Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 141456

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
956 AM EST Sun Jan 14 2018

Canadian high pressure will settle over the eastern U.S. today
and then begin to lift out Monday. A clipper system will bring a
cold front through the area Tue night. Low pressure will develop
offshore Wed or Thu followed by moderating temperatures and high
pressure for the late week.


Canadian high pressure will continue to settle overhead
today...bringing dry and cold conditions despite sunshine. Max
temps will be in the 20s for most locations...perhaps close to
30 degrees in central Virginia and in downtown Washington DC.

High pressure will remain overhead tonight. Light winds and dry
air will provide a good setup for radiational cooling. There
will be some high clouds ahead of an upper-level trough over the
Great Lakes into the southeastern CONUS. This may prevent
radiational cooling to some extent...but current thinking is
that the cloud deck will be thin. Therefore...min temps are
expected to range from the single digits in colder valleys and
rural areas to the teens across most other locations.


A potent northern stream system will cause upper-level low
pressure to dig into the northern Plains and western Great Lakes
Monday. This will continue to carve out an upper-level trough to
our west. Shortwave energy and a jetmax well ahead of the
upper-level low will pass through our area Monday while high
pressure slides just to our east. The jetmax will have decent
forcing with it since our area will be in its left-exit region.
However...there is plenty of dry air in place. Therefore...most
areas will just get high and mid-level clouds. A few flurries
cannot be ruled out...especially across eastern areas where
there may be a little more moisture to work with. Chilly
conditions will continue with highs in the upper 20s and lower
30s near Washington and Baltimore.

The upper-level low will slowly pass through the Great Lakes
Tuesday through Tuesday night. This system will be strong enough
for surface low pressure to develop over the same area. The
upper-level trough axis associated with this system will swing
closer towards neutral tilt during this time. A strengthening
jet will cause a band of precipitation to develop Tuesday and it
will slowly move south and east into our area. Exact timing
remains uncertain...but a period of snow is possible especially
later Tuesday into Tuesday night. Snow may mix with sleet/rain
briefly at the onset but the main ptype appears that it will be
snow. Accumulating snow is possible.


Global models have remained consistent showing an upper trof
deepening as it approaches the area Wed inducing weak sfc
cyclogenesis offshore Wed afternoon and night. A period of light
snow appears possible Tue night in the west and in the east Wed as
heights fall across the area and forcing for upward vertical motion
increases with the approach of the upper trof. Some uncertainty
lingers mainly with respect to timing and QPF with the Euro being
slower and snowier than the GFS, but this should be in general a
light QPF event under 0.1 inches water equivalent but with
relatively high SLRs. At the worst case scenario, this could be a
marginal advisory event. Trof axis crosses the area at the latest
06Z Thu, earlier on the GFS with snow ending by midnight Wed night
across far southern MD if not a lot sooner.

Temps begin to moderate quickly on Thu as trof departs and heights
rise quickly. By the end of next weekend, we could be looking at
very mild weather with Euro showing exceptionally high heights.


VFR conditions until at least Tue when the clipper cold front
could bring some light snow and lower cigs and vsbys. Stronger
winds this morning will gradually weaken during the day and Sun

Possible flight restrictions later Tue into Wed in light snow
eastern terminals as cold front, then upper trough, cross the


Small craft advisory conditions will persist today, but winds
will weaken and should be below criteria by late today or later
this evening. After that, lighter winds will be in control until
the clipper cold front passes later Tue.

SCA conditions expected Wed and Thu with possible gales Wed


MARINE...Small Craft Advisory until 5 PM EST this afternoon for
     Small Craft Advisory until 11 PM EST this evening for ANZ534-


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