Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 171632
Area Forecast Discussion
National Weather Service Blacksburg VA
1232 PM EDT Fri Mar 17 2017
High pressure over the region will shift offshore this afternoon
ahead of a warm front approaching from the south. This front
will lift northeast through the area overnight before a trailing
cold front pushes across from the west during Saturday. High
pressure will follow the front on Monday, then another
cold front crosses the Mid Atlantic region Monday night.
.NEAR TERM /THROUGH TONIGHT/...
As of 955 AM EDT Friday...
12Z soundings and corresponding surface observations continue
to show very dry air in place this morning ahead of deeper
moisture quickly advancing in from the west. This precip remains
along the leading punch of deeper warm advection aloft and
aided by low level isentropic lift ahead of the surface warm
front to the south. Latest HRRR continues to bring an initial
swath of precip into the far west shortly after noon with the
more widespread coverage holding off until late in the day per
dry air in place. Thus have sped up the onset of at least spotty
precip northwest despite dry air while beefing up clouds and
eastward expanse of higher pops by early this evening given
lift. Other concern with possible frozen precip, mainly over
Greenbrier and Bath counties, as guidance shows a delay in
exodus of the colder 850 temps later, while also expecting some
evaporative cooling espcly if precip arrival is a bit sooner.
This supports including a bit more sleet to snow over the far
northwest before all go to rain as warm advection aloft wins out
by this evening. Faster arrival of mid deck likely to put a
damper on temps espcly west to start. Therefore lowered highs
Blue Ridge west a few degrees for now, and left mostly 50s east,
where should see a bit more sun per deep downsloping flow off
Previous discussion as of 410 AM EDT Friday...
Closed low develops today over the western Great Lakes and moves
southeast. Relative humidity forecast from the models bring moisture
in above 700MB ahead of warm front approaching from the west. These
high clouds will reach the central Appalachians around 15Z/11AM. Low
level moisture does not arrive in the mountains until after 18Z/2PM.
Surface high pressure was overhead early this morning. This high
will move southeast today and will be off the southeast coast this
evening. Surface winds will turn southwest once the high moves
offshore and the warm front goes through.
Not seeing much support tin the forecast temperature profiles
for cooling enough for snow. Only the Elkins WV Bufkit sounding
showed the potential for snow this evening. Have removed nearly
all the snow from southeast West Virginia for this evening and
overnight. Used mainly the MET for guidance on high temperatures
today. Stayed on the warmer side of guidance since the area
will be south of the warm front tonight.
.SHORT TERM /SATURDAY THROUGH MONDAY/...
As of 300 AM EDT Friday...
A quasi-stationary surface front will reside over the foothills and
piedmont Saturday. The front does not slide south of the area until
the upper low over Lake Erie begins to track to the southeast
Saturday night. With the slower movement and exit of the front
Saturday evening, cold air will lag behind and so will the change
over from rain to snow across the mountains. Models are some what in
agreement with liquid precipitation amounts that when the P-type
does become snow, one to two inches may accumulate along the western
slopes of southeastern West Virginia late Saturday night into Sunday
morning. Temperatures are not expected to be too cold with readings
from the mid 20s along ridgetops to lower 30s across most mountain
valleys. Majority of the snow should melt on roadways overnight as
Saturday afternoon temperatures will warm into the 50s west of the
Blue Ridge. Also as low pressure moves off the Mid Atlantic coast
and high pressure enters the Ohio Valley, a pressure gradient will
sit over the area Saturday afternoon into Sunday morning. This will
bring breezy and gusty conditions to the area but speeds will not
reach advisory criteria.
Cool high pressure builds over the region Sunday. Sunday afternoon`s
temperatures will be close to normal with 40s across the mountains
and 50s east. High pressure will sit overhead Sunday night which
will allow temperatures to radiate down into the 20s and 30s.
Temperatures will warm into the 60s Monday following the exit of
high pressure and the passing of a warm front.
.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
As of 245 PM EDT Thursday...
On the heels of our weekend cold front, will be yet another cold
frontal passage Monday night into Tuesday, with a weak warm front
preceding it on Monday. Anticipate another round of patchy light
rain on Monday, before a switch to rain showers Monday night. Enough
cold air may arrive by Tuesday morning for a rain/snow mix across
western Greenbrier Co, WV. The front is expected to head south of
the area by Tuesday evening, with limited showers remaining across
the southern half of the area Tuesday afternoon into the evening
After only another small break in the activity, another warm front
is progged to lift north across the area Wendesday night into
Thursday. This one will be different from the previous. Its parent
low will have Pacific origins and will be making its way into the
central portion of the country. We may have a precipitation type
issue at the onset of the event based upon some of the early looks
at model low level thermal profiles. At this point, we will keep the
forecast simple with a basic rain versus snow forecast, with a
surface temperature of 32 degrees or less the determination for rain
Temperatures during this portion of the forecast will average around
five degrees below normal.
.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --As of 1230 PM EDT Friday...
VFR will gradually give way to deteriorating conditions from
west to east this afternoon into this evening as lowering cigs
and bands of precip spread east ahead of a warm front to the
south. May also see periods of MVFR in rain/sleet around KBLF
and perhaps a wintry mix at KLWB this afternoon before finally
switching to all rain this evening. Rain will also be spreading
toward KBCB/KROA where some sleet could also occur this
afternoon but thinking mostly VFR until more widespread rainfall
with the upstream cold front arrives this evening. Ceilings
will continue to lower overnight with MVFR/IFR across much of
the west and perhaps a period of MVFR east of the ridges this
evening/overnight. Also expecting a few hours of MVFR vsbys in
rain/fog mountains overnight and brief low end to MVFR out east.
The low level jet increases into the 50 knot range south of the
warm front which could lead to spotty LLWS. Since quite
isolated and mostly late tonight wont include mention for now.
Cold front moves across the region during Saturday resulting in
improving conditions espcly by afternoon from the Blue Ridge
east. Uncertainty remains over the west given developing upslope
northwest flow behind the front but for now appears there could
be a window of MVFR to even VFR at KBLF/KLWB before colder air
aloft arrives late in the day.
Extended Aviation Discussion...
Gusty post frontal northwest winds along with upslope western
mountain snow showers will develop Saturday night and continue
into part of Sunday. Best chances for sub-VFR with snow showers
at KBLF and perhaps KLWB will be Saturday night into Sunday
morning. High pressure building in on Monday should yield VFR
all terminals to start the week. However moisture ahead of
another cold front and associated weak low pressure may arrive
by Monday night, with sub- VFR possible later Monday night into
early Tuesday before improving conditions take shape into
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