555
FXUS62 KRAH 051141
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
741 AM EDT Wed Jun 5 2024

.SYNOPSIS...
A series of mid-level disturbances will move east and interact with
an unseasonably moist airmass over NC through Thursday. A pre-
frontal trough and cold front will move across the area Thursday
evening through early Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 420 AM Wednesday...

Although it will again be seasonably hot, with above average chances
of showers/storms, confidence in timing, coverage, and intensity of
that convection remains low.

The basal portion of a synoptic trough, now stretching from a
cyclone over the cntl SK/MB border ssewd through the upr/mid MS
Valley then swwd into the srn Plains, will move ewd in positive tilt
fashion and reach the cntl/srn Appalachians and TN Valley by 12Z
Thu. Preceding that trough and more influential for cntl NC this
period, a couple convectively-generated mid-level troughs and
vorticity centers/MCVs will move generally enewd across the Middle
and South Atlantic states. The first/lead one stretched this morning
from a well-defined MCV over ern KY ssewd across the w-cntl
Carolinas and should move ewd across cntl NC through early this
afternoon. The second, centered over the TN Valley and which
includes a couple of equally as prominent MCVS over wrn TN and w-
cntl AL, should extend from the OH Valley to the srn Appalachians by
this evening and move across the srn Middle Atlantic and Carolinas
overnight. Net, ~20-30 meter mid-level height falls will become
maximized over cntl NC tonight. Upstream VWP data this morning
depict modest, 25-35 kts of 700-500 mb mb flow centered over the TN
Valley; and this enhanced flow should move downstream and across
the srn Middle Atlantic/Carolinas later today and tonight.

At the surface, high pressure will persist and extend from near and
south of Bermuda wwd and across the South Atlantic states, while a
differential heating zone preceding the lead mid-level vorticity
lobe and associated cloud canopy, and a loosely-organized outflow
boundary from related rain/storms ongoing from the wrn NC Piedmont
swd into ern GA, will move east across cntl NC through early this
afternoon.

Given generally poor representation of the ongoing convection in
CAMs, generally non-existent in the HRRR, it remains unclear to what
degree this ongoing convection now moving across the srn and wrn NC
Piedmont will be maintained or intensity as it moves ewd through the
morning and early afternoon, and subsequently how unstable the
environment over cntl NC will be ahead of the trailing mid-level
trough/MCVs later this afternoon-tonight. It seems plausible that
this convection will increase in intensity as it, and its associated
differential heating zone and frontal-like circulation, encounters a
partly sunny and quickly, diurnally-destabilizing environment over
the NC Sandhills and Coastal Plain through early afternoon, with a
secondary instability maximum developing in its wake today over the
srn and wrn Piedmont and ahead of the trailing mid-level trough. The
relative greatest coverage and intensity of convection would then be
maximized over those wrn counties this evening. On the other hand,
the CAMs generally depict little coverage with this lead, ongoing
activity and dissipates that which it is initialized, and instead
tends to focus scattered to locally numerous showers/storms over the
wrn half of cntl NC this evening, with very little in the ern
Sandhills and Coastal Plain. Regardless, the aforementioned modest,
wly/wswly mid-level flow will favor clustering and preferential
multi-cell development on the ern flank of outflow, with an
associated risk of strong to severe outflow wind gusts.

It should otherwise be persistently hot in the mid 80s to around 90
F ahead of the differential heating zone, and up to several degrees
cooler to its west (ie. most likely the srn/wrn Piedmont and perhaps
wrn Sandhills). Given the uncertainties in convective evolution
described above, a broad, slight to low chance of convection will
be maintained overnight, with low temperatures again in mainly the
mid-upr 60s.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 300 AM Wednesday...

A surface low will be north of the Great Lakes Thursday morning with
a cold front arcing southeast towards Buffalo, then curving back to
the southwest across Tennessee and into Texas. This front will be
the primary weather maker on Thursday, bringing showers and
thunderstorms to the region. The established air mass over the
region has plenty of moisture, and CAPE values should range between
1000-2000 J/kg. Effective bulk shear does not appear to be too
strong, but could be strong enough to provide a little bit of
organized convection along the front. Frontal timing should be late
afternoon/early evening, with the bulk of the rain moving through by
sunset. Considering the timing of the front, reduced high
temperatures across the Triad which should have the thunderstorms
moving through before peak heating, keeping highs in the low 80s.
Elsewhere, highs should range from the mid 80s to the low 90s. The
cold front will not bring much of a change in air mass, so another
night of low temperatures in the 60s and low 70s is forecast
Thursday night.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 AM Wednesday...

On the heels of the rain-making cold front Thursday, a second cold
front is forecast to move through central North Carolina Friday
morning. While the second front still will not bring much cooler
air, it will be more notable for the drier air that will funnel into
the region. Have kept a slight chance of thunderstorms across
southern Sampson County Friday afternoon, but otherwise the front
should pass through the region without producing precipitation. High
pressure will briefly build across the southeastern United States
for the first half of the weekend before yet another front
approaches from the west. Timing continues to vary between different
model solutions, but it appears the most likely timing for
precipitation is Monday with the front then stalling along the
coast. Highs will mostly be in the 80s, although some low 90s could
appear across the south on Sunday. Lows will be in the upper 50s
near the Virginia border and in the 60s elsewhere.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
As of 740 AM Wednesday...

Ongoing IFR-MVFR ceilings over the wrn NC Piedmont (INT/GSO) will
gradually lift and scatter to VFR through late morning-early
afternoon, while MVFR convective cloud bases may develop otherwise
and elsewhere with daytime heating during the same time. Confidence
in location and timing of showers/storms remains somewhat lower than
average, with the relative best chances ahead of a lead mid-level
disturbance at FAY and RWI through early afternoon and then at
INT/GSO, ahead of a trailing mid-level trough, late this afternoon-
evening. Although a swly low-level jet will develop and strengthen
to near 35-40 kts tonight, light sswly surface winds may preclude
the development of low-level wind shear. Like this morning and in a
persistence pattern, there will then be another chance of IFR-MVFR
ceilings mainly over the Piedmont Thu morning.

Outlook: Initially scattered showers and thunderstorms are expected
to develop along a pre-frontal trough and congeal into a broken line
as they move across cntl NC Thu afternoon-evening. In the wake of
that convection, at least partial clearing atop continued
moist/humid low-levels will favor the development of fog/stratus Thu
night. The late night-Fri morning passage of a cold front and
following wly flow and drier air will tend to scour any such flight
restrictions from west to east through the morning Fri, with
following VFR conditions through the weekend.

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...Green
LONG TERM...Green
AVIATION...MWS