Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 202301

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

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.



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. Mild conditions
are expected with min temps ranging from the mid to upper 50s in
the colder valleys of the Potomac the lower and
middle 60s across most other near 70 in downtown
Washington and Baltimore.


High pressure 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.


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.


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.


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

Low chances of marine advisories or warnings through long term


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 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.


DC...Coastal Flood Advisory until midnight EDT tonight for DCZ001.
MD...Coastal Flood Advisory until 7 AM EDT Thursday for MDZ016-018.
     Coastal Flood Advisory until 1 AM EDT Thursday for MDZ508.
     Coastal Flood Advisory until 11 PM EDT this evening for MDZ011.
     Coastal Flood Advisory until 9 AM EDT Thursday for MDZ014.
     Coastal Flood Warning until 6 AM EDT Thursday for MDZ017.
VA...Coastal Flood Advisory until 7 AM EDT Thursday for VAZ057.
     Coastal Flood Advisory until midnight EDT tonight for VAZ054.


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