348
FXUS61 KRNK 250548
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
148 AM EDT Wed Sep 25 2024

.SYNOPSIS...
A slow-moving frontal system will meander along the Ohio River
Valley over the next several days, triggering rounds of showers
and thunderstorm activity through much of the workweek. Helene
is forecast to move northward from the Gulf of Mexico toward
the end of the work week, and may bring more widespread
rainfall to the region.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 130 AM EDT Wednesday...

Key Messages:

1) Heavy rain and thunderstorms to continue through the early
morning hours.

2) A lull in rainfall during the day, but will see an increase
in rain again tonight across the mountains.

Ongoing rain and thunderstorm activity this morning will
continue through daybreak in association with a stalled surface
front extended south from West Virginia into Western Virginia
and then into the North Carolina Piedmont. Favorable upper
divergence remains overhead as an upper low closes off over the
middle Mississippi Valley. High ambient moisture continue to
pool over the area, thus ongoing rain/storms this morning
continue to be very efficient rain producers. Therefore, the
threat for flooding continues this morning.

CAM guidance suggests there will be a lull in rain/storms late
this morning and into the afternoon hours as the stalled front
lifts north again as a warm front. May even have some pockets of
clearing and peeks of sun by the afternoon.

Attention then turns to the mountains tonight from northwest
North Carolina into far southwest Virginia as deep tropical
moisture begins to be drawn north and interacts with a stalled
front across the Tennessee Valley. A nearly unidirectional
southerly flow up to 500mb directly from the tropics will result
in bands of rain developing and repeatedly training from south
to north over the same areas. Heavy rainfall could begin as
early as tonight across the Carolina mountains and extend north
into southwest Virginia. Confidence has increased enough that a
Flood Watch will be introduced for this region.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Issued at 135 PM EDT Tue Sep 24 2024

Key Messages:

1: Outer bands of TS Helene will cause showers as early as Thursday

2: Heaviest and most widespread rainfall will be Friday and Friday PM


Moisture convergence over a weak wedge will continue to cause
showers and embedded storms Wednesday night. TS Helene will still be
in the Gulf, but entering the influence of a closed 500mb low near
the Arklatex and MS. This low will accelerate Helene quickly
northward, going from the FL panhandle to western Carolina in the
span of just 12 hours. This could place the outer bands of tropical
moisture and rain in our NC counties as early as Thursday afternoon.
Friday looks to be the most active day, with rain expected for most
of the day throughout the CWA. Flooding will be a definite concern
as we expect 3-4" along the southern Blue Ridge and in the High
Country, and 1-3" across the remainder of the CWA. As always with
banding in tropical systems, due to the nature of banding there
could be higher amounts in localized areas.

Flooding concerns will be exacerbated by the enhanced winds,
particularly near and south of the NC/VA border. Above 3kft
elevation, winds could gust up to 30kt. This will blow down early
dead leaves, serving to clog up drains, culverts and sewers.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 200 PM EDT Tuesday...

Key Messages:

1) Lingering moisture from Tropical Storm Helene will remain in the
area through the forecast period, with showers possible each day.

2) High pressure wedges back into the region on Sunday, decreasing
rain chances and keeping below average temperatures through midweek.

As Tropical Storm Helene begins to dissipate over the Appalachian
mountains early on Saturday, remnant moisture and breezy conditions
will remain across the area. Rain chances decrease significantly on
Saturday but remain possible. High temperatures will be in the 70s,
with eastern piedmont locations around 80. For Sunday, surface high
pressure over New England will begin to wedge back into the RNK CWA,
pushing drier and cooler air southward. Residual moisture from
Helene will continue to ride over top of this wedge, leading to
light showers and cloudy conditions continuing into early next week.

Due to the cloud cover and high pressure wedge, temperatures are
expected to remain below normal beginning on Sunday. Highs will be
in the 60s and 70s, with lows in the 50s to around 60 degrees
through midweek. Winds also remain slightly elevated due to the
wedge. There is some model disagreement with where the remnant low
and associated moisture will go early next week. The Ensemble
Situational Awareness Table continues to keep precipitable water
values around 1.5 inches for early next week. Due to this, PoPs are
kept modest through the forecast period, with showers possible each
day.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
As of 145 AM EDT Wednesday...

Poor flying conditions through daybreak with widespread IFR/LIFR
across the area. A combination of low cigs/vsby, along with
areas of heavy rain will continue through daybreak and may
linger a few hours after sunrise. Should see some slight
improvement during the late morning as rain begins to come to an
end. However, sub-vfr cigs are still likely for the mountains
throughout most of the day. A period of low end VFR for
ROA/LYH/DAN possible mid/later afternoon.

Rain and thunderstorms will increase again tonight along and
west of the Blue Ridge, and especially for the North Carolina
mountains and for southwest Virginia. Outside of the heavy rain,
low cigs/vsby will result in another round of widespread
IFR/LIFR late in the TAF period.

EXTENDED AVIATION OUTLOOK...

MVFR/IFR stratus and fog are expected to occur in rounds through
at least the end of the week, and increasingly likely to
persist through the end of the workweek.

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...Flood Watch until 8 AM EDT this morning for VAZ016-017-032>034-
     043>046-058-059.
NC...Flood Watch until 8 AM EDT this morning for NCZ003>006-020.
WV...None.

&&

$$

SYNOPSIS...BMG
NEAR TERM...BMG
SHORT TERM...VFJ
LONG TERM...JCB
AVIATION...BMG