FXUS61 KLWX 271142

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

High pressure overhead this morning will move
offshore later today. A wave of low pressure will move across
the area this afternoon or evening pushing 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.


Weakening t-storm complex over SW PA this morning is associated
with a low pressure system over Ohio. Weakening showers will
move across northern portions of the CWA through the rest of the
morning. The low pres center will move east across the area
this afternoon or this evening and will set up a warm front
across the southern half of the fcst area. NSSL WRF- ARW and
instability fcst fields from different models indicate the area
from Augusta county south and east through Charlottesville will
be the prime area for strong potentially severe convective
development later this afternoon and early this evening.
Damaging winds and large hail appear to be the main threat.
0-6km flow around 30kt should keep storms moving with flash
flooding risk low despite saturated soils and potential training
convection. The low pres system 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 morning 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.

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 will see minor flooding with the preferred
high tide mid-morning and an advisory is out through midday.

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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