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167
FXUS62 KRAH 230548
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
148 AM EDT Thu May 23 2024

.SYNOPSIS...
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Disturbances in westerly flow aloft will interact with an underlying
surface trough as they track from the lower Mississippi Valley to
the southern Middle Atlantic Thursday through the weekend.
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&&

.NEAR TERM /THROUGH TONIGHT/...
As of 900 PM Tuesday...

Isolated terrain driven convection that developed within the
instability maximum in place across the mountains and foothills has
fizzled out. Meanwhile, a convective complex of showers and
thunderstorms over eastern Kentucky and TN, is starting to weaken.
This weakening trend is expected to continue as the storms progress
eastward into an increasingly less unstable airmass. As such, dry
conditions are expected to persist overnight.  Western portions of
the forecast will see an increase in some debris cloudiness.
Elsewhere, it should remain mostly clear overnight mainly in the mid
60s, except for some lower 60s in the cooler locations.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 135 PM Wednesday...

By Thur morning, the ridge axis, both sfc and aloft, will be to our
east. Meanwhile, a couple short wave troughs will be centered well
to our N and NW, one just north of the Great Lakes and another over
the northern Rockies. SW flow between those features will gradually
increase over our area as this pattern slowly shifts east. Within
that SW flow will be several low-amplitude waves and likely to be
several MCVs from earlier convection, which models suggest will
support a round of showers and thunderstorms crossing our CWA during
the late afternoon and evening hours Thursday.

With the ridge to our east, southerly flow will result in a warmer-
than-average airmass over our region.  High temps Thursday will be a
bit warmer than today...highs from the mid 80`s NW to around 90 east
and southeast.  Given this warm airmass and dwpts in the mid 60s,
there will be plenty of instability for thunderstorm activity. That,
along with increase mid-level flow and resulting shear will support
a risk for isold severe thunderstorms with damaging winds and hail
the main threats.  The latest round of CAMs generally are fairly
close regarding timing... with a line or several clusters of
thunderstorms moving e/se across our CWA from about 21Z through 03Z
tomorrow.  After the storms move east, quiet weather expected the
rest of the night. Low temperatures will be in the 60s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...

The extended will features a series of chances for afternoon/evening
storms, though the main focus periods appear to be Fri/Sat and Mon
into Tue based on the ensemble and probabilistic guidance.
Temperatures will largely hover above normal through the period with
highs in the 80s to low 90s, perhaps cooling off slightly by midweek
in the 70s to mid 80s behind an early week cold front.

On Friday, models still depict a shortwave moving through some
portion of the area in the westerly flow aloft. However, guidance
differs on where the energy tracks, with the GFS the furthest south
over SC, while the ECMWF/CMC are over VA/NC. Convection from Thu may
bring an outflow through the area, which could focus daytime storms
more across our south and east, though instability will still be
high with moisture still elevated in the 1-1.5 inch range of PWs.
Given the lack of model agreement, hard to determine overall storm
coverage. For now, we have highest PoPs over the Sandhills to
Coastal Plain, in proximity to a sea-breeze and residual outflow
from Thu convection. Severe threat is also questionable with weak
shear, though a stronger storm is certainly possible in the
favorable instability.

That shortwave lingers into Sat, though will start to move off
toward the coastal waters of VA/NC in the afternoon, with ridging
trying to build in from the TN valley. Coverage of storms should be
more isolated, with the best chances along the trough axis - Coastal
Plain and Sandhills counties of central NC.

Ridging will start our day Sunday, but we will start to see
influence from a trough over the Midwest and upper MS valley. There,
models show an area of low pressure over MO/IL tracking into the
Great Lakes by early Mon. Increasing WAA and energy east of this
system will favor chances of isolated/scattered storm activity
during the aftn/eve Sun, most favored across the western Piedmont.

A better chance of area-wide showers/storms appears Mon into Tue as
the aforementioned low pressure system tracks up into Canada,
eventually trying to bring a cold front through the region sometime
Tue or Wed. Some guidance lingers the front over the area Tue before
it fully pushes through sometime Wed. Models show high instability
and increasing shear ahead of the front Mon, so this will be
something to watch in the coming days. For now, our PoPs are highest
in the Mon aftn/eve timeframe, with 30-40 percent chances on Tue and
trending drier by Wed.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
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As of 145 AM Thursday...

VFR conditions are expected to continue through this morning into
this afternoon. Showers and thunderstorms are expected to develop
over the NC mountains by 18z and track along a common cold pool from
INT/GSO (21z) through RDU (23z) and a weakening trend as they
approach RWI/FAY (00/01z). Trailing stratiform rain and isolated
thunder may linger for a few hours through midnight, especially at
FAY and RWI. Surface winds of 5-10 kts out of the southwest through
the afternoon will veer to generally westerly post showers/storms.
Reduced vsby and strong, gusty winds should be expected where storms
occur.

Looking ahead: Sub-VFR cigs and vsbys may develop in the wake of the
convection Thu night and linger through early Fri morning, but
confidence in spatial coverage and flight category is low at this
time. Primarily diurnally driven showers/storms will be possible at
all terminals Fri through Mon.
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&&

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

&&

$$
SYNOPSIS...MWS/CA
NEAR TERM...CBL
SHORT TERM...NP
LONG TERM...Kren
AVIATION...Swiggett/KC