Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 201814
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
214 PM EDT Wed Sep 20 2017

.SYNOPSIS...
High pressure both at the surface and aloft will build overhead
through the weekend. The remnants of Jose may affect the area
early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Upper-level ridge axis remains overhead this afternoon while an
upper-level disturbance approaches from the west. A few popup
showers have developed over the Potomac Highlands into the
central Shenandoah Valley due to limited instability associated
with the upper-level disturbance. However...coverage remains
isolated to widely scattered. Elsewhere...sunshine is expected
through late this afternoon along with unseasonably warm
conditions. Max temps will be in the mid to upper 80s across
most locations.

High pressure both at the surface and aloft will build over the
region as the upper-level disturbance shifts to the south
tonight. Patchy fog will again be a concern. More mild
conditions are expected with min temps ranging from the mid to
upper 50s in the colder valleys of the Potomac Highlands...to
the lower and middle 60s across most other locations...to near
70 in downtown Washington and Baltimore.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
High pressure both at the surface and aloft will remain over the
region Thursday through Friday night. More dry and warm
conditions are expected with max temps in the 80s for most
locations and min temps generally ranging from mid to upper 50s
in colder valleys to 60s across most other locations. A light
flow with high pressure overhead will allow for patchy fog
during the overnight and early morning hours each day.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Lots of uncertainty in long term forecast due to Jose and Maria.
The 20/12Z GFS deterministic and GEFS show the remnants of Jose
and an inverted trough associated with this system extending
westward into our area later on Sunday through Monday...possibly
bringing unsettled conditions to our area during this time.

Official NHC Maria forecast is still south of 35N latitude at
Mon 25/12Z, so much uncertainty as WPC surface front/SLP
forecast has it remaining well off the coast; and the 20/12Z
GEFS does keep 24-hour rainfall totals greater than 0.1 inches
east of our forecast area.

Otherwise, the 12Z MEX keeps max and min temps about 10 degrees
above normal for the entire long term, with max temperatures
generally in the mid 80s and min temps in the mid 60s, except
cooler at higher elevations.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
High pressure will build over the terminals through Friday
night. Patchy fog is possible during the overnight and early
morning hours each day...but much of the time will end up with
VFR conditions.

Low chances of sub-VFR conditions through long term period.

&&

.MARINE...
High pressure will build over the waters through Friday night.
Winds should remain below SCA criteria through Friday. A weak
pressure surge may cause north to northwest winds to channel
down the Bay Friday night. Confidence for an SCA is low at this
time.

Low chances of marine advisories or warnings through long term
period.

&&

.TIDES/COASTAL FLOODING...
Water piled up near the mouth of the Bay from Jose over the
past couple days. Those anomalies have spread across the Bay
and Tidal Potomac River. Anomalies over 1 foot above normal
remain across the entire Bay and Potomac River...so elevated
water levels are likely to continue for at least the next couple
tide cycles through late tonight...despite an offshore flow.
Coastal Flood Advisories are in effect from Baltimore
southward along the Bay and across the upper Tidal Potomac
River. A Coastal Flood Warning is in effect for St Marys County
where moderate flooding is expected.

Coastal Flood Advisories may need to be extended through the
high tide cycles Thursday and Friday since the offshore flow
will be light and it will be tough for water to recede.

Elevated water levels are likely during the weekend through the
early portion of next week. The remnants of Jose may cause an
elevated threat for tidal flooding early next week.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until midnight EDT tonight for DCZ001.
MD...Coastal Flood Advisory until 7 AM EDT Thursday for MDZ018.
     Coastal Flood Advisory until 11 PM EDT this evening for MDZ011.
     Coastal Flood Advisory until 9 AM EDT Thursday for MDZ014.
     Coastal Flood Advisory until 7 PM EDT this evening for MDZ016.
     Coastal Flood Warning until 7 PM EDT this evening for MDZ017.
VA...Coastal Flood Advisory until 7 PM EDT this evening for VAZ057.
     Coastal Flood Advisory until midnight EDT tonight for VAZ054.
WV...None.
MARINE...None.

&&

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


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