Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 041919
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
219 PM EST Mon Dec 4 2017

.SYNOPSIS...
High pressure will shift east of the area today. A
strong cold front will move through the area Tuesday night. Weak
high pressure returns to the area Wednesday and holds through
the end of the week. A coastal low pressure may pass east of the
area late in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A mix of sun and high cirrus is out there this afternoon with
light southeasterly flow. This has allowed temperatures to rise
into the 50s this afternoon across the majority of the region.

Southeasterly flow will continue tonight in the very low levels,
allowing for a marine air mass to be advected across portions of
the region. At the same time, southwesterly flow and warming
temperatures will move in aloft. Expecting plenty of high
clouds to start the night, with the potential for low stratus to
overspread areas from the Blue Ridge eastward late tonight and
into Tuesday morning. There may also be some fog/drizzle along
with a few showers towards morning. Temperatures will be milder
than previous nights with the return of clouds/moisture, so
lows generally in the upper 30s to mid 40s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
We`ll likely start the day with a stratus deck in place from the
Blue Ridge eastward, with the potential for some fog, drizzle,
or light showers. To the west, a cold front will be advancing
towards the area and rain showers will be increasing from west
to east through the morning, approaching the DC/Baltimore metros
later in the afternoon. South/southwest flow will also be
increasing through the day ahead of the front with some gusts up
to 25 mph developing by the afternoon. We should see one more
day of above normal temperatures before the frontal passage,
with highs in the 50s to around 60F.

Widespread rain showers will continue along and ahead of the
front this evening and tonight. Expecting frontal passage to
occur during the overnight and early Wednesday morning hours,
with winds turning westerly following passage. The rain may end
as some light snow showers across the higher terrain, but not
much in the way of accumulation expected as setup not that
conducive for continued upslope precipitation. Lows by Wednesday
morning in the 30s and 40s.

Default ridging noses back in overhead for Wednesday. Drying
westerly flow is expected with highs ranging from 40 to 50F, and
lows Wednesday night in the 20s/30s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
A deep upper level trough will be amplifying over the eastern
CONUS Thursday into Friday. The trough axis will be pushing off
of the east coast sometime on Sunday. Temperatures will be well
below normal with this cold air mass through this period.

Attention through this period is now focused on the
Friday/Saturday forecast as waves of low pressure track along
the baroclinic zone to our southeast along the coastline.
Southern stream energy may induce cyclogenesis off of the NC
coast while it moves northeast into Saturday and away from our
region. Uncertainty remains high, but with ECMWF solution,
precipitation would be most likely across our southeast.

On the other hand, 12Z GFS keeps the frontal zone further
southeast from our region but with some light precipitation
over parts of our CWA Friday into Monday as pieces of upper
level energy or clipper- like systems move over our area. GEFS
members are distributed between the two scenarios. Significant
snow is not likely with either scenario, but as with any winter
system, keep an eye on it.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Predominantly VFR expected through the rest of today with
cirrus streaming overhead. Stratus clouds then expected to
develop over eastern terminals late tonight into Tue morning
with MVFR and potentially IFR ceilings developing. Some light
fog/drizzle also possible. The greatest chance of IFR conditions
expected in the 12-15z timeframe.

Additionally, south/southwest winds will be increasing aloft,
and low level wind shear may become an issue with FL020 winds
about 40 knots.

Widespread showers will then overspread the terminals Tuesday
afternoon through Tuesday night with a cold front. Additional
sub-VFR conditions likely. VFR will return during the day
Wednesday and persist into early Friday.

Sub-VFR conditions possible Friday night into Saturday as some
precipitation could move through the terminals.

&&

.MARINE...
Winds less than 10 kts expected through this evening. Winds then
begin to strengthen late tonight across the southern waters as
winds turn more SSE or SE with. SCA winds expected across all
waters by Tuesday afternoon and behind frontal passage late
Tuesday night into Wednesday. SCA winds may continue into
Wednesday night.

Winds may remain near SCA criteria Thursday before falling below
by Thursday night and Friday.

&&

.TIDES/COASTAL FLOODING...
Water levels are expected to rise Tuesday
as surface winds strengthen. Minor coastal flooding is possible
at times of high tides Tuesday afternoon and Tuesday night.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 7 AM Tuesday to 6 AM EST Wednesday
     for ANZ530>533-537>542.
     Small Craft Advisory from 4 AM Tuesday to 6 AM EST Wednesday
     for ANZ534-543.
     Small Craft Advisory from 1 PM Tuesday to 6 AM EST Wednesday
     for ANZ535-536.

&&

$$
SYNOPSIS...MM
NEAR TERM...MM
SHORT TERM...MM
LONG TERM...IMR
AVIATION...MM/IMR
MARINE...MM/IMR
TIDES/COASTAL FLOODING...LFR/MM



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