridge will shift eastward from the Intermountain West
into the eastern U.S. through Day 5/Saturday while an upper-level
trough and cooler temperatures move into the Pacific Northwest,
mitigating fire weather concerns into the weekend. A mid-level
short-wave trough ejects into the Great Basin Days
3-4/Thursday-Friday bringing a period of stronger downslope flow
into western Nevada on Thursday, increasing the fire weather threat
amid drying fuels. A 50-60 knot mid-level jet associated with the
short-wave and an increasingly dry boundary layer will also support
stronger southwest winds across the southern Great Basin, increasing
wildfire spread potential. A mix of diurnally driven wet/dry
thunderstorms across the Intermountain West within a residual
monsoon moisture plume will decrease in coverage from west to east
as a dry southwest flow pattern is established across the Southwest.


...Days 6-8/Sunday-Tuesday...
Dry southwest flow aloft will keep monsoon moisture and associated
daytime convection primarily along the Continental Divide on Day
6/Sunday. A return of monsoon moisture into Lower Colorado River
Basin could return by Day 8/Tuesday in response to a nascent Four
Corners High, but forecast uncertainty in timing of moisture return
precludes introduction of critical probabilities at this time.

..Williams.. 07/01/2025

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

SPC 1930Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0234 PM CDT Tue Jul 01 2025

Valid 031200Z - 041200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
NORTHERN HIGH PLAINS...UPPER MIDWEST INTO THE GREAT LAKES...AND THE
NORTHEAST...

...SUMMARY...
Scattered storms capable of large hail and severe wind gusts are
forecast across the Northeast on Thursday. Isolated severe wind
gusts are also possible in the Northern Plains and parts of the
Upper Midwest into the Great Lakes.

...Synopsis...
A mid-level trough will deepen over New England as an upper trough
moves over the Midwest, and broad mid-level troughing with multiple
embedded impulses, overspreads the U.S. west of the Rockies on
Thursday. The East and West Coast upper troughs will encourage
surface troughing across the Northeast and the Plains states, as
well as weak surface low development over the Great Basin. Given the
presence of seasonal low-level moisture, and expected diurnal
heating, at least scattered thunderstorms will develop across much
of the Interior West, into the Plains, Midwest, and East Coast
regions. At least isolated strong to potentially severe storms could
develop over parts of the northern CONUS, where appreciable vertical
wind shear will overspread the warm, moist airmass to support
organized thunderstorms.

...Northeast...
As the surface trough progresses across the Northeast, deep-layer
northwesterly flow will overspread the region. Diurnal heating of a
seasonably moist boundary layer will foster modest buoyancy, with
500-1500 J/kg MLCAPE expected. As thunderstorms develop during the
afternoon, they will encounter roughly 25-35 kts of effective bulk
shear, characterized by elongated/straight hodographs. Multicells
and short line segments should be the main storm modes, with
isolated damaging gusts the primary threat with the stronger storms.


...Upper Midwest into the Great Lakes...
A belt of 35-45 kt northwesterly flow on the back side of the East
Coast upper trough will overspread the Great Lakes during the
afternoon hours, where diurnal heating of a moist low-level airmass
will destabilize the boundary layer. MLCAPE may exceed 2000 J/kg in
spots (locally higher to 3000 J/kg toward southeast MN given 7.5+
C/km mid-level lapse rates farther to the west). Forecast soundings
depict modestly curved and elongated hodographs, supporting
multicells and perhaps supercells with some of the stronger storms.
Isolated severe wind and hail may accompany the stronger storms.
Greater severe probabilities may be needed in future outlooks if
favorable trends in greater storm coverage are realized in later
available guidance.

...Northern High Plains... 
A mid-level impulse will traverse the broader western upper
troughing regime and eject into the northern High Plains Thursday
afternoon. By this time, steep mid-level lapse rates will overspread
upper 60s F dewpoints to promote moderate to locally strong
instability, with MLCAPE exceeding 3000 J/kg. Modest turning and
strengthening of the winds with height will support elongated
hodographs with slight low-level curvature, which will support
multicells and splitting supercells given the aforementioned
buoyancy. The storms are forecast to be isolated in coverage, with a
few instances of severe wind and hail expected.

..Squitieri.. 07/01/2025

SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0227 PM CDT Tue Jul 01 2025

Valid 012000Z - 021200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
MID-ATLANTIC REGION AND ACROSS WESTERN PORTIONS OF NEBRASKA AND
SOUTH DAKOTA...

...SUMMARY...
Scattered strong to severe storms are possible across parts of the
Mid-Atlantic into the Northeast this afternoon/evening.  A few
severe thunderstorms are possible over western parts of Nebraska and
South Dakota.

...20z Update...
A Marginal Risk was added across southwestern MT into central ID
with this outlook. While instability is modest, lapse rates are
steep and forecast soundings show characteristic inverted-v. This
suggests that the widely scattered thunderstorm activity this
afternoon will be capable of occasionally strong to severe winds,
supporting addition of a 5% wind risk. Otherwise, the outlook
remains unchanged. See previous discussion below for more
information.

