National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 300441
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1241 AM EDT Fri Sep 30 2016

.SYNOPSIS...
Upper level low pressure will rotate over Kentucky through Friday
before lifting north towards Michigan over the weekend.
Persistent onshore flow and localized heavy rain will continue to
occur over portions of 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 /UNTIL 6 AM THIS MORNING/...
Eastern Shore activity has diminished, so the Baltimore metro area
flash flood watch was cancelled. Threat in the east now is coastal
flooding from strong onshore flow.

The main threat out west is persistent moderate to locally heavy
rain over the Allegheny Highlands. Flash flood watch continues out
there and will let midnight shift decide its fate.

Upslope rain continues along the Blue Ridge where rates around one
to two tenths per hour will persist.

Elsewhere generally less than an inch additional rainfall
overnight with temps holding in the mid 60s.

&&

.SHORT TERM /6 AM THIS MORNING 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 /06Z FRIDAY THROUGH TUESDAY/...
Mainly drizzle and showers across the DC metros through Friday.
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...
Onshore flow continues in strong SCA range into Friday afternoon.
Gradient should begin to relax by later Friday evening...with SCA
winds becoming less likely Saturday into the Weekend as low
pressure over the Midwest weakens.

&&

.TIDES/COASTAL FLOODING...
-- Changed Discussion --
Anomalies running around 1.5 to 2 feet. Based on where low tide
bottomed out at Annapolis, needed to raise the forecast by at
least a quarter foot. Consequently posted a Coatal Flood Warning
for Anne Arundel County for the upcoming high tide. Since the
Friday PM tide cycle was forecast to be higher, ran that warning
for the next two cycles. Preserved the Watch for the Saturday pair
of tides.

Elsewhere, Coastal Flood Warnings for SW DC waterfront and St.
Marys County. The warning may expand to Alexandria. Advisories for
the rest of the coastline except for Harford Co. The east flow has
kept excess water for reaching the far northern extreme of the
Bay. That may change tonight (Friday night) into Saturday.

This is looking to be a prolonged event with coastal flooding
expected to continue at least into Sunday with continued onshore
flow.
-- End Changed Discussion --

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...Coastal Flood Warning until midnight EDT tonight for DCZ001.
MD...Flash Flood Watch until 8 AM EDT this morning for MDZ501-502.
     Coastal Flood Advisory until midnight EDT tonight for MDZ013.
     Coastal Flood Warning until midnight EDT tonight for MDZ014.
     Coastal Flood Watch from late tonight through Saturday evening
     for MDZ014.
     Coastal Flood Advisory until 8 AM EDT Saturday for MDZ016-018.
     Coastal Flood Warning until 8 AM EDT Saturday for MDZ017.
     Coastal Flood Advisory until 10 PM EDT this evening for MDZ011.
VA...Flash Flood Watch until 8 AM EDT this morning for VAZ025>027-
     036-037-503-504-508.
     Coastal Flood Advisory until midnight EDT tonight for
     VAZ052>055.
     Coastal Flood Advisory until 8 AM EDT Saturday for VAZ057.
WV...Flash Flood Watch until 8 AM EDT this morning for WVZ050-055-
     501>506.
MARINE...Small Craft Advisory until 7 PM EDT this evening for
     ANZ530>543.
-- End Changed Discussion --

&&

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