Area Forecast Discussion Issued by NWS Sterling, VA
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 121852
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
252 PM EDT Tue Mar 12 2024
.SYNOPSIS...
-- Changed Discussion --
High pressure will continue to influence the Mid-Atlantic through
mid-week with well above normal temperatures. A low pressure
system will approach the region by Friday, bringing increased
chances for rain showers. Another low pressure system
may affect the area Sunday or Monday.-- End Changed Discussion --
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
A large area of high pressure extends along the Gulf Coast
states and into the Atlantic this afternoon, with low pressure
centers over Maritime Canada and the upper Great Lakes. The
resulting pressure gradient will continue to result in gusty
winds of 20-30 mph this afternoon. The downsloping wind, very
dry airmass, and plenty of sun (even through the scattered thin
cirrus) are resulting in temperatures in the mid 60s to lower
70s.
Lighter winds are expected tonight with patches of cirrus
continuing to cross the sky. Overnight lows will be in the 40s
for most, but sheltered valleys could drop into the 30s.-- End Changed Discussion --
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
-- Changed Discussion --
The center of the high will move offshore Wednesday. With a
weaker pressure gradient, winds will be much less pronounced. A
shortwave trough aloft will introduce some mid and high level
clouds, but there should still be some sun at times.
Temperatures should be a degree or two warmer than today with
the airmass still being dry. Clouds will clear Wednesday night
with lows in the 40s to lower 50s.
Locally, little changes for Thursday, although a low pressure
system will be moving into the Mid Mississippi Valley, with a
warm front lifting through the Ohio Valley. A shower could reach
the Alleghenies by afternoon, but most will be dry and clouds
will be slow to increase. Expecting to add another few degrees
to daytime highs, so most will be in the 70s, and a few spots
could even hit 80. The warm front will extend across
Pennsylvania Thursday night while the low moves toward Lake
Erie. A few showers are possible across the northern half of the
area, although the latest model trends suggest most of the rain
will stay to our north. Overnight lows will only drop into the
mid 50s with increased cloud cover.-- End Changed Discussion --
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
The local area will reside in the warm sector Friday with high
temperatures in the low to mid 70s for most. However, clouds and
rain showers will dampen the mild spring day. Cannot rule out a few
thunderstorms given progged CAPE values of up to a couple hundred
Joules/kg. Overall QPF does appear to be fairly light with the
ensemble consensus of a few tenths of an inch (more in western MD).
Once the cold front comes through Friday night, the area will
quickly dry out. Highs Saturday will still average about ten degrees
above Mid-March norms.
Sunday likely starts dry, but guidance divergences on the emergence
of multiple waves of energy ahead of a potent sub-522 dm trough
progged to move through the area Monday into Tuesday. On the
backside of the trough, mountain snow showers are evident
across most ensemble guidance Monday into Tuesday.
A more pronounced cooling trend ensues which comes with
increasingly gusty northwesterly winds. The true extent of the
cold blast does not really take shape until Tuesday as
temperatures fall back into the mid/upper 40s.-- End Changed Discussion --
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
VFR conditions are expected through Thursday. For today,
westerly winds gusting 20-25 knots (lighter at CHO) will
continue this afternoon before diminishing by the evening hours.
Winds will be lighter out of the west Wednesday and south or
southwest Thursday. Only a few periods of mid/high level clouds
are expected.
S/SW winds Friday in the warm sector turn w`ly behind the cold front
Friday night. In the warm sector, scattered showers and
thunderstorms are possible. Therefore, sub-VFR conditions are
expected at times Friday, especially in any heavier showers or
thunderstorms. Behind the front Saturday, conditions will dry out
with winds out of the WNW gusting to 15-20 kts.-- End Changed Discussion --
&&
.MARINE...
-- Changed Discussion --
Small Craft Advisory remains in effect until 6 PM with westerly
winds gusting up to 25 knots. The strongest winds will be
closer to shore (due to warm air over cool waters), as well as
on the upper Potomac and north of North Beach. The tighter
pressure gradient weakens overnight tonight and into Wednesday,
allowing winds to lessen heading into the middle part of the
week.
Winds take on a more southerly component Thursday but will
remain light through the day. As a low pressure system moves
into the Great Lakes Thursday night, winds will increase
further, potentially requiring SCAs. However there is some
uncertainty since even overnight, air temperatures will likely
be warmer than the water temperatures.
Typical Spring situation Friday over the waters with warm air being
in the warm sector over the cooler waters. Soundings continue to
show low-level inversions. Cannot rule out SCA conditions in the
S/SW flow, but SCA conditions become more likely along the front.
Any shower or thunderstorm could produce gusty winds as well. SCA
winds will continue out of the WNW Saturday before diminishing near
sunset Saturday evening.-- End Changed Discussion --
&&
.FIRE WEATHER...
-- Changed Discussion --
RH values of 20-30 percent and west winds gusting 20-30 mph
continue this afternoon. Winds will abate quickly this evening
except along the ridgelines. Relative humidities recover to 70
to 90 percent.
Lighter winds are expected Wednesday with only slight increases in
humidity in a continued very warm and dry airmass, and many areas
will still fall below 35 percent. There will also be some
increase in mid and high level clouds. Thursday will be warmer
still but with further increases in RH with winds becoming
southerly.
A low pressure system will approach the area Friday and bring the
next chance of rain.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
-- Changed Discussion --
Tidal anomalies are on the increase with lighter west winds in
place, and that upward trend will continue through the end of
the week. Some tidal sites may near minor flood stage Thursday
and Friday as winds turn southerly ahead of the next low
pressure system.-- End Changed Discussion --
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for
ANZ530>543.
&&
$$
SYNOPSIS...ADS
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...CPB
AVIATION...ADS/CPB
MARINE...ADS/CPB
FIRE WEATHER...ADS
TIDES/COASTAL FLOODING...ADS