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104
FXUS61 KLWX 091901
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
301 PM EDT Thu May 9 2024

.SYNOPSIS...
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Shower and thunderstorm chances continue through Friday as a slow
moving front pushes south and east of the region. The front will
bring the potential for severe weather and flooding to areas mainly
south of Interstate 66 later today. Precipitation chances slowly
decrease behind the front going into the weekend with cooler
temperatures and high pressure nearing the area. Shower and
thunderstorm chances along with warmer temperatures return by the
middle of next week as high pressure pushes offshore.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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A frontal boundary currently draped over the forecast area,
will slowly push south throughout the afternoon before exiting
the area this evening. North of the front, cool and stable air
will limit severe thunderstorm potential, though heavy rain
remains a threat. High temperatures north of the front will be
in the 60s to low 70s with plenty of clouds expected.

South of the frontal boundary, warmer temperatures and breaks in
cloud cover will allow for increased instability and more
favorable conditions for severe thunderstorm development. With
CAPE 500-1000 J/kg and 50 knots of effective shear, isolated
strong to severe thunderstorms are possible, mainly for those
south of Cumberland to Washington DC. SPC has removed the slight
risk from our area with the southwestern portion of the forecast
area in a marginal risk for severe weather. While damaging wind
gusts greater than 60 mph and large hail 1"+ remain the main
threats, the tornado threat as diminished significantly. Storms
will likely start developing in the next few hours, and will
persist through the evening. South of the front, high
temperatures will be in the 70s to low 80s.

Thunderstorm chances diminish overnight as rain shower chances
continue through Friday morning. As the frontal boundary drifts
south of the forecast area, cloud cover will increase with
overnight temperatures dropping into the upper 40s to 50s.
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&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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An upper level trough will pivot over the region Friday with a
potent shortwave passing to our north. This will lead to
continued shower and thunderstorm chances for the forecast area.
In the wake of a cold front, temperatures will be noticeably
cooler with high temperatures in the 50s and 60s for most. Those
in the southernmost portions of the area will see high
temperatures in the low to mid 70s where cloud cover will be
less. Precipitation chances decrease gradually overnight Friday
with low temperatures in the 40s to low 50.

Saturday will begin dry with dry air aloft inhibiting any
precipitation chances. A low pressure system approaching from
the Great Lakes will bring increasing shower and thunderstorm
chances Saturday afternoon. Temperatures will be in the 60s for
most of the area.
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&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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Longwave troughing/upper level trough axis will swing offshore
Sunday afternoon as mid and upper level ridging build back into the
region. Some showers and isolated thunderstorms will be possible
Sunday morning into Sunday afternoon especially north of I-66/US-50
where better forcing with the departing trough axis can be found.
Areas further south will likely stay dry with surface high pressure
building eastward from the Ohio River Valley into the central
Appalachians region. Severe weather will not be concern although any
showers or thunderstorms that due form could put down a brief
downpour along with small hail.

Monday looks to be our driest day of the next 7 days as 500 mb
heights rise with surface high pressure sitting just to the south of
the region. This will yield a nice late Spring day with highs in the
mid to upper 70s underneath partly cloudy skies.

Unfortunately, the dry time will be brief as an upper trough
develops in the lee of the Rockies, and deepens as it tracks into
the south central US and Gulf Coast states during the middle part of
workweek. Meanwhile, high pressure will shift off the VA/NC coast
Tuesday into Wednesday allowing for south to southeasterly return
flow to ensue. This will allow Atlantic and eventually Gulf of
Mexico moisture to increase across the region yielding daily
isolated to scattered chances for showers and thunderstorms.
Uncertainty remains in the placement and timing of the heaviest
precipitation with a focus mid to late week (Wednesday and
Thursday). This is due largely in part to a warm frontal boundary
that will be lifting northward into the region. As for severe
weather, it cannot be ruled out, but overall predictability remains
too low at this point to pick a given day out. CSU learning machine
and CIPS probabilities point toward the Wednesday and Thursday
timeframe given the front lifting and added moisture lifting into
the area. Highs will continue to be in the low to mid 70s for areas
east of the Allegheny Front (60s). Lows will drop down mostly in the
60s during the middle part of the week.
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&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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Conditions are currently VFR at all terminals with the
exception of KMRB where IFR conditions are present. Conditions
will drop to MVFR this evening and then IFR at all terminals
tonight. Showers and thunderstorms could impact all terminals,
bringing periods of reduced CIGs and VSBYs due to heavy rain.
During thunderstorms, gusty winds are possible as well. The
greatest chances for thunderstorms is at IAD, DCA, CHO, and MRB,
but thunder cannot be ruled out at BWI and MTN. The best
chances for showers and thunderstorms is this evening and into
the overnight, with thunder chances decreasing right before
midnight.

IFR conditions continue Friday as precipitation chances linger.
Conditions improve to VFR on Saturday. Winds shift to
northeasterly tomorrow before becoming southerly on Saturday.

SCA level winds return SUnday in the wake of a shortwave trough
pushing offshore and high pressure building to the south. SCA
conditions will likely continue Monday, Tuesday, and Wednesday as
low pressure approaches from the south and high pressure pushes
offshore.
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&&

.MARINE...
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Northeasterly to easterly winds will remain below SCA criteria
throughout the day. Tonight, easterly winds may reach SCA criteria
as a weak area of low pressure moves to the south of the waters.
Winds diminish by early Friday morning. Winds remain out of the
northeast on Friday, while blowing right at or just below SCA
criteria in the afternoon. Rain showers and thunderstorms could
impact the waters today and Friday, mainly in the afternoon. Winds
shift to northerly Friday night before shifting to southerly for the
weekend.

SCA level winds return SUnday in the wake of a shortwave trough
pushing offshore and high pressure building to the south. SCA
conditions will likely continue Monday, Tuesday, and Wednesday as
low pressure approaches from the south and high pressure pushes
offshore.
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&&

.TIDES/COASTAL FLOODING...
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North to northeasterly winds should allow water levels to continue
to decrease this afternoon and evening. Additional minor flooding is
possible at some sensitive locations (Annapolis, Straits Point, and
DC Waterfront) late tonight into early Friday morning as southwest
flow returns. Levels should drop well off by Sunday when offshore
northwest flow kicks in across the area.
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&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
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&&

$$

SYNOPSIS...EST
NEAR TERM...AVS
SHORT TERM...AVS
LONG TERM...EST
AVIATION...AVS/EST
MARINE...AVS/EST
TIDES/COASTAL FLOODING...EST