-- Discussion containing changed information from previous version are highlighted. --
726
FXUS62 KRAH 091811
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
211 PM EDT Thu May 9 2024

.SYNOPSIS...
A series of upper level disturbances will interact with an
unseasonably moist airmass over North Carolina through early Friday,
bringing unsettled weather. A cold front will move across the region
on Friday, ushering in drier and less humid air for the weekend.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 1025 AM Thursday...

The severe threat for today has lowered, particularly across the N.
Recent update included a reduction in convection coverage today, esp
across the N and NE, along with timing adjustments according to
trends and new high-res model runs. The latest surface map shows a
trough/outflow across our extreme E and SE, with the showers and
isolated storms that crossed our far S into SC overnight having
dissipated and moved well to our E. We`re left in a weakly unstable
environment, with marginal SBCAPE in our E but plenty of SBCINH. The
next area of rain/storms is now moving into our W, although all of
the lightning so far has held S of the NC/SC state line. The
northern end of the strongest line of convection is holding just S
of CLT, and while this more robust convection is likely to scrape
across our far S and SE sections through the afternoon, the greatest
buoyancy and deep layer shear, and thus the greatest severe threat,
will hold to our S across GA/SC. The latest few RAP/HRRR runs latch
onto the scenario of the stronger convection across our S, perhaps
into the central Coastal Plain, with limited recovery potential
overall, esp across the NW where stabilizing low clouds remain
locked in. Highs were nudged down slightly in a few spots, esp W,
where diurnal heating will be minimal. Highs in the upper 70s to
lower 80s. -GIH

Earlier discussion from 225 AM: An upper level shortwave is
supporting a MCS that is just about to enter the forecast area.
While the nocturnal timing will help to limit overall instability,
the line of thunderstorms is expected to hold together through most
of the forecast area. High-resolution models are not in total
agreement as to the evolution, but with greater instability to the
south, the odds of the line holding together across the forecast
area will be higher across the south. The bulk of the rain appears
to be near the I-95 corridor around sunrise and pushing east of the
area by mid-morning. Unfortunately, models diverge as to the
evolution of precipitation for the rest of the day. Will go with
scattered thunderstorms through the afternoon, but models might have
a better handle on the environment across the area once the current
line of showers/thunderstorms moves through. The entire forecast
area is under a slight (level 2 of 5) risk for severe thunderstorms,
with the primary threat coming from damaging wind gusts. The
greatest threat is likely to come in the morning with the overnight
line of thunderstorms departing the region, but the scattered
thunderstorms in the afternoon could also generate strong winds.
Model guidance has come in a few degrees cooler than the previous
forecast, which removes the 90s from the forecast, but still has
highs in the 80s everywhere.

Scattered thunderstorms could continue east of US-1 into the
evening, but conditions should dry out overnight. Lows will range
from the upper 50s to the upper 60s.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 300 AM Thursday...

A positively-tilted shortwave trough will approach from the TN
Valley on Friday, becoming more neutrally-tilted as it crosses
central NC on Friday evening. An MCS will also be moving east across
GA and SC early in the day, and while the exact location it will be
is still unclear, most high-res guidance keeps it to our south as it
exits into the Atlantic. At the surface, a cold front will begin to
cross through central NC as a wave of low pressure rides along it,
but exactly how far south and east it gets is a bit uncertain. The
aforementioned shortwave will provide some upper forcing for ascent,
so scattered showers will be possible anywhere on Friday afternoon
and evening, but the main threat of storms will be along and ahead
of where the front sets up. The 00z HREF has CAPE values around 500-
1000 J/kg across our southernmost tier of counties, which is where
the SPC expanded a marginal (level 1 of 5) risk of severe storms.
Damaging straight-line winds and hail are the main threats.
Instability and moisture will not be as high as today or yesterday
even down there, so convective coverage doesn`t appear great enough
to justify likely POPs anywhere, but they are still around 50% in
the far south. Forecast highs range from mid-70s far north to lower-
80s far south. Any precipitation will come to an end Friday night as
the cold front sweeps off the coast and lows turn slightly below
normal (upper-40s to mid-50s).

