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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 091930
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
330 PM EDT Sun May 9 2021

.SYNOPSIS...
Low pressure will track just to our north and west today into
tonight, eventually dragging a cold front through the area on
Monday. High pressure will build back in toward the middle of
the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Breaks of sun have developed early this afternoon as a warm
front lifts northward through the area. However, high clouds are
starting to filter back in from the west in advance of a mid-
level shortwave and associated surface low situated over the
Ohio Valley. Winds have picked up out of the south in advance of
the area of low pressure and will become quite gusty later this
afternoon into this evening. Showers have moved back into far
northwestern portions of the forecast area. As low pressure
tracks along the Mason-Dixon Line tonight, a few showers can`t
be ruled out anywhere, but it won`t be a washout by any means.
As low pressure lifts off to our northeast later tonight, it
will drag a cold front through the area, bringing an end to any
shower activity. Winds will abruptly shift to northwesterly
behind the front, allowing cooler and drier air to filter into
the area once again.
-- End Changed Discussion --


&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
A fairly stagnant pattern will persist across the area through
Monday and Tuesday, with mid-upper level troughing to our north
over the Great Lakes, and persistent northwesterly flow at the
surface locally. Northwesterly flow will maintain a supply of
cool and dry air, with temperatures both days running well below
normal for mid-May. Highs both days will be in the 60s for most,
with overnight lows primarily in the 40s. Some 30s may even be
possible across the higher elevations Monday Night, and across
most spots to the west of the Blue Ridge Tuesday night. Frost
and Freeze headlines may eventually be needed Tuesday night. In
terms of sensible weather, tomorrow should feature increasing
sunshine through the day, with a mix of sun and clouds on
Tuesday. A stray shower or two can`t be ruled out Tuesday
afternoon as the upper level trough to our north nudges
southward toward our area, but confidence was too low to
incorporate into the forecast at this point.
-- End Changed Discussion --

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
-- Changed Discussion --
By mid-week, a broad negative height anomaly lingers over the
Canadian Maritimes with an attendant positively-tilted trough
crossing through the Mid-Atlantic. This will reinforce the cool air
mass in place as northwesterly winds ensue. A seasonably strong dome
of high pressure approaches from the west, with this ridge extending
from the Missouri Valley to the interior northeastern U.S. by
Thursday. This will provide continued chances for frost from the
Blue Ridge and Catoctins westward on Wednesday morning, with perhaps
another chance the following night. Winds need to remain relatively
light which would be one inhibiting factor here. Additionally, some
higher elevations of the Allegheny Front could deal with freeze
concerns. Daytime temperatures through Thursday are forecast to stay
around 5 to 10 degrees below average. This equates to mid/upper 60s
across the lower elevations with 50s in the mountains.

Late Thursday, an upper trough begins to approach from the Ohio
Valley. The 12Z CMC/GFS and 00Z ECMWF all depict its presence as it
slides toward the southeast into Friday. The GFS/GEFS solutions in
past days had advertised a coastal cyclone of sorts. However, the
last few model cycles favor weaker cyclogenesis that is displaced
well offshore. Depending on the strength of this upper low, some
showers may occur as it crosses through the Mid-Atlantic. In the
wake, high pressure further re-establishes its presence across the
eastern U.S. into next weekend. This continues the period of near to
below average temperatures. By next Sunday, ensembles show some
potential warmth ahead, albeit with quite a bit of model spread.
Another round of precipitation is possible, but is also very model
dependent.
-- End Changed Discussion --


&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
Winds have turned southerly and showers have moved out of the
area early this afternoon. The southerly winds will become quite
gusty this afternoon, with gusts of 25-30 knots possible just
prior to dark. Breaks of sun have developed, but clouds will
move in again later this afternoon. Chances for showers will
return again tonight, but activity will be intermittent in
nature. Ceilings may briefly become MVFR for a time tonight at
MRB, but elsewhere VFR conditions are expected. A sharp wind
shift is expected overnight as a cold front passes through,
with winds turning from southerly to northwesterly. Winds may
briefly gust to around 25-30 knots for an hour or two
immediately behind the front. Northwesterly winds and VFR
conditions are expected tomorrow through Tuesday, with gusts
generally between 15 and 20 knots both afternoons.

With Wednesday and Thursday looking dry given the presence of high
pressure, VFR conditions are quite likely. Winds will initially be
northwesterly with gusts possibly reaching 15 to 20 knots before
turning northeasterly by Thursday as the surface high closes in to
the west. Weaker gradients will favor a decrease in winds.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
Southerly winds will pick up as we move through the remainder of
the afternoon. They may briefly approach gale force this evening
just before dark, but warmer air moving over cooler waters may
be an inhibiting factor for those stronger gusts moving over the
waters. Solid SCA conditions are expected overnight, with an
eventual shift to northwesterly winds as a cold front passes
over the waters between roughly 3 and 6 AM. Winds may be close
to gale force again for an hour or two immediately in the wake
of the front, but current thinking is that it should remain just
below. Winds will remain northwesterly tomorrow through Tuesday,
and could reach SCA levels at times.

On Wednesday, northwesterly breezes across the area waterways may
approach small craft levels before diminishing in strength into the
night. Thereafter, gradients will decrease with high pressure
approaching the region. Thus, sub SCA conditions are likely with
somewhat variable winds at times.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Minor coastal flooding will be possible late tonight into Monday
morning as water levels rise on srly flow ahead of a cold front
Monday morning. Blowout tides expected Monday afternoon through
mid week on NW flow.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ530>543.
-- End Changed Discussion --

&&

$$
SYNOPSIS...LFR/KJP
NEAR TERM...KJP
SHORT TERM...KJP
LONG TERM...BRO
AVIATION...BRO/KJP
MARINE...BRO/KJP
TIDES/COASTAL FLOODING...LFR