Special Weather Statement, NWS Blacksburg, VA

Area Forecast Discussion
National Weather Service Blacksburg VA
251 PM EDT Mon Jun 21 2021

.SYNOPSIS...
A cold front from the Great Lakes to Texas will trigger showers and
thunderstorms tonight and Tuesday before it moves of the East Coast.
High pressure with cooler and less humid weather will cover the Mid
Atlantic region and Carolinas on Wednesday and Thursday. The next
chance of rain arrives for the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 230 PM EDT Monday...

   Pre-frontal storms tonight then cold front comes through on
Tuesday...

Air mass is becoming more unstable, with CAPES as high as 4000J/kg
west of the Appalachians. Best bulk shear remains just to the north
of the Greenbrier Valley. Strong mid level cap will continue to
erode with heating. After 21Z/5PM areal coverage of thunderstorms
will expand across the mountains and foothills. Hi-Res guidance
showed a cluster of storms in the North Carolina foothills and
another cluster tracing from northeast Tennessee into the New River
and Roanoke Valley before 00Z/8PM. Probability of precipitation has
been adjusted to fit these expected radar trends. Have added a gusty
wind and heavy rain threat to the attributes of the thunderstorm.

Precipitable water values will be in the 1.5 to 2.0 inch range
through midnight. Muggy air with surface dew points in the 60s to
lower 70s will limit drop in temperature tonight. Leaned toward the
warmer guidance for overnight lows.

Timing of the front and west edge of the deeper moisture is slightly
different between models with the GFS on the quicker side and the
RAP/NAM slower. All guidance has the front east into eastern
Virginia and North Carolina by the end of the day. But even
once the showers move southeast, abundant cloud cover will
remain. The combination of clouds and precipitation along with a
cooler air mass will result in maximum temperatures 5 to 15
degrees below normal. Stayed close to NBM guidance for highs on
Tuesday.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
     A Cool and Drier Midweek Period...

Tuesday evening into Tuesday night, the cold front will push south
and east of our area. An isolated storm is possible early. High
pressure over West Virginia Tuesday night will build eastward into
our area Wednesday. Low temperatures Tuesday night into Wednesday
morning will dip into the upper 30s in the coldest mountains valley
to the mid 50s in the piedmont. High pressure and a very dry air
mass building in across the area for Wednesday. Highs will warm into
the mid 60s in the mountains to around 80 degrees in the Piedmont.
Low temperatures will moderate Wednesday night to readings in the
mid 40s in the west to the mid 50s in the east. High pressure over
southern New England Thursday morning will move east into the
Atlantic ocean Thursday night. Under bright sunshine, High
temperatures Thursday will moderate to the lower 70s in the
mountains to the lower 80s in the piedmont. Low temperatures
Thursday night will be mild generally from the mid 50s in the
mountains to around 60 degrees in the piedmont.

Moderate confidence in the Short Term Forecast.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 145 PM EDT Monday...

     Increasing likelihood of convection into the Weekend and early
next week...

Surface high pressure will move off the Mid-Atlantic coast. A
southerly flow will push Atlantic moisture into the region. Aloft,
the trough in the East will retrograde or reposition itself in the
central U.S. as upper ridge amplifies off the Mid-Atlantic coast.

As a result, deep southwest flow aloft will develop into the weekend
advecting rich moisture into our region. Several disturbances
tracking through the area will result in a daily chance in showers
and thunderstorms into the weekend and early next week. At this
time, the severe threat appears low, the threat for locally heavy
rainfall will increase with several days of increasingly numerous
diurnal convection.

The wet pattern should continue for a while as upper troughing
remains parked in the central U.S. leaving the eastern U.S. in a
moist and unstable southwest flow.

Moderate Confidence during Long Term Period.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
As of 245 PM EDT Monday...

Scattered to numerous thunderstorms are expected through
midnight in the mountains and foothills of Virginia, North
Carolina and southeast West Virginia. Visibility and ceiling
will be MVFR with any of the stronger storms and gusty winds are
possible. Aside from any thunderstorms, the wind will be gusting
from the southwest up to 25 knots until sunset.

As a cold front approaches the area tonight and crosses the
region on Tuesday showers and thunderstorms will continue as
winds turn to the northwest. Precipitation will end from
northwest to southeast. Ceilings will also lower to MVFR behind
the front and may be into the IFR range along the western
Appalachians, including at KBCB, KLWB and KBLF.

Average confidence for ceiling, wind and visibility.

Extended Aviation Discussion...

A cold front will cross the area Tuesday. Expect MVFR to at
times IFR showers at all TAF sites Tuesday morning, before the
front clears the Piedmont some time Tuesday afternoon. Dry high
pressure will move in behind this front by Tuesday evening and
last until at least Thursday if not Friday as well before enough
moisture returns to increase scattered shower/tstm activity.
Winds behind the front will shift to the NW but not be
especially breezy, and already by Wednesday will switch back
around to light southeasterly as the high pressure moves off the
mid-Atlantic coast.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...KK
LONG TERM...KK
AVIATION...PM

Hazardous Weather Outlook
National Weather Service Blacksburg VA
224 PM EDT Mon Jun 21 2021

NCZ001-002-018-VAZ007-009>020-022>024-WVZ042>044-507-508-221830-
Ashe-Alleghany NC-Watauga-Tazewell-Smyth-Bland-Giles-Wythe-Pulaski-
Montgomery-Grayson-Carroll-Floyd-Craig-Alleghany VA-Bath-Roanoke-
Botetourt-Rockbridge-Mercer-Summers-Monroe-Eastern Greenbrier-
Western Greenbrier-
224 PM EDT Mon Jun 21 2021

This Hazardous Weather Outlook is for northwest North Carolina,
southwest Virginia, west central Virginia and southeast West
Virginia.

.DAY ONE...This afternoon and tonight.

Scattered thunderstorms are expected to develop this afternoon and
continue into tonight. A few of the storms could become strong to
severe this afternoon and evening. The main hazards would be damaging
wind gusts and cloud-to-ground lightning.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

There is a low probability for widespread hazardous weather.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed.

NCZ003>006-019-020-VAZ032>035-043>047-058-059-221830-
Surry-Stokes-Rockingham-Caswell-Wilkes-Yadkin-Patrick-Franklin-
Bedford-Amherst-Henry-Pittsylvania-Campbell-Appomattox-Buckingham-
Halifax-Charlotte-
224 PM EDT Mon Jun 21 2021

This Hazardous Weather Outlook is for north central North Carolina,
northwest North Carolina, central Virginia, south central Virginia,
southwest Virginia and west central Virginia.

.DAY ONE...This afternoon and tonight.

Isolated thunderstorms are expected to develop this afternoon and
evening. A few of the storms could become strong to severe. The main
hazards would be damaging wind gusts and cloud-to-ground lightning.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Scattered thunderstorms are expected to develop along and east of the
Blue Ridge late Tuesday morning into the afternoon. There is a
marginal threat for strong to severe thunderstorms with this
activity ending by sunset. Damaging wind gusts and cloud-to-ground
lightning would be the main hazards with these thunderstorms.

For the remainder of the period, the probability for widespread
hazards is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed.