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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 211418
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1018 AM EDT Sun Apr 21 2024

.SYNOPSIS...
Low pressure will pass south of the area today. High pressure
will build overhead Monday and Tuesday. A cold front will cross
the area Wednesday, followed by high pressure for the end of the
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Mid-morning update: Skies are currently overcast across the
entire forecast area. Radar imagery shows returns across
Central Virginia and the Central Shenandoah Valley, but the 12z
IAD sounding shows ample dry air at low-levels. As a result,
little, if any of this precipitation is making it to the
ground. The column may eventually saturate, allowing some light
rain to fall from Central Virginia to Southern Maryland late
this morning into early this afternoon, but dry conditions are
expected elsewhere. Previous discussion follows...

A front is stalled across the southeastern states this morning
with multiple waves of low pressure along it. High level clouds
have spread northward across the forecast area, and mid level
clouds will follow suit after sunrise. Overall it will be a
mostly cloudy day, which combined with the cooler post frontal
airmass, will mean that temperatures will remain below 60 for
most areas. A shortwave will cause overrunning rain to spread
northeastward from the frontal zone later this morning into the
afternoon. The cutoff for this precipitation will be very close
to Nelson and St. Marys Counties, with 00Z guidance indicating
an increased chance for light rain across far southern Maryland.

Skies will clear this evening, but the passage of a trough and
pressure rises may mean winds remain elevated for a time. It
does appear winds should slack during the second half of the
night, especially west of the Blue Ridge. With dew points in the
upper 20s, there is potential for subfreezing temperatures, and
have thus issued a Freeze Watch. Probabilities are slightly
higher in the central Shenandoah Valley. In addition, Frost
Advisories may be needed for locations west of the I-95 corridor
as temperatures likely dip to the mid 30s.
-- End Changed Discussion --

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
High pressure will build in from the west Monday and Monday
night with mostly clear skies expected. While slightly warmer
overall, temperatures will still be a little below normal. Frost
may be a concern for rural areas again Monday night.

The high will push to the south and east on Tuesday. Increasing
southerly flow will result in temperatures warming into the mid
60s to lower 70s. Clouds will gradually increase ahead of a low
pressure system moving through the Great Lakes. Showers ahead
of this system may reach the Appalachians during the evening and
definitely overnight as the cold front approaches. While some
showers may spread across the remainder of the area, recent
guidance has been trending drier east of the mountains.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
High pressure will move east to the coast Wednesday. A cold front
will push across the region Wednesday morning. The possible timing
of frontal passage early in the day, along with a developing
westerly downsloping flow, could reduce the possibility of any
strong thunderstorms or prolonged periods of showers. As a matter of
fact, many areas to the east of the Appalachians may not see any
rainfall Wednesday into Wednesday night. High temperatures Wednesday
will be near average. An upslope wind into the ridgeline of the
Appalachians could lead to some enhancement of shower activity, but
probably not widespread or flood potential.

An area of cooler high pressure is expected to build behind the
front Thursday with a reinforcing center of high pressure
expected on Friday. Dry conditions expected each day with high
temperatures a couple of degrees below average. Highs near 60 to
lower 60s each day.

By Saturday, the secondary high moves to the east. A developing warm
front to our southwest Friday night will push east and north Friday
night and during the day Saturday. Increased light rain chances and
perhaps some elevated thunder are possible ahead of and along this
warm front late Friday night and Saturday. Temperatures will be
closer to average, if not a few degrees above average on Saturday.
This will depend on how far the warm front pushes east and
north.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
VFR conditions are expected through Tuesday. Mid and high level
ceilings are expected through this afternoon. North to northwest
winds are expected through Monday at 10 kt or less. Increasing
southerly flow on Tuesday may gust to 20 kt.

VFR conditions Wednesday through Thursday night. Winds southwest
becoming northwest and increasing 15 to 25 knots Wednesday and
Wednesday night. Winds northwest 10 to 15 knots gusts up to 20 knots
Thursday. Winds becoming northeast 5 to 10 knots Thursday night.

&&

.MARINE...
-- Changed Discussion --
Sub-SCA winds are ongoing, but a surge of NNW winds is expected
tonight, and a SCA has been issued for that time period.

Lighter winds are expected Monday and Monday night as high
pressure builds overhead. Increasing southerly flow will
develop Tuesday and Tuesday night. SCAs will likely be needed.

Small craft advisories likely Wednesday through Thursday morning.
Small craft advisories may still be possible Thursday afternoon. No
marine hazards Thursday night. Winds becoming northwest 15 to 25
knots gusts up to 30 knots Wednesday through Thursday morning. Winds
northwest 10 to 20 knots Thursday afternoon. Winds becoming
northeast around 10 knots Thursday night.
-- End Changed Discussion --

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None.
MD...Freeze Watch from late tonight through Monday morning for
     MDZ003.
VA...Freeze Watch from late tonight through Monday morning for
     VAZ025>031-507-508.
WV...Freeze Watch from late tonight through Monday morning for
     WVZ050>053-055.
MARINE...Small Craft Advisory from 10 PM this evening to 6 AM EDT
     Monday for ANZ530>532-539-540.
     Small Craft Advisory from 10 PM this evening to 10 AM EDT
     Monday for ANZ533-534-537-541-543.
-- End Changed Discussion --

&&

$$

SYNOPSIS...ADS
NEAR TERM...ADS/KJP
SHORT TERM...ADS
LONG TERM...KLW
AVIATION...ADS/KLW
MARINE...ADS/KJP/KLW