657
FXUS61 KLWX 051853
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
253 PM EDT Thu Jun 5 2025

.SYNOPSIS...
An area of low pressure down across the Carolinas will slowly drift
north toward the southern Delmarva this evening bringing
increased humidity and cloud cover to the region. Meanwhile, a
cold front will slowly work east from the Ohio River Valley
tonight into Friday increasing the chances for showers and
thunderstorms. More widespread shower and thunderstorm activity
is expected Saturday into Sunday as the front drops into the
region. Daily shower and thunderstorm chances look to continue
through Tuesday with a stronger cold front set to cross by the
middle of next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Overall most of today looks dry outside of a few scattered
mountain showers or thunderstorms west of I-81 and south of
I-64. This is consistent with radar and the current Day Cloud
Phase RGB which shows bubbling cumulus over the Allegheny Front
and points west into southwest PA. A Marginal Risk for severe
weather (Level 1 out of 5) is in place today for much of western
MD and northeast WV. Damaging winds will be the primary threat
with any storms that form along with locally heavy rainfall.
Isolated thunderstorms are possible further east although
convection will be shunted given the leftover subsidence
overhead.

The bigger theme of today will be the uptick in humidity as well as
mid and high level cloud cover. This is due largely in part to an
area of low pressure working north from the coastal Carolinas toward
the southern Delmarva and an encroaching cold front from the Ohio
River Valley. Meanwhile, high pressure will continue to slide
offshore with just enough influence over the area today to keep most
locations dry outside of the Potomac Highlands, Alleghenies, and
central Blue Ridge where orographic lifting may help touch off
a few showers/t-storms given the warm/humid airmass overhead.
Shower and t- storm chances will remain capped at 20-30 percent
today given the leftover subsidence from the buckling
ridge/departing high pressure system offshore.

With the added mid and high level cloud cover expect slightly cooler
temperatures especially south of I-66/US-50 as low pressure pushes
north from the Carolinas and west of the Alleghenies due to the
incumbent front from the Ohio River Valley. Highs in these
aforementioned locations will remain in the upper 70s and low 80s.
Elsewhere expect highs in the mid to upper 80s with filtered
sunshine as additional high clouds funnel into the region. Some haze
has also been observed this morning across north-central MD and
northern VA due to the Canadian wildfire smoke. Air quality alerts
remain in place for northern Baltimore and Harford counties in MD as
well as the eastern WV Panhandle where the concentrations of ozone
and fine particulates remain the highest. Any smoke will once again
be diffuse given increased south to southeasterly flow into the
region.

Cloud cover and humidity will continue to increase tonight as low
pressure pushes up along the Delmarva coast. With low pressure
nearby, a few showers cannot be ruled out over southern MD, the
northern neck of VA, and the southern/middle portion of the
Chesapeake Bay. Any shower activity should be fairly light with
precipitation chances capped at 30 percent. A few lingering showers
and thunderstorms also cannot be ruled out in locations west of I-81
given the proximity of the encroaching front nearby. The loss of
daytime heating combined with subsidence on the outer edge of low
pressure will subdue the progression of this shower/storm activity
east of the Potomac Highlands/Alleghenies until Friday. Some fog is
possible in the river valleys and down over southern MD/northern
neck of VA late tonight into early Friday morning given the
increased moisture over the area. Lows tonight will fall back into
the low to mid 60s with upper 60s in the Baltimore/DC metro centers.


&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
It`s an active end to the workweek as shower and thunderstorm
chances increase across the region. This activity is in association
with a cold front pushing east from the Ohio River Valley and area
of low pressure working up along the Delmarva. Ahead of the front is
a prefrontal shortwave trough which looks to be the catalyst
for thunderstorm development especially in areas west of the
Blue Ridge Friday afternoon. Eventually this activity will swing
east Friday night and into the day Saturday as the main cold
front is slow to cross the region. For now, continuing to
maintain likely PoPs west of the Blue Ridge given the pre-
frontal trough and chance Pops further east. There still remains
some uncertainty in the progression of showers and t-storms
east of I-81 given added subsidence on the outer edge of the
departing low pressure system off the Delmarva coast. As for the
threat of severe weather, the risk remains low. The Storm
Prediction Center continues a Marginal Risk for severe weather
(Level 1 out 5) along and west of US-15. Damaging wind will be
the primary threat with storms along with locally heavy rainfall
and frequent lightning. MLCAPE values will be around 1000-2000
j/kg with 0-6km bulk effective shear values less than 25 kts.

Outside of the shower and thunderstorm chances expect a continuation
of increased humidity and added cloud cover. Highs will push into
the upper 70s and low to mid 80s with dewpoints in the mid to upper
60s. Lows Friday night will fall back into the low to mid 60s with
upper 60s expected in the metro areas.

