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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 120138
AFDLWX

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

.SYNOPSIS...
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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 /UNTIL 6 AM SUNDAY MORNING/...
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Upper level ridging is building overhead leading to increased
subsidence which is clearing out the sky this evening. Winds
won`t go as calm as last night which should limit widespread
decoupling. Patchy dense fog expected in the most sheltered
spots with lows in the upper 50s to mid 60s.
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&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
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The 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 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, have
kept pops relatively low 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 /02Z SUNDAY 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 altitude smoke may 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 high
pressure shifting offshore will lead to southerly channeling of
winds. A small craft advisory is in effect through Sunday
night and it likely will need to be extended into Monday.

Southerly channeling as high pressure is positioned offshore
may require SCAs during the middle portions of the work week.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
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.

&&

.CLIMATE...
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Unseasonably warm weather this week may result in some record
warm temperatures, though at this time we think the probability
is below 50 percent. As a reminder, low temperature records are
for the period 1 AM EDT to 1 AM EDT (midnight EST to midnight
EST).

Record high maximum temperatures
SITE   Sun 9/12    Mon 9/13    Tue 9/14    Wed 9/15    Thu 9/16
DCA   98 in 2019  94 in 1925  95 in 2016  97 in 1930  96 in 1991
BWI   97 in 2019  97 in 1952  94 in 1931  97 in 1927  98 in 1991
IAD   95 in 2019  94 in 1974  95 in 1998  95 in 1998  97 in 1991

Record high minimum temperatures
SITE   Sun 9/12    Mon 9/13    Tue 9/14    Wed 9/15    Thu 9/16
DCA   75 in 1983  74 in 2008  75 in 2008  75 in 2005  75 in 2005
BWI   75 in 1931  74 in 1915  74 in 1915  74 in 1915  73 in 2005
IAD   71 in 1963  71 in 2018  72 in 2018  71 in 2005  69 in 2005
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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 AM EDT Monday for ANZ532>534-537-
     539>541-543.
     Small Craft Advisory until 6 PM EDT Sunday for ANZ530-538.
     Small Craft Advisory from 6 PM Sunday to 6 AM EDT Monday for
     ANZ542.
     Small Craft Advisory until 6 PM EDT Sunday for ANZ531.
-- End Changed Discussion --

&&

$$
SYNOPSIS...JMG/RCM
NEAR TERM...JMG/RCM
SHORT TERM...JMG/RCM
LONG TERM...ADM
AVIATION...JMG/ADM/RCM
MARINE...JMG/ADM/RCM
TIDES/COASTAL FLOODING...LWX
CLIMATE...BRO/RCM