Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 130203
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1003 PM EDT Thu Oct 12 2017

.SYNOPSIS...
High pressure over New England will extend into the area through
Saturday before moving offshore Sunday. A cold front will push
into the Mid Atlantic Sunday night followed by a return to high
pressure early next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
High pressure over New England will extend south toward our
area through tonight. An onshore flow has allowed for low-level
moisture to be trapped underneath the subsidence
inversion...resulting in low clouds along with patchy
drizzle. This will continue through the night. Min temps will
be in the 50s across most areas to the lower 60s in southern
Maryland.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
High pressure over New England will continue to extend south and
west into our area through Saturday morning. An onshore flow
will continue and moisture will remain trapped underneath the
subsidence inversion...resulting in low clouds along with areas
of light rain and drizzle. High pressure will begin to move
offshore Saturday and some sun may break out as the marine layer
thins out...but confidence is low for this happening along/east
of the Blue Ridge Mountains. Max temps will be well into the
70s.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
A cold front will push across the eastern Ohio Valley into the
mid-Atlantic region Sunday into Sunday night. Ahead of the front,
there is a chance for rain showers, mainly Sunday night into
Monday morning. High temperatures ahead of the front, on
Sunday, will reach the lower to middle 80s. As the front passes,
temperatures will cool late Sunday through Monday.

High pressure is expected to build into the region Sunday night
through Thursday. Dry conditions and cooler temperatures
expected Monday afternoon through Thursday.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
An onshore flow will continue to cause low-level moisture to be
trapped underneath the subsidence inversion...resulting in low
clouds along with areas of drizzle through Saturday morning.
Mainly MVFR conditions are expected, but intervals of IFR are
likely as well, and a few periods where drier air works in from
the northeast can also result in some VFR conditions as we
currently have in spots at the moment. Cigs should improve
later Saturday...but confidence is low at this time. Areas of
low clouds/fog may develop again Saturday night as a southwest
flow ushers in plenty of moisture.

Sub-VFR conditions possible with any rain showers Sunday night
and Monday morning. Otherwise, VFR conditions will be expected
at the terminals. Wind southwest 5 to 10 knots Sunday, becoming
northwest around 10 knots gusts up to 20 knots Sunday night
through Monday night.

&&

.MARINE...
A pressure surge has caused gusty east to northeast winds today.
High pressure will continue to extend south and west into our
area into this evening. A Small Craft Advisory is in effect for
all of the waters. Winds should gradually diminish later tonight
through Friday...but a Small Craft Advisory remains in effect
for portions of the waters. High pressure will build overhead
Saturday before moving offshore Saturday night.

No marine hazards expected Sunday. Small craft advisories are
possible Sunday night through Monday night. Winds southwest
around 10 knots Sunday, becoming northwest 10 to 15 knots
gusts 20 knots Sunday night through Monday night.

&&

.TIDES/COASTAL FLOODING...
Onshore flow will continue through Friday. Minor Coastal
Flooding is likely. A Coastal Flood Advisory is in effect for
the Maryland Chesapeake Bay from Anne Arundel County southward
through tonight. The advisories may need to be extended north
into the Potomac River and northern Bay for the high tide cycle
late tonight. Coastal Flood Advisories will likely be needed
Friday into Saturday as well. Moderate flooding cannot be ruled
out...especially near Straits Point. A Coastal Flood Watch may
be needed for the high tide cycle Friday night.

&&

.CLIMATE...
A surge of warm air is expected Sunday ahead of the cold front.
We are not currently forecasting records, but we are expecting
temps to be close.

...Warm Temperature Records for October 15 (Sunday)...
     High             Warm Low
DCA  87 (1975)        67 (2008)
BWI  86 (1989, 1975)  66 (1941)
IAD  88 (1989)        64 (1985)

&&

.EQUIPMENT...
The NWS 88D Sterling radar (KLWX) will be down during the day
from 7 AM through 5 PM through Saturday this week. This is for
nationally scheduled maintenance on the radome. Our surrounding
88D radars as well as FAA terminal radars will be operational
during this downtime.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory until 2 AM EDT Friday for MDZ018.
     Coastal Flood Advisory until 3 AM EDT Friday for MDZ014.
     Coastal Flood Advisory until 2 PM EDT Friday for MDZ017.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ531>533-
     539>541.
     Small Craft Advisory until midnight EDT tonight for ANZ530-535-
     536-538-542.
     Small Craft Advisory until midnight EDT Friday night for
     ANZ534-543.
     Small Craft Advisory until 6 PM EDT Friday for ANZ537.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL/RCM
SHORT TERM...BJL
LONG TERM...KLW
AVIATION...BJL/KLW/RCM
MARINE...BJL/KLW/RCM
TIDES/COASTAL FLOODING...BJL
CLIMATE...DFH
EQUIPMENT...LWX



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