Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 201428
Area Forecast Discussion
National Weather Service Blacksburg VA
1028 AM EDT Mon Mar 20 2017
High pressure over the eastern United States will move southeast off
the coast by this evening. Low pressure over the Central Plains will
move east today and tonight, which will push a warm front across the
Mid Atlantic region tonight and by Tuesday the low will be over
Virginia with a front trailing back across the Tennessee Valley.
This front will drift slowly south as a large high builds over the
eastern United States Wednesday and Thursday.
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 1015 AM EDT Monday...
Still keeping an eye on a decaying thunderstorm complex moving
southeast into eastern Kentucky/western West Virginia from Ohio.
Rapid update models indicate a few residual showers from this
complex approaching our southeast West Virginia/far western
Virginia counties during early afternoon, and associated clouds
entering the area before noon. Have lowered daytime temperatures
across southeast West Virginia 2 to 3 degrees in anticipation
of increased debris clouds from this system entering our area,
though have not yet increased rain chances. Will wait to see how
quickly the system decays through noon before considering
adjustments to rain chances today.
Precipitable water values are up in the 0.75 to 1.0 inch range
after 00Z/8PM. High pressure over Virginia this morning will
move off the southeast coast by this evening. A cold front with
waves of low pressure along the boundary approaches the region
tonight and by late tonight will extend from Virginia through
Kentucky into Oklahoma. As a broad east- west oriented
baroclinic zone develops, this front will provide some of the
lift needed for precipitation. Have increased probability of
precipitation after midnight.
-- End Changed Discussion --
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 AM EDT Monday...
The upper ridge flattens Tuesday as surface high pressure shifts to
the southeast. This will allow a weak disturbance and its associated
cold front to travel east across our region. The cold front will
progress into the region on Tuesday afternoon and evening, then push
south Wednesday as the wave of low pressure pushes into the Atlantic
ocean. Increased dynamics and instability Tuesday afternoon will
yield greater coverage of showers, along with the potential for some
isolated thunderstorms across roughly the southern half of the
region. The day 2 convection outlook placed a marginal severe threat
to our south and west. High temperatures on Tuesday will be mild
about ten to fifteen degrees above normal, with readings from around
50 degrees in the northwest to the mid 70s in the southeast.
The showers will continue into the Tuesday night, until the
reinforcing cold front exits the southern half of the region early
Wednesday morning. Any lingering moisture may change to snow showers
in the northwest mountains. Any snow accumulations will be light
and generally less than an inch. Low temperatures Tuesday night will
vary from the mid 20s in northwest Greenbrier county to the mid 40s
along the southern Blue Ridge.
Both the ECMWF and GFS showed high pressure builds into the area
Wednesday into Wednesday night. High temperatures on Wednesday will
range from the lower 30s in the northern mountains to the mid 50s in
the Piedmont. It will be dry and cold Wednesday night will low
temperatures from around 20 degrees in the north to around 30 in the
.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 300 AM EDT Monday...
High pressure will build southeast across our region Thursday and
slide off the coast Thursday night. With the GFS keeping the
moisture to our north for Thursday night into Friday morning,
removed the mention of rain and freezing rain for northern portions
of the forecast area. Dry weather will continue on Friday as
shortwave passes to our north. As the center of the high creeps
east, clockwise flow around the high will draw increasing moisture
back into the area Friday night into Saturday, in the form of patchy
light rain. Saturday night into Sunday, a cold front is expected to
cross the area. Look for increasing chance of showers during this
time frame, with a slight chance of thunderstorms Sunday afternoon
across most of the region. The unsettled weather will continue on
Temperatures during this portion of the forecast will be around ten
degrees below normal on Thursday, but trend to readings about ten
degrees above normal by Sunday. Temperatures will trend cooler on
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
As of 735 AM EDT Monday...
High pressure was centered over the Carolinas this morning.
Just high, thin clouds from upstream thunderstorms expected
through noon. Winds were light and variable.
Mid/high clouds will be increasing by the afternoon ahead of an
approaching frontal system with sub VFR cigs toward the end of
the valid period in the mountains, though any precipitation
looks to hold off until after 03Z/11PM tonight. Models were
showing some differences with the southern extent of the
precipitation tonight. Most confident of showers north of a KBLF
to KCHO line, including at KLWB overnight. MVFR visibilities
are expected with the showers and ceilings will gradually lower
late tonight in the mountains to MVFR.
Extended Aviation Discussion...
Precipitation and MVFR or lower ceilings will cover much of
southwest Virginia, southeast West Virginia and northwest North
Carolina on Tuesday into Tuesday night due to the cold front
moving slowly south through the region. High pressure builds in
for Wednesday which should improve ceilings back to VFR.
By Thursday the high will wedge in from the northeast so will
stay VFR though some residual lower cigs may get trapped espcly
along and east of the Blue Ridge Wednesday night into Thursday
resulting in possible MVFR cigs. Dry and warmer weather is
expected on Friday.