Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 131401
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1001 AM EDT Fri Oct 13 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 PM THIS EVENING/...
An onshore flow will continue around high pressure over New
England. Low-level moisture will remain trapped underneath the
subsidence inversion...resulting in more low clouds along with
areas of light rain/drizzle. The best chance for any light rain
or drizzle will be along and east of the Blue Ridge Mountains.
Across the central Shenandoah Valley into the Potomac
Highlands...the marine layer will be a bit thinner and with a
downsloping flow off the Blue Ridge Mountains there should be a
few breaks of sunshine.

Max temps will top off on the 60s for most locations with 50s in
the mountains and perhaps across northern Maryland...eastern
West Virginia and extreme northern Virginia.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
CAD will persist tonight along with low clouds and easterly
winds. Lows in the 50s west of I-95, lower 60s east.

Generally it takes a synoptic system to rid the forecast area of
the clouds associated with CAD, and that will happen Sunday,
but will take a pessimistic approach to Saturday even as the
high pressure area moves offshore, keeping the region under
extensive cloud cover. Exception may be west of the Blue Ridge.
Temperatures are forecast to climb back into the mid 70s, but
this may have to be trimmed back depending on cloud cover.

But skies should definitely improve Sunday as a cold front
approaches from the west. East coast will be on warm southerly
flow, and temperatures will likely rise back into the mid 80s -
about 15 degrees above normal. See climate section below. There
will be chances for showers west of the Blue Ridge during the
afternoon.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Cdnft will be crossing the area early Sun evening with
scattered showers behind the front. Showers could linger over
srn MD into Mon morning. High pressure then builds later Monday
and holds through the end of next week. It will feel more like
fall during the first half of next week with temperatures
trending more normal for the second half as heights rise due to
building ridge over the east.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
Overcast skies will continue at the TAF sites today. MVFR will
be the predominant ceiling into early this afternoon...but cigs
may lower a bit this afternoon and especially tonight with IFR
conditions becoming more likely along with areas of
drizzle/light rain. Some improvement may occur on Saturday. By
Sunday VFR will prevail.

Cdfnt will be crossing the area Sun evening with scattered showers
expected. Gusty NW winds expected Sun night behind fropa with gusts
up to 25 kt.

&&

.MARINE...
Winds are expected to become lighter as the day progresses. SCA
in effect for bulk of the MD portion of the Bay and lower
Potomac through 16Z, then only south of Drum Point and lower
Potomac through midnight.

There is a chance that SCA-level winds could occur Sunday
afternoon ahead of the approaching cold front.

Solid small craft advzy conditions expected Sun into Tue. A very
small chance (<5%) of gale force winds exists Sun night as a strong
pressure surge moves over the waters.

&&

.TIDES/COASTAL FLOODING...
A persistent onshore flow has caused tidal anomalies around 1.5
to 2.5 feet above normal. The onshore flow will weaken a bit
today into tonight. However...the high anomalies persist across
all of the Bay so it will take a bit longer for the anomalies to
drop...and when they do it will be slow.

Therefore...minor to moderate flooding is anticipated through
the high tide cycle Saturday morning. Coastal Flood Advisories
and warnings are in effect. Additional minor flooding is
possible later Saturday into Sunday.

&&

.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 is for nationally
scheduled maintenance on the radome. Surrounding 88D radars as
well as FAA terminal radars will be operational during this
downtime.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until 7 AM EDT Saturday for DCZ001.
MD...Coastal Flood Advisory from 2 PM this afternoon to 10 AM EDT
     Saturday for MDZ508.
     Coastal Flood Advisory until 2 PM EDT Saturday for MDZ016-018.
     Coastal Flood Advisory until 8 AM EDT Saturday for MDZ011.
     Coastal Flood Warning from midnight tonight to 4 AM EDT
     Saturday for MDZ014.
     Coastal Flood Advisory until midnight EDT tonight for MDZ014.
     Coastal Flood Advisory from 4 AM to 5 PM EDT Saturday for
     MDZ014.
     Coastal Flood Warning until 1 PM EDT Saturday for MDZ017.
VA...Coastal Flood Advisory until 2 PM EDT Saturday for VAZ057.
     Coastal Flood Advisory until 7 AM EDT Saturday for VAZ054.
WV...None.
MARINE...Small Craft Advisory until noon EDT today for ANZ531>533-
     539>541.
     Small Craft Advisory until midnight EDT tonight for ANZ534-537-
     543.

&&

$$
PRODUCTS...BJL/WOODY!/LFR/DFH



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