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --
As of 211 PM Thursday...

In the wake of the departing upper trough Friday night, NW flow will
take hold across the area on Saturday. This will allow for continued
dry advection and noticeably cooler temperatures, as highs will only
reach the low to mid 70s across the area. A weak shortwave trough is
expected to rotate through southern VA/northern NC late in the day
Saturday which will bring about a brief increase in cloud cover and
perhaps a stray shower or two, but that`s about it. Model guidance
has been consistent in showing limited precip across the area thanks
in large part to a dry BL featuring dewpoints in the 40s. PoPs in
the 15-20 percent range across the northern tier of counties still
seems appropriate based on today`s ensemble guidance (but even this
may be overdone a bit). Any showers that do manage to make it into
the forecast area should dissipate quickly after sunset with dry
weather expected Saturday night. Lows will range from the upper 40s
to lower 50s.

Sunday will see mostly sunny skies and continued cool/dry conditions
as weak cyclonic flow aloft gradually flattens out as a ridge builds
to our west. Look for another day of below normal highs (mid 70s)
with low temps once again falling into the upper 40s to low 50s. No
concerns about precip as all forcing will be displaced well to the
northeast of the area.

The overall pattern next week looks to be active once again. An
upper low over the Central Plains will slowly migrate eastward on
Monday, inducing downstream ridging across the Southeast states and
ultimately resulting in a fairly quiet day across NC with near
normal temps and dry weather. This will ultimately change though as
the low migrates into the Ohio Valley on Tuesday. Broad/weak forcing
for ascent will overspread much of the Southeast on Tuesday
coincident with an increase in moisture transport (PW`s will be back
above 1.5 inches by Tuesday morning). Showers are expected across
the area on Tuesday although just how quickly they arrive is still a
little unclear (daybreak Tuesday vs afternoon). Regardless, Tuesday
is likely to see widespread cloud cover and rainfall with cooler
temps as a result. While thunder seems unlikely at this stage
(instability displaced well to the south), precip chances will
likely be maximized during the daytime hours with lesser chances
Tuesday night into Wednesday morning.

Wednesday will see continued precip chances as the upper low opens
up and moves through the central Mid Atlantic. As PW`s will remain
elevated and the area will be well within the warm sector,
instability will be much more readily available on Wednesday ahead
of the trough and shower/thunderstorm chances should be a bit higher
(60-70 percent range) especially during the afternoon hours. It`s
also likely that we`ll have at least some clearing to start the day
and temps should make it up into the low/mid 80s prior to the
arrival of the trough.

Thursday should start off dry in the wake of the departing low, but
this looks to be short lived. While shortwave ridging aloft will
build in early in the day, this will quickly turn southwesterly as
yet another longwave trough sets up across the Central Plains and
kicks out a series of embedded shortwaves across the Southeast
states through the end of the week. This would favor diurnally
driven showers and thunderstorms Thursday afternoon/evening,
followed by drying overnight.
-- End Changed Discussion --

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
As of 140 PM Thursday...

The coverage of showers and storms has trended much lower than what
we expected earlier, as the stronger storms have held south of the
NC/SC border, leaving central NC with just isolated showers at most.
Earlier IFR to MVFR cigs over the Piedmont terminals (INT/GSO/RDU)
has lifted and mixed to scattered, and we should see scattered 2-
3kft clouds plus a mix of scattered higher base cu with patchy mid
and high level clouds for the next 24 hours. Another round of
scattered showers and storms is expected across the S and SE Fri,
but this risk will be limited to near FAY and most likely after the
end of the TAF valid period. Surface winds will be around 10 kts or
less from the SW through tonight and from the W Fri, with a few
gusts to 15-20 kts possible this afternoon.

Looking beyond 18z Fri, S and E sections including FAY may see a
storm pass nearby during the mid to late afternoon Fri. Otherwise,
VFR conditions are expected through at least Mon, with a cooler and
less humid air mass moving in starting late Fri. Rain and isolated
storms are expected to move in Tue morning, with an increasing
chance of sub-VFR conditions. -GIH

&&

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

&&

$$

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