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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 111837
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
237 PM EDT Sat Sep 11 2021

.SYNOPSIS...

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Bermuda high pressure will remain in place over the eastern half of
the US through this weekend and then will settle off-shore through
next week. A back door cold front will drop down into PA and remain
stalled nearby to our region to the north.
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&&

.NEAR TERM /THROUGH TONIGHT/...

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A weak and subtle upper trough has produced an area of high level
clouds that are slowly moving eastward through out region this
afternoon. High pressure remains in place over the eastern half of
the US which led to continued mostly dry condition`s along with the
formation of a light southerly flow. A warming trend begins today
with afternoon highs expected to peak in the lower 80s. Temps would
have the possibility of peaking higher but a scattered low level
deck has hampered afternoon heating.

Upper level ridging is expected to build overhead later this evening
leading to increase subsidence which should help clear out the sky
this evening. Winds won`t go as calm as last night which should
limit widespread decoupling this evening. Patchy dense fog will be
less widespread overnight with lows expected in the upper 50s to mid
60s.
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&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...

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The Bermuda high pressure over the eastern half of the US starts to
shift of the eastern seaboard on Sunday. This high is expected to
linger off the eastern seaboard through at least the early parts of
next week. Upper level ridging will move overhead and lead to mostly
clear conditions on Sunday with an increasing southwesterly flow.
High level smoke from the fires out west may lead to hazy look on
Sunday and may limit the amount heating that our region can
experience through the early parts of next week. Warm air advection
will increase Sunday into Monday leading to afternoon highs peaking
in the upper 80s to lower 90s both Sunday and Monday with Monday
being the warmest day so far in September. Overnight lows will
remain above normal in the mid to upper 60s.


Persistent ridging aloft along with high pressure at the surface will
lead to continued dry conditions through Monday afternoon. A
backdoor front is forecast to drop into southern NY and PA on
Monday. Models generally have this front stalling to our north as
the Bermuda high remains entrenched over our region. A few model
runs have suggested the possibility that showers and thunderstorms
could form over PA and drop southward into our region late Monday
evening. As we will have multiple days of warm and humid conditions
early next week, there will be enough CAPE in the environment for
these storms to possibly persist for a bit. Since the threat remains
fairly low at this time, I have kept 20 pops in the NE parts of our
CWA to stay consistent with previous shifts considering the  very low
end threat.
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&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...

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There are a number of scenarios that could unfold for the long term
period. A cold front is expected to move from the Great Lakes region
during midweek with a number of variables attached to it still yet
to be zeroed in on with respect to timing and intensity. For now,
Wednesday afternoon looks to be the greatest chance for convective
activity, mainly west of the Blue Ridge Mts for now. This could
expand further east depending on the timing of the frontal passage
along with daytime heating availability.

The other feature of interest is a low pressure signal that many
deterministic models are picking up on off the NC/SC coast by late
Thursday, early Friday and moving to the NNW towards the Chesapeake
Bay area. Ensembles are more in disagreement with an output for this
time frame with only some members signaling the low pressure system.
Otherwise, many models introduce weak high pressure for the start of
the weekend. With this potential system being many days away,
guidance will continue to zero in on a solution and if something
tropical in nature occurs, visit nhc.noaa.gov for further
information.
-- End Changed Discussion --

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...

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High pressure will remain overhead of our region through Monday.
Winds will continue out of the south to southwest with VFR
conditions  expected. High smoke make lead to some high broken
ceilings Sunday and Monday.

Mainly VFR conditions Tuesday and Wednesday aside from a few showers
or thunderstorms (mainly Wednesday afternoon) that may cross the
terminals, leading to momentarily sub-VFR conditions.
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&&

.MARINE...

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A strengthening south to southwesterly flow due to a Bermuda high
pressure will lead to southerly channeling of winds. A small craft
advisory is in effect through Sunday afternoon and it likely will
need to be extended through Monday morning.

Southerly channeling as high pressure is positioned offshore may
introduce SCAs during the middle portions of the work week.
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&&

.TIDES/COASTAL FLOODING...

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A continued southerly flow may lead to tidal sites along the
western shore of the northern Chesapeake Bay reaching close to
minor flood stage over the next few tidal cycles.
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&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT Sunday for ANZ530>534-537-
     539>541-543.
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&&

$$
SYNOPSIS...JMG
NEAR TERM...JMG
SHORT TERM...JMG
LONG TERM...ADM
AVIATION...JMG/ADM
MARINE...JMG/ADM
TIDES/COASTAL FLOODING...