930
FXUS61 KRNK 011748
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
148 PM EDT Fri Aug 1 2025

.SYNOPSIS...
Front to continue to slide south into the southeast U.S. tonight
into Saturday while high pressure pushes into the northern Mid-
Atlantic states. Drier and cooler air will start to filter in
Saturday and become more established to close out the weekend.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 130 PM EDT Friday...

Key Messages:

1) Flood Watch for portions of southwest VA into northwest NC
through this evening.

2) Still humid but temperatures lower.

3) Saturday will be less humid and mild.

Main front is over central NC this morning but an inverted
trough still remains across our area with higher RH. 12z RNK
sounding is moist from sfc to 150 mb, with pwat 1.76". Showers
and few storms line up from southeast WV into the New and
Roanoke Valleys toward Lynchburg mid morning where this axis of
instability/sfc convergence exist.

With some training of cells and rainfall rates of 2-4"/hr in
heavier storms, have opted to issue a flood watch from around
the Roanoke/Bedford VA area southwest into the NC
mountains/foothills. Though the NC counties have not had as much
in the past 24 hours, antecedent conditions along with
topography could lead to flooding quicker than usual if said
rates occur.

As for severe storms, cannot rule out an isolated downburst with
water loading but better chances for severe will be down across
southern NC. Any strong/severe storm if it occurs would be along
the better instability/convergence axis running up I-77 in NW
NC.

Dense fog and low stratus for the mountains are possible
overnight tonight, but with cloud cover, dense fog should be
mainly confined to the mountaintops.

Deeper moisture continues to shift south Saturday but residual
inverted trough axis may linger across the southern Blue Ridge
leading to scattered showers/a few storms Saturday.

Lows tonight will be in the 60s, and most will start feeling the
less humid air by Saturday as dewpoints drop into the upper 50s
to mid 60s. Cloud cover with the wedge will hold temps down as
well Saturday with highs in the 70s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 1130 AM EDT Friday...

Key Points:

1. Below normal temperatures.
2. Isolated/Scattered showers/storms confined to mainly far western
parts of the forecast area.

A look at the 1 Aug 00Z NCEP Ensemble Mean 500mb Geopotential
Heights shows a longwave trough centered over ME to just off the mid-
Atlantic coast Saturday evening. A shortwave trough is expected to
be crossing James Bay. A broad upper ridge is expected to extent
over most of the southern half of CONUS. A closed low is expected to
be over the Gulf of Alaska. For Sunday/Sunday night, a shortwave
trough will progress east through far southeast Canada. A weaker
shortwave trough will head east across ND. A closed low will remain
parked over the Gulf of Alaska, and a broad ridge will be over
southern CONUS. For Monday/Monday night, a weakness develops
within the center of the w-e oriented ridge over southern CONUS,
within the mid-Mississippi Valley. The low over the Gulf of
Alaska opens into a more progressive wave and approaches the
Pacific Northwest.

At the surface on Saturday night a front is expected to be situated
w-e over the Gulf Coast states. A broad area of high pressure will
extend from the Upper Mississippi Valley east to off the New England
coast. A nose of high pressure is develop south within the lee of
the Appalachians. Additionally, an inverted trough is expected
to extend north from the Gulf Coast front, north into eastern
parts of KY/TN. For Sunday/Sunday night, the center of the
surface shifts to over the mid-Atlantic region, and the lee side
ridge is expected to extend south to parts of GA/SC. A front
remains over the Gulf Coast states, however the inverted trough
is expected to pivot clockwise to over the mid-Mississippi
Valley. On Monday/Monday night, the lee side ridge remains in
place. The front over the Gulf Coast states also remains, but
becomes a bit more robust as low pressure develops over west
TX.

A look at the 1 Aug 00Z NAEFS Ensemble Situational Awareness data
shows 850mb temperatures around +12C to +14C Saturday night through
Sunday night. The low end of this range touches the 2.5 to 10
percentile of the 30-year CFSR climatology. For Monday and Monday
night values are a little high at +14C to +15C.

The above weather patterns offers the following forecast. With high
pressure nosing south along the lee of the Appalachians, we will
find ourselves withing a summertime version of a cold air damming
pattern. We are expecting below normal temperatures for the region.
Additionally, with an inverted trough over parts of KY/TN and weak
anti-cyclonic flow around the nose of the high, the far western
portion of the area will be a candidate for late
afternoon/evening isolated/scattered showers and storms.
Temperatures through the period are expected to average three to
five degrees below normal.

