651
FXUS61 KLWX 100120
AFDLWX

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

.SYNOPSIS...
Showers and thunderstorms will continue through Friday as a slow
moving front pushes southeast across the region. 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.

&&

.NEAR TERM /THROUGH FRIDAY/...
The radar as of 9pm Thursday is showing widely scattered rain
showers along the Mason-Dixon line near Northeast Maryland, a
few patches of rain showers near and southeast of Washington
D.C., scattered showers in parts of northeastern West Virginia,
and a broad band of heavier showers and embedded strong
thunderstorms extending from the northern West Virginia
Panhandle to western Maryland. The more intense thunderstorms
along this broad band have been producing occasional lightning
and very heavy rainfall. As a matter of fact, dual-pol radar
indicates rain rates of 1 to 1.5 inches per hour with more on
the way over the next couple of hours. A Flash Flood Warning has
been issued and is currently in effect for northwestern parts
of Garrett County in western Maryland until 1145pm. Additional
heavy showers and thunderstorms could prompt additional flood or
flash flood warnings over the next few hours. So be aware
across western and central Maryland, northeastern West Virginia,
and into far northwestern parts of Virginia. Lows tonight will
be cooler with temperatures dropping into the 50s.

A low pressure system over north- central West Virginia will
move east overnight and during the day Friday. A stalled front
to our south will slowly move northward as a warm front
overnight and Friday morning. The warm front may only make its
way into northern Virginia before it is shunted eastward with
the low pressure system and its trailing cold front later
Friday. The combination of the stalled front, the low pressure
system and the cold front will make for an unsettled prolonged
period from late this evening right into Friday evening.

An upper level trough will pivot over the region behind the
surface low pressure system on Friday. This upper trough will
aid in additional development of showers and thunderstorms. In
the wake of a cold front late Friday into Friday evening,
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.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
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.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
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.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
MVFR conditions over the northeastern Maryland terminals, while
VFR conditions and some rain showers around are near DCA and
IAD. Expect IFR conditions at all terminals overnight. Showers
and thunderstorms could impact all terminals with focused
attention to the broad band of heavy showers and thunderstorms
approaching MRB in the next hour to hour and a half. Gusty winds
are possible with thunderstorms The best chances for showers
and thunderstorms is the remainder of this evening into the
overnight. Thunderstorm chances should decrease shortly after
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.

&&

.MARINE...
Easterly winds have increased some since late this afternoon.
There are occasional gusts of SCA in scattered areas of the Bay
and Potomac River. A SCA will be issued for this evening into
early overnight. Winds diminish 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 overnight 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.

&&

.TIDES/COASTAL FLOODING...
The increase in easterly winds over the Bay could allow for
sensitive areas like Annapolis, Straits Point and SW Washington
DC waterfront to reach minor stage late overnight into early
Friday. Levels should drop well off by Sunday when offshore
northwest flow kicks in across the area.

&&

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

&&

$$

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