Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 231453

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1053 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. A clipper system will cross
the Mid Atlantic region Monday morning, followed by high pressure
for mid-week. Low pressure will approach from the west late in
the week.



Today will be another well-mixed windy day; although not as
strong as yesterday, we will likely see gusts 30 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 H85 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.


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. Tuesday night lows look to be in
the mid 30s along the Mason-Dixon Line and west of the Blue Ridge
bringing the possiblity of frost.


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.


Strong west/northwest winds for all terminals during the day today
and Monday. No ceiling or visibility restrictions through the TAF

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


Small Craft Advisories 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.


MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ530>534-
     Small Craft Advisory until 6 PM EDT this evening for ANZ535-
     Small Craft Advisory from 6 AM to 6 PM EDT Monday for ANZ535-


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