Special Weather Statement, NWS Blacksburg, VA

Area Forecast Discussion
National Weather Service Blacksburg VA
1017 AM EDT Mon Aug 6 2018

.SYNOPSIS...
High pressure was centered over the southeastern United States
providing typical summer weather conditions with a daily threat
for mainly afternoon and evening thunderstorms and near
seasonal temperatures. A weak cold front will approach from the
west by midweek bringing a better chances for organized showers
and storms for Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM EDT Monday...

Issued an update to the forecast as fog has almost dissipated
across the Greenbrier and southern Shenandoah Valleys this
morning. We also lower PoPs through the morning as skies have
become mostly sunny with little to no cumulus formation. PoPs
increase around noon for the Bluefield and Mountain Empire area
and around 1 PM for the NC High County as a cluster of storms,
currently in eastern KY, track towards this area. Isolated
storms are expected across the rest of the mountains later this
afternoon.

As of 400 AM EDT Monday...

River valley fog formation occurred this morning in the
Greenbrier, upper James, and New River Valleys. This fog will
disperse by 0900 once daytime heating begins.

Weak ridging aloft will keep steering flow weak today. The
center of the surface high was over GA/AL with light westerly
flow around the northern periphery. Moisture increasing from the
TN valley will be advected into the west side of the
Appalachians today providing for more cloud elements as compared
to yesterday. This increasing moisture will bubble into
scattered deep convection this afternoon with highest pops along
and west of I-77. Westerly steering winds will allow any
activity that develops to move east reaching the foothills and
piedmont this evening, although less confident of coverage and
leading to lower probabilities there.

Temperatures today are forecast to be a degree warmer than
yesterday. It was +19 deg C at 850MB yest evening, and forecast
around +20 deg C today. This should yield surface highs in the
lower 90s east of the Blue Ridge and 80s in the mountains.

Loss of diurnal heating will bring demise to daytime boundary
layer driven deep convection with temperatures tonight settling
back to around 70. May begin to see flickers of so called heat
lightning (from distant thunderstorms) as an upper trof allows
for nocturnal thunderstorms across the Ohio Valley.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
As of 345 AM EDT Monday...

Mainly zonal upper flow expected to prevail as a series of weak
short wave trofs move from west to east through the Blacksburg
forecast area Tuesday through Wednesday night. Timing of each wave
is somewhat problematic since features will be compounded by daily
upstream convective activity over portions of the MS and TN valleys
and associated introduction of new mesoscale vorticity centers and
associated weak forcing.

Result in Blacksburg area of concern will be a continuation of
diurnally driven scattered showers/thunderstorms maximized during
the afternoon and evening hours - especially over the western
mountains where local upsloping and differential heating will
support slightly enhanced upward vertical motion fields.

Slight uptick in convective potential expected by Wednesday
afternoon into Wednesday night when a more defined short wave trof
expected to move east through the area - providing better dynamic
forcing than the preceding day (Tuesday).  Forecast soundings do not
indicate sufficient instability or shear to support anything other
than an isolated severe weather threat on Tuesday; however, slowly
increasing low level winds in advance of the approaching wave may
support a scattered severe weather threat for mainly damaging
straight-line winds Wednesday afternoon/evening, especially
along/north of Highway 460, where the better low level shear
forecast to reside.

Passage of short wave trof Wednesday night and perhaps a period of
weak subsidence and increasing capping inversion may limit amount of
any additional convective activity on Thursday, but timing
uncertainties this far out, and the hint of yet another upstream
wave trying to encroach on at least the extreme western portion of
the forecast area by late in the day warrants maintaining at least a
low threat area wide.

Little change in airmass expected throughout the entire short term
period.  Daytime highs expected to remain generally in the 70s
across the highest elevations to lower 90s across the Piedmont -
with 60s in the mountains to around/near 70 east at night.

Forecast confidence is high for temperature ranges through the
forecast period, and moderate for timing and extent of daily
convective activity.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
As of 215 PM EDT Sunday...

For the weekend, models bring an upper level trough and a cold
front over the area Saturday. This trough is expected to become
a closed low by Sunday. The GFS has this low over the Ohio
Valley, whereas the ECM centers it over the Midwest. The ECM
solution is the wettest, tapping into Gulf moisture, allowing
for several days of rain going into early next week (mid
August). The GFS has rain as well, but not continuous, as dry
air gets wrap into the low over time.

Temperatures will be near normal Friday, then a few degrees
cooler than normal over the weekend. Overnight lows will remain
muggy and in the 60s.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
As of 800 AM EDT Monday...

Generally VFR through the 24 hour TAF period, with the following
two exceptions...

Daytime heating and cloud buildups over the mountains will
result in widely scattered shra/tsra from 18Z/2PM-00Z/8PM.

Development of mountain/river valley fog between 06Z/2AM-
daybreak along the rivers with high probability of LIFR at KLWB
and Tempo LIFR at KBCB. Elsewhere fog expected to be patchy
ground fog.

Winds through the period generally light and variable except for
outflow near shra/tsra.

Extended...

