361
FXUS61 KLWX 210102
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
902 PM EDT Mon May 20 2024

.SYNOPSIS...
Warmer temperatures and mostly dry conditions are expected through
Wednesday as high pressure meanders overhead. A cold front will
approach from the Ohio River Valley Wednesday night into Thursday
bringing renewed chances for showers and thunderstorms. Additional
shower and thunderstorm chances are likely Friday into the weekend
as the front stalls nearby. Drier conditions return by the middle of
next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Current satellite imagery shows a few high clouds around, with
mostly clear skies across the majority of the forecast area.
Mostly clear skies are expected to persist through the first
half of the night as high pressure settles just off the coast.
Winds have already gone calm in most locations. The combination
of mostly clear skies and calm winds will lead to efficient
radiational cooling, which should allow temperatures to drop
back to near the dewpoints in the upper 50s. Fog/low cloud
formation is expected during the second half of the night. Any
fog or low clouds should continue through daybreak, and
dissipate shortly thereafter as daytime heating and resultant
mixing commences.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Quiet weather conditions are expected Tuesday and Wednesday as
surface high pressure gradually pushes offshore. Upper level
ridging will persist Tuesday, squashing any convection that may
form in the diurnal peak heating period. The exception to this
will be over the mountains where a pop up shower or thunderstorm
remains possible thanks to terrain circulations. Tuesday will
be much warmer than Monday with 850 mb values climbing to around
+14 to +17 degrees across the region. This will yield high
temperatures in the low to mid 80s with upper 70s across the
mountains.

Strong low pressure over the upper Great Lakes region and it`s
associated cold front draped across the Upper Midwest/Ohio River
Valley will gradually push east Wednesday as the upper level ridging
breaks down. 12z guidance continues to slow the progress of the
front eastward Wednesday afternoon/night with most of the guidance
favoring Thursday into Thursday night. This is due in part to the
placement of the departing surface high off the Mid-Atlantic coast
and secondary surface high pressure over the southeastern U.S. Even
with that said, a few showers and thunderstorms (some of which could
be strong) remain possible in areas west of the Blue Ridge Wednesday
afternoon and evening as an initial piece of shortwave energy
pivoting around the upper level low passes through. Most locations
will remain dry with increased south to southwesterly winds boosting
temperatures into the mid to upper 80s to near 90 outside the
mountains/bay.

Scattered shower and thunderstorm chances will continue especially
west of the Blue Ridge Wednesday night into Thursday morning. This
is in association with the cold frontal boundary and trough as it
inches closer to the region. Cloud cover/convective debris that
occurs from this activity could play into how much of severe threat
we see going into Thursday afternoon. More in the extended below.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
We return to an active pattern on Thursday as a potent upper trough
moves through southeastern Canada, carrying a slow moving cold front
into the area Thursday into Friday. Timing remains uncertain yet
critically important as it often is. Recent guidance has been more
consistent, however, in having the cold front move through our area
during peak heating, increasing confidence for severe potential.
With ample moisture and CAPE (+1500 J/kg) from previous persistent
southerly flow, the area will be primed for thunderstorm
development. The latest guidance has also placed us in the favorable
right entrance region of a jet, with deterministic guidance having
30-50kt of bulk shear. If these parameters continue to be favorable,
strong to severe thunderstorms will be possible Thursday, especially
as the front moves through in the afternoon/evening. Setup would be
less favorable if timing shifts forward or back, but could still see
some strong storms given the instability. Will continue to monitor.

Unsettled weather continues through the weekend as the cold front
stalls to our south. A series of minor disturbances are expected to
move through the area in this time as well, resulting in continued
shower activity in the vicinity of the front each day. Temperatures
in the mid/upper 80s on Thursday will cool a bit into the upper 70s
to low 80s and moderate around there through the weekend.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Mainly clear skies are expected tonight with additional low
clouds and patchy fog tonight especially within the river
valleys and terminals closest to the bay. Any low clouds/fog
should form between 8-14z/4am-10am. Fog and low clouds will
quickly burn off starting at the mountain terminals before
working east toward the corridor around daybreak. Outside of the
early morning MVFR/IFR fog/low cloud restrictions, VFR
conditions should prevail at all terminals Tuesday and Wednesday
afternoon. The exception to this will be in areas west of KMRB
where a spotty shower or thunderstorm could pop up in advance of
the front Wednesday afternoon.

Sub-VFR conditions are possible at times Thursday and through the
weekend. A cold front moves through Thursday, bringing strong and
possibly severe storms to the area. Timing is still coming into
focus, but currently best chance for shower and thunderstorms will
be in the afternoon and early evening hours. Any precipitation
moving over the terminals could bring restrictions. Additionally,
the front is expected to stall to our south through the weekend,
likely keeping shower activity in the area for the duration.

&&

.MARINE...
Light south to southeast winds are expected through Wednesday
although some channeling/river or bay breeze enhancement is possible
during the afternoon and evening hours. Winds should stay sub-SCA
level through Tuesday morning with high pressure overhead. Marginal
to sporadic SCA gusts are possible over the open waters Tuesday
afternoon and evening. Confidence is low for SCAs given the short
time window these conditions may occur. Some SCA level southerly
channeling is possible Wednesday into Wednesday night ahead of an
approaching cold front from the Ohio River Valley.

SCAs are not expected Thursday or Friday. However, as a cold front
moves through, showers and thunderstorms are expected on Thursday.
Special Marine Warnings may be required for the stronger storms.
Unsettled conditions continue through the weekend as the front
stalls nearby. Winds shift to west-northwest behind the front Friday
as it stalls south of the waters.

&&

.TIDES/COASTAL FLOODING...
Elevated water levels are expected to persist through Wednesday with
persistent light onshore (S/SE) flow. Minor flooding is likely
along vulnerable shoreline particularly during the
overnight/early morning high tide cycles (the higher of the two
astronomically). The higher end of the guidance envelope
approaches moderate flooding at Straits Point and Annapolis, but
this seems unlikely given the light flow. Coastal Flood
Advisories are in effect for these two locations along with DC
Waterfront for the upcoming high tide cycle.

Winds turn offshore behind a cold front Thursday, which will
cause a subsequent decrease in water levels.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until 9 AM EDT Tuesday for DCZ001.
MD...Coastal Flood Advisory from midnight tonight to 9 AM EDT
     Tuesday for MDZ014.
     Coastal Flood Advisory until 3 AM EDT Tuesday for MDZ017.
VA...None.
WV...None.
MARINE...None.

&&

$$

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