338
FXUS61 KRNK 190933
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
533 AM EDT Wed Jun 19 2024

.SYNOPSIS...
High pressure will cover the region through the end of the
week. This will result in unseasonably warm temperatures and
mainly dry conditions. Any rainfall is expected to be isolated.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM EDT Wednesday...

Key Messages:

1) Warm and dry. Temperatures about 5 degrees above normal.

500mb (597dm) anticyclone is centered over the northern Mid-
Atlantic...this persistent ridge of High pressure poised to
remain nearly stationary through the near term...amplifying with
time. Clockwise flow around the center (vcnty IAD) of the High
will continue to focus main heat risk from Ohio Valley and Great
Lakes into New England where westerly low level winds will
advect plume of well above normal warmth across areas to our
north. Our forecast area is positioned just south of the
anticyclone with wind flow primarily coming from the southeast
and off the Atlantic Ocean. This will mute our temperatures to
some degree maintaining only minor heat related risks compared
to our neighbors to the north. Temperatures over the next 24
hours across our forecast area will average about 5 degrees
above the seasonal norm, but nothing extreme (yet). Longer range
guidance suggests we will get a taste of this airmass by the
weekend as the center of the upper ridge retrogrades and allows
for a shift to westerly flow aloft and the formation of a lee
trof over the southern Mid-Atlantic. Until then, our weather
should feel seasonally warm for the time of year...skewed
slightly to the above normal range with respect to the
temperature...highs ranging from the upper 70s to mid 80s in the
mountains and upper 80s to around 90 in the foothills and
piedmont.  Dewpoints today and tonight should remain at or
below 65 and may even mix into the upper 50s. This little bit of
drying should be enough to keep the heat index in check...the
temperature generally mimicking the heat index. The dry air is
also not good for CAPE, so not expecting any deep convection for
our CWA today or tonight.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
As of 445 AM EDT Wednesday...

Key Message:

1). Hottest temperatures of this event expected Friday through
Sunday.

2). Thunderstorm chances increase, especially across the
mountains.

The strong 598dm subtropical upper ridge and associated blob of
very warm 850mb temperatures on the order of +20C to +22C will
gradually sag southward over our forecast area during this
period. This will displace the local maritime air mass which
will continue to temper the heat across the Mid-Atlantic and
central Appalachians until late week. The upper ridge and its
associated hot blob will be centered over the forecast area
Friday evening before sliding further to the southwest during
the weekend. The upper ridge will also weaken just a tad as
well. The suppression of the upper ridge southward will be aided
by a northern stream short wave tracking from west to east
across the northern tier of U.S. states.

As 500mb heights lower from the 598+ dm levels to the 588dm
levels by the weekend as the upper trough approaches
simultaneously as temperatures cool aloft and low-level
moisture increases from the south/southeast, the atmosphere will
become more unstable and more favorable for convection. This
pattern change will first be realized across the western
mountains Thursday afternoon as isolated diurnally drive
showers/thunderstorms develop, largely from differential heating
and orographic lift. For Friday and Saturday, as atmospheric
conditions continue to become more favorable for convection,
look for a good chance of showers/thunderstorms, especially
during the afternoon and evening, across much of the forecast
area. Areas along and west of the Blue Ridge look to be the most
favorable areas for rainfall. Nonetheless, am not comfortable
with any "likely" pops at this point given the potential for
lingering capping aloft from the upper ridge.

Temperatures will peak at their highest levels Friday and
Saturday with 85 to 90 west and 90 to 95 east. A few upper 90s
will be possible in urban areas such as Roanoke. These
temperatures are about 10-degrees above normal. Friday will
probably be the hottest day west of the Blue Ridge as
thunderstorms may inhibit strong heating by Saturday afternoon.
For the piedmont and especially the North Carolina foothills
and piedmont, Saturday will likely be the hottest day. Heat
index values should top out right around the 100-degree mark for
the piedmont on Saturday with readings closer to 90 in the
western counties. At this point, it appears that we will remain
shy of heat advisory criteria.

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

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 515 AM EDT Wednesday...

Key Messages:

1) Increasingly unsettled weather conditions during this period,

2) Temperatures remaining warm, but trending closer to normal
values for late June.

As the upper ridge continues to drift south to southwest
through the period and a short-wave trough tracks along/near the
40-degree latitude line, look for lower temperatures, higher
humidity levels, and increasing chances for much needed
rainfall over the weekend. Conditions appear to be most
favorable for widespread showers and thunderstorms Sunday and
Monday although there is not enough confidence at this point to
advertise likely pops.

While this timing is a tad slower than thought a few days ago,
the good news is that it now appears the upper trough will be
strong enough and deep enough to push the attendant frontal
boundary into the southeast states. This should allow cooler and
drier air to flow into the region for the first part of next
week before the upper ridge appears to build back to the east
some later in the week.

Sunday will still be hot, through early afternoon, before
showers and thunderstorms cool things down during the mid and
late afternoon. By Monday and Tuesday, temperatures will trend
downward a bit each day with lingering chances for
showers/thunderstorms, especially across the southeastern half
of the forecast area as the front moves further southeast
Widespread temperatures in the 90s Saturday will give way to 70s
mountains and 80s elsewhere for the most part by Tuesday.
Muggy/warm low temperatures in the mid 60s to lower 70s Saturday
and Sunday will be mostly in the 60s and even a few 50s in the
mountains by Tuesday morning.

/Confidence Levels in Forecast Parameters/
- Moderate Confidence in Temperatures,
- Moderate Confidence in Precipitation Probabilities,
- Moderate Confidence in Wind Direction and Speed,
- Moderate Confidence in Thunderstorm Potential.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
As of 330 AM EDT Wednesday...

Some patchy areas of fog across the mountain valleys,
particularly at LWB, this morning, otherwise expecting
widespread VFR through the 24 hour TAF.


EXTENDED AVIATION OUTLOOK...

Thursday Through Sunday...High pressure will cover the region.
Aside from some morning river fog in the mountain valleys,
conditions are expected to be primarily VFR. Little or no chance
for rain is expected through Friday...then increase for the
weekend. Heat and humidity will also increase for the weekend.

&&

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

&&

$$

SYNOPSIS...PM
NEAR TERM...PM
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...PM