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Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
325 am EST Mon Dec 16 2019

high pressure will push offshore this morning as a warm front
remains stalled across southern Virginia. Low pressure will move
along this boundary across the area Tuesday. High pressure will
build over the region for the end of the week.


Near term /through tonight/...
a early stationary boundary remains across the Tennessee Valley
and southern Virginia early this morning. With ample lifting
mechanisms, a band of snow has developed, mainly Winchester-
Washington District of Columbia and points north. Its been a bit too warm for much
to stick yet, but with wet bulb cooling, anticipate that will
come soon.

The p-type forecast remains tricky today. While much of the
ongoing precip is snow, low level temperatures are mostly above
freezing, and temperatures aloft will be warming. Thus, we're
looking for a change over to sleet, and then rain...with
freezing rain where low level cold air remains trapped. Latest
href runs generally match current forecast evolution, and thus
have not changed much in that regard. The only concern is
whether there is too much emphasis on freezing rain in central
Virginia based on current temperatures.

By noon, most locations will be seeing just rain, with perhaps
northern Maryland and the northern Shenandoah valleys as the
exceptions. Further, most guidance sources suggest there will be
a bit of a lull in precipitation between shortwave impulses. For
that reason, will not be extending advisories beyond 1pm at this

In summary...a Winter Weather Advisory is in effect for immediate
Metro Baltimore, the farther northern and western suburbs of
Washington/Baltimore and for locations near/west of the Blue
Ridge and catoctin mountains. A Winter Storm Warning is in
effect for western Allegheny and western Mineral counties where
several inches of snow are expected before changing to ice from
freezing rain.

A stronger disturbance will approach this evening, causing
steadier precipitation to break out once again. During this
time, most areas will be rain, but freezing rain is expected
across western Maryland and western Mineral County in WV. Freezing
rain may also hang on for the higher elevations near the Mason-
Dixon line into the Potomac Highlands. Winter headlines may have
to be adjusted near the Mason-Dixon line into the Allegheny and
Potomac Highlands due to the possibility of freezing rain.
Confidence is too still low to do so at this time.


Short term /Tuesday through Wednesday night/...
the stronger wave of low pressure will pass through Tuesday
morning. Steady precipitation is expected across much of the
area during this time, with the heavier precipitation amounts
most likely across the northwestern half of the County Warning Area (wash/balt
Metro areas north and west).

The low will move off to the northeast Tuesday afternoon and
drier air will slowly filter in from the northwest.
Precipitation will diminish for most areas, but a few showers
may persist. Snow showers are possible along/west of the
Allegheny Front.

High pressure will approach Tuesday night, bringing blustery and
cold conditions...which will continue into Wednesday.


Long term /Thursday through Sunday/...
the long term period will feature an extended period of quiet
weather across the region. We'll have gusty winds out of the
northwest on Thursday. These winds should gradually relax through
the day as high pressure builds in from the west. Temperatures will
be cold on Thursday, with temperatures only recovering into the 20s
to low 30s after starting the morning out in the teens to low 20s.
With high pressure in control, sunny skies are in the forecast

High pressure will translate off to the east on Friday, leading to a
moderating trend. Dry condtions are forecast, with high temperatures
in the low 40s for most. A disturbance will approach the area from
the west on Saturday. While a few showers can't be ruled out with
this disturbance, the vast majority of both deterministic and
ensemble guidance keeps conditions dry. The aforementioned
disturbance should depart off to our east on Sunday, leading to dry
conditions. Temperatures should finally recover to around normal,
with highs in the mid 40s.


Aviation /08z Monday through Friday/...
flight conditions will gradually deteriorate this morning as
light snow develops. Low ceilings will be the primary culprit,
but expect vsby restrictions in periods of snow through the
morning push. Precipitation type will be tricky...but will
generally feature a transition from snow to sleet/freezing rain
and then rain. Believe all terminals will be rain by noon except
perhaps mrb. (Mixed precip will hold on the longest Metro
baltimore). Low ceilings (subifr) will extend into Tuesday.

Low pressure will cross the terminals during the day on Tuesday.
In the wake of this low, conditions will improve, but with gusty
winds, which will extend into Wed.

VFR conditions are expected through the latter portions of the
upcoming week. Winds will be gusty out of the northwest Thursday
morning, before gradually relaxing through the remainder of the week.


winds have dropped below small craft thresholds, and will remain
that way until low pressure pushes past the area on Tuesday.
Behind the low, solid Small Craft Advisory conditions anticipated through
Wednesday. Small Craft Advisory level winds appear likely on
Thursday in northwesterly flow. Winds should gradually subside
to sub-Small Craft Advisory levels Thursday night and remain below Small Craft Advisory-levels
through the remainder of the week.


Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...Winter Weather Advisory until 1 PM EST this afternoon for
Winter Storm Warning until 7 PM EST this evening for mdz501.
Winter Weather Advisory until 10 am EST this morning for
Virginia...Winter Weather Advisory until 1 PM EST this afternoon for
WV...Winter Weather Advisory until 1 PM EST this afternoon for
Winter Storm Warning until 7 PM EST this evening for wvz503.



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