771
FXUS61 KRNK 041442
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1042 AM EDT Thu Jul 4 2024

.SYNOPSIS...
A strong subtropical ridge will gradually weaken over the Mid
Atlantic region today as upper level troughing steers multiple
surface boundaries into the area. As a result, shower and
thunderstorm chances increase by this afternoon and evening, and
continue daily through Saturday. Anomalously hot and humid
weather is expected for today and especially Saturday. Next week
remains active as another storm system moves out of the Plains.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1015 AM EDT Thursday...

Modest adjustment made to the timing of rain chances and
temperatures for this afternoon based on current satellite and
radar trends. Rapid update weather forecast models are in
general agreement of shower and storms developing in a broken
line that drifts across the Piedmont during the 3 pm to 9 pm
timeframe. Still looking like storms will diminish for most
areas west of Highway 29 in time for fireworks displays. Little
change with this update in expected afternoon highs, though am
keeping an eye on scattered clouds developing along the lee side
trough stretching from Surry County northeast through Amherst
County that will delay heating into early afternoon. Still,
expect these clouds to scatter by early afternoon. Heat index
values will still reach just above 100F across the Piedmont.

As of 230 AM EDT Thursday...

Key Messages:

1) Those attending July 4 festivities should seek shelter
during thunderstorms.

2) Heat index values reach 100F over the Piedmont and central
VA. Remember to drink plenty of water and stay in the shade if
you must be outside.

Subtropical ridging begins to break down over the Mid Atlantic
and sink south towards the Gulf of Mexico today and tonight.
This opens the door for westerly flow which will steer short
wave energy aloft in from the WNW. An area of convection was
currently over KY, OH, and northern WV, and the remnants of this
or at least the associated forcing mechanisms (including
outflow boundaries) will reach SE WV by late morning. Surface
analysis shows a lee trough in the area, and this will help
kickstart convection over the mountains, and expect convection
to begin over the Blue Ridge around noon. Showers and storms
will push into SW VA and eventually northern NC by the
afternoon and early evening. Most of the activity will push out
to the southeast by 7-9 PM, so perhaps we will be clear of most
of the wet weather in time for July 4 firework displays, but it
will be close in some spots.

As for temperatures, we will remain shy of heat advisory
criteria, but temperatures will range from the low to upper
80s for the mountains, and the mid to upper 90s for the
Piedmont and Roanoke. Heat indices will be slightly higher than
this as moisture increases today. The EFI and Shift of Tails
indicate that tomorrow will be the hotter day compared to today.
Nevertheless, still take precautions...stay in A/C and don`t
leave children/pets in cars. There are a couple places that
will be within 2-3 degrees of breaking records, but with cloud
cover and rain, this looks unlikely. See Climate section below.

Looking at severe weather parameters, we should have about
1000-1500 J/kg instability. Cloud cover may inhibit this
somewhat, but steepening lapse rates and increasing dew points
should counteract this some. Storm organization will be lacking
in a big way, with bulk shear around 10-20 kts, and 0-1 km
around 5 kts. Therefore not expecting many strong/severe storms,
with most of these being straight up and straight down pulse
type cells. We could get a rogue damaging winds gust however
with some dry air lingering in the mid levels.

While the whole system will be drifting south, the individual
cells will be moving westerly around 15 mph along the surface
trough, and training and slow movement could lead to flooding
issues. PWATs will be over 1.5" in the mountains, and will top
out over 2" over the Piedmont of VA and NC and Southside VA.
These numbers are supported by anonymously high figures for
specific humidity and PWATs on the NAEFS SAD, and maximum
integrated water vapor on the NCEP atmospheric river viewer. So
the main concerns will be lightning (with so many people
outdoors), as well as heavy rain leading to urban and small
stream flooding.

Overnight, additional short wave energy will reach areas in SE
WV and along the WV/VA border, bringing more showers/storms
through morning. Overnight lows will be in the mid 60s to low
70s, with some fog and stratus expected.

Confidence in the above scenario is moderate to high.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
As of 200 AM EDT Thursday...

