Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 271434

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1034 AM EDT Sat May 27 2017

Weak low pressure will move across the area late this afternoon
into the evening which will push a weak front south of the area
late tonight. A stronger cold front will move through the area
Monday. High pressure will return to the area mid next week.


Remnant showers shifting east across the Balt-Wash metro area
through the midday. Weak low pressure (1011mb) is centered over
OH and will slowly shift east across the area late this
afternoon into the evening. A warm front will set up across the
southern half of the fcst area. 12Z HRRR continues to prog mid
to late afternoon thunderstorms developing over the central
Shenandoah County and shifting east across Charlottesville. Low
end severe threat there with damaging winds and large hail as
the main threats. 0-6km flow around 30kt should keep storms
moving with flash flooding risk low despite saturated soils and
potential training convection. The low and associated front
will push south of the area later tonight with showers ending.


Sunday will likely start out quiet, but with plenty of low
clouds. Low pressure will be tracking from the mid-MS valley to
southwest Ontario by late Sunday night. A sfc trof will
establish across the area during the afternoon with PWATs
increasing over 1.5 inches. Widespread convection appears likely
Sun afternoon and evening with potential for flash flooding
especially west of the Blue Ridge given saturated soils.
Convection begins to weaken and shift east late Sun night due to
loss heating and sfc trof shifting east. Convection could
redevelop east of the Blue Ridge Mon afternoon with actual
frontal passage.


Upper level low pressure will be slowly moving across Ontario and
Quebec during the Tuesday through Thursday time frame. While overall
flow will be from the SW to W aloft, there will still be
opportunities for shortwave troughs to dive through the area. It
does appear there will be two additional boundaries following
Monday`s front that will drop southeast through the middle of the
week. The second (likely late Wednesday or Thursday looks to be the
stronger of the two in terms of airmass change. While this pattern
is a little unsettled, rain chances should be scattered and
instability for thunderstorms limited.

Ensemble spread increases toward the end of the weak regarding the
upper air pattern and evolution of the closed low. However, there
should be a dry period at some point as surface high pressure builds
into the area behind the cold front.

Above normal temperatures on Tuesday will decrease through the
remainder of the week behind the frontal passages. Highs will settle
into the 70s with lows in the 50s, which is near normal.


VFR conditions become MVFR in late morning/midday showers for
DC metros and north. KCHO is most vulnerable to t-storms today
with brief MVFR/IFR conditions possible. Widespread convection
Sun evening with flying restrictions likely.

Overall Tuesday and Wednesday should be VFR, but there could be some
scattered showers and perhaps a thunderstorm as weak fronts move
through the area.


Light and variable flow this morning becoming south as weak low
pressure approaches through the day. The weak low crosses the
VA part of the Chesapeake Bay this evening with more variable
flow becoming NEly overnight.

Flow becomes southerly Sunday with a weak cold front moving
through the waters Monday/Memorial Day. Thunderstorms possible
this evening particularly over southern MD waters then again
Sunday night into Monday/Memorial Day as a cold front

Winds are forecast to remain below SCA criteria Tuesday and
Wednesday, although a cold front on Wednesday could lead to slightly
higher winds.


Elevated water levels continue from recent onshore flow. The
immediate DC area is under and advisory until 1pm.

Weak low pressure crosses the Chesapeake Bay this evening with
light southerly flow this afternoon and again Sunday.

Elevated water levels persist through the rest of the holiday
weekend with Straits Point in St. Marys county being the most
susceptible to minor flooding, particularly on the preferred
high tide.




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