Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 302042
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
345 PM EST Mon Jan 30 2023

.SYNOPSIS...
High pressure will remain over the area through tonight while a
slowly migrating cold front hangs up along the Appalachians. This
front will stall across the area through Thursday, before a strong
high pressure system migrates across the eastern US on Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 307 PM Monday...

Low-level downslope flow has led to substantial clearing of the
cloud field across most of the central/western Piedmont the last
several hours. Expect this gradual scattering out of clouds to
advance east of I-95 through early this evening.

Further west, a slowly migrating cold front was observed from
northern Mississippi extending northeastward through TN/KY and up
into OH/PA. This cold front will hang up along the Appalachians
through the overnight period.  Aloft, swrly flow in the mid-levels
will turn more wrly through the overnight period as anomalous mid-
level ridging maintains across the southeast.  This synoptic setup
will promote dry conditions through tonight/early tomorrow morning.
Low-level clouds will quickly sock back in across our area tonight,
promoting similar overnight lows as last night in the upper
40s/lower 50s.

Latest high-res guidance continues to signal the potential for
widespread areas of fog across central NC early to mid Tuesday
morning. Given last night`s rainfall, no expected appreciable change
in this moist airmass, and the potential for a strong subsidence
inversion (supported via forecast soundings), it appears
conceptually likely that widespread fog, some dense, will develop
tomorrow morning across all of central NC. Will leave it up to the
evening shift to assess observational and model trends, but a Dense
Fog Advisory may be needed as potential impacts to the early Tuesday
morning commute seem possible.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 307 PM Monday...

The cold front should be northwest of the region Tuesday morning,
with a chance of rain expanding from northwest to southeast as the
morning progresses. Decided to slightly expand the region of likely
pops a little further south towards US-64, although it still appears
that the best forcing for precipitation will remain to the north
across Virginia. This should not bring much more than a tenth of an
inch of rain. After a brief lull in rain Tuesday evening, it appears
that another wave of forcing will bring another round of rain,
mostly between midnight and noon on Wednesday. This batch of rain
should be a little heavier, with amounts up to four-tenths of an
inch. Most of the region should dry out temporarily once again late
Wednesday afternoon into Wednesday evening before yet another round
of rain moves in from the west overnight, with likely pops primarily
extending from Raleigh and Fayetteville to the west. Temperatures
should be slightly above normal Tuesday and Tuesday night in advance
of the cold front moving through the region. As the widespread cloud
cover continues Wednesday and Wednesday night, the diurnal
temperature cycle will be reduced, resulting in below normal highs
and above normal lows.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 345 PM Monday...

Overview: Wet and cool weather is a near certainty Thu into Fri
morning, followed by clear and sharply colder weather late Fri
through Sat night before temps rebound starting late Sun. Two main
areas of interest are the Thu/Thu night rain and possible light
wintry precip in the W Piedmont early Sun.

Thu/Fri: Likely to categorical pops are warranted Thu into early Fri
as the mid level positively tilted shortwave stretching from the Mid
Miss Valley to TX early Thu pushes eastward toward NC. At the
surface, the high pressure area will drift off the Mid Atlantic
coast, then a low over LA tracks ENE along the front to our S,
slowly weakening as its energy is transferring to a strengthening
low near the NC coast. The front will hold to our S, keeping us in
the cooler air and resulting in very small diurnal temp change. As
the surface low and mid level trough approach, forcing for ascent
will strengthen via height falls and a strengthening/tilting upper
jet to our N, with NC in its right entrance region. Surface temps
areawide should be comfortably above freezing Thu morning such that
the risk of wintry precip is negligible. And it still appears that
the polar surface high building in from the NW early Fri will be
chasing the moisture, which will limit any wintry threat as the
system pushes SE and away from central NC. Expect chilly highs
mostly in the 40s Thu with a cold rain spreading in, making for a
dismal day. Lows Thu night will be in the mid 30s to lower 40s,
followed by highs Fri in the mid 40s to lower 50s, as the surge of
truly colder air is a bit delayed by the higher terrain. We`ll have
precip ending and partial clearing NW to SE through the day.

Fri night-Mon: Subsidence clearing and strengthening CAA will
dominate Fri night/Sat as the shortwave trough departs with a fast
NW steering flow. Temps will be quite frigid, with lows in the upper
teens to mid 20s and highs in the 30s to lower 40s as thicknesses
bottom out 40-50 m below normal. The pattern gets complex Sat night
into Sun, as the polar surface high`s center passing over the St
Lawrence Valley, providing plentiful cold air southward into NC. The
cold high then shifts to off the Canadian Maritimes through early
Sun, allowing a coastal inverted trough or front to begin tracking
inland. Meanwhile, aloft, a shortwave trough over the Plains late
Sat amplifies as it heads E into the E CONUS through Sun night,
strengthening moist upglide up and over the lingering wedging cold
pool deposited by the Arctic high. Several models and ensemble
members indicate deep enough saturation and lift generated by DPVA
and moist upglide for spotty precip late Sat night through Sun, and
the thermal profile suggests that it could begin as a light
snow/sleet mixture over the Piedmont before becoming mostly freezing
rain and then rain by midday. At this time, the model lift is not
particularly robust with the incoming trough, but given the
preceding anomalously cold air in place and timing of overrunning,
we may indeed see a chance of wintry precip late Sat night through
Sun morning -- again, starting out as very light snow/sleet before
evolving to a chance of freezing rain, then just rain, with the
wintry precip focused on areas W of Hwy 1, and lasting the longest
through the core of the NW Piedmont including the Triad. A lot could
change here, so stay tuned. Expect lows Sat night mostly in the 20s,
followed by highs Sun from the 40s W of Hwy 1 to the 50s from Hwy 1
E, as the inland moving coastal/wedge front bifurcates the forecast
area. Low rain chances clear out W to E late Sun and the mid level
trough will exit to our E early Mon as high pressure builds in,
resulting in fair skies and seasonable temps. -GIH

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 1258 PM Monday...

This morning`s IFR CIGs have scattered out at KINT/KGSO/KRDU early
this afternoon, but still remain at KFAY and KRWI.  KINT/KGSO/KRDU
should maintain VFR conditions through early tonight as partial
clearing continues across the Piedmont the next several hours. KRWI
should scatter out to VFR by ~19 to 20Z, followed by KFAY around ~20
to 21Z.

With no expected appreciable change to this moist air mass the next
24 hours, aviation conditions are expected to rapidly deteriorate
once again tonight through mid-morning Tuesday. CIGs will once again
drop to IFR/LIFR at all terminals from around ~04Z and continue into
the early to mid afternoon.  Additionally, there is a strong signal
in the guidance for widespread areas of fog, some dense, to develop
early Tuesday morning and persist into the mid-morning period. One
caveat, however, is that increasing mid to high level clouds tonight
could dampen fog potential some. But given the expected strength of
the subsidence inversion (via forecast soundings), recently moist
soils from last night`s rain, and the lingering moist air mass, it
appears conceptually that widespread fog is likely early Tuesday
morning.  Lastly, some spotty light rain/drizzle may reach KINT/KGSO
within a few hour window late Tuesday morning/early afternoon.
Elsewhere should remain dry through the end of the TAF period.

Looking beyond 18Z Tuesday: More periods of rain and restrictions
are then expected from Tuesday through early Friday, with the best
chance on Thursday and Thursday night.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Luchetti
NEAR TERM...Luchetti
SHORT TERM...Green
LONG TERM...Hartfield
AVIATION...Luchetti/Danco


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