Scientific Forecaster Discussion
fxus61 krnk 190416
Area forecast discussion
National Weather Service Blacksburg Virginia
1116 PM EST Thu Jan 18 2018
high pressure shifts from the Gulf Coast states tonight to the
southeast coast by Saturday. This high pressure system will then
linger over the southeast states into Monday before a cold
front enters from the west Monday night into Tuesday.
Near term /through Friday/...
as of 900 PM EST Thursday...
Low temperatures the main concern overnight as winds remain
gusty on the ridges while have decoupled in spots across the
valleys and out east. This continues to make for a wide range in
values from the mid teens in spots to the mid 30s at elevation.
Evening soundings show a 35-40 kt westerly 85h jet that continues
to mix down given such dry air and a very low inversion. Models
show this jet slowly weakening overnight as the high to the
south slips east but enough with possible waves breaking to keep
speeds up past midnight. This should also hold lows in the 20s
along the ridges overnight with some teens elsewhere, as would
only take a short period of lighter winds over snow cover and
low dewpoints for readings to plummet. Therefore only making
small changes to the earlier update of gridded temperatures with
the ongoing advisory/sps for black ice continuing into Friday.
Previous discussion as of 210 PM EST Thursday...
Winter Weather Advisory for refreeze of snowmelt in NC through
Friday morning, per policy agreement with NC EM officials. Rest of
County Warning Area will likely be under a Special Weather Statement to cover
Otherwise, looking at high pressure building in with winds subsiding
this evening but not quite going calm. Still a chilly night with
lows in the teens, but at least wind chills will not be as low given
less wind. One possible concern tonight besides the slick roads
would be fog. With warm advection and somewhat lighter winds over
snow, fog can sometimes form. However, given limited melting the low
levels stay a little dry and winds may stay up enough overall to
restrict fog formation, but still possible, especially in the
We continue to stay in a split flow pattern into Friday with heights
rising and 8h temps rising per warm advection. Under sunny skies,
temperatures should reach into the 40s. We should start to see
better snowmelt Friday.
Short term /Friday night through Sunday/...
as of 115 PM EST Thursday...
This period of the forecast will be highlighted by a warming trend
across the area. An upper level ridge will build across the
southeast U.S., All while the synoptic flow across our region turns
zonal. By the end of this time period, low level trajectories that
clip far western parts of the area will have their origin from
across the western Gulf of Mexico. The result will be moderating
temperatures with eventually increasing clouds by the end of the
weekend, especially across the west, with also the potential for
some isolated showers across the far west by Sunday. By Sunday, high
temperatures will range from the low to mid 50s across the
mountains, and mid 50s to around 60 across the Piedmont.
Long term /Sunday night through Thursday/...
as of 130 PM EST Thursday...
The mild weather will continue Sunday night into Monday in advance
of an approaching cold front. Also, isolated to scattered showers
will start to increase across the area during the day in advance of
this same front. Look for showers to become more numerous Monday
night into early Tuesday morning as the front passes through the
region. While temperatures will decrease behind the front, readings
will still remain above normal for this time of year heading through
the middle part of the week.
After Monday night, our next chance for precipitation will be a
small one Wednesday night into Thursday as a weak disturbance passes
through FL/GA/SC. Otherwise, dry weather is expected as another area
of high pressure builds into the region.
Aviation /04z Friday through Tuesday/...
as of 1115 PM EST Thursday...
VFR to prevail under clear skies through the period. West-
northwest winds will continue to slowly diminish across the
ridges overnight although could still see gusts in the 20-25
knot range into pre dawn hours of Friday along the higher peaks.
These lingering stronger winds above the near surface inversion
may result in low level wind shear in spots across the western
sites for a few hours overnight as surface winds diminish.
As the surface high to the south slides east should see lighter
westerly winds on Friday with speeds generally 10 kts or less
with perhaps a few gusts to 15-20 kts along the ridges during
High pressure will cover the region Saturday through Sunday.
VFR conditions are expected as well as warming temperatures.
Moisture will return to the west Sunday night into Monday night
with sub- VFR conditions possible in low clouds and rain
showers ahead of another cold front. VFR conditions return
during Tuesday as weak high pressure follows the front in from
as of 245 PM EST Thursday...
National oceanic and atmospheric administration weather radio, wxl60 (roanoke transmitter) which broadcasts at
162.475 mhz remains off the air. The phone company continues to
investigate and no estimated time has been given for restoring
this. We apologize for the outage.
NC...Winter Weather Advisory until noon EST Friday for ncz001>006-