495
FXUS62 KRAH 212005
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
405 PM EDT Fri Jun 21 2024

.SYNOPSIS...
High pressure aloft will remain in control ahead of a weak upper
level trough that will move across the Middle Atlantic on Sunday. A
pre-frontal trough and weak cold front will move into NC Monday
afternoon and night, then lift northeastward across the Middle
Atlantic as a warm front Tuesday and Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 320 PM Friday...

The slightly weaker but still strong 596 dam mid-level anticyclone
will continue to slowly weaken and drift further SW from the TN
Valley to the lower MS Valley through tonight. At the surface, high
pressure east of VA/NC will continue to nose westward with the
center moving south close to Bermuda. This is switching the low-
level flow to a S/SE direction, resulting in slightly warmer high
temperatures across central NC compared to yesterday (lower-to-mid-
90s). Meanwhile an inverted trough extending from a 1018 mb area of
low pressure just east of Jacksonville is grazing our southern areas
today. This trough is advecting in higher dew points, with quite a
gradient in SE NC separating dew points in the lower-to-mid-70s
(including 71F at KCTZ) from dew points in the mid-50s to lower-60s
(including 56F at KHRJ and KPOB). Other than our far SE, dew points
are mixing out well which is keeping heat indices very close to the
air temperatures.

Radar depicts bands of showers from enhanced moisture convergence in
the inverted trough currently moving NW across far SE NC, some of
which has briefly made it into southern Sampson County. This is
where SPC mesoanalysis depicts 500-1500 J/kg of MLCAPE. So continue
slight chance POPs there until 00z, but only there as any showers
have been quick to dissipate when trying to move further inland into
the drier air, and CAMS suggest that will continue. Tonight will
have milder lows in the upper-60s to lower-70s as the higher dew
points begin to overspread the whole area. Guidance shows a decent
chance of patchy fog late tonight over the Sandhills and Coastal
Plain where the greatest low-level moisture will be.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 400 PM Friday...

Slightly hotter yet, with forecast high temperatures about 6-12 F
above average and centered in the middle 90s, or about a category on
average higher than those of Fri.

A mid-level high now over the srn Appalachians and TN Valley will
continue to gradually weaken while retreating swwd across the lwr MS
Valley and srn Plains through 12Z Sun. An associated ridge axis will
continue to extend from the center of the high newd and across the
srn Appalachians and wrn Carolinas, while a weak mid-level
trough/low now just offshore the NC coast will meander there and
promote weakly cyclonic flow and slightly cooler mid-level
temperatures over the ern Carolinas. Observed 500 mb temperatures
were minus 7 C at MHX this morning versus minus 5 C at GSO, for
example; and that should remain the case on Sat.

At the surface, on the wrn periphery of high pressure that will
become anchored near and just northeast of Bermuda, an Appalachian-
lee trough will develop and remain over the srn Middle Atlantic
Foothills and wrn Piedmont. Surface flow, which in recent days has
maintained a considerable ely to nely component around the Bermuda
high, will assume a sly direction and favor both warming
temperatures and increasing moisture/humidity. That sly flow will
also favor appreciable inland penetration of a sea breeze across
sern and cntl NC through Sat evening.

The aforementioned increasing low-level moisture/humidity will favor
areas of morning fog and stratus through the srn/cntl Coastal Plain
and ern Sandhills, with surface dewpoints mostly in the lwr 70s in
the morning (except for lingering 60s F probable over the nw
Piedmont). That moisture will remain somewhat shallow and prone to
vertical advection/"mixing out" for one more day, however, such that
the 70s of the morning should decrease into the mid/upr 60s with
strong diurnal heating/mixing during the afternoon (except a
lingering 70-72 F from CTZ to GSB) As such, despite the increasingly
hot temperatures, related Heat Index values are apt to remain mostly
in the mid to upr 90s, to around 100 F in climatologically-favored
areas roughly east of US 1.

It will also remain mainly dry, though with a slight-small chance of
afternoon showers/storms over the srn-cntl Coastal Plain and
Sandhills (similar to that now over sern NC), where sea breeze
forcing and the aforementioned slightly cooler mid-level
temperatures will coincide. It will become increasingly muggy and
warm overnight, with the development of areas of stratus
accompanying a resurgence of surface dewpoints in the the lwr-mid
70s, and with similar low temperatures.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 300 PM Friday...

...Dangerously hot temperatures expected this weekend and into early
next week...

Sunday/Monday...Fairly high confidence heat forecast for
Sunday/Monday, with a few caveats as precip chances return to the
forecast for the first time in a while.

