990
FXUS62 KRAH 031838
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
238 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 THROUGH SUNDAY NIGHT/...
As of 230 PM Friday...

Aloft, the sub-tropical ridge will stall along the eastern seaboard
through Sat night. A southern stream disturbance will move into the
Southeast US on Sat, then lift newd through the area as a sheared
out northern stream s/w moves through the OH Valley/Great Lakes Sat
night. The sub-tropical ridge will shift offshore and breakdown
Sun/Sun night as the disturbances move through the mid-Atlantic and
Northeast US. Another southern stream s/w will develop over the
southern Plains on Sun, then move eastward into the lower/mid-MS
Valley Sun night. At the surface, as high pressure sits over the New
England coast, the backdoor cold front is expected to stall over
nrn/nern NC through Sat and into Sat night then lift northward late
Sat night/Sun. The high should move eastward over the Atlantic as a
low moves through the Great Lakes and into the Northeast Sun/Sun
night.

Precipitation/Convection: Still fairly high confidence/chances for
showers and possible storms Sat and Sun. Best threat for storms will
be across the Piedmont, mainly along and south of the surface
boundary, where surface-based CAPE will be maximized. Bulk shear
still appears weak, and PWATs are expected to range from 1.4 to 1.8
inches. Do not expect the entire day to be a wash-out by any means,
and Sat could start dry for most, but there will be a chance for
showers across all of central NC, with greatest coverage from Sat
eve through Sun aft. Highest chances NW, lowest SE. Given the high
PWATs and scattered, somewhat disorganized mode of convection,
isolated locations could receive locally heavy rainfall, with any
potential for minor flooding issues largely limited to urban areas.

Temperatures: A bit tricky on Sat, as there is some bust potential
north of the front. Widespread overcast skies should somewhat limit
heating as well. For now expect highs to range from the mid 70s
along the NC/VA border to mid 80s SE. Sat night temps should be
continued mild, mainly in the low to mid 60s. On Sun, with the
retreat of the front northward, areas across the north may be a few
degrees higher than Sat, but given the expected showers/storms
through the day, temps may otherwise be limited. Highs in the upper
70s north to low 80s south.

&&

.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/...
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.

&&

.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...KC
LONG TERM...CBL
AVIATION...MWS