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483
FXUS61 KRNK 210641
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
241 AM EDT Fri Jun 21 2024

.SYNOPSIS...
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High pressure will remain over the area into the weekend,
keeping the weather mostly dry, though isolated showers and
storms over the mountains are possible over the weekend and into
the beginning of next week. Better chances for storms come
midweek. Above normal temperatures and increasing humidity
through the Monday will lead to increasing risks of heat related
impacts over the weekend.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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As of 230 AM EDT Friday...

Key Messages:

1. Above normal temperatures.
2. Chance of afternoon storms along and west of VA/WV border.

A strong ridge of high pressure will maintain a grip on our
region into the upcoming weekend. Subsidence will generally mute
any chance for deep convection, with only minimal cumulus
development. Convective allowing models (CAMs) do indicated
narrow axis of weak convergence developing along the
Appalachian divide, so cumulus cloud formations may result in
some moderate to towering cumulus over the higher terrain
beginning mid-day, and an opportunity for a few showers and
isolated thunderstorms from BLF north across eastern WV to along
the WV/VA border this afternoon and evening.

Surface winds will become more southerly today, the easterly
component from the past few days weakening. This suggests
temperatures will now begin to creep upward with respect to
afternoon highs. The dewpoints will also start to go up
promoting increasing mugginess and potential for heat related
hazards.

High temperatures today are expected to climb into the 80s in
the higher elevations and lower to mid 90s across the foothills
and piedmont. To the body, the temperature may feel slightly
warmer if exposed to the sun. A heat index in the mid to upper
90s is possible for the urban areas of Roanoke and Lynchburg.

For tonight, any daytime shower activity over the mountains
should dissipate at sunset, leaving us with some scattered
debris clouds across the Highlands, but clear elsewhere.
Temperatures are expected to dip back into the 60s to
around 70 for lows.
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&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 1200 PM EDT Thursday...

Key Messages:

1. The worst heat and humidity stay out of our forecast area, but we
will be hot and somewhat humid through Monday.

2. Weak front Sunday night into Monday will bring scattered
showers/storms mainly to the mountains.

3. Cooler and drier in the mountains behind the front for Monday.

High pressure at the surface drifts south and weakens its hold
somewhat over the Mid Atlantic on Friday, and further retreats east
into the western Atlantic over the weekend. Aloft, the oppressive
ridge bringing heat to much of the area will be over the TN Valley
Friday, and spreads west to cover most of the southern/southwestern
CONUS over the weekend. This puts us just inside the envelope of the
 higher temperatures, and opens the door for slightly higher
humidity for the weekend. That said, it is not exceptionally humid,
with 925 dew points of 12-14C during this time close to the daily
mean according to ECMWF ENS percentiles for this time.

Looking at the Integrated Water Vapor forecast from NCEP, much of
the front`s mid and high level moisture actually funnels clockwise
from TS Alberto in northern Mexico, up through the Plains and
finally sags south from the OH Valley Sunday and Monday.

A weak front/surface trough drifts into the area by Sunday night,
and should trigger showers and thunderstorms. A few storms may pop
up as early as Saturday afternoon over the higher terrain, but
spatial coverage will be low due to capping. For Sunday, models
indicate this feature may break up along the higher terrain, so most
if not all the measurable rain is expected over the western
mountains. CAPE does not look especially impressive, nor does shear
through the weekend, so if anything would be concerned with brief
heavy rain and perhaps a rogue downburst with inverted V soundings.

We are around 1-3 standard deviations above normal for temperatures
during this time, with temperatures in the 80s and 90s for highs,
and heat indices staying below 100 degrees, even in the Piedmont.
Overnight lows will be in the 60s with a few 70s possible. Possible
record high and record warm low temperatures in jeopardy Sunday and
Monday, see Climate section below. Of the 3 days, Sunday looks the
worst as far as heat, with the ECMWF Extreme Forecast Index pegging
highest that day for our area.

Confidence in the short term is high.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 1100 AM EDT Thursday...

Key Messages:

1. Heat and humidity continues, but remain below Advisory/Warning
criteria.

2. Scattered showers/storms Monday, but especially towards Wed/Thu.

On Monday we will be in NW flow aloft as a northern trough swings
east, and continues to push a weak front out of our southwestern
counties on Monday. The mountains remain a touch cooler, with highs
in the 80s, but the Piedmont remains hot with heat indices just shy
of 100 degrees.

Monday scattered showers and storms will be possible, mainly over
the mountains and ahead of and along a front which pushes through in
the heat of the day. Tuesday looks dry behind the front, which will
make things less humid, but it still looks very hot, especially for
the Piedmont. The heat continues in this manner through mid week,
with a stronger frontal passage expected Wednesday or Thursday.
925mb dew points increase to about 18C ahead of the front. CSU
machine learning site show a possibility of severe weather Monday
and again Wednesday/Thursday with these feature.

Heat indices remain below Heat Advisory/Excessive Heat Warning
criteria for both the mountains and the Piedmont, and this is
supported by GEFS probabilistic forecasts.

Confidence in the long term is moderate for most parameters, but
lower for timing of showers and storms.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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As of 200 AM EDT Friday...

Mainly VFR expected through the 24 hour TAF.

River fog possible in the mountain valleys this morning,
otherwise skies to remain mostly clear and visibilities
unrestricted. Daytime heating may lead to some cloud buildups
over the mountains this afternoon and evening. A few showers and
thunderstorms are possible from BLF north along the spine of the
Appalachian Divide between Noon and sunset (17Z/00Z). Steering
winds are weak, so and showers activity is expected to remain
nearly stationary.

Light winds, up to around 5 knots, generally turn more south-
southeasterly once daytime mixing begins today.

Forecast confidence is high, but low for fog restrictions at LWB
and BCB. If the fog comes off the river at LWB it may get deep
enough to result in a few hours of LIFR around daybreak. Fog at
BCB should be more shallow, in the form of ground fog with
potential for a few hours of MVFR just before daybreak.


EXTENDED AVIATION OUTLOOK...

Pattern favors dry conditions into Saturday with increasing
chance for storms Sunday into Monday. Overall VFR through the
period aside from any morning fog at LWB and storms Sunday and
Monday. Chances for showers and storms increase again for the
middle of next week.
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&&

.CLIMATE...
As of 1100 AM EDT Thursday...

The following record high and record warm low temperatures may
be in jeopardy this week:

Sunday 06/23/2024
ROA record high minimum, forecast 73, record 75 (set in 1996)
LYH record high, forecast 97, record 98 (set in 1911)

Monday 06/24/2024
ROA record high minimum, forecast 73, record 72 (set in 2010)

Wednesday 06/26/2024
LYH record high, forecast 99, record 98 (set in 1952)

&&

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

&&

$$

SYNOPSIS...AS/PM
NEAR TERM...PM
SHORT TERM...SH
LONG TERM...SH
AVIATION...PM
CLIMATE...SH