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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 211906
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
306 PM EDT Tue Mar 21 2023

.SYNOPSIS...
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High pressure will move offshore tonight through Thursday. A
cold front will drop into the area from the north Thursday night
into Friday. The front will stall out nearby through Friday
night. Low pressure will pass to our west Saturday into
Saturday night before high pressure briefly returns Sunday.
Another low may impact the area early next week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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High pressure will move offshore tonight. A light and persistent
southerly flow will result in milder temperatures tonight. Lows
will be in the 30s to the lower 40s in downtown Washington and
Baltimore. A weak piece of mid-level energy will move into the
area late tonight. An isolated shower or sprinkle cannot be
ruled out over the Allegheny Highlands. Most areas will be dry.
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&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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Another piece of energy will pass through the region on
Wednesday. The southerly flow will increase some during the
afternoon. Mild temperatures, similar to this afternoon, are
anticipated Wednesday afternoon. Highs mainly in the 60s with
slightly cooler temperatures in the mountains and along the
Bayfront.

A long positively tilted trough of low pressure will setup over
the Great Lakes into the Rockies Wednesday night. The surface
cold front associated with this trough will remain over the
same area. Southerly winds will continue to usher in milder
conditions for Wednesday night with lows in the 40s for most
areas (near 50 in downtown Washington and Baltimore). Stronger
warm advection will draw in some more moisture from the Gulf of
Mexico. The warm and moist air overrunning cooler air near the
surface will increase lift, and this combined with shortwave
energy means that there will be a better chance for showers,
especially near and north of Interstate 66 and US 50.

Low pressure will likely pass by to our north Thursday with a
southwest flow across our area. Warmer temperatures expected
with highs in the 70s and dry conditions.

A cold front, associated with the low pressure system, will
drop into our area from the north Thursday night, bringing an
increased chance for showers.
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&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
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Temperatures later this week are forecast to be well above normal,
but there still remains a good bit of uncertainty regarding the
temperature forecast for Friday and Saturday. A stalled frontal
boundary will be to our north/northwest creating a large spread in
temperatures across the area. Uncertainty remains regarding where
the boundary stalls and where the cooler temperatures are each day.
The most likely scenario shows temperatures in the upper 60s and 70s
for the southern portions of the forecast area with temperatures in
50s along the Pennsylvania and Maryland state border.

In addition to the large temperature spread on Friday and Saturday,
the stalled frontal boundary will bring increased rain chances. Up
to half an inch of rainfall is possible in the northern portions of
the forecast area with those along and west of the Alleghenies
possibly receiving over an inch of rainfall. Given how dry it has
been, rainfall looks to be mostly beneficial at this time. As an UL
trough pivots over the region on Saturday, there is a risk of
thunderstorms. With CAPE values near 200 J/kg and over 70 knots of
bulk shear, convection cannot be ruled out.

Dry conditions return on Sunday as high pressure temporarily builds
overhead. Rain chances return Sunday night into Monday as another
system approaches the area.
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&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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VFR conditions are expected through Thursday. High pressure to
the east and offshore will allow for a south to southwest flow
to develop, persist, and increase some through the next 36 to 48
hours. A few showers are possible Wednesday night into early
Thursday, but most places will be dry.

A cold front will likely drop into the area Thursday night,
increasing the chances for showers and subVFR conditions.

Sub-VFR conditions are possible Friday and Saturday during rain
showers as a frontal boundary stalls nearby.
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&&

.MARINE...
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A southerly flow will develop and continue through Thursday.
This flow should increase enough that small craft advisories
have been issued for the Upper Potomac and the northern half of
the Bay.

The gradient will strengthen for Wednesday through Thursday, and
an SCA will likely be needed for portions of the waters. The
breeziest conditions will most likely be Thursday afternoon with
some gusts around 20 to 30 knots possible (mainly away from the
open waters). A cold front may drop into the area from the north
Thursday night, but an SCA may still be needed.

Northerly winds on Friday will be right at SCA criteria throughout
the day. Winds shift to easterly on Saturday and will likely be SCA
criteria. Gusty winds are possible during convection.
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&&

.FIRE WEATHER...
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A southerly flow is expected to continue with dry conditions.
The relative humidity will stay near 15 to 25 percent for most
areas. Temperatures will be in the 60s for most areas. Southerly
winds of 10 to 15 mph.

The next weather system will approach Wednesday and atmospheric
moisture will begin to increase. Small chances of light rainfall
exist Wednesday and Thursday, but higher chances of areawide
rainfall won`t arrive until the end of the week.
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&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 2 PM to 10 PM EDT Wednesday for
     ANZ530>532-535-538>540.
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&&

$$
SYNOPSIS...BJL
NEAR TERM...KLW
SHORT TERM...KLW
LONG TERM...AVS
AVIATION...AVS/KLW
MARINE...AVS/KLW
FIRE WEATHER...KLW