Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Blacksburg Virginia
746 PM EDT Wednesday Mar 12 2014
Arctic high pressure building in through the night will result in
very cold temperatures and gusty northwest winds through Thursday
morning. Arctic high pressure will pass across the region Thursday
night...with warming temperatures for the weekend.
Near term /through Thursday/...
as of 620 PM EDT Wednesday...
Severe watch 28 cancelled as line of gusty showers/storm have
moved east of the County Warning Area. Will be dealing with Arctic air rushing in
and already getting snow as far east as the higher elevations
of central Grayson...and the NC mountains adjusted probability of precipitation to clear the
east faster and have limited snowfall early in the west. No other
headline changes at this time...as winds will continue be strong
as higher pressure rises are still northwest of US.
Previous valid discussion...
The cold front will exit our area for the coastal plain by early
evening...leaving a 10+mb pressure gradient setup across our
region by this evening as Arctic high pressure builds in from the
west. This tight pressure gradient...with support from the base of
an upper level trough passing overhead...will support occasional
60 to 65 miles per hour gusts late this evening through the early morning
hours of Thursday...particularly along the higher ridgelines. As
such...the High Wind Warning remains in effect for the mountains
and foothills. Winds are not expected to be as strong across the
lower elevations of the Piedmont...and therefore have a Wind
Advisory in effect through early Thursday morning.
In addition to the strong winds...very cold air will also build
into the region such that overnight lows will range from the low
teens in southeast West Virginia...to the middle/upper 20s across
north central North Carolina. These chilly temperatures combined
with the gusty winds will result in very cold wind chills west of
the Blue Ridge...falling into the -5f to -15f range by sunrise
Thursday. As such...have a Wind Chill Advisory in effect for our
mountain counties. Will also see snow showers develop this evening
for our western upslope areas...with 2 to 3 inches of snow for
western Greenbrier County. 1 to 2 inches can be expected across
portions of the remainder of southeast West Virginia...the
mountain Empire and the North Carolina mountains.
By late morning Thursday...the pressure gradient will relax enough
that wind speeds will be significantly lower across our area...
although remain occasionally gusty...and snow showers will come
to an end across the mountains. Arctic air in place will remind US
that it is still officially winter...as highs will struggle to
reach the freezing mark across the mountains...and will warm into
the low 40s across the Southside.
Short term /Thursday night through Friday night/...
as of 300 PM EDT Wednesday...
High pressure tracks over the region Thursday night. Cold dry air
under good radiational cooling conditions will allow the
temperatures to drop into the 20s across the area. Western slopes
and higher elevations with snow on the ground could drop back into
the teens. The wind and wind chills will not be a factor Thursday
night with high pressure over the region.
Surface high pressure drifts off the Carolina coast Friday.
Southwest low level flow and zonal flow aloft will bring back warmer
temperatures on Friday...possible approaching seasonal levels. With
this warmup...24 hour temperature change from Thursday afternoon
into Friday afternoon could be on the order of 20 degrees.
Long term /Saturday through Wednesday/...
as of 320 PM EDT Wednesday...
Could Thursday be the last attack of winter weather for the season?
March into April is a season transition time where we could have
warm temperatures for a few days...then cold again for a day or two.
The good news is that with the higher sun angle and warmer air
advancing farther north...the duration of cold spells will be brief.
The chances for wintry precipitation also exist...but the odds of a
significant snow or ice event is on a decline but not out of the
question...ie March 1993.
With that said...a weak cold front is expected to track over the
area Saturday night and stall over North Carolina Sunday. Waves of
low pressure will track along this front...keeping the chances for
precipitation high starting Sunday night. An upper level trough
will move out of The Rockies and over the southern plain states
Saturday night into Sunday. A stronger wave of low pressure is
forecasted to track along the Gulf states Sunday and off the
southeast coast Monday morning. Meanwhile across the north...high
pressure will wedge down the East Coast Sunday into Monday. Models
do look similar to the last weeks March 6-7 2014 event. The GFS
keeps bulk of the precipitation south of the area. The ecm has the
higher precipitation amounts over the area Sunday afternoon/night
from overrunning and with a deformation zone pivoting over the
mountains Monday morning. At this time...thermal profiles support
mainly snow in the northern half with a wintry mix over the
southern half. Will trend temperatures colder while keeping
weather element as rain Sunday transitioning to snow early Monday.
We will get into more details of this system as the forecast
becomes more clear and models hopefully become in agreement.
Outside of the Sunday-Monday event...the weather pattern is quiet
with near normal temperatures.
Aviation /00z Thursday through Monday/...
as of 740 PM EDT Wednesday...
Winds will be the aviation issue through the period...but
especially tonight into early Thursday morning. Surge of Arctic
air from the northwest will bring a period of strong winds. Gusts
up to 45 to 50 knots is not out of the question...but most of
time...gusts will range from 30 to 40 knots...and sustained around
20-25 knots from the northwest. MVFR ceilings will stay sitated over
blf/lwb/bcb going into the evening...with scattering to VFR by
early Thursday morning in bcb...and toward middle morning lwb/blf. A snow
shower or two could affect blf/lwb with small window of MVFR vbsys
but period of time to low to add to tafs.
Winds will start to wind down Thursday afternoon.
Thursday night...high pressure will settle over the area and
bring a decrease in wind speed and a return to VFR conditions for
the entire area. Another weak cold front will drop through the
region during the weekend with sub-VFR possible over the south and
west as deeper moisture with yet another low pressure system
spreads east along the front by Sunday. This system has the
potential for extended period of sub VFR into Monday as the low
deepens off the coast.
dry conditions will linger in the wake of a strong cold front
passing across the region this afternoon. Relative humidity
values will quickly become critical east of the mountains during
the day Thursday. In addition...windy and gusty conditions will
remain through the day and greatly enhance fire danger.
Virginia...High Wind Warning until noon EDT Thursday for vaz007-009>020-
Wind Chill Advisory until noon EDT Thursday for vaz007-009>020-
Fire Weather Watch from Thursday morning through Thursday
afternoon for vaz032>035-043>047-058-059.
Wind Advisory until 4 am EDT Thursday for vaz043>047-058-059.
NC...High Wind Warning until noon EDT Thursday for ncz001>003-018-
Wind Chill Advisory until noon EDT Thursday for ncz001-002-018.
Fire Weather Watch from Thursday morning through Thursday
afternoon for ncz003>006-019-020.
Wind Advisory until 4 am EDT Thursday for ncz004>006-020.
WV...High Wind Warning until noon EDT Thursday for wvz042>045.
Wind Chill Advisory until noon EDT Thursday for wvz042>045.