993
FXUS61 KLWX 041828
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
228 PM EDT Tue Jun 4 2024

.SYNOPSIS...
High pressure has pushed off the northeast coast this afternoon,
meanwhile an upper-level ridge is centered overhead. Unsettled
weather returns for the whole forecast area Wednesday and
Thursday as a series of fronts cross the region. Precipitation
chances decrease on Friday in the wake of the cold front. A slow
moving upper trough approaches the area from the Great Lakes
this weekend leading to more unsettled conditions.

&&

.NEAR TERM /THROUGH TONIGHT/...
Convection is starting to fire, mainly west of the Blue Ridge,
this afternoon. High pressure offshore is funneling in
southeasterly flow to the region, which is leading to terrain-
induced convection. Given the temperatures well into the 80s
with dew points into the mid to upper 60s, there is plenty of
juice out there for thunderstorms to develop (on the order of
1500-2000 J/kg of SBCAPE). The question will be just how tall
they are able to get with the ridging aloft. Per the latest RAP
mesoanalysis, there is actually about 15-20 knots of shear out
there, which isn`t negligible. Low-level lapse rates are of
course quite high, as is typical during summer convective
events, so anything that does manage to get tall has the ability
to bring down some gusty winds. Would expect any severe
thunderstorms to be very few and far between given the upper-
level ridge aloft, but definitely can`t rule out one or two this
afternoon.

Showers and t-storms may gradually shift south and east during
the evening hours, though the best chance looks to remain south
of the DC metro.

Similar to previous nights, patchy fog development is possible,
particularly where showers and storms occur in the afternoon
and evening. Lows fall into the 60s to low 70s.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A potent upper low will dive into the Great Lakes region
Wednesday into Wednesday night, eventually bringing a cold front
through on Thursday morning. The warm front will lift through
the region by mid-late Wednesday morning, likely spawning an
initial line of convection. There is a lot of uncertainty
regarding the amount of instability that will be available,
owing to morning cloudcover. However, mean CAPE values look to
be on the order of 1000-1500 J/kg of CAPE. The shear values to
go along with this stay below 30 knots, as much of the upper-
level energy passes well to our north. This would lead to a
lesser severe threat tomorrow. However, the flash flooding
threat is on the increase.

Looking at forecast soundings for tomorrow, there are plenty of
ingredients present to support a flash flood threat. First off,
PWATS are going to be on the order of 1.8-2" area-wide once the
warm front pushes through. Additionally, forecast soundings show
long and skinny CAPE profiles. The environment will be very
efficient at producing heavy rainfall tomorrow, so any storm
that does develop could drop a couple of inches very quickly.
Have held off on watch issuance at this time due to uncertainty
in exact location, but could see the need for one in a future
update.

After this, there may be a brief lull for a few hours before a
second line of convection develops along the pre-frontal trough.
This line will be very progressive and move from west to east,
but will be within the same environment conducive to heavy
rainfall. So a flash flood threat remains as that moves through
during the evening hours.

At least some spotty convection could continue into the
overnight hours. Low temperatures only drop to around 70 for
most, so a very warm night expected once again.

The cold front arrives Thursday morning and showers and possible
thunderstorms could linger in these same areas into the evening,
with chances decreasing over time as we dry behind the cold front.
Low temperatures drop into the 50s to upper 60s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Upper level troughing will remain overhead throughout the long term
period, bringing unsettled weather conditions. Daily rain chances
are expected primarily in the northwestern portions of the forecast
area, peaking in the afternoon with daytime heating. The best chance
for precipitation will be Sunday as a cold front is pushed across
the region. Highest chances for precipitation remain in the
northwest portions of the forecast area, with those along and east
of I-95 only having a slight chance of showers and thunderstorms.

There still remains a good bit of model uncertainty with the track
of a cut-off upper level low pressure system navigates eastward.
Where the low ends up going will dictate which areas see highest
precipitation chances and how much precipitation each area receives.

Temperatures each day will be in the 70s to low 80s for most with
those at higher elevations staying in the 60s. Overnight lows will
dip into 50s to low 60s.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
VFR conditions are expected through the evening hours. However,
CHO could see impacts from showers and storms over the next
couple of hours. Convection likely stays away from the other
terminals this evening.

Low clouds move in late tonight into Wednesday morning, and
some areas could even see some patchy fog. This would be most
likely in areas that manage to get some rain this afternoon.

Numerous showers and thunderstorms will bring restrictions to
the terminals on Wednesday, with the best chance in the afternoon
and evening. Some showers and possible t-storms could linger
into the overnight for MRB, BWI and MTN. Conditions improve on
Thursday behind a cold front.

VFR conditions are expected Friday and Saturday with westerly winds
blowing 5 to 10 knots. Precipitation is possible each afternoon with
the highest chances being at KMRB.

&&

.MARINE...
Sub-SCA winds are generally expected today across the waters.
Seeing some convection go up along the Bay Breeze on the eastern
shore, but think those should stay far enough away from the
water to not cause many issues.

A frontal system arrives on Wednesday with gusty southerly
winds over the waters approaching SCA criteria by Wednesday
afternoon. Gusty winds could also occur due to thunderstorms
traversing the region during the afternoon/evening hours.

SCAs will likely be needed Wednesday night into Thursday
morning. Winds diminish behind the cold front on Thursday.

Westerly winds remain below SCA criteria on Friday over the waters.
Winds remain out of the west on Saturday, with SCA criteria gusts
possible in the afternoon.

&&

.TIDES/COASTAL FLOODING...
Flow has turned onshore this afternoon as high pressure pushes
off the northeast coast. This has started to bring tidal
anomalies up, but tidal flooding threat still minimal at this
time. By tomorrow however, winds will pick up a bit out of the
south, which should push many areas closer to minor flood stage
over the next couple of days. This will be even further enhanced
by the presence of a New Moon which is set to happen on June
6th.

A weak cold front crosses the area early Thursday, with the
resulting west winds causing tidal anomalies to drop.

&&

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

&&

$$

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