Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 291825
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
225 PM EDT Thu Sep 29 2016

.SYNOPSIS...
Upper level low pressure will rotate over Kentucky through Friday
before lifting north towards Michigan over the weekend.
Persistent onshore flow and periods of heavy rain will occur
across the Mid-Atlantic through Friday. The low is forecast to
track to the northeast early next week. High pressure will build
into the area during the first part of the new week.

&&

.NEAR TERM /THROUGH TONIGHT/...

A PNS was issued around 11 am with 30+ hour rainfall totals which have
been fairly impressive...but in most cases (not all) the rain has
fallen over a long enough time and into dry ground/low stream
levels that flood problems have been minimal.

The IAD and DOV VWP`s continue to Low level easterly flow of 30
knots. Yesterday I thought this would prove to be a big problem
for the eastern slopes of the mountains. So far this has not
materialized. A possible reason may be the convection off the
Delmarva which to some degree is blocking the heavier rainfall
from reaching the western side of the Bay. Despite this there is
still a potential that a band of heavy rainfall could set up over
one particular area. Hence the flash flood watch will remain in
effect overnight.

SPC continues to have the extreme southern portion of CWA in a
marginal risk.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...

Beginning Friday the upper level low will gradually retrograde
and move north as it begins to weaken. Rain rates are expected to
gradually become less intense as activity becomes more scattered
through the day.

Gradual drying trend continues into Saturday...as the upper low
continues to weaken and drift northward. While not a washout by
any means...scattered shower activity will remain possible.
Temperatures should climb back into the low/mid 70s.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...

Influence of upper-level low finally begins to diminish late in
the weekend into early next week as it passes by to our north and
moves out to sea...while high pressure builds into the area in its
wake. Most of Sunday appears dry...aside from some possible
lingering early morning showers.

Remaining dry with temperatures near climatology as high pressure
remains over the area through early next week.

This is a week away...but the word "Matthew" may be on everyone`s
minds next Tue or Wed. This is currently well south of Puerto Rico
but is forecast to make a northward turn and be positioned between
Cuba and Turks and Caicos in the first part of next week. GFS and
Euro have very different solutions on location and timing but one
solution has this along the Mid Atlantic coast during the middle
of next week. But the middle of next week is along way away.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Upper level low will continue to impact the area through
Friday...bringing periods of IFR/LIFR to all the terminals. Low
ceilings are possible through Friday night with persists onshore
flow.

Gradual improvement Saturday...with a return to VFR by Sunday.

&&

.MARINE...
Solid SCA for all waters for the remainder of the afternoon and
tonight. SCA has been extended through Friday afternoon. Gradient
should begin to relax by later Friday evening...with SCA winds
becoming less likely Saturday into the Weekend.

&&

.TIDES/COASTAL FLOODING...
Anomalies running around 1.5 feet. A coastal flood advisory is in
effect for western shore of Chesapeake Bay/Tidal Potomac through
Friday morning. This may need to be extended.

Water levels will continue to be an issue through at least
Saturday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flash Flood Watch through Friday morning for DCZ001.
     Coastal Flood Advisory until noon EDT Friday for DCZ001.
MD...Flash Flood Watch through Friday morning for MDZ003>006-011-
     013-014-016>018-501>508.
     Coastal Flood Advisory until 10 AM EDT Friday for MDZ011-016.
     Coastal Flood Advisory until 8 AM EDT Friday for MDZ014-017-
     018.
VA...Flash Flood Watch through Friday morning for VAZ025>031-
     036>040-050>057-501-502-505>508.
     Coastal Flood Advisory until 10 AM EDT Friday for VAZ057.
     Coastal Flood Advisory until noon EDT Friday for VAZ054.
WV...Flash Flood Watch through Friday morning for WVZ050>053-055-
     501>504.
MARINE...Small Craft Advisory until 7 PM EDT Friday for ANZ530>543.

&&

$$
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