889
FXUS62 KRAH 041449
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
1045 AM EDT Thu Jul 4 2024

.SYNOPSIS...
Surface high pressure will extend across the western Atlantic and
Deep South through tonight and then weaken and shift east on Friday.
A cold front will approach the region from the northwest late Friday
and then move into the Carolinas during the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1045 AM Thursday...

* Hot and humid conditions will return this afternoon.
* Scattered thunderstorms will drift into north-central NC this
  afternoon and move into the NC Piedmont this evening as they weaken.
* Storms will be efficient in producing strong gusty winds.

The morning surface analysis shows high pressure centered across the
western Atlantic extending west into the eastern Carolinas and the
eastern Gulf of Mexico. A cold front extends from the eastern Great
Lakes southwest across the western OH Valley and into the MO Valley.
A weak lee trough is noted across central VA and NC. Further aloft
an anomalously strong west to east 500mb ridge was centered across
the Deep South. The main belt of westerlies extend from a trough
across across western KS/NE and into the Great Lakes.

The air mass across central NC this morning is warm and relatively
moist with PW values of 1.6 to 1.8 inches or around 110% of normal.
Morning low level thickness values ranged from about 1410 to 1420m,
with the greatest thickness values extending south to north across
the western Piedmont of the Carolinas. KGSO observed a thickness
values of 1418m this morning, that`s 25m greater than yesterday at
12Z.

Regional radar imagery shows a few clusters of showers and storms
moving across eastern KY and southern WV early this morning. This
convection is supported by a series of disturbances around the
periphery of the upper level ridge including a couple of MCVs from
overnight convection. The latest visible satellite imagery shows
mainly clear skies across central NC with some enhanced cumulus
clouds in the NC mountains and cloudiness across KY/WV associated
with the convection.

The upper level ridge will relax a bit today allowing the train of
disturbances across the TN Valley to take a slightly more southern
trajectory into southern VA and perhaps northern NC this afternoon
and evening. With a slightly weaker ridge, mid-level lapse rates
will steepen slightly and strong diurnal heating combined with
dewpoints in the upper 60s to lower 70s will result in moderately
unstable airmass this afternoon with MLCAPE values ranging around
1500 J/kg. Isolated convection may develop late this afternoon near
the lee trough with slightly better convective coverage likely
across southern VA in the stream of disturbances aloft that will be
aided by differential heating, the lee trough, and outflow from
ongoing convection to the north. This area of widely scattered
convection will shift south and east into northern NC late this
afternoon and into the Piedmont this evening as it weakens. Recent
high res guidance suggest a downward trend in coverage from last
nights guidance, especially during the evening, focusing rain
chances in the Triad and near the VA border counties. With strong
heating today and deep boundary layer mixing, inverted-V
thermodynamic profiles are expected supporting DCAPE values well in
excess of 1000 and likely resulting in efficient production of
strong gusty winds with convection. With limited forcing for ascent,
expect the convection to wane during the mid evening and would be
surprised if much if any rain makes it south of KRDU or KRWI with
all of the convection dissipating by midnight.

With a hotter airmass and low level thickness values 25m higher than
yesterday in many locations, highs today will range between 6 and 9
degrees hotter than on Wednesday and range in the mid 90s to around
100. Expect highs to reach daily records at RDU and FAY. With
boundary layer mixing, dewpoints will mix out a bit this afternoon
and temper heat index values that will range in the upper 90s to
lower 100s in most locations with a few spots including KRDU, KFAY
and KGSB flirting with 105F.

Skies will be partly cloudy overnight with a mix of some patchy high
clouds and perhaps some patchy stratus or low clouds across the
south and southeast. It will remain warm and muggy tonight, with
lows mainly in the mid 70s. -Blaes
&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 410 AM Thursday...

...Hot and humid conditions bring the risk for heat related
illnesses Friday and Saturday...

