216
FXUS61 KLWX 201827
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
227 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/...
Low and mid level clouds continue to scatter out along and east
of the Blue Ridge this afternoon with mostly clear skies
further west as high pressure settles overhead. Once the low and
mid level clouds break scattered to broken high based
stratocumulus will be leftover during the afternoon and evening
hours especially east of the Blue Ridge. An outside chance of a
spotty shower remains over the higher ridges of the
Appalachians, but overall most locations will remain dry. High
temperatures today will range from the mid to upper 70s to
around 80 along and west of US-15 with low to mid 70s further
east where the cloud cover has held on the longest.

Mainly clear skies are expected this evening as subsidence under the
surface high fully asserts itself across the region. This will allow
for additional stratus migrating in from the east and areas of fog
in the river valleys. The bulk of this fog and stratus should
lift out early Tuesday morning after sunrise. Lows tonight will
fall into the mid to upper 50s and low 60s.


&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Sensible weather conditions are expected Tuesday and Wednesday as
surface high pressure gradually pushes offshore. Upper level ridging
will persists 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 orographic lift. 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 /18Z MONDAY THROUGH SATURDAY/...

Any leftover stratus should scatter out across the corridor
terminals after 18z/2pm. Terminals west of the corridor will
continue to see SKC conditions with high based stratocumulus passing
through during the diurnal peak heating period. VFR conditions
should prevail for the remainder of the afternoon and evening as
high pressure settles overhead.

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...EST
SHORT TERM...EST
LONG TERM...CAS
AVIATION...CAS/EST
MARINE...CAS/EST
TIDES/COASTAL FLOODING...DHOF/EST