-- Discussion containing changed information from previous version are highlighted. --
460
FXUS62 KRAH 241106
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
706 AM EDT Fri May 24 2024

.SYNOPSIS...
A warm and humid air mass over our region, combined with the passage
of a series of upper level disturbances over the area, will produce
unsettled weather through Monday, with daily chances of showers and
storms. A drier air mass will arrive by the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 350 AM Friday...

A convectively induced disturbance over the Virginias this morning
will slowly drift through southern and eastern VA through this
evening with a trailing shear axis pivoting across central NC. Ahead
of this feature, smaller scale forcing from MCVs moving through the
western Piedmont will overlap with a moist (PWAT around 1.7") and
unstable (MUCAPE 1000-1500 J/kg) environment over central NC to
develop showers and storms early this morning and move eastward
across the area through daybreak. Overnight, these showers and
isolated storms will likely remain elevated as MLCIN remains
relatively strong (100-200 J/kg) and result in mostly a heavy rain
and lightning threat. After daybreak, point soundings from the HRRR
and RAP suggest boundary layer heating, eroding MLCIN and increasing
MLCAPE (500-1000 J/kg) where we may see a brief surge in updraft
intensity over the Coastal Plain before exiting to the east. Overall
bulk shear of 20-30 kts may lead to some loosely organized clusters
with most likely sub-severe wind gusts as the primary threat given
the unfavorable diurnal timing in the early morning.

Behind the morning convection, additional showers and thunderstorms
will be possible this afternoon and evening as MLCAPE rises to 1000-
2000 J/kg from NW to SE across central NC. Hi-Res guidance is in a
general agreement that the greatest coverage will likely be tied to
the shortwave pivoting across VA into northeast NC Piedmont and
Coastal Plain. Additional airmass storms will be possible farther
south across the southern Piedmont, Sandhills and Coastal Plain
where the greatest plume of instability will exist. Coverage across
the area should be less than the previous 24 hours as drier air at
500mb spreads across the area through the afternoon and evening
hours. Bulk shear will be relatively weak (10-20 kts) where
instability will be maximized over the Sandhills and southern
Coastal Plain and result in mostly a pulse type storm mode. Within
the strongest updrafts, an isolated risk for strong to severe
downdrafts capable of strong to severe wind gusts and hail will be
possible. Convection should dissipate with loss of diurnal heating
as shortwave ridging builds in over central NC into VA.

A drier thermo-profile overnight will result in mostly clear skies
minus some thin cirrus and result in a more optimal radiational
cooling night and potential for patchy to areas of fog to develop
into early Sat morning. Lows will dip down into the low/mid 60s.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 305 AM Friday...

A shortwave trough, likely a remnant MCV from the current convective
complexes over SE OK into the Arklatex region, is expected to be
over NC early Sat (although it is worth noting that the
predictability of individual perturbations and convective initiation
within such a wavy flow that is so heavily influenced by
convectively-induced PV maxima and near-surface outflows is rather
low). Weak surface troughing will hold across our Piedmont. Low
level lapse rates should be fairly high with good mixing and warm
surface temps, and the HREF members show SBCAPE peaking Sat
afternoon at 1000-2000 J/kg with PW around 1.5", near the 90th
percentile. But the GFS/ECMWF have somewhat low mid level lapse
rates, and mid level flow is likely to be very weak, so the risk of
severe storms appears to be lower than previous forecasts suggested.
With high moisture through the column and high dewpoints in the
upper 60s to around 70, scattered to numerous storms are possible
with heating, with highest coverage across the Coastal Plain and E
Sandhills, E of the surface trough. The anticipated slow storm
motion could lead to some heavy rain rates and isolated minor
flooding threats. Expect dwindling pops overnight as the shortwave
trough shifts off the coast and our heights aloft begin to rebound.
Highs 84-90 and lows 64-70. -GIH

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 155 AM Friday...

Best rain chance in this stretch will be Memorial Day into the
night. A pattern change should bring a dry period for mid to late
week.

Starting Sun, with the shortwave trough expected to be shifting well
off the Mid Atlantic coast early, we`ll be under the influence of
mid level shortwave ridging building in from the W, ahead of a
potent northern stream low/trough over MT into the Midwest. While
the weak surface trough will hold in place through the NC Piedmont,
there will be little opportunity for low level moisture influx until
late in the day into Sun night, and even this is more focused to our
W. The warm and relatively stable mid levels and lull in mid level
flow along with the limited moisture transport into the area should
greatly limit rain chances, and will keep late day and evening pops
mainly in the far NW to account for any mountain convection spilling
toward our area. It`ll remain warm and humid for this time of year,
highs in the upper 80s-lower 90s and lows in the upper 60s/lower 70s.

Rain chances may increase late Sun night with an upturn in low level
moisture and greater PW spreading in ahead of a pronounced low to
mid level trough that will move in from the W, attending an
approaching surface cold front. Winds at all levels will strengthen,
including a low level pump from the Gulf that starts ramping up Sun
night. The improving kinematics and vorticity maxima moving through
the mean trough base across our area in tandem with this
increasingly deep moisture should prompt high rain chances. The
severe threat with any storms is tough to pin down, as an early
arrival of frontal showers and clouds will hold down SBCAPE,
although the incoming cooling aloft and rising low and mid level
lapse rates should still allow for a risk of a few strong storms.
Still warm and muggy with highs in the upper 80s-lower 90s. Lower
dewpoints should start to filter into the NW Mon night, so expect
slightly lower lows there, mid 60s with upper 60s to around 70
across the S and E.

Behind this front, as mid-upper level longwave troughing sets up
over E NOAM with low level CAA and drying through the column, we
should see largely dry weather Tue through Thu. Some deterministic
models do slow down the cold front such that a passing wave produces
convection chances across the S and E Tue, so will leave in a low
chance there. Otherwise, will have dry conditions through Thu with
temps running close to normal. -GIH

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
As of 705 AM Friday...

A decaying band of showers and isolated storms is currently
progressing through FAY and south of RDU and will move through RWI
through 14z this morning. Mostly light rain and a brief MVFR cig may
accompany this band. VFR conditions will return to all TAF sites
this morning with light winds generally out of the southwest veering
towards northerly through the afternoon/evening. Scattered showers
and storms will again be possible this afternoon that develop over
north-central NC and move east-southeast. Most likely site to see
storms will likely be RDU and RWI, but direct terminal impacts are
uncertain given the scattered nature of the afternoon convection.
Thin cirrus overnight and calm winds within a moist airmass may
prompt patchy fog over central NC tonight, but confidence in areal
coverage and density is too low at this time to include at this time.

Looking ahead: Primarily diurnally driven showers/storms will be
possible at all terminals through Tue, with the best chances Fri,
Sat, and Mon.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...Hartfield
NEAR TERM...Swiggett
SHORT TERM...Hartfield
LONG TERM...Hartfield
AVIATION...Swiggett/KC