A mid-level subtropical ridge centered over the GOM states will
extend up through the southern Mid-Atlantic in between broad
troughing over the central CONUS and a closed low drifting by
Bermuda through Sat. At the surface, an occluded low over the Upper
Great Lakes will slide ENE into southern Quebec by Sat evening as a
compact shortwave lifts through the eastern edge of the longwave
troughing. Within the deep tropospheric southwesterly flow, low-
level thickness steadily rise to around 1445m (30m above normal) and
850mb temperatures soar to 21 to 23 C Fri afternoon. In the absence
of showers and convective outflow during the afternoon, this pattern
will support well above normal temperatures into the upper 90s and
low 100s with heat index values ranging from 100 to 107 degrees.
Little overnight recovery is expected Fri night as continued humid
airmass and lingering cloud cover will keep lows in the mid to
potentially upper 70s in spots. This would result in heat illnesses
likely for anyone without access to effective cooling and/or
adequate hydration. Some afternoon relief will be possible on Sat
especially over the western Piedmont mid/upper level clouds spread
in from the west ahead of trailing cold front. The cooler and drier
air behind the cold front will likely struggle to traverse the
mountains with another night of mid 70s expected.

As for convective potential, on Fri greatest coverage of
showers/storms will likely originate over the NC mountains in the
vicinity of the lee trough and slowly shift eastward through the
afternoon into the evening hours. The airmass within and ahead of
the storms will be characterized by around 2000 J/kg of MLCAPE and
20 kts of 0-6km shear. Little storm organization is expected given
the weak deep layer shear, but isolated strong to potentially severe
wet downbursts and isolated congealed clusters could certainly be
possible with above normal moisture and DCAPE around 1000 J/kg. By
Sat, the mid/upper trough will sag farther southeast and direct more
perturbed 500mb flow into the western Piedmont and combine with lee
trough and/or differential heating boundaries to develop more
widespread showers/storms. Deep layer shear will again be weak, but
closer to 15-25 kts (highest NW) and may result in some cold pool
organized clusters resulting in mostly a wet downburst threat as
well. Confidence on Sat is low given it will likely depend on the
prior day activity.

&&.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 410 AM Thursday...

Overall a stagnant pattern will exist over Southeast and the Mid-
Atlantic through the remainder of the forecast period. Central NC
will be tucked between broad reinforced troughing through the
central CONUS with the stationary sub-tropical high broadly draped
across the western Atlantic in the eastern GOM. At the surface a
diffuse pressure gradient will feature a lee-trough redeveloping
over the region each afternoon with unseasonably moist deep layer
moisture in place as PWAT values remain at-or-above 2 inches.

This pattern will favor continued above normal temperatures with
highs in the mid 90s in the urban areas and overnight lows only
reaching into the mid 70s. With continued heat related stresses heat
related illnesses will be possible especially among individuals
sensitive to heat and do not have access to effective cooling and/or
adequate hydration. Diurnally favored showers/storms and storms will
also be possible each afternoon into the evening, likely focused
along the lee-trough and any subsequent outflow boundaries
thereafter. Organized convection appears to be at a minimum with
deep layer shear remains weak around 10 to 20 kts, strongest across
the NW Piedmont, and result in mostly pulse summer-time
showers/storms. Greatest coverage could be Tues into Tues night with
proximity of mid/upper troughing swings through the Great Lakes
region.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
As of 800 AM Thursday...

VFR conditions, influenced by high pressure extending from just
offshore the Middle Atlantic coast southwestward into the Carolinas,
will continue through early afternoon. An Appalachian-lee surface
trough and/or outflow from upstream convection will provide foci for
shower/storm development that will probably affect INT/GSO and
surrounding vicinity across the nw NC Piedmont this afternoon-
evening. Some of that gusty outflow, and focus for additional,
isolated to widely scattered showers/storms, may drift to near RDU
and RWI through 00-03Z, before dissipating.

Outlook: A chance of showers/storms will exist Fri and especially
Sat through Mon, as a pre-frontal trough and surface front move into
and stall over cntl NC. Late night-early morning stratus and fog
will also be possible this weekend.

&&

.CLIMATE...
Record High Temperatures:

July 4:
KGSO: 98/1970
KRDU: 101/2012
KFAY: 98/2019

July 5:
KGSO: 98/2012
KRDU: 102/1999
KFAY: 101/2002

July 6:
KRDU: 102/2022
KFAY: 99/1990


Record High Minimum Temperatures:

July 4:
KGSO: 73/2018

July 5:
KGSO: 74/1999
KRDU: 78/1902
KFAY: 77/2005

July 6:
KGSO: 76/1999
KRDU: 79/1900
KFAY: 76/2017

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

&&

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

&&

$$
SYNOPSIS...Blaes
NEAR TERM...Blaes
SHORT TERM...Swiggett
LONG TERM...Swiggett
AVIATION...MWS
CLIMATE...RAH