More widespread shower and thunderstorm chances look to arrive
Friday night into Saturday as the front slowly drops into the
region. Once again, we are not looking at a washout by any means
with a focus during the early morning and again during the late
afternoon/evening hours. Cloud cover will continue to thicken
Saturday which should taper instability to a degree especially
north of I-64. SPC maintains a Marginal Risk (Level 1 out of 5)
for severe weather mainly south of I-64 where better instability
resides and few more breaks in the clouds can be noted. Once
again the main threat with any of these storms looks to be
damaging winds along with locally heavy rainfall and perhaps
some small hail. Some localized flooding cannot be ruled out if
storms train over the area given recent FFG less than 1.50") and
PWATS running above 1.50-2.00 inches. Highs Saturday will sit
in the upper 70s and low to mid 80s. Lows Saturday night will
fall back into the upper 50s and low to mid 60s. Shower and
thunderstorm chances will likely linger during this time with
the front stalling across central and southern parts of the
region (i.e in the vicinity of central VA).

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Models have trended to a more active weather pattern to finish the
weekend, and that looks to continue through the middle of next week.

The front that crossed south of the area by early Sunday looks to
stall over southern VA, as a weak wave of low pressure approaches
from the OH Valley. A backdoor cold front could move into northeast
MD as high pressure builds over PA/NY. The front likely does not
have enough forcing to scour out higher moisture, so we remain in an
unstable airmass that fuels another round of showers and
thunderstorms. Rain chances continue to increase Sunday, now at 60-
70pct, with higher chances for thunderstorms too. Slightly cooler
highs in the mid to upper 70s.

The disturbance over the area quickly moves east Sunday night as a
stronger upper trough approaches from the Great Lakes. Several
embedded shortwave troughs swing across the Mid-Atlantic Monday
through Wednesday bringing rounds of showers and thunderstorms.
Tuesday looks to be the wettest day where locally heavy rainfall is
possible. Highs in the upper 70s to 80s each day. A cold front moves
through Wednesday afternoon and finally brings drier conditions by
Wednesday night.


&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
VFR conditions look to continue through this afternoon with perhaps
brief periods of sub-VFR mainly west of KMRB and KCHO due to spotty
showers and thunderstorms. Better chances for MVFR with perhaps a
few pockets of IFR (mainly west of MRB/CHO) look to arrive tonight
as clouds lower with low pressure working along the Delmarva
coast and a cold front dropping in from the Ohio River Valley.
Highest confidence of low end MVFR and high end IFR looks to be
around KCHO and points south and west. Went ahead and lowered
the clouds to SCT025 based on guidance along with adding a
little fog with vsbys between 3-4SM heading into early Friday
morning.

Additional shower and thunderstorm chances are expected Friday
leading to periods of sub-VFR especially at terminals west of the
Blue Ridge (i.e KCHO, KMRB, and KSHD). The shower and thunderstorm
chances are in association with a slow moving cold front approaching
from the west along with departing low pressure offshore and a
prefrontal trough draped over the mountains. The highest confidence
for showers and thunderstorms looks to be west of the corridor
terminals although some activity could push east from the mountains
late Friday afternoon and evening after 21z Friday. Low pressure off
the coast looks to provide the corridor terminals with enough
subsidence to limit thunderstorms given it`s modeled placement and
track. VFR conditions are expected otherwise with light south to
southeast winds occasionally gusting up to 15 knots.

Additional sub-VFR conditions (mainly MVFR) are increasing in
likelihood Saturday as a cold front drops into the region. The
front will bring widespread showers and thunderstorms to the
region throughout the day with a focus toward the
morning/evening hours. SOme storms could be locally strong with
damaging winds as the main threat. Locally heavy rainfall will
also be an issue reducing vsbys down below 6SM.

Periods of showers and thunderstorms are forecast to move across the
area each afternoon Sunday into early next week. While conditions
remain VFR outside of convection, any shower/storm that moves over a
terminal could produce brief sub-VFR conditions.

&&

.MARINE...
South to southeasterly winds will continue across the waters this
afternoon as low pressure works north and east from the coastal
Carolinas. Some brief southerly channeling is possible especially
over the open waters later this evening although confidence appears
low for any advisories at this time. The remainder of the day should
be dry although an isolated shower/thunderstorm cannot be ruled out
over the southern bay late tonight into Friday morning.

Marginal southerly channeling is possible along the bay late Friday
afternoon and evening. This is in association with a tightening
gradient between an incoming front from the west and area of low
pressure sliding along the Delmarva coast. A few thunderstorms may
be possible late Friday afternoon and evening (after 4pm) yielding
the potential need for SMWs given the warm/humid airmass.
Storms may have trouble maintaining themselves toward the waters
given the fact that the bay and tidal Potomac will sit on the
periphery of the passing coastal low pressure system yielding
subsidence over the region.


More widespread marine hazards are likely Saturday into Saturday
night as a slow moving cold front drops into the region. SMWS may be
needed for strong thunderstorms during the afternoon and evening
hours. Gusty winds and lightning strikes will be the biggest threat
to mariners along with locally heavy rainfall which could reduce
vsbys at times. Winds southwest becoming northwest 5 to 15 knots
late Saturday afternoon into Saturday night.

Winds are forecast to remain below SCA levels Sunday into early next
week. The main threat to mariners will be from daily afternoon
thunderstorms that could produce gusty winds, in addition to
lightning strikes.


&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...Air Quality Alert until 10 PM EDT this evening for WVZ050>053-
     055-501>506.
MARINE...None.

&&

$$

SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...EST
LONG TERM...KLW
AVIATION...KRR/EST
MARINE...CJL/KRR/EST