Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 240041

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
841 PM EDT Sat Sep 23 2017

High pressure will remain in place through the weekend and the
first part of the week. This will slowly weaken its grip over
the area by the midweek as Hurricane Maria moves northward
through the Western Atlantic.



High pressure in control of the synoptic pattern both at the
surface and aloft. Anticipate that tonight`s weather will be
comparable to last night. Guidance backing off slightly on fog
coverage, which is slightly curious. Would think that Virginia
would be preferred due to light onshore flow. Am carrying patchy
coverage, favoring the valleys of the Piedmont and foothills.
Lows in the mid 50s-lower 60s, except 65-70 in the urban


The synoptic pattern will change little Sunday and Monday. If
anything, ridging aloft will only grow stronger until a weakness
emerges as a result of Maria. A slight warming surface through
925 mb suggests that upper 80s/near 90 will be within reach
Sunday afternoon. Highs may retreat a degree or so by Monday.

Latest guidance does suggest that Maria will be approaching the
NC coast Tuesday. It is unclear how close or what the full
impacts will be, although they likely will be minimal through
Monday night. Have increased cloud cover and PoPs Monday
night...but only enough for partly cloudy skies and a slight
chance of precip over the tip of southern Maryland. Consult the
latest bulletins from NHC on the latest thinking on the progress
of Maria.


High pressure on the surface an aloft will allow for dry
conditions over the region part of Tuesday. At the same time
Hurricane Maria will be moving north-northwest Tuesday.
Guidance suggests that Maria will get close to the NC Outer
Banks and it will stall there Tuesday night into maybe Thursday
when an upper trough/cold front pushes it out to sea. Most
guidance does not show significant impact to our region. Please
visit the National Hurricane Center`s website
for more information.

The cold front that is expected to move through our CWA Thursday
will increasing the chance of showers over our area. Dry
conditions return behind it later Thursday and Friday. Another
front approaches Saturday.


VFR flight conditions will prevail for the valid TAF period,
aside from early morning fog concerns. CHO/MRB terminals will be
the most impacted. Am forecasting MVFR at this point. IFR
possible, but its likely to be brief and would be tough to

The pattern will be similar through Monday. There may be an
increase in cloud cover on Monday night in advance of Maria; its
extent unclear at this point.

Mainly VFR conditions expected Tuesday into Thursday but some
sub-VFR conditions possible later with maybe some showers
around. A further deviation northwest in the track of Maria
could bring worse conditions.


Light north flow (10 kt or less) will prevail thorugh Monday
night. Wind gusts increase Tuesday into Thursday with Hurricane
Maria over the west Atlantic Ocean. Small craft advisory
anticipated. If the storm`s track deviates further northwest,
more significant impacts are possible (though not likely). Refer
to latest NHC statements for up- to-date information on Maria.


Water levels remain between a foot and a foot and a half above
astronomical normals. There has been a slight weakening in this
influx though, something that guidance suggests will continue.
While the pattern will support minor inundation for several
days, confidence in any inundation is highest for the upcoming
tide cycle. Ensemble guidance supports this approach.

Advisory in effect for the overnight cycle for DC/Alexandria
and Annapolis, and through Sunday morning for St Marys and

Beyond that, will need to monitor trends and latest guidance.
Anticipate the threat of minor inundation at sensitive
locations will be an issue for several days at least.


DC...Coastal Flood Advisory until 2 AM EDT Sunday for DCZ001.
MD...Coastal Flood Advisory until 8 AM EDT Sunday for MDZ017-018.
     Coastal Flood Advisory until 1 AM EDT Sunday for MDZ014.
VA...Coastal Flood Advisory until 2 AM EDT Sunday for VAZ054.


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