Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 181148
Area Forecast Discussion
National Weather Service Blacksburg VA
748 AM EDT Sat Mar 18 2017
Low pressure was over Michigan this morning with a warm front
that was moving north over West Virginia and Virginia and a
cold front that trailed into the Mid Mississippi Valley. The
cold front will cross east through the Mid Atlantic region
today. High pressure will follow the front for Sunday and Monday
then another low pressure system and series of fronts will move
through the region on Monday night and Tuesday.
.NEAR TERM /THROUGH TONIGHT/...
As of 450 AM EDT Saturday...
Short wave tracking into northern Kentucky was triggering
showers and a few thunderstorms across Tennessee and North
Carolina. Radar trends since 2AM have been for decreasing
coverage of precipitation over West Virginia and Virginia.
Expect showers to diminish even across North Carolina by around
12Z/8AM. Then there will be a break before the next chance of
A cold front extended from a low in Michigan to northern
Arkansas. This front will move east today and will be pushing
off the Virginia coast this evening. HRRR indicated showers and
isolated to scattered thunderstorms will develop ahead of the
front from northeast Tennessee to southwest Virginia, while the
RAP and other guidance had the precipitation developing just
east of Lynchburg and Danville. With this spread in possible
locations, have added a chance of precipitation across much of
the area this afternoon. Upper low moving out of the great lakes
will provide cooler air aloft today and therefore larger lapse
rates, especially with any heating. Models showed CAPES around
400 J/Kg this afternoon with Lifted Index values as low as -4.
Guidance also showed a large difference in solutions for maximum
temperatures today. Since area will be in the warm sector for
part of the day and some sun will break through later this
morning have leaned toward warmer guidance which was well
represented by the Hi-Resnmm and Hi-Resarw.
Best advection of colder air will be late tonight. Pressure
rises and cold air advection support gusty wind. Also tonight
low level moisture remains banked up along the western slopes
of the Appalachians. Temperatures will be cold enough for snow
but lack of depth of moisture makes dendritic crystal growth
more questionable. Liquid equivalent precipitation amounts
remain less than one quarter inch. Snow accumulations of any
consequence will be confined to Western Greenbrier County.
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 330 AM EDT Saturday...
An upper level low will track off the Virginia coast Sunday morning.
Until this low departs, short waves tracking around it will bring
upslope snow showers to western slopes of SE WV/SW VA through most
of the morning. Once this low moves out to sea in the afternoon, a
chilly surface high will build over the region and end northwest
upslope snow showers. High temperatures Sunday will vary from the
mid to upper 40s across the mountains to mid to upper 50s east into
the piedmont. This high will be centered over the area Sunday night.
Under mostly clear skies and light winds, temperatures will radiate
down into the upper 20s to lower 30s.
This area of high pressure will sink south to the Gulf Coast during
the day Monday. Meanwhile, a warm front will track across the Ohio
and Tennessee Valleys Monday and Monday night. By late in the day,
this warm front and a lee trough will help bring in a few scattered
showers across the mountains. Mountain showers may persist into the
night as a cold front approaches the area from the north. The best
chance for widespread showers will come Tuesday as the cold front
moves over the region. Rainfall amounts should remain light Monday
afternoon and night as high pressure blocks moisture from returning
from the Gulf. Temperatures Monday will warm into the 60s and
overnight remain mild in the 40s.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 400 PM EDT Friday...
The cold front should move from northwest to southeast over the CWA
on Tuesday. Meanwhile, another upper level trough will dig southward
from eastern Canada to bring colder air behind the frontal passage.
If the cold air arrives quickly enough, it could change the rain to
snow in the higher elevations of southeast West Virginia and the
northwest North Carolina mountains by Tuesday night. Cold air
advection will continue through Wednesday as a strong high pressure
area builds southeastward from the Great Lakes. Once overhead by
Wednesday night, expect another cold night with temperatures well
below freezing. This high should slide eastward toward the coast on
Thursday, and the numerical models hint that some wedging may occur
east of the Blue Ridge. A warm front will also approach from the
west due to a potent low pressure system over the northern Plains on
Friday, so the CWA should break free of the wedge with good
southwesterly flow and a building upper level ridge.
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --As of 740 AM EDT Saturday...
Precipitation over northern North Carolina will continue to
move away from the central Appalachians this morning. Area of
LIFR stratus and fog was west of a line from KBCB to KHLX. There
will be slow improvement in this area this morning with
conditions back to MVFR by noon.
The cold air aloft associated with the approaching upper low
will create good lapse rates and potentially enough instability
for isolated to scattered showers and thunderstorms in the
afternoon along and ahead of a cold front. Medium confidence on
the timing of showers and thunderstorms this afternoon. HRRR
showed it farther west and RAP showed development east of KLYH
and KDAN. Think the best chance will be from 18Z/2PM through
Upslope snow showers will develop after 21Z/5PM and will
continue for much of the night with MVFR ceilings and
visibilities, including at KBLF and KLWB. Ceilings at TAF sites
east of the Blue Ridge will be VFR today away from the
precipitation. Winds will be gusty behind the front with gusts
up to 30 knots along and west of the Blue Ridge.
Extended Aviation Discussion...
Gusty post frontal northwest winds continue 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 midweek.
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