-- Discussion containing changed information from previous version are highlighted. --
708
FXUS61 KRNK 210910
AFDRNK

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

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TONIGHT/...
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.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
-- Changed Discussion --
As of 445 AM EDT Friday...

Key Messages:

1). Hot Saturday, but conditions remain below Heat Advisory
Criteria.

2). Increasing chance for showers and thunderstorms, especially
Sunday into Monday.

3). Notably cooler and less humid by Monday.

Some notable changes in the synoptic pattern expected through
this period that will bring a good chance for much needed rain
and cooler temperatures by the end of the weekend and the first
part of next week.

The mammoth 598+dm subtropical upper ridge that currently
extends from off the northern Mid-Atlantic coast southwest into
the southern Plains will retrograde further southwest through
the weekend and also shrink somewhat as well as weaken markedly
from its current state. This will occur as the westerlies sag
southward across the northern tier of the U.S. states in
response to a vigorous short wave tracking from west to east
just south of the Canadian border. An associated frontal
boundary sags southward into the region by Sunday night into
Monday and will serve as a focusing mechanism for showers and
thunderstorms.

Saturday will be hot as the upper ridge drifts over our area on
its journey to our southwest by the first part of next week.
The blob of hot air aloft (i.e., 850mb temperatures > +20C)
attending the core of the upper ridge will simultaneously drift
over the region. Thus, Saturday, high temperatures should reach
their highest levels of this spell, barring increased convection
which is certainly a possibility. Maximum temperatures on
Saturday are expected to average in the mid 90s east of the Blue
Ridge/Piedmont with mostly 80s to near 90, depending on
elevation west of the Blue Ridge. Dewpoints remain low enough
that heat indices are expected to remain below 105 degrees, but
some heat index readings of 100-103 are possible across the
Piedmont, including location such as Lynchburg, Danville, and
Roanoke. Sunday could prove to be just as hot, especially east
of the Blue Ridge. However, the degree of heat Sunday will be
even more so dependent on convection and associated cloud cover
and precipitation, thus overall less of a concern than Saturday
at this point.

The frontal system finally moves through the CWA Sunday night
into Monday. Timing of the front during maximum heating late
Sunday should bring much of the CWA a good chance of showers and
thunderstorms. Clouds and showers linger into Monday morning,
with redevelopment of stronger convection likely again Monday
afternoon along and east of the Blue Ridge. This will result in
temperatures being some 5-10 degrees cooler on Monday,
especially west of the Blue Ridge. While rainfall amounts will
be spotty, some locations could receive substantial rain from
heavier thunderstorms. Now that parts of the RNK CWA are in a
D2-level drought, the rainfall will be welcome. The bigger
concern with thunderstorms on Sunday appears to be the potential
severe threat, not rainfall. With the hot temperatures ahead of
the front and a strong short wave passing by to our north, a
few severe thunderstorms are possible Sunday afternoon/evening
across the northern parts of the CWA. A "marginal" Level 1
Severe Threat has been indicated by SPC for areas near and north
of the I-64 corridor. Intuitively, given the expected pattern
and frontal location, Monday afternoon should bring a
"marginal" threat for isolated severe storms across the NC/VA
Piedmont, although below SPC`s 15% threshold for depicting such
on Day4.

/Confidence Levels in Forecast Parameters/
- Moderate Confidence in Temperatures,
- Moderate Confidence in Precipitation Probabilities,
- Moderate Confidence in Wind Direction,
- High Confidence in Wind Speed,
- Moderate Confidence in Thunderstorm Potential.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY 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 /09Z FRIDAY THROUGH TUESDAY/...
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.

&&

.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...RAB
LONG TERM...RAB
AVIATION...PM
CLIMATE...SH