784
FXUS62 KRAH 161927
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
327 PM EDT Mon Sep 16 2024

.SYNOPSIS...
An area of low pressure centered just inland along the South
Carolina coast will drift through the Carolinas tonight into Tuesday
morning. This system will linger and gradually dissipate across the
western Carolinas through mid week.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 325 PM Monday...

A Wind Advisory remains in effect until 2 AM Tuesday. A Flood Watch
remains in effect until 8 AM Tuesday.

Conditions will continue to rapidly deteriorate through the
remainder of the afternoon into the overnight time frame. The center
of low pressure will pivot north-northwest and track along the NC/SC
border through midnight, and in the process pulling multiple hazards
into central NC.

Flooding Threat: Scattered to potentially numerous instances of
flash flooding will be possible through the afternoon into this
evening. The main hazard will be multiple hours of moderate to heavy
rain as the center tracks closest to our area. Upstream observations
along the coast NC coast has shown a steady feed of heavy rain to
the north of the elongated pressure center producing 1 to 3 inch per
hour totals. This area will spread northwest into the
southern/central Coastal Plain and the Sandhills from now through
roughly 10 PM. Rain rates and greatest flooding threat will likely
be highest over this area as an arc of up to 500-1000 J/kg of MUCAPE
accompanies this band. This will result in an additional 2-5 inches
on top of the 0.5 to 1.5 inches that has fallen so far. Hi-Res
guidance suggest that locally higher amounts of 7 to 8 inches will
be possible. Farther west into the southern Piedmont, rain rates
should start to lower as this band outruns the instability axis, but
persistent moderate/heavy rain should still result in a continued
swath of 1-3 inches with up to 5 inches possible over this area.

Wind Threat: The secondary threat will be the strong wind gusts
expected through the afternoon/evening hours. A tightening pressure
gradient associated with the approach of the low pressure center and
the surface high pressure over the Northeast will steadily increase
winds through the late morning through the evening hours. Northeast
winds near the NC coast close to the center have been producing
gusts of 35 to 45 mph. These gusts will lift into the area by this
afternoon into the southern Coastal Plain, Sandhills and southern
Piedmont through the evening before gradually weakening through 2 AM
Tuesday. Farther north, greater distance from the center in a stable
airmass should temper gusts to up to 25-35 mph with sporadic gusts
up to 40 mph.

Tornado Threat: A low-end conditional threat for isolated tornadoes
will be possible, mainly across the southern Coastal Plain this
afternoon and pivoting northward into the central Coastal Plain
through the early overnight period. An axis of low 70s dew points
advecting into the southern Coastal Plain and limited diurnal will
result in 500-1000 J/kg of MLCAPE overlapping 100-200 SRH in the 0-
1km layer. Any organized cell that can develop within this regime,
they would be capable of producing a tornado or two.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 212 PM Monday...

The remnant surface low is projected to be somewhere over north-
central to northwest SC at the start of the period. The system will
continue to track west-northwestward during the day/night, occluding
and filling, weakening as it does so. While the mid-level dry slot
is forecast to lift through during the morning and afternoon from
south to north, continued moisture transport from 925-850 mb will
remain in place, especially along and north of US-64 and into the
northwest Piedmont. As such, highest shower chances during the day
will be in these areas, with lower chances across the southern
Piedmont, Sandhills, and southern Coastal Plain. Wind gusts will be
highest in the morning, between 20 and 30 mph and some occasional
gusts to 35 mph, along and north of US-64 and over the Triad. Gusts
should then start to weaken by the afternoon and evening as the low
occludes and the pressure gradient relaxes. Additional rainfall
amounts one to three quarters of an inch are possible along/north of
US-64, with a tenth of an inch or less across our southern counties.
Some isolated spots of the Triangle to north of US-64 could be
higher per the 12z HRRR/HREF with any training storms, which is
consistent with WPC`s marginal excessive rainfall in this area.

As for severe potential, SPC currently is not highlighting any area
of concern. There does remain, however, a chance of some low-topped
supercells capable of brief tornadoes mainly east of I-95 and north
of US-64, roughly from a line east of Raleigh to Rocky Mount to
Roanoke Rapids. This corridor appears most favored for instability
coupled to stronger low-level shear. It would appear the threat
would be from the morning hours into midday. Thereafter, the low-
level wind field lessens, thereby reducing the severe threat.

Highs Tue should be in the low 70s over the far NW, including the
Triad, to the upper 70s to near 80 along/east of US-1. Rain chances
should lessen by evening/overnight as the low weakens and activity
shifts into VA into far western NC, with lows in the low to mid 60s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 212 PM Monday...

The surface and mid/upper low from Mon is forecast to continue to
weaken as it slowly migrates from far western NC Wed into the Mid-
Atlantic Thu and Fri from a closed low to a general open trough.
While ensemble guidance is not in complete agreement, it appears
troughing will remain in place through the weekend over the Mid-
Atlantic and NC and perhaps into early next week as a blocking
pattern remains in place. At the surface, the surface low in western
NC will weaken Wed into Thu. Meanwhile, development of a persistent
offshore low off the Mid-Atlantic and Coastal NC will set up Fri
through probably early next week. This along with cooler high
pressure poised to extend into our area from the NE US and Canada
will promote a persistent NE flow late in the period into next week.

As for our sensible weather impacts, we are presently not
anticipating any high-impact weather during the extended. Showers
and isolated storms will remain in the forecast Wed and Thu (30-50
percent) as the upper-low remains over the area with afternoon
instability and a lingering surface trough/boundary. Once we get
into Fri, it would appear rain chances should lessen as the mid-
level trough axis slides east and weak high pressure builds in from
the north. Over the weekend, rain chances will persist, but are
currently projected to be favored along eastern sections of NC over
the Coastal Plain, mainly along and east of the I-95 corridor. This
region is most favored where onshore moist flow will reside and
closer to the trough and offshore low pressure. Ensemble solutions
start to deviate late this weekend and early next week, so kept PoP
chances on the low end (20-30 percent).

As for temperatures during the period, highs will start out near to
just slightly above normal Wed-Sat in the mid/upper 70s to low/mid
80s, then below normal highs Sun-Mon in the low to mid/upper 70s.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 200 PM EDT Monday...

Widespread moderate to heavy rainfall, lowering cigs, MVFR/IFR vsby,
gusty winds 25 to 25 kts and low-level wind shear of 45-50kts will
continue to spread across central NC through the afternoon into the
overnight hours. The strongest winds and threat for thunder will be
greatest at KFAY through 02z tonight. An axis of heavy rain along
the coast will also pivot north towards RWI around 05z and may bring
a risk for thunder, but confidence is low. As the widespread rain
lifts north into VA precipitation will likely transition to a more
showery nature through the remainder of the TAF period. Some
improvement towards MVFR conditions at RWI/FAY near the end of the
forecast period.

Outlook: Conditions will improve to VFR at FAY and perhaps RWI Tues
afternoon before a return to IFR/LIFR cigs Tues night into Wed.
Showers and isolated thunder will be possible at the northern TAF
sites Tues afternoon/evening. The threat for afternoon
showers/storms and early morning stratus will continue through
roughly Thurs night.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Tuesday morning for NCZ007>011-021>028-038>043-
073>078-083>086-088-089.
Wind Advisory until 2 AM EDT Tuesday for NCZ038>042-073>078-083>086-
088-089.

&&

$$

SYNOPSIS...Blaes/Swiggett
NEAR TERM...Swiggett
SHORT TERM...Kren
LONG TERM...Kren
AVIATION...Swiggett