Key Messages:

1. Well above normal temperatures but trending slightly cooler
each day.
2. Heat Index values over 100 deg possible Friday afternoon in
the foothills and piedmont.
3. Daily chances of showers and storms, possibly dry on Sunday.

Scattered showers and thunderstorms should develop in the
afternoon ahead of a cold front approaching the area from the
northwest. Storms look to start across the mountains early in
the afternoon then move into the foothills around the evening
commute. Storms associated with the front will enter southeast
West Virginia and far southern Virginia around sunset, making it
to the Blue Ridge by sunrise Saturday. A few strong storms are
possible with the frontal passage during the evening.

The front will be over the foothills Saturday morning with
convection starting by noon. This front will continue its slow
track across the area, moving over the piedmont in the evening.
With ample moisture and heat to work with, severe thunderstorms
are highly likely in the piedmont from Lynchburg to Danville VA
eastward. By Sunday morning, this front should be in the
coastal piedmont where it will stall and washout. Most of the
area should have a dry day Sunday, but that will depend on the
final resting place of the front.

High temperatures Friday will range from the mid 80s to lower
90s across the mountains and mid to upper 90s in the foothills
and piedmont. Dewpoints will run in the upper 60s to mid 70s,
creating heat index values in the 90s west of the the Blue Ridge
and between 100F to 105F east. Clouds and showers will cut back
on the heat Saturday with highs in the 80s in the mountains and
low to mid 90s east of the Blue Ridge. Sunday`s high
temperatures will be a few degrees cooler than Saturday.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 210 AM EDT Thursday...

Key Messages:

1. Warmer than normal temperatures with daily storms early next
week.
2. Trending cooler and possibly drier by mid week.

An upper level disturbance will approach the Carolina coast
Monday, bring Atlantic moisture into the area.
Diurnal/orographically driven showers and thunderstorms are
expected during the afternoon and evening hours, mainly along
and east of the Blue Ridge. Models have a cold front moving
across the region Tuesday, but that remains to be seen as the
coastal disturbance stalls off the coast. If the front does
clear the area Tuesday night, high pressure should keep the area
dry for a few days. If there is no frontal passage, this
boundary will stall in or near the area, keeping the chance for
daily showers and thunderstorms through most of next week.

Warmer than normal temperatures expected Monday and Tuesday. Near
normal temperatures possible Tuesday through Thursday.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
As of 300 AM EDT Thursday...

SHRA/TSRA will develop over WV in the late morning hours, and
spread south towards VA and northern NC in the afternoon and
evening. Expect a mix of MVFR to low VFR clouds, with periodic
lowerings of visibilities in moderate to heavy rain. Most of
this activity pushes south of DAN by 05/01Z. Chances for TSRA
were higher than usual, so included them in most TAFs.
Additional SHRA/TSRA possible for BLF and LWB overnight into
Friday morning. MVFR or lower fog and stratus may develop Friday
morning where it does rain and then clear out.

Average confidence for ceiling, visibility, and wind.

OUTLOOK WEDNESDAY NIGHT THROUGH SUNDAY...

Friday night through Saturday night: SCTD SHRA/TSRA remain
possible as a storm system continues impacting the region.
Flight category reductions are likely, especially Friday and
Saturday afternoon and evening.

Sunday and Monday: the probability of showers and thunderstorms
decreases, but remains possible in the afternoons and evenings.
Prevailing conditions will be VFR.

&&

.CLIMATE...
As of 300 AM EDT Thursday...

Record highs and warmest lows temperatures for July 4th and 5th.

Thursday 07/04/2024
Site  MaxT Year  HiMin Year
KBLF    92 1957    68 2018
KDAN    99 1925    74 1999
KLYH    98 1966    76 1902
KROA    99 1999    74 2018
KRNK    94 1966    71 1941


Friday 07/05/2024
Site  MaxT Year  HiMin Year
KBLF    93 1948    71 1969
KDAN   103 1919    76 1926
KLYH    98 2012    75 1900
KROA   100 1999    76 2012
KRNK    94 1930    78 1949

&&

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

&&

$$

SYNOPSIS...SH
NEAR TERM...NF/SH
SHORT TERM...RCS
LONG TERM...RCS
AVIATION...SH
CLIMATE...RCS/SH