Summer pattern will feature mainly VFR. Any sub-VFR will be
associated with scattered mainly afternoon and evening shra/tsra
and development of early morning fog/stratus in the mountain
valleys...all of which are temporary.

Best coverage of storms will occur mid-week (Wednesday)
associated with an upper level trof and weak surface cold front.
The fog/stratus should be limited to pre-dawn hours and
confined mainly to the mountain river valleys with impacts to
KBCB/KLWB.

&&

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

&&

SYNOPSIS...PM
NEAR TERM...PM/RCS
SHORT TERM...WERT
LONG TERM...RCS
AVIATION...PM

Hazardous Weather Outlook
National Weather Service Blacksburg VA
439 AM EDT Mon Aug 6 2018

VAZ007-010>014-016>020-022>024-032>035-043>047-058-059-WVZ042>044-
507-508-070845-
Tazewell-Bland-Giles-Wythe-Pulaski-Montgomery-Carroll-Floyd-Craig-
Alleghany VA-Bath-Roanoke-Botetourt-Rockbridge-Patrick-Franklin-
Bedford-Amherst-Henry-Pittsylvania-Campbell-Appomattox-Buckingham-
Halifax-Charlotte-Mercer-Summers-Monroe-Eastern Greenbrier-
Western Greenbrier-
439 AM EDT Mon Aug 6 2018

This Hazardous Weather Outlook is for central Virginia, south
central Virginia, southwest Virginia, west central Virginia and
southeast West Virginia.

.DAY ONE...Today and tonight.

The probability for widespread hazardous weather is low.

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

A weather disturbance is expected to move east through the area on
Wednesday. Scattered showers and thunderstorms are expected to
develop in advance of this system. Some of the strongest storms may
produce locally damaging winds. The greatest potential for severe
weather on Wednesday will be during the afternoon and evening hours,
mainly along and north of Highway 460.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

NCZ001>006-018>020-VAZ009-015-070845-
Ashe-Alleghany NC-Surry-Stokes-Rockingham-Caswell-Watauga-Wilkes-
Yadkin-Smyth-Grayson-
439 AM EDT Mon Aug 6 2018

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

.DAY ONE...Today and tonight.

The probability for widespread hazardous weather is low.

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

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Wert

Special Weather Statement
National Weather Service BLACKSBURG VA
112 PM EDT MON AUG 6 2018

NCZ002-VAZ015-016-061745-
Alleghany-Grayson-Carroll-
112 PM EDT MON AUG 6 2018

...A STRONG THUNDERSTORM WILL AFFECT
NORTHEASTERN ALLEGHANY COUNTY IN NORTHWESTERN NORTH CAROLINA...
SOUTHWESTERN CARROLL AND EASTERN GRAYSON COUNTIES IN SOUTHWESTERN
VIRGINIA AND THE CITY OF GALAX...

Until 145 PM EDT.

At 111 PM EDT, a strong thunderstorm was located near Elk Creek,
moving east at 15 mph.

Winds in excess of 30 mph and pea size hail are possible with this
storm.

Locations impacted include...
Galax...
Independence...
Fries...
Ennice...
and Bridle Creek.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 3664 8131 3675 8129 3675 8086 3645 8098
TIME...MOT...LOC 1711Z 282DEG 12KT 3667 8117

JR

Special Weather Statement
National Weather Service BLACKSBURG VA
117 PM EDT MON AUG 6 2018

NCZ002-003-019-061815-
Surry-Wilkes-Alleghany-
117 PM EDT MON AUG 6 2018

...A STRONG THUNDERSTORM WILL AFFECT
CENTRAL ALLEGHANY...WESTERN SURRY AND NORTHEASTERN WILKES COUNTIES IN
NORTHWESTERN NORTH CAROLINA...

Until 215 PM EDT.

At 117 PM EDT, a strong thunderstorm was located over Stone Mountain
State Park, moving east at 15 mph.

Winds in excess of 30 mph and pea size hail are possible with this
storm.

Locations impacted include...
Elkin...
Fairview...
Sparta...
Dobson...
and Traphill.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 3629 8125 3655 8114 3645 8098 3651 8096
      3646 8061 3626 8068 3627 8073 3628 8074
      3626 8075 3627 8078 3626 8078 3625 8080
      3625 8084
TIME...MOT...LOC 1717Z 256DEG 12KT 3637 8107

JR

Special Weather Statement
National Weather Service BLACKSBURG VA
131 PM EDT MON AUG 6 2018

NCZ019-061800-
Wilkes-
131 PM EDT MON AUG 6 2018

...A STRONG THUNDERSTORM WILL AFFECT
SOUTHWESTERN WILKES COUNTY...

Until 200 PM EDT.

At 131 PM EDT, a strong thunderstorm was located over Elkville,
moving southeast at 10 mph.

Winds in excess of 30 mph and pea size hail are possible with this
storm.

Locations impacted include...
Maple Springs...
Darby...
and Elkville.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 3604 8140 3605 8139 3607 8141 3608 8143
      3607 8144 3609 8146 3609 8147 3610 8148
      3610 8151 3611 8153 3619 8138 3604 8137
TIME...MOT...LOC 1731Z 320DEG 7KT 3609 8141

JR