..Thornton.. 07/01/2025

.PREV DISCUSSION... /ISSUED 1104 AM CDT Tue Jul 01 2025/

...Mid-Atlantic into the Northeast...
Recent satellite imagery shows a well-defined shortwave trough
extending from western QC through the middle OH Valley into the Mid
MS Valley. Regional radar imagery depicts showers and thunderstorms
preceding this wave from across the mid/upper OH Valley, with the
stronger storms occurring along an associated cold front that
extends from far western NY southwestward across western PA and
along the WV/OH border through eastern KY.

The general expectation throughout the day is for this shortwave
trough and associated cold front to progress eastward into the
increasingly moist and unstable airmass downstream, promoting
widespread thunderstorm development this afternoon. Moderate
mid-level flow extends through the eastern periphery of this wave,
with the strongest flow (i.e. around 40 kt at 500 mb) expected to
move across NY and New England. Given the more northern trajectory
of the stronger flow, there will be limited overlap between the
strongest flow and the better buoyancy, which will remain farther
south across the Mid-Atlantic. Even so, the overall environment will
support some organization of storms into line segments/clusters.
Scattered thunderstorms will increase in coverage with time and
numerous thunderstorms are expected by mid-late afternoon while
moving east from PA/WV in NJ/VA/MD. Recently issued MCD #1529 also
addresses the severe potential in this region. More limited storm
coverage is anticipated farther north. Strong to severe gusts (50-65
mph) are possible with the stronger downdrafts.

...Black Hills/SD into the Central High Plains... 
A weak shortwave trough is currently progressing through eastern MT
and eastern WY, throughout the northern periphery of the upper
ridging that extends from the southern Plains through the northern
Rockies. This wave is forecast to continue eastward/southeastward,
eventually interacting with the moderate low-level moisture expected
to advect northward across western portions of KS, NE and SD. Ascent
attendant to this wave will augment low-level convergence near an
associated surface low to foster afternoon thunderstorm development.
Low-level southerly flow veering to northwesterly aloft will foster
moderate effective shear (i.e. 30 to 40 kt) and the potential for a
couple of supercells. Large hail will be the primary risk with these
storms.

Some additional thunderstorms are possible later tonight across far
southern ND and central/eastern SD as a strengthening low-level jet
contributes to warm-air advection across a developing warm frontal
zone. Moderate shear and steep mid-level lapse rates will support a
few stronger storms capable of producing isolated large hail.

...Central Appalachians into the Southeast...
Afternoon thunderstorms are expected across a large area from the
central Appalachians and Carolinas southwestward into the Southeast,
along or just ahead of a weak, eastward-progressing cold front.
Limited vertical shear should promote less organized storms,
although a few strong, water-loaded downdrafts capable of producing
damaging winds are possible.

SPC Day 2 Fire Weather Outlook

Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0159 PM CDT Tue Jul 01 2025

Valid 021200Z - 031200Z

...Northwest... 
A mid-level trough and attendant accelerating mid-level flow will
support stronger onshore flow into western OR/WA. Stronger gap winds
through the Columbia Gorge along with enhanced downslope drying into
the Columbia Basin will bring elevated fire weather conditions to
the area Wednesday in conjunction with dry fuels. Thunderstorm
development is expected again Wednesday across northern CA into
southeastern/eastern OR. Northeast storm motions to the northeast of
25-30 mph will limit precipitation duration although ignition
efficiency may be limited owing to limited fuel receptiveness,
precluding dry thunderstorm highlights for Wednesday.

..Williams.. 07/01/2025

.PREV DISCUSSION... /ISSUED 0120 AM CDT Tue Jul 01 2025/

...Synopsis...
A mid-level trough slowly progressing across portions of central
California will continue to provide southerly transport of monsoon
moisture into portions of the Great Basin on Wednesday, while a
shortwave trough located further north over British Columbia will
provide support for dry/windy conditions across northern Oregon into
southern Washington. 

...Dry/Windy...
Modest mid-level westerly/southwesterly flow, coupled with deep
mixing of dry boundary layer profiles, will support at least
Elevated fire-weather conditions across portions of northern Oregon
into southern Washington. The strongest winds will be confined to
portions of the Cascade gaps/Columbia Gorge, with ERCs across the
region nearing or meeting the annual 90th percentiles.

...Dry Thunderstorms...
A mix of wet and dry thunderstorms will be possible from
east-central Nevada into western Utah, and portions of far southeast
Idaho into far western Wyoming. Fuels across significant portions of
the Great Basin exceed the 98th annual percentiles, and a
combination of low to modest total precipitable water vapor content
and 0 - 6 km mean wind speeds ranging from 15 - 25 MPH will result
in low precipitation efficiency with thunderstorm updrafts. This
will support potential lightning ignitions, particularly with fast
moving cells and on the edges of the most intense downdraft cores.

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