Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 210653

Area Forecast Discussion
National Weather Service Blacksburg VA
253 AM EDT Wed Mar 21 2018

A complex area of low pressure across the region will
consolidate offshore this morning before deepening and heading
north along the Mid-Atlantic coast this afternoon. The system
will finally pull moisture out of the region later tonight into
Thursday as it continues to strengthen while passing off New England
by Thursday morning. High pressure briefly returns to the
region on Friday followed by another potential winter weather
system over the weekend.

As of 225 AM EDT Wednesday...

Latest radar trends show that precip across the region has
become more spotty/banded in nature with a long band lingering
along the Blue Ridge while some spots have switched back to rain
where precip has become lighter. This likely due to some weak
subsidence in the wake of the meso low that brought the initial
batch of heavier snow/sleet before midnight. Otherwise not a lot
of change to going headlines with the upper low now west of the
mountains progged to cross the region this morning allowing the
surface low off the Va capes to deepen while heading slowly
north by this afternoon. Expect once this happens and the flow
becomes more northwest, will see snow increase across the
western ridges per enhanced upslope with some filling in
elsewhere of at least light snow as the transition takes place
and the conveyor belt of deeper moisture swings back south for a
bit. This supports continued heavy snow espcly north/northeast
sections to along the Blue Ridge. Elsewhere questions about
coverage southern sections before things get too warm this
morning and along the I-77 corridor where currently see some
rain and where the HRRR leaves a void this morning. Otherwise
will continue with high pops early this morning, then tapering
central/west after midday as downsloping increases and lift in
the deformation zone quickly shrinks away to the north. This
should lead to only a few bands of snow/rain remaining by mid to
late afternoon except for continued upslope snow showers in
spots. Kept highs below mos although a late day surge could
occur southern sections where snow will be less.

System wraps up well to the northeast overnight allowing the
pressure gradient to ramp up on strong cold advection around the
deepening coastal system. This likely to bring advisory level
winds to the Blue Ridge given a decent jet aloft and packing of
isotherms along the mountains. Therefore will continue to wrap into
the current warning for now. However upslope snowfall looks to
wane after midnight as things dry from aloft and the flow turns
a bit more northerly. This supports trimming back on pops and
added amounts overnight out west with clouds lingering until
late elsewhere. Lows quite cold with most in the 20s making for
wind chills in the teens or perhaps single digits by morning.

As of 245 AM EST Wednesday...

Better subsidence arrives Thursday as we slide in between the
exiting low to the northeast and the next upstream system
organizing to the northwest. However appears overall clearing
may be slow on Thursday given some trapped low level moisture
and containing strong upslope flow in the west. Therefore kept
highs on cool side of guidance pending the degree of insolation
that develops espcly east where could jump into the 50s with
upper 30s to 40s elsewhere.

Models also show a 85h 40 knot jet persisting across the
mountains into Thursday as expect wind advisory speeds may
linger at least during the morning given the degree of
subsidence. Also below guidance for highs on Thursday where
little to no sunshine expected.

Will gradually see some warm advection kick in on Friday just in
advance of the next upstream system that may bring back high
clouds during the day and lowering cloud bases from northwest to
southeast Friday night. Some spotty light rain or snow could
also work in far western sections late but likely wont include
for now. Highs again mostly 40s to low 50s.


As of 140 PM EST Tuesday...

Low pressure tracks from Missouri on Saturday night, across the
Tennessee Valley and Carolinas to the western Atlantic by Sunday
night. Some differences in the guidance how far south this low will
move, which in turn will impact where the winter weather will be on
the northern side of the baroclinic zone. Timing has been
consistent, keeping the best probability of precipitation from
Saturday afternoon into Sunday morning.

Surface high pressure wedges down the east slopes of the
Appalachians Monday and Tuesday. Precipitation over the Tennessee
and Ohio Valley may spill east into the mountains but the
probability remains low. Temperatures will remain below normal
through the period, especially daytime highs.


As of 1250 AM EDT Wednesday...

Poor flying conditions to continue overnight with widespread
sub-VFR in snow and mixed precipitation including mountain
obscurations. This system will linger into Wednesday and
overall looking at sub-MVFR conditions through at least midday
Wednesday before winds shift to the west and northwest which
should bring steady precip to an end with more showery nature
though snow showers will persist into the afternoon along/west
of the mountains, with rain/snow shower mix in the east.
Cigs/vsbys anticipated to at least go MVFR Wednesday afternoon
outside of the WV mountains.

Northwest winds are expected to become gusty in the afternoon
with a few gusts over 30kts not out of the question.

Extended Aviation Discussion...

Wednesday night into the daytime Thursday, the upslope snow
showers will continue to gradually decrease in coverage with
northwest winds remaining strong until Thursday night.

Mainly VFR conditions are expected by Thursday night through
Friday night.

Saturday into Sunday, a return to sub-VFR conditions is expected
as our next potential winter weather system crosses the area.


As of 335 PM EDT Monday...

The Mount Jefferson NWR remains off the air. The radio unit
needed to repair the system is expected to arrive on Wednesday.
The earliest this system will again be operational will be
Wednesday afternoon.


VA...Winter Storm Warning until 8 AM EDT Thursday for VAZ007-
     Winter Weather Advisory until 6 PM EDT this evening for VAZ032-
     Winter Storm Warning until 6 PM EDT this evening for VAZ034-
NC...Winter Storm Warning until 8 AM EDT Thursday for NCZ001-002-
     Winter Weather Advisory until noon EDT today for NCZ003>006-
WV...Winter Storm Warning until 8 AM EDT Thursday for WVZ042>044-


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