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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
358 am EDT sun Oct 23 2016

the mid-Atlantic region will be wedged between surface high
pressure building over the southeast U.S. And deep low pressure
over eastern Quebec today and tonight. Meanwhile, a clipper
system will move across the Great Lakes region today, then
continue east across southern Ontario tonight. The clipper's cold
front will cross the region early Monday, followed by cool high
pressure for mid-week. A low pressure system will approach from
the west late in the week.


Near term /through tonight/...
at 300 am, winds were still strong across the higher elevations
and the warmer waters, with the strongest winds still at gale
force over Tangier Sound. Temperatures were well mixed across the
region, generally in the mid 40s to near 50 in the urban areas;
however, several stations in sheltered valleys such as Stafford,
Warrenton, and New Market have decoupled with temperatures in the
mid 30s.

Today will be another well-mixed windy day; although not as
strong as yesterday, we will likely see gusts 30-40 mph during
peak heating as the strong surface pressure gradient between the
Quebec low and the southeast U.S. High continues. Max temps this
afternoon will be in the mid 60s.

Tonight, a clipper low will cross from the Great Lakes towards
Ontario. Winds will be stronger at higher elevations as a local
Max 850 mb wind speed Max crosses the region per the 00z GFS. There
will be some low level moisture advection that will increase
dewpoints, so min temps will be from the low 40s at higher
elevations and sheltered valleys to near 50 in the urban corridors
to the Chesapeake.


Short term /Monday through Tuesday night/...
on Monday, the clipper's cold front will cross the forecast area
with additional cold air advection. This will keep temperatures
seasonable Monday and Monday night, then about 5 degrees below
normal for Tuesday and Tuesday night. Expect scattered upslope
rain showers on Monday morning on strong northwest flow dragging
moisture from the Great Lakes.


Long term /Wednesday through Saturday/...
a ridge of high pressure will extend from the eastern Great Lakes
to the mid Atlantic and Carolinas on Wednesday, providing mostly
sunny skies albeit still a touch on the cool side. As the ridge
axis slides east Wednesday night and Thursday, warm advection will
increase aloft. Any thermal gains will be mitigated by increased
cloud cover and potential showers from isentropic upglide.

Guidance in better agreement than it was yesterday for the Thursday-
Friday timeframe. The most likely scenario has a shortwave tracking
east from the Great Lakes to the northeast, dragging a surface cold
front across the mid Atlantic. Flow in the mid levels still
remarkably amplified, the extent of which is still up for a little
debate. This suggests there are timing details yet to be ironed out.
Will maintain focus of pops more on Thursday night; would not be
outright surprised to see showers linger into Friday if these trends
maintain some continuity.

Will be in a west/northwest flow pattern on the back side of the
trough late Friday into Saturday. Its still unclear, though, how
much cold air will reside behind the front.


Aviation /08z Sunday through Thursday/...
strong west/northwest winds for all terminals during the day both
Sunday and Monday. No ceiling or visibility restrictions through
the taf period.

VFR Wednesday under high pressure. Showers may approach Thursday
ahead of a cold front. Periods of MVFR possible.


needed to extend the Gale Warning until 4 am as Crisfield was
still gusting to 41kts at 120 am. Otherwise the small craft
advisories will continue through Monday, and possibly through
Tuesday. However, the upper tidal Potomac may not reach criteria
Sunday night and Monday night as some decoupling may be possible.

Light winds under high pressure Wednesday. South flow will increase
ahead of a cold front on Thursday. Small Craft Advisory conditions
would be possible at that time.


Lwx watches/warnings/advisories...
District of Columbia...none.
Marine...Small Craft Advisory until 6 PM EDT Monday for anz530>534-
Small Craft Advisory until 6 PM EDT Monday for anz543.
Gale Warning until 4 am EDT early this morning for anz543.
Small Craft Advisory until 6 PM EDT this evening for anz535-
Small Craft Advisory from 6 am to 6 PM EDT Monday for anz535-


near term...Lee
short term...Lee
long term...heights

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