792
FXUS61 KLWX 050135
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
935 PM EDT Fri Apr 4 2025

.SYNOPSIS...
A front wavers across the Mid Atlantic through Sunday, then it
finally pushes south of the area as a cold front. A secondary cold
front moves through Monday night. Strong high pressure builds in by
the middle of next week.

&&

.NEAR TERM /UNTIL 7 AM SATURDAY MORNING/...
The latest surface analysis depicts a wavy frontal boundary
which stretches from Chincoteague back across I-64 and down
toward the North Carolina/Virginia border. To the north of this
stationary front, the air mass is characterized by mainly
northerly winds and dew points in the 50s.

With high amplitude meridional flow in place across the central
to eastern U.S., a series of disturbances continue to lift
poleward from the Tennessee and Ohio Valleys. At this point,
just some light showers continue to graze portions of the area.
While soundings are fairly moist with precipitable waters around
1.25 inches, there are plenty of areas of dry air within the
surface to 900-mb and 750-550 mb layers. It will take further
bouts of showers to really begin moistening this column.

The front remains south of the area tonight. Overrunning moisture
brings another round of showers and drizzle tonight, along with low
clouds and some fog/mist. Temps in the 60s this evening slowly
settle in the 50s overnight. Isolated thunderstorms are possible
tonight as model guidance continue to depict elevated instability
overspreading the region north of the frontal boundary. However,
any such thunderstorms will be somewhat spotty in nature.

&&

.SHORT TERM /7 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
The frontal boundary begins to lift north across the area on
Saturday, though it is going to struggle due to relatively light low
level wind fields and a sharp inversion due to the low clouds and
drizzle. This is especially true for areas north of I-66/US-48 where
cloudy and shower/drizzly conditions are likely for most of
tomorrow. To the south of that, the low-level wind flow is forecast
to increase enough to break the inversion (boundary layer winds peak
above 20kt) by the late afternoon.

This is going to cause a tight temp gradient across the area once
again, with highs in the upper 70s to low 80s south of I-66/US-48
and in the lower 60s in north to northeast MD. By late afternoon to
early evening the front is forecast to be around the MD/PA border,
though given its wavy nature the areas of northeast MD likely remain
underneath the inversion for the entire day.

The morning showers/drizzle slowly begin to be pushed north as the
front itself moves north, then with building instability along and
south of the front some thunderstorms are possible. Most of the CAM
guidance keeps conditions dry south of the front, and this is in
line with the global guidance and NBM. Some additional elevated
instability could result in a few thunderstorms north of the boundary
as well.

SPC has added small area of Marginal Risk (level 1 of 5) for severe
storms on Saturday afternoon/evening, mostly in western MD and the
surrounding Potomac Highlands. This is due to that area of low
pressure moving across the OH Valley and its associated cold front.
This threat is going to be very conditional on how quickly the warm
front lifts through the area. If the warm front lifts quicker than
models indicate, greater instability develops that could support a
few strong to severe thunderstorms. If the front fails to lift
north, convection moving in from the OH Valley will struggle in the
more stable environment (though will need to watch for elevated
thunderstorms that pose a hail threat).

As the pattern aloft begins to shift and a wave of low pressure
passes, the front will return southward as a cold front late
Saturday night into Sunday. This will slowly increase rain chances
from northwest to southeast. At this time, instability looks fairly
limited locally, resulting in a minimal chance for any
thunderstorms. With the front bisecting the area Sunday, there will
likely be another large range in temperatures from the 50s in the
northwest to near 80 in the southeast. Even though the front will
likely be south of the area by evening, favorable upper level
dynamics and a wave of low pressure riding the boundary will renew
rain chances across the area Sunday night. At this time, all rain
looks to be beneficial in nature. Any precipitation which lingers
the second half of the night along the Alleghenies will start to
change over to snow.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Showers will end from west to east throughout the day on Monday as a
low pressure system and its slow-moving cold front pushes across the
region and then off to our southeast. Temperatures will be cooler
than average given the showers and cloud cover. Highs in the middle
to upper 40s in the mountains to the middle 50s in eastern Virginia
and southern Maryland.

High pressure will build in behind the departing front Monday night
through Tuesday night. There could be some upslope rain and snow
showers in the mountains leading to little snow accumulations.
Otherwise, dry conditions and a gusty wind will evolve late Monday
night through midday Tuesday across the region. Winds could gust
over 40 mph in the mountains Tuesday morning. After a chilly start
Tuesday morning with temperatures in the 30s, high temperatures
could only reach the upper 40s to lower 50s widespread.

The area of high pressure will move to the east Wednesday. Winds
will back around from the northwest to the southwest through the day
into Wednesday night. Dry conditions expected through the period
with temperatures that will not be as chilly as Tuesday. Highs in
the middle to upper 50s.

Thursday will be more seasonable with temperatures reaching 60
degrees or higher in many places. Dry conditions will continue
through much of the day. There will be a low pressure system that
will work its way to the east from the Ohio Valley and Lower Great
Lakes Thursday into Thursday night. Rain chances will increase from
west to east, but mostly be confined to the higher ridges of the
Appalachians.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
Multi-hour trends in local observations have shown some decrease
in ceilings. However, the area does remain VFR for now. Low
clouds are expected to build later this evening, first at CHO
when isolated showers start moving in from the west. IFR
conditions are likely after midnight tonight through Saturday
morning, along with some visibility reductions in mist and light
rain showers. A couple nocturnal thunderstorms are possible
across the area, though confidence in coverage and location are
too low to include in the TAFs at this time.

Conditions gradually improve Saturday afternoon, especially for CHO
where increasing south winds break the inversion keeping clouds
around. However, there is uncertainty for the other terminals
regarding timing of when ceilings break, especially at BWI/MTN that
could keep low clouds the entire day. Winds eventually shift back to
the south during this time.

Sub-VFR conditions return Sunday and Sunday night as the front drops
back south through the area. Several waves of showers are likely
during this time, but thunder chances are low. Gusty south winds
shift to the north with frontal passage.

MVFR conditions possible at MTN, BWI, and DCA terminals Monday
morning with showers overhead. VFR conditions should unfold from
west to east as these showers depart. Wind northwest 5 to 10 knots
gusts 15 knots Monday, increasing 10 to 15 knots gusts 20 knots
Monday night. Winds northwest 15 knots gusts up to 25 knots Tuesday,
diminishing northwest 10 knots Tuesday night.

&&

.MARINE...
A frontal boundary has mostly moved south through all the local
waters, with a northerly wind in place. The front eventually
lifts back north as a warm front on Saturday, with southerly
winds increasing Saturday afternoon but remaining below SCA
levels. There is the potential from SCA conditions Saturday
night in southerly channeling, and continue Sunday into Sunday
night as the cold front moves through and winds turn
north/northwest behind the front.

No marine hazards Monday. Winds north 5 to 10 knots. Small craft
advisories likely to develop later Monday night and continue through
the day Tuesday. Winds becoming northwest and increasing 10 to 20
knots gusts up to 25 knots Monday night and Tuesday. Small craft
advisories possible in the open Chesapeake Bay and Tidal Potomac,
but not expected elsewhere Tuesday night. Winds northwest around 10
knots gusts up to 20 knots over open Chesapeake Bay and Tidal
Potomac Tuesday night.

&&

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

&&

$$

SYNOPSIS...KRR
NEAR TERM...BRO/KRR
SHORT TERM...ADS/KRR
LONG TERM...KLW
AVIATION...BRO/KLW/KRR
MARINE...BRO/KLW/KRR