369
FXUS61 KRNK 231907
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
307 PM EDT Mon Sep 23 2024

.SYNOPSIS...

High pressure is situated across the Mid-Atlantic today, wedged
against the eastern face of the Appalachians. A slow-moving
cold front will meander along the Ohio River Valley over the
next several days, triggering rounds of showers and thunderstorm
activity that will persist through much of the workweek. PTC 9
lifting northward from the Gulf of Mexico toward the end of the
work week may bring more widespread rainfall to the region.


&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 PM EDT Monday...

Key Messages:

1) Rounds of widely scattered showers and thunderstorms mainly
impacting the mountains during the afternoon and into the
evening are expected today.

2) Additional rounds of showers and thunderstorms are expected
again on Tuesday, with another marginal risk for excessive
rainfall forecast across a majority of the forecast area. A
marginal risk for severe thunderstorms is also forecast across
western portions of the forecast area for Tuesday.

3) Cloudy conditions again tonight are expected with patchy fog
and periods of drizzle.

A mid-level shortwave vorticity perturbation is expected to
push across the region late Tuesday afternoon and evening. This
coupled with a stalling cold front west of the Appalachian
mountains, and an upper level trough digging into the mid-
Mississippi valley will provide sufficient upper level
support/forcing for ascent for widespread shower and
thunderstorm developing Tuesday afternoon. A surface wedge
situated across the coastal plain will lead to southeasterly
flow across the VA/NC border during the afternoon and evening
hours on Tuesday. Current CAM guidance suggests that a warm
front will remain situated along or just north of the VA/NC
border tomorrow, which may provide a focus for severe weather,
and training thunderstorms. The biggest caveat will be the
placement of this boundary Tuesday afternoon, and the amount of
clearing south and west of this boundary to allow for
destabilization. WPC currently has an areawide marginal risk for
excessive rainfall on Tuesday as widespread rainfall totals of
1-2 inches are forecast. SPC similarly has a marginal risk for
severe thunderstorms for much of the western portion of the area
where destabilization is expected to be greatest. Overall,
expect highs in the upper 70s where clearing occurs across SW
Virginia and the VA/NC border, and low 70s to upper 60s where
low clouds hang around across interior Piedmont locations.


Confidence in the near term is moderate.

&&


Short Term .../TUESDAY NIGHT THROUGH THURSDAY NIGHT/
As of 215 PM EDT Monday...

Key Messages:

1: Daily showers and storms

2: Potential for outer bands of PTC9 to bring further rain Thursday


A glacially slow cold front attendant to a low in the southern Great
Lakes will continue its march to the east in our direction. The
southerly flow will fetch plenty of Gulf moisture to interact with a
stationary front over the Mid-Atlantic, leading to showers and
storms for most of the day through Wednesday evening. Wednesday
there is a marginal risk of severe storms west of the Blue Ridge,
where orographic effects could enhance the freely available moisture
and moderate instability into stronger convection. Main threat would
be damaging thunderstorm winds. Localized flooding may also be a
concern, as PWATs will be in the 1.5-1.75" range for most of the
CWA, and storms in this environment have been observed to be
extremely efficient rain producers. This problem could be
exacerbated by freshly fallen leaves as we are getting into the fall
season, which could be piled up from the aforementioned thunderstorm
winds. This can clog drains and sewer openings, preventing runoff in
streets and sidewalks.

By Thursday evening, we may be close enough to feel the impacts of
Potential Tropical Cyclone 9`s outer rain bands. PTC 9 is progged to
be quite a wide storm, so even though the center of the storm
(according to the current NHC track) will be near the panhandle of
Florida, the outer rain bands (and tropical moisture to interact
with the pre-frontal environment) could impact our NC counties as
early as Thursday evening.

Temperatures will be around normal, with little diurnal sway due to
high dewpoints and widespread thick cloud cover.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 200 PM EDT Monday...

Key Messages:

1) Confidence is increasing that Potential Tropical Cyclone Nine
will affect the area Friday into the weekend, though exact impacts
remain uncertain.

2) Rainy, cloudy, and breezy conditions will persist and keep below
average high temperatures in place through the weekend.

High pressure over New England and the Great Lakes region will begin
to back out of the area on Friday, as PTC9 moves northward towards
our area. This high pressure, along with a cutoff upper-level low
over the Great Plains will steer PTC9 towards the northwest. Where
this turn occurs is still uncertain and will determine the magnitude
of impacts seen across the RNK CWA. Most model ensembles continue to
indicate the center of the low somewhere in the southern Appalachian
Mountains on Friday, but the past few model runs have not been
consistent with the track post-landfall, varying east to west.
Should the current forecast track continue with the storm moving
into far western North Carolina, heavy rainfall will be expected
across the CWA on Friday into Saturday as models are consistently
showing a band of rain spreading over the area.

Regardless of the exact track of the system, moisture is expected to
increase with showers possible each day through the period. PoPs
have been raised to reflect recent model runs and taking into
account that a tight gradient between the low pressure system to the
south and the high pressure system to the north will allow strong
easterly upslope flow to further enhance rainfall across the area.
This setup will continue into Saturday, though PTC9 will weaken as
dry air begins to overtake the system.

The aforementioned high pressure over New England will wedge back in
on Saturday, keeping cloudy and cool conditions in place, but
decreasing rain chances. Showers remain possible Sunday into Monday,
though Monday is trending drier. Highs throughout the period will
generally be in the 60s and low 70s, with breezy conditions
persisting. Low temperatures will remain mild, around 60 degrees
this weekend before lowering into the 50s next week.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
As of 130 PM EDT Monday...

MVFR to IFR CIGs are still present across much of the Piedmont
this afternoon. Some drier air aloft is trying to sneak into the
region from the west, and is aiding in VFR conditions at BLF,
BCB, and LWB; however, it is unlikely to reach LYH and DAN. ROA
may lift to VFR conditions briefly this evening before quickly
dropping back into MVFR to eventually LIFR CIGs during the
overnight hours. All sites are expected to drop to LIFR CIGs
during the overnight hours before some breaking/lifting in the
clouds across the VA/NC border lifts north throughout the
afternoon on Tuesday.

EXTENDED AVIATION OUTLOOK...

MVFR/IFR stratus and fog are expected to occur in rounds through
at least the middle of the week, and increasingly likely to
persist through the end of the workweek. Rounds of showers and
thunderstorms will also continue to pass across the lower Mid-
Atlantic.

Low pressure lifting northward from the Gulf of Mexico toward
the end of the week may bring more widespread rainfall and sub-
VFR conditions to the region.

&&

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

&&

$$

SYNOPSIS...NF
NEAR TERM...EB
SHORT TERM...VFJ
LONG TERM...JCB
AVIATION...EB/NF