038
FXUS62 KRAH 261908
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
310 PM 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 /UNTIL 6 AM THURSDAY MORNING/...
As of 1055 AM Wednesday...

For the near term update this morning, the previous morning
stratocu coverage across a decent portion of the south and east
has mixed/cleared out quickly. This doesn`t appear to have
limited much of the daytime heating in the last few hours so the
previous temp/dewpt trend appears to be on track. The current
Heat Advisory therefore remains in effect today with near 105
deg heat indices expected within the advisory area.

As far as afternoon chances for any convection... only the Nam
nest looks to be the outlier from some other CAMs with
triggering and there doesn`t seem to be much of a forcing
mechanism today so am not biting on that solution and will keep
it mainly a dry forecast through the daytime period. The greater
chances remain for later this evening into overnight with the
progression of an upper shortwave/disturbance and possible
outflow from upstream development.

Previous discussion follows...

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 both along/in the vicinity of
the sea breeze (Sandhills and srn Coastal Plain) and lee trough (far
nw Piedmont) 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 /6 AM THURSDAY MORNING THROUGH 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 WEDNESDAY/...
As of 310 PM Wednesday...

This above-normal temp stretch will hit yet another crescendo this
weekend, with convection chances peaking late in the weekend. A
brief temp respite arrives early next week, however this will
quickly give way to a return to excessive heat midweek.

Fri/Fri night: The weak surface front is likely to settle across our
S areas Fri morning, then quickly wash out as the surface high to
our N shifts offshore by afternoon, resulting in a trend to light
low level flow out of the SE as warm mid level ridging spreads into
the Carolinas from the W. PW will be lower across the N but remain
close to 2" across the S, where weak low level confluent flow may
help organize scattered afternoon convection. Will carry chance pops
across the SE, where an inland-moving sea breeze could help focus
scattered convection, with a secondary chance over our NW given the
potential for terrain convection to drift into the Triad region.
Overall, though, coverage will be low as PW will be at or below
climo. Expect little or nothing across the NE, within the exiting
surface ridge, where LREF probabilities of substantial SBCAPE are
low. Highs should be in the upper 80s to the mid 90s. Heat index
values are projected to be 100-103 from the Triangle to the SE.

Sat-Sun night: Low level thermal ridging builds back into central NC
over the weekend from the SW, as a flat mid level ridge extends E
from the S Plains into NC through early Sun, our thicknesses rising
to 10-15 m above normal with deep mixing and weak lee surface
troughing over the Piedmont. Pops Sat will be similar to Fri, low
chances focused across the SE and NW. This ridge aloft then
retrogrades by late Sun as a potent northern stream trough moves
from the Upper Midwest/N Great Lakes through S Que/St Lawrence
Valley and into the interior Northeast by Sun/Sun night, digging
down the Mid Atlantic coast. Deep layer shear will be marginal Sun,
but moderate SBCAPE is expected, and the increasing and deepening
moisture (projected PWs nearly 2.5") with the approaching surface
front tied to the trough aloft will support higher pops in the good
chance to likely range, highest across the NW Sun afternoon through
the evening before shifting to the S and E as the front pushes to
our SE overnight. Expect highs from the low 90s NW to upper 90s SE
with high dewpoints well into the 70s, indicative of increased heat
stress as heat index values reach 100-110 over all but the extreme
NW both days (but likely a bit higher Sun than Sat), although
confidence in reaching extreme heat levels is lower Sun given the
potential for clouds and convection.

Mon-Wed: As the front settles along our S and E early next week,
pops should be on the low side, chance pops mainly S Mon and even
lower Tue, as surface high pressure builds in from the N within mid
level troughing. Low level thicknesses suggest highs fairly close to
normal, with highs in the upper 80s to lower 90s. The heat will
begin to return Wed as the surface high pressure exits and strong
mid level ridging builds once again, centered over the Mid South and
N Gulf states, sending thicknesses soaring back above normal once
again. After highs in the upper 80s to lower 90s Mon/Tue, highs
should again be in the low-upper 90s Wed. -GIH

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
As of 200 PM Wednesday...

While predominantly VFR conditions are expected across central NC
through this evening, isolated showers and storms may develop,
particularly across the Sandhills/southern Coastal Plain (including
FAY) and NW Piedmont (including INT and GSO). Any storm may result
in brief sub-VFR visibilities and gusty winds. Another area of
showers and storms may graze the northern Piedmont and northern
Coastal Plain as it moves east from about 03z to 12z. IFR or MVFR
ceilings can`t be ruled out at RDU and RWI as it moves through. Even
though FAY should stay dry late tonight and early tomorrow morning,
IFR/MVFR ceilings from low stratus are still possible there, as has
occurred the last couple mornings. Conditions should improve to VFR
everywhere by mid to late morning, but some light stratiform
rain/sprinkles may linger across the north.

Outlook: IFR-MVFR stratus will again be possible especially at FAY
and RWI in the early morning from Fri through the Mon. The chance of
mainly afternoon-evening showers/storms will be highest on Thu at
FAY and RWI, 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 until 8 PM EDT this evening for NCZ025>027-
040>043-075>078-083>086-088-089.

&&

$$

SYNOPSIS...MWS
NEAR TERM...MWS/AB/AS
SHORT TERM...Green
LONG TERM...Hartfield
AVIATION...Danco/MWS
CLIMATE...RAH