Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 041425
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
925 AM 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/...
Main weather issue this morning has been areas of fog, locally
dense, along the Chesapeake Bay and lower Tidal Potomac. This
should gradually lift with visibilities improving through the
morning hours.

Otherwise, cirrus will continue to spread east this morning and
through the day, although should see some thinning by later this
afternoon. Highs will top out in the low to mid 50s. Plenty of
high clouds tonight, then stratus clouds expected to develop
late tonight into Tue morning with some guidance showing light
precip developing after 09Z east of the Blue Ridge, but most
precip should hold off until after 12Z Tue. Mild with lows in
the 40s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Plenty of moisture will spread nwd on Tue ahead of sharp cdfnt
with PWATs expected to rise as high as 1.5 inches or nearly 275%
of normal. Widespread showers expected ahead and along sharp
cdfnt Tue afternoon and evening. Despite very high moisture
content, QPF totals will be somewhat limited due to very
progressive movement of front with amts ranging from 0.25 to 0.6
inches. Showers will end quickly with fropa after midnight Tue
night. Over the mtns, sfc trajectories will be more from the
west as opposed to NW with low-levels drying out rapidly. Only
expecting a trace of snow accumulation over the mtns. Turning
chillier Wed-Wed night as front pushes well south and weak high
pressure builds in.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Upper level troughing will amplify over the Ohio Valley Thursday
into Friday, causing early season cold to plunge southward from the
Arctic towards the Mid-Atlantic. A piece of southern stream energy
will eject into the western Atlantic Ocean Friday, inducing surface
cyclogenesis east of the Carolinas. Current model forecasts tend to
keep this energy sheared out and thus the surface low tracks well
offshore. However, highly meridional (north to south) upper level
flow, with a very strong ridge positioned near 120 W longitude
during this time argues there is room for error in this forecast
track. This time period bears watching in the coming days.

Deep upper troughing lingers over the eastern U.S. through the
weekend, with several clipper-like waves of energy riding around it.
This would tend to favor a scenario of (potentially disruptive) snow
showers or squalls over the weekend as opposed to widespread heavy
snow. It also results in reinforcing shots of cold Arctic air
through at least early next week, and possibly well beyond (see CPC
8-14 and Week 3-4 Outlooks). Leaned on colder model 2-meter
temperatures as opposed to statistical MOS guidance which was warmer
and tends to lean on climatology too much at the long range in an
a-climatological setup such as this.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
Some MVFR being observed this morning in light fog at MTN/BWI,
but expecting improvement after 15z or so. Otherwise VFR with
cirrus through the remainder of today. Stratus clouds then begin
to develop over eastern terminals late tonight into Tue morning
with sub-VFR cigs developing. Widespread showers expected Tue
into Tue night with cdfnt. Fropa expected around 03Z Wed with
showers ending by 12Z Wed. IFR cigs possible Tue-Tue night with
showers.

Sub-VFR possible in any snow showers that develop late this
week into the weekend. Otherwise NW flow AOB 10 knots Thu-Fri.

&&

.MARINE...
Areas of dense fog being observed this morning will gradually
dissipate by noon. Otherwise winds less than 10 kts through
this evening. Winds begin to strengthen late tonight across the
southern waters as winds turn more SSE or SE. SCA winds expected
across all waters by Tue afternoon and behind frontal passage
late Tue night into Wed. Winds will begin to diminish Wed
morning and should drop below SCA by midday Wed.

Winds become light (10 knots or less) Thursday into Friday
as transient high pressure moves overhead. Low pressure will likely
scoot by to the south and east later Friday, with multiple clipper-
like systems bringing in blustery NW flow and SCA conditions over
the weekend.

&&

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

&&

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

&&

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



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