752
FXUS62 KRAH 261916
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
315 PM EDT Wed Jun 26 2024

.SYNOPSIS...
Hot southwesterly flow will persist this afternoon and evening
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 slowly move south into portions of
the area early Friday before lifting back north as a warm front.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 315 PM Wednesday...

A shortwave trough and cold front currently over the mid-MS Valley
will move east to the Appalachians by tomorrow morning. Meanwhile
S/SW flow around Atlantic high pressure is bringing a very hot and
seasonably humid airmass into the region, with widespread
temperatures in the mid-to-upper-90s. Dew points have mixed out into
lower-to-mid-60s across the Piedmont but are still in the upper-60s
to mid-70s across the Sandhills and Coastal Plain. This is resulting
in observed heat indices as high as 105-110, and a Heat Advisory
remains in effect from the Triangle south and east until 8 PM this
evening.

There is also potential for isolated to widely scattered showers and
storms for the rest of the afternoon into early evening. Scattered
cumulus has developed and a few tiny showers have popped up over the
western Piedmont, but deeper convection remains over SC. CAMS vary
greatly on coverage, with the ARW and NSSL quite aggressive compared
to the HRRR, but the aggressive models appear to be overdoing it
based on current radar. Furthermore, unlike yesterday we don`t have
a strong moisture boundary/convergence axis across the area to act
as a focus for deeper convection. Despite this, SPC mesoanalysis
does depict 1000-3000 J/kg of MLCAPE across central NC, highest in
the SE. The best chances for any convection are in the Sandhills and
central/southern Coastal Plain with the sea breeze, and over the NW
Piedmont with the lee surface trough in place. Shear is virtually
non-existent so any cells should be short-lived and organized severe
weather is not expected. But given the high DCAPE out there (1000-
1600 J/kg), an isolated damaging wind gust can`t be ruled out.

As the mid-level trough and cold front approach later tonight, the
northern Piedmont and northern Coastal Plain could be grazed by an
associated area of showers and storms moving from west to east
across VA from about 03z to 12z. However, given the best forcing
will be to our north and the unfavorable diurnal timing, it should
be fairly weak and only have slight to low chance POPs. Lows tonight
will be quite mild once again, in the lower-to-mid-70s (7-10 degrees
above normal).

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 315 PM Wednesday...

A Heat Advisory has been issued for portions of central NC Thu, with
heat indices between 102 and 108 over portions of the Triangle,
Sandhills, and Coastal Plain.

A frontal boundary will likely be draped northeast to southwest from
the Mid-Atlantic into eastern TN to far western NC early Thu. The
front will try to move south and east through the day and evening as
high pressure settles into the northern Mid-Atlantic in western NY.
However, the front will most likely get hung up along the NC/VA
border sometime early Fri.

Some of the high-res models are indicating a secondary boundary
draping southward with convection from Wed night to early Thu
morning along US-64. Perhaps this is related to the lingering
discontinuity currently over southern VA. However, other guidance
indicates less of a defined wind shift. How this evolves may
ultimately depend on what happens with convection tonight across
northern NC and southern VA. With the uncertainty, we believe that
with warm overnight lows tonight in the mid 70s, high dewpoints in
the 70s again Thu, and max temperatures over the Triangle,
Sandhills, and Coastal Plain in the mid to upper 90s, will lead to
another heat risk across the region. Heat indices could be as high
as 108 over the far eastern Sandhills and southern Coastal Plain.
The only fly in the ointment is whether convection/clouds start
earlier in the day to limit daytime heating. For now, though, we
hedged toward enough solar heating for the higher heat risk. Highs
will be lower in the northwest Piedmont with upper 80s to near 90.

As for convection, some CAMs are showing the greatest coverage south
and east of the Triangle along their effective boundary, while
others extend convection further west to mainly along/east of US-1.
We hedged with this further west solution, thinking that any
boundary would be draped along US-64. Machine-learning models and
guidance suggest the prime storm risk would be between 1 pm and 8
pm, with greatest coverage along/east of US-1, with storms waning by
late evening and overnight as a mid-level trough axis slides south
of the region. SPC has continued a marginal risk of severe storms
mainly over the Sandhills to Coastal Plain. However, we would not be
surprised if that expands north and west to include the Triangle in
later updates. Point forecast soundings indicate high instability
upwards of 2000 J/kg, DCAPE around 1000 J/kg, and decent shear of 20-
30 kts from the WSW supportive of a damaging wind threat with any
stronger organized cells. Hail can also not be ruled out. As
convection wanes overnight, low stratus or fog may develop by early
Fri with lows in the upper 60s to mid 70s.

&&

.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.
Heat Advisory from 11 AM to 5 PM EDT Thursday for NCZ041-042-077-078-
085-086-088-089.

&&

$$

SYNOPSIS...Kren
NEAR TERM...Danco
SHORT TERM...Kren
LONG TERM...Hartfield
AVIATION...Danco/MWS
CLIMATE...RAH