642
FXUS61 KRNK 051502
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1102 AM EDT Wed Jun 5 2024

.SYNOPSIS...
Warm and moist airmass today ahead of a cold front will lead to
a better coverage of showers and storms. Front moves through
Thursday with drier and cooler weather to start the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1100 AM EDT Wednesday...

Key Messages:

1) Watching for more storms today with heavy rain the main threat.

Forecast remains on track. Coverage of showers/storms expected
to increase early afternoon as daytime heating combines with
abundant moisture resulting in cloud buildups and deep
convection. Regional soundings from 12Z were very moist with
PWATs 1.60 to 1.80. Mean wind is from the west-southwest at 20
kts...so storms today will be moving a bit faster compared to
yesterday...20-25 mph forward speed. This should cut down on
residence time, but with PWATs above normal, activity will be
very rain efficient and still justifies marginal risk for
excessive rainfall and localized flooding. DCAPE is less than
yesterday but trade off will be faster mean wind, so still think
there is modest wind threat with down-draft wind speeds on the
order of 30 kts with potential for isolated wind damage.

Weather map shows cold front from the upper Mid-West to North
Texas with Gulf moisture streaming north ahead of the front, the
eastern CONUS bathed in near 70 degree dewpoints. There are a
couple of MCVs embedded within the moist southwest flow ahead of
the front, one of which was moving NE through central WV, and
the other over the southern Appalachians...both features
providing lift for better thunderstorm organization today,
compared to yesterday. The Mesoscale Convective Vortex (MCV)
over WV will likely impact NOVA and into Maryland this
afternoon. The MCV entering the southern Appalachians will
provide focus for thunderstorm activity over KY/TN/NC with
downstream implications into our CWA as mean wind carries
activity from SW-NE. In addition, little or no capping inversion
will allow for local development as well. With the favorable
thermodynamic and dynamic set-up, will maintain high chance for
measurable rainfall this afternoon and evening.

In general, expecting shower/storm coverage to increase this
afternoon. PWATs will increase to near 2.0 inches which enhance
rainfall rates. Hence, any storms that move across the area
today will be efficient rain producers with rates of 2-4
inches/hr possible. Had some reports yesterday with the storms
producing .80" in 15 minutes.

Convective allowing high-res models favor storms firing up noon-2pm
across the mountains, then spreading into the piedmont soon
thereafter. As for severe threat, with a moisture laden
airmass, wet microbursts would be the main threat, though
severe threat is relatively low due to cloud cover limiting full
solar insolation and weakening the lapse rates.

Lull in the showers/storms this evening, but not completely dry.
Front tracks toward the central Appalachians late tonight so am
thinking showers/few storms will likely reach our WV counties by
then so have pops in the 50-75 percent range here, with less chances
east of the Blue Ridge.

Todays highs will be at or just cooler than Tuesday with 70s in the
mountains, to lower to mid 80s east. No change in airmass tonight so
lows in the 60s areawide.

Forecast confidence is above average on storm coverage today but
average on sky cover and temps.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
As of 200 AM EDT Wednesday...

Key Messages:

1. Lingering mountain showers and storms Thursday, with heavy rain
possible.
2. Drier weather returns Friday and Saturday.
3. Cooler temperatures Friday through the weekend.

To start off the short term forecast period, a deep upper level low
will sit over south central Canada, with the negatively tilted
trough reaching the Mid Atlantic. This feature will slowly shift
eastward through the end of the week and into the weekend, and its
associated surface cold front will cross the area Thursday. Showers
and storms are possible along and ahead of the front Thursday, with
the highest chances over the mountains earlier in the day, but
increasing instability over the Piedmont due to diurnal heating
may lead to some isolated storms in the east Thursday afternoon.
Above normal precipitable water values will still be above the 90th
percentile relative to climatology by Thursday afternoon, though not
as high as Wednesday, continuing the potential for heavy rain within
any of the stronger storms.

Any shower and storm activity Thursday will wane after sunset with
the loss of daytime heating, and progression of the front farther
eastward. Surface high pressure pushes into the area behind the
front on Friday, and bring the return of dry weather to the area.
However, pressure rises and cold air advection behind the front will
lead to breezy conditions. Saturday also looks to be dry for most,
but another cold front will be approaching from the west. Models
differ on the speed of this front, which will impact the timing of
any showers to the area.

Cooler and drier air flows into the area following the frontal
passage Thursday, and negative 500mb height anomalies suggest cooler
than normal temperatures through the end of the week and into the
weekend. Dewpoints also decrease behind the front, thus lowering
humidity heading into the weekend.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
As of 200 AM EDT Wednesday...

Key Messages:

1. Chances for showers and possible storms Sunday and Monday.
2. Cooler temperatures through the start of the work week.

The 500mb low continues to sit over southeastern Canada through the
weekend, with general troughiness persisting over the eastern US,
before finally moving farther eastward by the first half of the work
week. A cold front will approach the area from the west by Sunday,
increasing chances for showers and storms Sunday and Monday
afternoon and evening. As mentioned in the short term discussion,
models show differences in the progression of this front, and
therefore the timing of showers and storms.

Slight ridging builds back overhead heading into Tuesday as the
trough axis heads farther east, which will bring drier weather to
the area for the middle of the week, as well as start temperatures
on a gradual warming trend, but still near to a few degrees below
normal.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
As of 1035 AM EDT Wednesday...

Showers/storms will be on the increase through the day with
best coverage after 19z-01z. Still hard to pinpoint when a storm
will impact a terminal so will go more with VCTS putting tempo
1-2 hour window in at BLF/LWB as better coverage looks to be in
this area. Amendments will likely be needed but aviation
interests should monitor radar/surface trends during the day.

Outside any storms, winds will be southwest 5-12kts a few gusts
to 20kts under VFR broken ceilings of 4-7kft.

A lull in the storms later Wed evening with winds subsiding. Fog
may develop overnight but cloud cover and an approaching area of
showers may limit this so kept vsbys no worse than MVFR mainly
in the mountains. Shower chances will be too low for now to have
beyond 06z/Thu.

Forecast confidence is average on all elements.

EXTENDED AVIATION OUTLOOK...

Passage of a cold front is expected Thursday with scattered
showers and thunderstorms, flight restrictions favoring MVFR (or
lower). Showers/storms could be close to BLF/LWB by 12z Thu.

Friday is expected to be drier and a better probability of VFR
conditions behind the front. A few showers possible Sat-Sun in
the mountains but mainly VFR.

&&

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

&&

$$

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