914
FXUS62 KRAH 041806
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
205 PM EDT Tue Jun 4 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 1005 AM Tuesday...

Latest satellite data shows clouds thinning in the NE region after a
morning of heavy continuous rainfall across the region. The Flash
Flood Advisory has been lifted as the rain has dissipated and
shifted east. Reports estimated rainfall amounts of 2 to 4 inches
fell in the northern portions of Nash county. No major updates to
temperatures or dew points this morning and only minor updates to
PoPs for this afternoon. Similar to yesterday, scattered afternoon
showers and storms are expected to develop across the region with
pulse like storms at which, some could be strong to border-line
severe with strong winds and heavy rainfall. Highs today will be
around 5 degrees above average ranging from mid 80s NW to around 90
in the south/east.

As of 350 AM Tuesday... Hot and humid, with a ~30-40 chance
showers/storms maximized this afternoon-evening.

A weak upr-level/tropopause-based disturbance now centered over the
wrn Carolinas will move sewd and off the SC coast later this
morning. A mid/upr-level ridge will otherwise continue to extend
across the Middle Atlantic, while a couple of MCVs now over MS will
track along its wrn periphery and across the TN Valley today and the
srn Appalachians and wrn Carolinas tonight-early Wed.

At the surface, high pressure centered near and south of Bermuda
will extend wwd and across the South Atlantic states, while a weak
backdoor cold front/trough will move swwd along the Middle Atlantic
coast and reach sern VA and perhaps the nrn Outer Banks of NC.
Additionally, an outflow boundary and focus for ongoing showers over
the ne NC Piedmont and nrn Coastal Plain may linger today.

Daytime heating, into the mid 80s to around 90 F, of a humid airmass
characterized by surface dewpoints mostly in the mid-upr 60s, will
favor moderate destabilization and minimal cinh by this afternoon.
Weak and somewhat nebulous forcing mechanisms, including the outflow
boundary noted above and probably others from Monday`s convection,
will tend to focus pulse-type showers/storms amid weak wly steering
flow again this afternoon, most of which should dissipate with loss
of heating through this evening. The exception will be across the
far srn/wrn NC Piedmont, where forcing related to the approaching
MCVs from MS may either maintain some degree of upstream convection
or encourage new development there. It will otherwise remain muggy
and mild tonight, with lows mostly in the mid-upr 60s.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 425 AM Tuesday...

A banner of convectively-enhanced mid-level vorticity, which will
probably include a couple of initial MCVs now over MS, will move
enewd across cntl NC on Wed. Another MCV from convection now over
OK may follow a similar track as the first and across the TN Valley
and srn Appalachians Wed and the Carolinas Wed night. Initially
weak, wly/wswly mid-level flow (700-500 mb) will increase to around
30 kts on Wed, locally higher equatorward of the strongest MCV
(wherever it may be) by that time.

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 MCV and associated
cloud canopy, and/or a loosely-organized outflow boundary from
related rain/storms, will probably move east across cntl NC during
the day.

The differential heating zone will provide a primary focus
for the redevelopment or intensification of showers and storms on
Wed. A combination of modest wly/wswly mid-level flow and a strongly-
heated and steep lapse rate-bearing boundary layer to the east of
the differential heating zone will be supportive of multi-cell
clustering that may pose a risk of strong to severe wind gusts.
While the SPC DY2 outlook depicts general thunder at this time,
5%/MRGL probabilities may become justified for a portion of the
Carolinas, as mesoscale uncertainties from the foregoing pattern
become clearer.

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). It remains unclear how much convective overturning
may result from the lead MCV on Wed, so questions regarding the
degree of instability for the trailing one forecast to move across
the region Wed night warrant just a 20-30 percent chance of
overnight convection at this time, with low temperatures again in
mainly the mid-upr 60s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 330 AM Tuesday...

By Thursday morning, an upper low will be over southwestern Ontario
with a surface low a bit farther to the northeast. The surface cold
front should extend southeast across the Great Lakes into
Pennsylvania, then arc back to the southwest along the I-85/95
corridor. While some minimal changes were made to the area of likely
shower coverage on Thursday, likely pops generally remain to the
southeast of US-1. MUCAPE should be on the order of 1000-2000 J/kg,
while effective bulk shear remains at or below 30 kt. Thursday also
appears to be the warmest day out of the next seven, with west-
southwesterly flow providing warm advection allowing highs to max
out between the mid 80s and lower 90s.

Although slight chance pops will continue from US-1 to the east
Thursday evening, have continued the inherited dry forecast for
Friday as the GEFS has finally come in line with other models
showing all precipitation to the east of the region. Friday appears
to be the day that noticeably drier air will arrive, with dewpoints
dropping into the 50s (and upper 40s in the Triad). The dry forecast
continues through Saturday into Sunday. Unfortunately, different
runs of the GFS/ECMWF and their respective ensembles continue to
flip-flop as to when the next front will approach the southeastern
United States, so this part of the forecast has below normal
confidence. For now, have slight chance pops Sunday night and chance
pops everywhere Monday. The Thursday/Friday front won`t bring much
change in high temperatures, with highs remaining in the 80s through
the weekend. However, there will be some relief each night, with
overnight lows in the lower 60s instead of the upper 60s.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
As of 205 PM Tuesday...

Isolated showers and storms are beginning to develop across portions
of the CWA, but ceilings are generally around 3k-4k ft over the
Triad and 4k-7k elsewhere. Mostly VFR conditions are expected this
afternoon and evening with the exception of periods when storms move
over/near the terminals causing reduced vsby and ceilings. As the
mid level disturbance moves across the region tonight and early
morning, this could result in some flight restrictions early
Wednesday morning ahead of the cold front.

Outlook: Showers ans storms associated with a cold front that is
expected to come through the region late Wednesday /Thursday will
result in flight restrictions of MVFR or lower in some areas. VFR
conditions are expected to return Friday through the weekend before
another disturbance moves into the region early next week.

&&

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

&&

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