Confidence in the above weather scenario is high.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 1130 AM EDT Friday...

Key Point:

1. Temperatures slowly trending from slightly below normal readings
to readings slightly above readings during the period.


A look a the 1 Aug 00Z NCEP Ensemble Mean 500mb Geopotential Heights
shows two distinct centers of high pressure, one over the Four
Corners to TX region, and another off the SE US coast. A general
area of relatively lower heights rests between them over
Mississippi River Valley. A trough is over the Pacific Northwest
with a leading shortwave trough over MT. For
Wednesday/Wednesday night, a general height weakness continues
over the Mississippi Valley, flanked west and east by broad
regions of high pressure. The trough over the Pacific Northwest
is expected to broaden into a longerwave feature. For
Thursday/Thursday night, the height weakness over the
Mississippi Valley shifts east to over parts of the Lower Ohio
and Tennessee Valleys while still being flanked west and east by
high pressure centers. A broad trough will be moving across the
Canadian prairies. For Friday, while the ensembles are fairly
washed out, the weakness in the height field may make additional
progress east to over our region. Broad high pressure remains
situated near the Four Corners region.

At the surface, a ridge continues to hold fast over the lee of the
Appalachians. within a cold air damming scenario. However, there is
some indication that this ridge will start to lift northeast. A
front remains situated from low pressure over west TX to the Lower
Mississippi Valley. However, this front may start to take on
characteristics of a warm front. For Wednesday/Wednesday night, the
warm front is expected to approach our region and the impact of cold
air damming continue to weaken but not conclude. For Thursday,
Thursday night, and Friday there may not be large differences in the
overall pattern across central to eastern CONUS as compared to
Wednesday.

A look at the 1 Aug 00Z NAEFS Ensemble Situational Awareness data
shows 850mb temperatures on Tuesday and Wednesday are expected to
range from +14C to +15C across the region. For Thursday, values inch
higher to +15C to +17C. Likewise for Friday, expect slightly
higher values of +17C to +18C.

The above weather patterns offers the following forecast. The
summertime cold air damming scenario which started over the weekend
will continue into early next week. As we approach mid-week, and by
the close of the work week, we expect the strength of the cold air
damming to lessen, and perhaps start eroding from southwest to
northeast. After another slightly below normal temperature day
on Tuesday, values will start to trend higher as the week
progresses. By Friday, values may be slightly above normal.
Shower/Storm chances will trend from being primarily confined
to the far western sections on Tuesday, to a greater
distribution across the forecast area mid to late week.

Confidence in the above weather scenario is moderate.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 140 PM EDT Friday...

MVFR to IFR cigs persist for this afternoon with
showers/storms mainly occurring southeast of a line from BLF-
BCB-ROA, so have some VCSH/VCTS at times along with tempo groups
for moderate/heavy rain especially at ROA/LYH/DAN/BCB. LWB will
have the least coverage as more stable air starts to work in
from the north. Cannot rule out some VFR at times north of BLF-
BCB later this afternoon, but overall with a wedge setting up
starting tonight all sites will stay sub-VFR with IFR or worse
likely after midnight, mainly from ceilings. However IFR vsbys
possible as well, and LIFR at LWB.

Think showers fade to drizzle at all sites tonight but low
ceiling will likely carry the tafs into 18z Saturday, with some
lifting to high end MVFR by then.

Northerly and light winds turn more ENE tonight through
Saturday.

.EXTENDED AVIATION OUTLOOK...

Morning fog will continue to be a daily threat, but lessening
moisture may help inhibit widespread fog development beginning
Sunday. We may see a few isolated afternoon storms over the
southern Blue Ridge through Sunday, but otherwise VFR expected
into early next week. A warm front starts approaching the area
midweek which may bring showers/storms back into the forecast
along with sub-VFR ceilings/vsbys.


&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Flood Watch until midnight EDT tonight for VAZ010>017-022-
     032>034-043.
NC...Flood Watch until midnight EDT tonight for NCZ001>003-018-019.
WV...None.

&&

$$

SYNOPSIS...WP
NEAR TERM...WP
SHORT TERM...DS
LONG TERM...DS
AVIATION...WP