-- Discussion containing changed information from previous version are highlighted. --
776
FXUS62 KRAH 251146
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
745 AM EDT Tue Jun 24 2024

.SYNOPSIS...
High pressure will build across and offshore the southern Middle
Atlantic today, then continue to extend westward across the South
Atlantic states through Wednesday. A pre-frontal trough, then weak
cold front, will move across NC Thursday and Thursday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 350 AM Tuesday...

Continued hot with temperatures 5-10 F above average, but with
another day of seasonably low mixed/afternoon surface dewpoints in
the upr 50s over the nrn Piedmont to low-mid 60s elsewhere.

A 320 dam 700 mb anticyclone centered over the mid-South in 00Z/25th
upr air data will move east and extend across the TN Valley and NC
by tonight, as will its related ridge of warm and dry air through
the mid-levels. That warming and drying will reinforce an already
strong subsidence inversion evident around 700 mb on the 00Z-
observed GSO and RNK RAOBs.

At the surface, a weak cold front now over sern NC will will settle
settle swd and dissipate over SC through tonight, while a ~1016 mb
high will build across and offshore the srn Middle Atlantic. Light,
generally nely flow around that high will gradually veer to sely/sly
later today-tonight. Associated onshore flow will direct a sea
breeze into the Sandhills and srn-cntl Coastal Plain this evening.

An isolated, afternoon-evening shower or storm will be possible
across the far srn Sandhills and srn Coastal Plain, where point
forecast soundings depict a little lee prominent subsidence/capping
inversion that may be breached with sea breeze forcing, with dry
conditions otherwise and elsewhere. High temperatures will again
reach the 90s area-wide, with lows, accompanied by areas of morning
stratus, in the upr 60s-lwr 70s.

&&

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

Hotter, and slightly more humid.

A 700 mb anticyclone will weaken a few decameters as it builds
across and offshore NC. It will do so downstream of a shortwave
perturbation, now over srn BC, which will amplify slightly while
pivoting from the upr MS Valley at 12Z Wed ewd and across the Great
Lakes and nrn Middle Atlantic through 12Z Thu. The models indicate
the equatorward portion of the trough will be accompanied by a
positively-tilted, convectively-amplified mid-level trough from the
srn Middle Atlantic to the TN and lwr MS Valleys through the same
time. 850 mb standardized temperature anomalies beneath and
downstream of the 700 mb anticyclone are forecast to be around 3
sigma above average over the Carolinas, with daily record 850 mb
temperatures possible at GSO.

At the surface, weak high pressure that will migrate off the srn
Middle Atlantic coast through 12Z Wed will become absorbed by a
larger and stronger high anchored over the cntl Atlantic. An
associated ridge, and broad sly/swly flow, will extend wwd and
across the South Atlantic states, while an Appalachian-lee trough
will develop Wed over the srn Middle Atlantic Foothills/wrn
Piedmont. A synoptic cold front will meanwhile approach from the
northwest and settle into the pre-frontal/lee trough position and
extend from the Delmarva swwd to the srn Appalachians/wrn Carolinas
by 12Z Thu. The front/trough may be preceded by remnant convective
outflow over the srn Middle Atlantic Piedmont, including in cntl NC.

The pattern described above will favor what may be the hottest day
yet during the ongoing stretch of heat 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-upr 60s will yield Heat Index values 2-5
F on average higher than air temperatures and in the upr 90s over
the nw Piedmont to 100-105 F elsewhere. Isolated convection will be
possible particularly along/in the vicinity of both the lee trough
(over the far wrn Piedmont) and sea breeze (Sandhills and srn
Coastal Plain) during the afternoon-early evening, followed by a
slightly higher chance (25-40%) 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, overnight. It will otherwise be muggy and quite
mild, with low temperatures 5-10 F above average and mostly in the
lwr-mid 70s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY...
As of 300 AM Tuesday...

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. At this point, Thursday afternoon
currently looks like the best chance for rain in the next 7 days,
with likely pops extending south and east from Raleigh. While
instability values should be modest, between 1000-2000 J/kg, the
vertical wind profile shows very little shear, which will make it
hard for any thunderstorms to become organized and produce severe
weather. The chance for thunderstorms will continue into the
evening, and another round of thunderstorms will be possible Friday
afternoon with the front loitering in the region - ensembles show
the chance of showers/storms extending a bit farther to the north on
Friday than they did 24 hours ago. An isolated storm cannot be ruled
out on Saturday, but the next chance of storms across the region
will come Sunday, Sunday night, and Monday with another front. The
NAEFS shows a higher probability of rain Sunday night than Thursday,
but this remains an outlier solution.

There will be minimal relief from the heat with Thursday`s front,
although highs should drop 3-5 degrees from Wednesday`s values.
Still, most of the region will reach the 90s again. Friday`s high
will be similar to Thursday`s, then an upper ridge will build over
the Southeast for the weekend, bringing a renewed surge of heat and
humidity. Saturday and particularly Sunday are the days with the
highest heat indices, with nearly all locations over 100 degrees on
Sunday. While humidity will remain high on Monday, highs should be 5-
10 degrees cooler compared to Sunday.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
As of 745 AM Tuesday...

Primarily VFR conditions, and a couple of layers of stratocumulus (5-
6 thousand ft) and altocumulus (8-10 thousand ft), are expected
through tonight. The exception will be a chance of IFR-MVFR ceilings
mainly at FAY around daybreak Thu. Light, generally nely surface
winds this morning are forecast to veer to sely/sly today-tonight,
around high pressure that will build across and offshore the srn
Middle Atlantic.

Outlook: IFR-MVFR stratus will be possible mainly at FAY and RWI Thu
and Fri morning. A chance of mainly afternoon-evening showers/storms
will also return to the forecast for Wed through the weekend, with
the relative highest probabilities at FAY/RWI on Thu. Additionally,
the development of an Appalachian-lee, nocturnal low-level jet
across and offshore the Middle Wed night may result in marginal low-
level wind shear in cntl NC during that time.
-- End Changed Discussion --

&&

.CLIMATE...

Record High Temperatures:

June 25:
KRDU: 100/1952
KFAY: 102/1914

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

June 27:
KFAY: 102/1998

June 30:
KFAY: 102/2012


Record High Minimum Temperatures:

June 25:
KRDU: 77/2010
KFAY: 75/1952

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...
None.

&&

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