522
FXUS62 KRAH 072341
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
740 PM EDT Sun Jul 7 2024

.SYNOPSIS...
A weak frontal zone extending from the Chesapeake Bay into the
Piedmont of the Carolinas will linger and weaken before dissipating
by Tuesday. Mid and upper level high pressure will then build across
the area before another cold front approaches late in the work week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
As of 325 PM Sunday...

* Scattered to numerous showers and storms with locally
  torrential rain will be focused across the western and
  northwest Piedmont and VA border counties this evening.

The latest surface analysis shows a cold front extending from
southern Chesapeake Bay southwest across southeastern VA into
the northwestern Piedmont of NC and into far upstate SC. The air
mass across central NC is very moist with PW values of 2.0 to
2.3 inches. Southeast of the front, dew points range in the
mid to upper 70s. Breaks of sunshine have allowed temperatures
to climb into the 90 to 95 degree range in parts of the
southern Coastal Plain. Northwest of the front, a light
northeast wind is observed in the Triad and in the VA border
counties in a cooler and more stable air mass. With the
widespread rain and cooler air mass, temperatures are only in
the upper 70s to lower 80s. Further aloft a 594dm mid and upper
level anticyclone is centered over the eastern Gulf of Mexico,
sandwiched between Beryl and the closed mid/upper level low east
of the Carolinas. The mid and upper flow across NC is rather
light from the west and southwest.

Multiple clusters of convection continue to move east and
northeast across the western and northwester Piedmont this
afternoon. These storms are being enhanced by a warm
southwesterly flow atop a cooler air mass near the surface and
in a region of convergence near the front. CAMS suggest that
this convection will continues for the next several hours with
other more widely scattered convection expected across the rest
of central NC. The air mass across southern NC and especially
the Coastal Plain is much greater with MLCAPE values in excess
of 2000 J/Kg. Convection across the southwestern NC Mountains
will shift east into SC tonight, and should just skirt the
southern portion of the forecast area. Other storms may fire
later this evening in the Coastal Plain as outflows converge in
this area. The main weather hazard tonight will be slow moving
convection in a moist and weakly to moderately unstable
environment will be produce some locally heavy rain and possible
flooding concerns.

It will remain warm and muggy overnight with considerable
cloudiness and some patchy areas of fog late. Lows will range
in the lower to mid 70s. -Blaes

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
As of 250 PM Sunday...

* Continued shower/thunderstorm chances, albeit it with lower areal
  coverage
* Brief periods of heavy rain likely the primary threat with any
  storms that develop

We should have a very similar synoptic setup across the area
tomorrow with PW`s still running around 2 to 2.2". The presence of a
stalled surface boundary may be lacking though and with only a lee
trough and sea breeze to contend with, the overall triggering
mechanisms for convection may ultimately be the limiting factor.
Storms are once again favored across the western Piedmont along with
the Sandhills/southern Coastal Plain, with lesser chances elsewhere.
Storms are likely to be outflow dominant and pulse-type in nature
given very weak steering flow around 15kts or less. While wet
microbursts would be a possibility with any storms that approach
severe limits, locally heavy rainfall from slow moving/training
storms would likely be the primary threat tomorrow.  However given
relatively limited areal coverage, we shouldn`t need any flood
watches. PoPs in the 20-40 percent range area-wide are the general
consensus from the NBM, HREF, and other global models and this seems
reasonable at this point.

Temps will be on par with today`s values with highs in the upper
80s/lower 90s with lows falling into the lower 70s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 250 PM Sunday...

* Typical summer pattern through the weekend
* Some storms possible Tuesday/Wednesday, becoming more numerous
  late in the week

Precip chances look to decrease on Tuesday as an offshore upper low
off the NC coast dives southwestward toward Florida. In its wake,
mid level heights appear to increase by a few meters and this may be
enough to further inhibit storm development across the area. While
similar PW`s will be in place area-wide, very limited forcing and
instability outside of an area near a lee trough across the western
Piedmont should keep storms isolated/widely scattered in nature.

Meanwhile, the remnant circulation and moisture associated with T.C.
Beryl will be drawn inland and absorbed into a longwave trough
approaching the western Great Lakes later this week. This will spawn
a relatively deep surface cyclone that will track northward across
the Great Lakes into southern Ontario. An attendant surface boundary
will make an eastward run at the mountains, but likely stall/wash
out before it makes it across. However the remnant boundary and/or
lee troughing will likely result in an area of enhanced surface
convergence which will be stall out and be slow to exit the area.
Nearly all global models suggest a plume of increased PW`s will be
drawn inland from off the SE coast on Wednesday, interacting with
and serving as a necessary ingredient for increased shower and
thunderstorm coverage to close out the week. There is a general
consensus among the ensembles that Thursday and Friday could be
particularly active as a weak surface low develops along the stalled
surface boundary to our south and tracks through central NC. Looking
at the 100 member grand ensemble of the Canadian, GFS, and EC
ensemble forecast systems, nearly 80 percent suggest precip across
the area on Thursday and nearly 90 percent on Friday, which is an
unusually high amount of agreement for this time of year at this
lead time. Of course exactly how much rain will fall, and exactly
where the surface boundary and low track set up, is still TBD but
the trend of increasing late-week PoPs will continue. Precip chances
should remain elevated (although slightly lower as compared to
Thursday/Friday), as we get into the weekend.

Temperatures this week should be within a few degrees of normal.
Through mid week with mid level ridging sneaking in from the east,
temps should make a solid run into the mid 90s area-wide and it is
on these days (Tuesday and Wednesday) where heat indices could make
a return to dangerously high values. However increased cloud cover
and precip chances will knock readings back into the mid/upper 80s
Thursday, especially Friday, and possibly into Saturday as well
before returning to normal by Sunday. Lows throughout the period
generally upper 60s to mid 70s.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 740 PM Sunday...

Through 00Z Tuesday: Convection is slowly diminishing in coverage
this evening; however we are seeing a variety of flt conditions
across central NC attm depending on where the rain is falling. As
the evening progresses into the overnight hours, the rain should
mostly end, however across much of the Piedmont we expect a shield
of stratus to form, which will lower flt conditions aob IFR after
05Z across much of the Piedmont, including KINT, KGSO, and KRDU, and
possibly extending as far east as KRWI and KFAY.  This stratus will
linger through about 14Z before cigs slowly lift back to VFR by 17
or 18Z Monday.  Winds will generally be aob 10kt, but direction will
be highly variable based on outflow boundaries, and the locations of
the synoptic front which currently extends from KAFP to KPOB to
KGSB.

After 00Z Tuesday: A rather typical summer pattern of scattered
afternoon and evening showers and storms along with some late night
and early morning stratus and fog is expected through the period
with the coverage of storms and restrictions expected to uptick on
Wednesday and increase for Thursday and especially Friday.

&&

.CLIMATE...
Record High Minimum Temperatures:

July 7:
KGSO: 73/2019
KRDU: 77/1900
KFAY: 78/2017

July 8:
KGSO: 76/2010
KRDU: 78/1986
KFAY: 79/2012

July 9:
KGSO: 76/1987
KRDU: 74/2014

&&

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

&&

$$

SYNOPSIS...Blaes
NEAR TERM...Blaes
SHORT TERM...DL
LONG TERM...DL
AVIATION...np
CLIMATE...RAH