Synoptically...Sunday will see the upper ridge responsible for the
widespread heat begin a slow migration westward toward the Four
Corners. This will result in somewhat lower heights aloft across the
area as the flow becomes increasingly northwesterly, yet
temperatures and heat indices will still approach dangerously high
values Sunday afternoon. At the surface, the combination of
increased southerly flow from the Bermuda High, along with increased
remnant moisture from the weak trough over GA/SC will push dewpoints
well into the mid 70s by Sunday morning, with little hope of mixing
out much below the lower 70s later in the day. This, along with
afternoon temps in the mid 90s, will likely translate to heat
indices generally in the 102-105 degree range, especially for areas
along and east of US-1 although arguably the entire forecast area
(even the western Piedmont) could be within a degree or two of
triple digit heat indices. One caveat at this point is the potential
for cloud cover with the weak trough over GA/SC as it moves
northward, along with the potential for some much-needed scattered
showers and storms across the Sandhills/southern Coastal Plain later
in the day. If these showers develop (probabilities in the 20-30
percent range), it`s likely they won`t occur until after we`ve
reached out high temperature for the day. We will continue to
message the potential for dangerously hot temperatures not only
Sunday, but into Monday as well.

At the same time, a weak synoptic surface boundary will be making
its way through the Ohio Valley, gradually crossing the mountains
and arriving in NC at some point during the day on Monday. Strong
southerly flow ahead of the front will allow for another dangerously
hot/humid day on Monday. There is a signal in the guidance for a
period of cloud cover/showers/isolated storms coincident with the
frontal passage, but the exact timing at which this will happen is
still unclear. Most of the guidance advertises a decaying line of
showers moving through the area overnight, eventually redeveloping
across the Coastal Plain Monday afternoon. Thu guidance is clear
that somewhat drier air will follow the front, with dewpoints in the
Triad retreating in the mid 60s by the afternoon while remaining in
the low to mid 70s to the east. Thicknesses behind this front aren`t
notably lower, thus temperatures will once again top out in the
mid/upper 90s. However with drier air in place to the west, the
primary threat area for heat-related concerns appears to once again
be located from US-1 eastward.

Tuesday/Wednesday: Tuesday will see limited precip chances across
the area as the influences of subsidence in the wake of Monday`s
departing trough take hold over the area, not to mention the
intrusion of lower dewpoints (mid 60s) across the area. Once again,
thicknesses remain relatively unchanged and temps within the post-
frontal regime will reach the mid to upper 90s. Return flow around
the Bermuda High will allow dewpoints to return to the 70s on
Wednesday and with temps once again in the mid/upper 90s, heat
indices are likely to make another return into the triple digits
Wednesday afternoon. Scattered showers will be possible especially
across the western Piedmont and Sandhills Wednesday as moisture
returns to the area, although chances remain low in the 20-30
percent range.

Thursday/Friday: Another longwave trough and associated surface
convergent boundary appear on target to cross the mountains and
sweep through the Mid Atlantic late in the week, at this point with
the highest probabilities Thursday afternoon/evening. Grand ensemble
precip probabilities are generally in the 40-50 percent range for
Thursday and this seems more than reasonable at this stage given an
approaching surface boundary, abundant moisture, and instability.
Much like the boundary earlier in the week, somewhat lower dewpoints
will be drawn into the area to close out the week, but this time
also accompanied by slightly lower temps in the upper 80s/lower 90s.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 155 PM Friday...

24-hour TAF period: VFR conditions will prevail through this evening.
A few showers and maybe an isolated storm will be possible in the
far SE, mainly Sampson County. Otherwise it will be dry with just
some scattered mid-level cumulus. Guidance shows a good signal for
fog and IFR/LIFR stratus late tonight and early tomorrow morning
across the Sandhills and Coastal Plain, especially around FAY. VFR
will return everywhere by mid-morning. Winds will be light and
mostly S/SE today, shifting to more SW tomorrow.

Outlook: VFR and dry conditions are expected to persist through
Saturday. An approaching cold front will support a slight chance of
showers and storms and related sub-VFR restrictions on Sunday, with
better coverage on Monday. Tuesday should be mostly dry before
isolated showers and storms may return on Wednesday especially west.

&&

.CLIMATE...

Record High Temperatures:

June 22:
KRDU: 100/2022
KFAY: 101/2022

June 23:
KRDU: 100/1986
KFAY: 102/1981

June 24:
KRDU: 99/2010
KFAY: 102/1914

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

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


Record High Minimum Temperatures:

June 22:
KGSO: 75/1981
KRDU: 78/1933

June 23:
KGSO: 74/2015
KRDU: 77/1890
KFAY: 77/2017

June 24:
KGSO: 76/2015
KRDU: 76/1888
KFAY: 79/2010

June 25:
KGSO: 75/2015
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

&&

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

&&

$$
SYNOPSIS...CBL/MWS
NEAR TERM...Danco
SHORT TERM...MWS
LONG TERM...Leins
AVIATION...Danco/CBL
CLIMATE...RAH