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877
FXUS62 KRAH 270130
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
930 PM EDT Sun May 26 2024

.SYNOPSIS...
A cold front will approach late today and move through the region
Monday night. Dry high pressure will settle into the region toward
the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 930 PM Sunday...

The severe thunderstorm watch remains in effect until 11 PM for our
northwestern counties. Satellite and radar imagery reveals a well-
defined MCV northeast of Mount Airy over far south-central VA. As
such, the strongest storms are currently along and east of this
feature, stretching from the northeast/northwest Piedmont and
southwest to just northwest of Charlotte. Based on latest trends,
the main severe risk looks to be across the northern and northwest
Piedmont. However, a strong line also exists just northwest of
Stanly County and this is roughly moving ESE. Damaging straight line
winds appear the main risk into late this evening. As the late
evening wears on, it is difficult to say how the storms may hold
together as they track into the Triangle, Sandhills, and Coastal
Plain. Most CAMs have the storms either splitting to the north and
south of the Triangle, though this will be something to watch for.
Certainly convective inhibition will play a role as the night wears
on, limiting overall storm coverage. We do think that the storms
should start to dissipate after midnight as the MCV pushes to the
east. However, upstream convection currently over MO/IL/KY is
forecast to reach portions of the southern Appalachians by early Mon
and could reach the Triad toward sunrise, though convective
inhibition will keep most activity sub-severe until the better
chance comes Mon aftn/eve. Lows should dip into the mid 60s to
around 70, with some patchy fog possible.
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&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
As of 316 PM Sunday...

There is decently high uncertainty wrt to thunderstorms on Monday.
An upstream MCS is forecast to interact with the mountains early
Monday morning. Most guidance suggests the mountains should eat this
up before reaching our western areas. However, there is will still
likely be some ongoing showers (and perhaps a little thunder)
through about mid-morning across the western to central Piedmont
associated with this decaying MCS. Lingering cloudiness may persist
through late Monday morning, however clouds should clear enough in
the afternoon to support the development of scattered thunderstorms.
The spatial extent for afternoon showers/storms will largely depend
on 1) where outflow boundaries set up from the upstream morning
convection and 2) where mid-level vorticity/MCV features traverse.
The recent RAP runs suggest mid-level features could maximize along
and south of the NC/SC border Monday afternoon. It`s therefore not
surprising that latest HRRR runs tends to focus late afternoon
convection across our Sandhills/Southern Coastal Plains (and moreso
active in central SC). Additional weaker perturbations are depicted
further north into central VA maximizing over the Chesapeake Bay. As
such, some high-res guidance (eg. NamNest, ARW) depict a bit more
activity further north across our central to northern
Piedmont/Coastal Plain Monday afternoon associated with these
perturbations.

Any storms that do develop Monday afternoon will have increasing
effective shear to work with (up to 30 to 40 kts). As such, severe
thunderstorms will be possible with any stronger storms that fire. In
fact, guidance is pretty riled up about some stronger mid-level
lapse rates (~7.5 to 8 C/km) developing across our far southern
areas eastward towards the coast. Additionally, model-derived
hodographs, HREF max/min helicity neighborhood probabilities, and
model-derived STP values all support the potential for rotating
storms (and possible tornadoes) from roughly US-1 east across the
inner/outer banks Monday afternoon and evening. Given this
potentially juicy parameter space, it`s no shock that the SPC has
outlined our area in a 15% probability for severe hail and wind
(supported by strong mid-level lapse rate potential), with a smaller
area of up to 5 % probability for tornadoes across locations east of
Raleigh. The overall mean-layer flow should be strong enough to
preclude any widespread flooding concerns, however, can`t rule out
isolated urban flash flooding with any heavier downpour.

Rain chances should diminish late Monday night into the overnight
hours. Persistent swly flow will promote highs in the mid to upper
80s/lower 90s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 155 PM Sunday...

By Tuesday morning, a cold front should be along the coastline of
the Carolinas or immediately offshore. This should keep a slight
chance of thunderstorms in the forecast along the I-95 corridor, but
by nighttime, a several day period of dry weather should begin. The
front will slowly push east, and a surface high will establish
itself over southwestern Ontario Wednesday morning. The high will
expand to the southeast through the rest of the week, with the
center reaching West Virginia by Saturday morning. An upper ridge
along the East Coast will begin to break down on Saturday, and a
shortwave could bring some isolated showers across western counties
Saturday afternoon/evening, although this scenario is only shown in
ensembles and not by deterministic models. A stronger shortwave
appears likely to move across the Appalachian mountains Sunday and
bring a chance of showers to all locations. Surprisingly, the GFS is
showing a decent cap on Saturday and Sunday, so do not have
lightning in the weekend forecast.

Temperatures will trend downward through the beginning of the
period, with highs ranging from the mid 70s to the low 80s on
Friday. High temps will then rebound for the weekend, returning into
the 80s. Thursday and Friday nights will be the coolest, with
widespread lows in the 50s.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 734 PM Sunday...

Main forecast challenge in the near-term will be the threat of
showers and storms with upstream convection over western NC and VA.
The radar trends the last few hours have brought high confidence in
TSRA reaching GSO/INT, roughly between 00 and 02z, with lesser
confidence at RDU/FAY/RWI. As such, greatest restrictions are
expected at GSO/INT. Confidence remains low on how the storms
upstream will hold together as they track ESE toward RDU/FAY and
perhaps RWI as well. As such, the TEMPO groups were retained but for
the MVFR range. Shower/storm activity should wane after 05-06z as
the storm complex pushes east of the terminals. Guidance indicates a
low-end chance of sub-VFR stratus or low VIS at GSO/INT Mon morning.
Otherwise, another upstream MCS in the Midwest could bring -SHRA in
the morning on Mon, most favored at GSO/INT/RDU. A better chance of
storms appears in the aftn/eve period ahead of a cold front.
However, confidence is low on where storms may develop. Right now,
guidance would suggest the best chance would be along/east of US-1.
Hence, we introduced PROB30 groups at RDU/FAY/RWI. Ahead of any
storms, southwest winds Mon afternoon will gust to 25-30 kt.

Outlook: A broken line of showers and storms may impact the
terminals Mon evening, with the highest chance at RDU/FAY/RWI.
Activity should move out by early Tue, with VFR persisting much of
the upcoming week.

&&

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

&&

$$
SYNOPSIS...Badgett
NEAR TERM...Kren
SHORT TERM...Luchetti
LONG TERM...Green
AVIATION...Kren