337
FXUS62 KRAH 260814
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
414 AM EDT Wed Jun 26 2024

.SYNOPSIS...
Hot southwesterly flow will result today between high pressure over
the Atlantic and a cold front that will approach from the northwest
and reach the western Carolinas by Thursday morning. The front will
then move slowly east across the central and eastern Carolinas later
Thursday through Thursday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 410 AM Wednesday...

A Heat Advisory has been issued for today for the Sandhills and a
portion of the Coastal Plain and Piedmont in central NC.

A 320 dam 700 mb anticyclone centered over the TN Valley in 00Z/26th
upr air data will weaken several decameters as it builds across and
offshore NC through tonight. 850 mb standardized temperature
anomalies beneath and downstream of the high are still forecast to
be around 3 sigma above average over the Carolinas, with daily
record 850 mb temperatures possible at GSO. Meanwhile, a couple of
shortwave perturbations now over MN and NE will modestly amplify and
phase as they pivot across the Great Lakes and OH Valley,
respectively. The trailing/equatorward portion of an associated
positive tilt, synoptic trough will be comprised of convectively-
amplified mid-level disturbances/MCVs (including some from a large
area of ongoing convection centered over MO) that will extend from
srn New England swwd to the Delmarva and TN and lwr MS Valleys by
12Z Thu.

At the surface, sprawling high pressure anchored over the cntl
Atlantic will extend wwd and across the South Atlantic states, where
hot, sly/swly flow will exist today. On the wrn periphery of the
ridge, an Appalachian-lee trough will develop over the srn Middle
Atlantic Foothills/wrn Piedmont. An effective cold front, the
combination of a synoptic front and composite convective outflow,
will meanwhile approach from the northwest and settle into the pre-
frontal/lee trough position and extend from the Delmarva swwd to the
w-cntl Carolinas by 12Z Thu.

The pattern described above will favor what will probably be the
hottest day yet during the ongoing stretch of hot conditions that
began over cntl NC this past weekend, with forecast high
temperatures 8-14 F above average and mostly in the mid 90s to
around 100, including near the daily record of 102 F at RDU.
Seasonable, mixed/afternoon surface dewpoints mostly in the mid 60s
west to upr 60s to around 70 F east will yield Heat Index values
several degrees on average higher than air temperatures and in the
upr 90s over the nw Piedmont to 100-105 F elsewhere. While the most
likely locations to reach and marginally exceed traditional Heat
Advisory criteria (105 F) will be over the urban Triangle
(Raleigh/Durham) and Fayetteville, a combination of near 105 F heat
indices and a forecast of major HeatRisk warrant a lager Heat
Advisory area for much of the southeastern half of cntl NC.

Isolated convection will be possible particularly along/in the
vicinity of the sea breeze (Sandhills and srn Coastal Plain) during
the afternoon-early evening, followed by a slightly higher chance
(20-30%) of showers/storms accompanying the approach/arrival of the
aforementioned convectively-amplified mid-level trough and
convective outflow, mainly over the Piedmont and nrn Coastal Plain,
tonight. Trailing that possible convection, areas of light
stratiform rain/sprinkles, remnant to that or other upstream
convection and within a broader mid-level cloud band related to the
aforementioned convectively-amplified, mid-level trough, may linger
over the Piedmont overnight-Thu morning. It will otherwise be muggy
and quite mild, with low temperatures 5-10 F above average and
mostly in the mid 70s.

&&

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

A cold front should extend from northeast to southwest across the
forecast area Thursday morning, and it will continue to slide
southeast through the day. It still appears that the bulk of the
showers and thunderstorms will occur behind the front, with greatest
coverage during the mid afternoon decreasing through the late
afternoon into the evening. Vertical wind shear still remains very
low, meaning it should be hard for an organized cluster of storms to
develop. However, instability values between 1000-2000 J/kg should
be enough to allow isolated strong to severe thunderstorms to
develop, with the primary hazard coming from damaging wind gusts.
The chance of thunderstorms should linger everywhere into the
evening, then remain confined east of I-95 after midnight. While
dewpoints may be slightly increased from today, high temperatures
should come down between 3-7 degrees. This should result in a day
with heat index values in the 90s north of US-64 and in the low
triple digits south of US-64.

&&

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

Friday: It still appears that morning precipitation should remain
confined to southeastern counties, but as the previous day`s front
retreats back to the north, a chance of thunderstorms should return
to most locations in the afternoon. An upper level shortwave moving
through Friday night will allow the chance of showers/storms to
continue overnight, particularly across western counties. Highs
should range from the upper 80s to the mid 90s, with heat index
values over 100 south of Raleigh.

Weekend: Ensembles are a bit faster than deterministic models
bringing precipitation to the east in advance of the next front.
Have increased pops to chance to most locations Saturday afternoon,
although precipitation will retreat west overnight. However,
deterministic and ensemble models continue to have good agreement
with the front moving through Sunday/Sunday night, and have
continued with likely pops during the afternoon/evening time period.
These two days will likely be the warmest days in the extended
forecast, with widespread mid to upper 90s for highs. Heat index
values will probably reach heat advisory criteria of 105 degrees in
many locations, although there is more uncertainty in reaching these
values with the chance of rain in the forecast.

Monday/Tuesday: The front will be slow to move through, and will
maintain chance pops nearly everywhere Monday afternoon and across
southern counties Tuesday afternoon. Both temperatures and humidity
should definitely be lower behind the front, with air temperatures
ranging from the mid 80s to the low 90s and heat index values close
to the air temperatures as a result of the lower humidity.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
As of 220 AM Wednesday...

An area of stratus based between 1000-1500 ft AGL now blossoming
over nrn SC/srn NC will likely continue to expand nwd, amid light
sly flow in that layer, and overspread FAY; RDU; and RWI through
11Z, then lift and disperse to VFR by 13-14Z. It may also locally
lower to IFR as the sub-cloud layer further cools and moistens
through sunrise. While an isolated storm cannot be ruled out mainly
around FAY with daytime heating and lift from the sea breeze, there
will be a slightly better chance of a few showers and isolated
storms over the Piedmont tonight, as a mid-level trough and outflow
boundary/front approach from the northwest - likely to be
highlighted with a PROB30 group with 12Z TAF issuance.
Additionally, the development of an Appalachian-lee, nocturnal low-
level jet across and offshore the Middle tonight may result in
marginal low-level wind shear mainly from nrn NC/srn VA to the
Middle Atlantic coast.

Outlook: IFR-MVFR stratus will again be possible especially at FAY
and RWI in the early morning from Thu through the weekend. The
chance of mainly afternoon-evening showers/storms will be highest,
especially at FAY and RWI on Thu, and again area-wide Sun-Sun night.

&&

.CLIMATE...

Record High Temperatures:

June 26:
KRDU: 102/1952
KFAY: 101/1951

June 27:
KFAY: 102/1998

June 30:
KFAY: 102/2012


Record High Minimum Temperatures:

June 26:
KGSO: 74/2010
KRDU: 76/1902
KFAY: 76/1997

June 27:
KGSO: 76/1969
KRDU: 76/1952
KFAY: 77/1998

June 28:
KGSO: 76/1969
KRDU: 76/1952
KFAY: 78/1914

June 29:
KGSO: 74/2010
KRDU: 78/1914
KFAY: 76/1969

June 30:
KGSO: 74/1936
KRDU: 80/1936
KFAY: 79/1936

July 1:
KGSO: 77/1970
KRDU: 75/2012
KFAY: 76/1990

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM this morning to 8 PM EDT this evening for
NCZ025>027-040>043-075>078-083>086-088-089.

&&

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