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Area forecast discussion...updated
National Weather Service Baltimore Maryland/Washington District of Columbia
1017 am EST Sat Dec 14 2019

Synopsis...
low pressure will move northeast of the region today. High pressure
will briefly build overhead for Sunday before low pressure impacts
the area Monday. The cold front associated with this low will pass
through Tuesday.

&&

Near term /through tonight/...

Negatively tilted shortwave-trof will swing through the area
from southwest to northeast this afternoon with last round of
rain expected to move through in the next several hours with back
edge of mid-level dry slot now moving into the southern County Warning Area.
Expect rain into early afternoon and ending last across northern
areas by mid afternoon. Fog will improve rapidly once moderate
rain arrives. Upslope rain showers will turn into snow showers
mid to late afternoon as colder air wraps behind departing low
pressure center. Considering the need for a winter wx advisory
for western Grant and western Pendleton counties for tonight for
the potential of 2-4 inches of snow.

Clouds will gradually burn off overnight on Saturday, with dry
conditions expected, as high pressure builds into the region.
However, will still have some lingering upslope snow showers to
contend with along the Allegheny Front. Low temperatures in the
mid 30s can be expected overnight, except for the higher
elevations of course, who will stay in the mid to upper 20s.

&&

Short term /Sunday through Monday night/...
high pressure will continue to build over our region late
Saturday and through Sunday. Should become mostly clear on
Sunday with some mid to high level clouds lingering along the
Allegheny Mountain range. Temperatures will be warmer in the 40s
to low 50s during the day with cooler temps in the 30s for
Sunday night.

A warm front will lift through our region late Sunday into early
Monday. The shield of precipitation associated with this boundary
will start to affect our area late Sunday evening with outer
portions of the District of Columbia Metro near sunrise on Monday. Areas north and
west of the I-95 corridor may experience periods of wintry mix in
the form of rain, sleet, and snow, with best areas for snow
being northern Maryland, norther Virginia and West Virginia.
Guidance has generally been trending a little cooler, so will
have to continue watching this system for impacts farther south
and east. Still a good bit of variability amongst the models,
and this system will be very dependent on when warm air aloft
arrives, as is often the case. So, won't be getting too specific
with precipitation types at this point.

&&

Long term /Tuesday through Friday/...
cold front will be crossing the area Tuesday. Showers will be ending
with fropa. Once again it becomes an issue of exit of showers vs
arrival of cold air. At this point, will keep all precipitation as
rain, except for a brief period of snow showers in the mountains.

For the rest of the week, a ridge of high pressure will provide dry
albeit cool weather, with highs in the 30s to lower 40s and lows in
the 20s.

&&

Aviation /15z Saturday through Wednesday/...
rain into early afternoon with IFR/LIFR conditions gradually
improving to IFR/MVFR late today. Winds will begin to strengthen
late with gusts to 20 kt developing late today and tonight.

Periods of subvfr conditions likely Monday, as another area of
low pressure impacts the rejoin. Periods of wintry mix expected
for mrb. Iad/dca/BWI/mtn could see some wintry mix as well, but
not as confident at this point there. This will all be in the
morning, before changing to all rain by noon.

Flight restrictions likely in showers Tuesday. Could be some gusty
winds (20-25 kt) too, especially along and behind the passing cold
front. Gusty winds will continue into Tuesday evening, but VFR will
prevail into Wednesday.

&&

Marine...
winds across the waters will gradually increase through the
morning into early afternoon. Small craft advisories have been
issued for all water zones through tonight. Winds will increase
over the central Bay and then spread north throughout the
afternoon. Advisories will likely also be needed into Sunday
afternoon.

Winds begin to die down Sunday evening, and should remain below
Small Craft Advisory criteria through Monday.

Small craft advisories (20-25 kt gusts) likely Tuesday and Tuesday
night. The gradient will relax overnight Tuesday and on Wednesday as
high pressure builds.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory from 4 PM this afternoon to 4 PM EST
Sunday for anz530>532-538>540.
Small Craft Advisory until 4 PM EST Sunday for anz533-541-542.
Small Craft Advisory until 2 PM EST Sunday for anz534-537-543.
Small Craft Advisory from 4 PM this afternoon to 1 am EST
Sunday for anz535-536.
Small Craft Advisory from 10 am to 2 PM EST Sunday for anz535-
536.

&&

$$
Synopsis...heights

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