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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 101833
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
233 PM EDT Fri Sep 10 2021

.SYNOPSIS...
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High pressure will become centered overhead tonight before moving
offshore tomorrow. High pressure will remain offshore through early
next week. A cold front may approach the area from the northwest by
the middle of the week.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
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High pressure is currently centered off to our west over the
Ohio Valley. Northwesterly winds in advance of the high are
transporting cooler and drier air into the region today. As a
result, dewpoints are holding in the upper 40s and lower 50s,
while temperatures have climbed into the low-mid 70s. A mix of
sunny skies and some fair weather cumulus will persist through
the remainder of the afternoon. Winds are currently gusting to
around 20-25 mph, but should gradually decrease in magnitude
through the second half of the afternoon as high pressure moves
closer and the pressure gradient weakens.

The aforementioned area of high pressure will move overhead
tonight. This will set the stage for ideal radiational cooling
conditions, with clear skies and calm winds in place. With this
in mind, have hedged below both raw NWP and statistical guidance
on low temperatures tonight. We`re currently forecasting low
temperatures in the upper 40s and lower 50s for most locations
with lower to middle 40s in higher elevation mountain valleys,
and around 60 in the downtown DC and Baltimore, where urban heat
island effects will hold temperatures up. Areas of fog may also
be possible during the second half of the overnight hours,
especially to the west of the Blue Ridge.
-- End Changed Discussion --


&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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High pressure will start off the day tomorrow located directly
overhead. As the day progresses, the high will gradually drift
offshore, allowing light southerly flow to develop in its wake.
Southerly flow will transport slightly warmer air into the area,
but dewpoints will remain in the 50s. Skies tomorrow will be mostly
sunny, and high temperatures will reach into the lower 80s for most.
Skies will stay mostly clear tomorrow night, but temperatures will
be noticeably warmer compared to tonight. Light southerly winds
will continue through the night, and low temperatures will
bottom out in the 50s to middle 60s.

High pressure will remain anchored offshore on Sunday as ridging
starts to build in at mid-upper levels. Much warmer air will
advect into the area on westerly flow at 850 hPa/southerly flow
at the surface. Skies will remain sunny with ridging overhead,
but it will be much warmer, with highs in the upper 80s and
lower 90s for most. It will also become notably more humid,
with dewpoints creeping up into the 60s. Our stretch of dry
weather will continue through Sunday night, but it will be
warmer than previous nights, with lows in the mid 60s to low
70s.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
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Upper level ridging continues into Monday as surface high pressure
settles overhead. Heat and humidity return as a southerly flow
ensues. With abundant CAPE albeit no major forcing, a few late
afternoon pop-up showers and/or thunderstorms may arise across
portions of the Alleghenies given weak terrain circulations. However
subsidence should make for generally dry weather elsewhere. Tuesday
appears to be similar in nature with temperatures in the 90s for
most and dew points in the low 70s. By mid-week a cold front will
approach the region from the west. Guidance is split on the exact
timing of the FROPA which will determine exact impacts for the CWA.
Regardless, at this time, Wednesday into Thursday appears to have
the best potential for more widespread showers and thunderstorms,
some of which may have the potential to be severe. Any slow moving
storms also have the potential to produce isolated instances of
flooding given the abundance of rainfall as of late. Weak high
pressure looks to return for Friday.
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&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Prevailing VFR and dry conditions are expected through Sunday. Some
fog may try to form late tonight at MRB or CHO, but any fog will
quickly burn off tomorrow morning.

Winds will be out of the northwest today, and will gust around 20-25
knots at times. Winds will weaken overnight as high pressure
builds overhead. Winds will turn light out of the south-
southwest tomorrow, and remain south-southwesterly on Sunday.

Mainly VFR conditions expected across the terminals Monday and
Tuesday with high pressure in control. Winds will generally be out
of the south.
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&&

.MARINE...
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SCA conditions are ongoing over the waters in northwesterly flow.
Winds should slacken later tonight as high pressure builds
overhead. Winds will turn southerly tomorrow and remain
southerly through Sunday. Winds may approach SCA levels in
southerly channeling both tomorrow night and Sunday night.

Relatively quiet weather expected over the waters both Monday
and Tuesday with high pressure in control. However chances for
additional periods of SCA may be required for southern portions
of the bay as a southerly flow ensues.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Strengthening southerly winds Sat night could result in minor
coastal flooding at Annapolis Sat night into Sunday.

&&

.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...KJP
NEAR TERM...KJP
SHORT TERM...KJP
LONG TERM...SOUZA
AVIATION...SOUZA/KJP
MARINE...SOUZA/KJP
TIDES/COASTAL FLOODING...LFR