-- Discussion containing changed information from previous version are highlighted. --
059
FXUS62 KRAH 031836
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
236 PM EDT Fri May 3 2024

.SYNOPSIS...
Sub-tropical high pressure will extend across the South Atlantic
states today, while a backdoor cold front will move through eastern
VA and northeastern NC. The front will settle southwestward and into
north-central NC tonight, where it will stall through Saturday
night, then weaken and move northward into VA on Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1145 AM Friday...

A mid/upr-level ridge centered near the srn Middle Atlantic coast
will remain so through tonight, while a mid-level trough and
embedded, weak MCVs now over the ern OH and TN Valleys will be
directed around the ridge and into the cntl Appalachians.

At the surface, a 1019-1020 mb sub-tropical high will remain
situated off the coast of the Carolinas. Meanwhile, a backdoor cold
front, now stretching from the mouth of the Chesapeake Bay nwwd to a
1014 mb frontal low over OH, will merge with a developing bay breeze
and move swwd to the vicinity of the Roanoke River between 22Z-00Z. A
separate, srn stream front extending from cntl TX enewd and across
the lwr MS and TN Valleys, to a 1013 mb frontal low over Middle/wrn
TN, then ewd across nrn GA and the Piedmont of the Carolinas, will
move little through the period.

With no airmass change from Thu and continued influence of ridging
aloft, today will be persistently, unseasonably warm, with
temperatures continuing at 10-15F above average - mid 80s to around
90. Showers and isolated storm will focus today along both fronts
noted above, including into the NC nrn Coastal Plain and far ne
Piedmont early this evening and also with diurnal heating along a
differential heating zone evident in late morning visible satellite
and surface observational data along the srn stream front from AGS
to HKY. The latter activity, should it indeed develop, would then be
steered in weak wswly steering flow and into the srn and wrn NC
Piedmont late this afternoon-evening.

Areas of persistence fog and low stratus will likely redevelop into
the srn-cntl Coastal Plain and ern Sandhills tonight, while a
separate area of post-frontal, very low stratus will develop behind
the backdoor front across the ne Piedmont and nrn Coastal Plain.
Temperatures tonight will remain unseasonably mild and mostly
persistent in the upr 50s to mid 60s.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
-- Changed Discussion --
As of 225 AM Friday...

Confidence is high on increasing chances for showers and a few
storms, although no one will see rain the entire day, and
pinpointing the location and motion of what should be shower/storm
clusters is challenging. PWs will continue to rise, with models
indicating a swath of 1.5-1.75" values surging up through central
NC, in the 90th percentile and even nearing daily records. This will
occur in tandem with increasing low level moisture flux drawing
Atlantic moisture into our area. As the backdoor front settles
further into the area Sat morning, followed by a very gradual
weakening and washing out, the considerable stratus over much of the
area, esp N and W sections, will hinder heating and destabilization
until it retreats and breaks up later in the day. And our large
scale dynamic forcing for ascent will be poor, given the weak mid-
upper level flow, but we may still feel the effects of MCVs
emanating from today`s Plains convection as it shifts into our area
late Sat through Sat night. All of this supports scattered to
numerous clusters of showers and storms, particularly in areas W of
I-95 where moisture will be deepest, with the highest pops in the
Triad and perhaps a secondary focus along the weakening backdoor
frontal zone. The storm threat will be limited, given the weak deep
layer bulk shear and modest CAPE, but a few storms will remain
possible mainly in the afternoon and evening. Rain chances will
persist overnight with further moistening of the low levels with
confluent 925 mb southerly flow strengthening to 15-25 kts with both
Atlantic and Gulf taps. While areally averaged rainfall amounts
aren`t likely to be high, given the anomalously high PW and somewhat
slow storm motion with cell mergers possible, isolated areas could
see local rainfall totals that could present minor urban flooding
issues, esp in the Triad region, despite the recent dry weather.
With mostly cloudy to cloudy skies, expect highs from the mid 70s N
and W to lower-mid 80s SE. Lows in the 60s. -GIH
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH THURSDAY...
As of 250 AM Friday...

...Elevated Rain Chances Will Linger Through Monday...

...Heat Returns Middle Part of Next Week...

Sunday and Sunday night: The stalled sfc front sagging across
northern portions of the forecast will retreat north early Sunday,
leaving all of central NC in the warm sector. Subtle upper
disturbances coupled with the development of weak to moderate
buoyancy during the afternoon will act upon the elevated PWATS (150-
160% of normal)in place over the region to support afternoon showers
and storms. Shear is generally less than 20 kts, so the threat for
organized severe storms is near zero.

The moist PWATs and associated mostly cloudy skies and rain chances
should temper afternoon temps. Highs in the upper 70s north to lower
80s.

Convection should largely dissipate as BL nocturnally cools and
stabilizes. Under mostly cloudy skies, mild overnight temps in the
60s.

Monday and Monday night: A compact shortwave trough over the Mid MS
Valley will become increasingly sheared as it crosses the central
and southern Appalachians Monday afternoon and through the Mid
Atlantic States Monday night.  PWATs are forecast to increase to
~200% of normal as the trough and associated DPVA moves through the
area.  As such, expect another healthy uptick in diurnal coverage
and PoPs Monday afternoon and into the evening. Shear remains weak.
Thus, the threat for severe storms remains low. Low-level
thicknesses are on par or slightly higher than Sunday. Highs 80-85.
Lows in the 60s.

Tuesday through Thursday: Rain chances will lessen during this
period, with weak disturbances moving atop the ridge providing the
primary focus for scattered shower and storms, mainly across
northern portion of the forecast area. The main weather headlines
will be the return of the heat during the second half of the work
week. Highs Wednesday and Thursday are expected to top out in the
mid/upper 80s north lower 90s over interior and southern portions of
the forecast area. Expect very warm nights as well, potentially
record warm, with lows 65 to 70.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
As of 235 PM Friday...

Isolated to widely scattered showers and storms will focus this
afternoon-evening along a differential heating zone and surface
trough over the Foothills and wrn Piedmont of NC (including at
INT/GSO) and also along a backdoor cold front that will reach the
Roanoke River vicinity (including near and just north of RWI) around
sunset. Areas of very low overcast and fog will likely redevelop
through sern NC, including to around FAY between 10-12Z, in a
persistence regime of humid, sly flow there. Meanwhile, a separate
area of post-frontal, low stratus in enely flow, will develop behind
the backdoor front and reach RWI and all Piedmont sites around the
same time (between 10-12Z). Ceilings in both regimes should then
lift through MVFR through midday Sat, during which time showers/
storms are apt to redevelop with diurnal heating. The greatest
concentration of that convection should be along the front, which
will likely become quasi-stationary between I-85 and US-64 on Sat.

Outlook: IFR-MVFR ceilings are likely to redevelop each night-
morning through Monday, as are scattered to locally numerous
showers/storms each afternoon-evening.
-- End Changed Discussion --

&&

.CLIMATE...

Record High Temperatures:

May 3:
KGSO: 92/1959
KRDU: 93/1959
KFAY: 95/1913

Record High Minimum Temperatures:

May 4:
KGSO: 65/2022
KRDU: 68/1938
KFAY: 68/1942

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...Hartfield
LONG TERM...CBL
AVIATION...MWS