-- Discussion containing changed information from previous version are highlighted. --
948
FXUS62 KRAH 220726
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
325 AM EDT Sat Jun 22 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/...
-- Changed Discussion --
As of 325 AM Saturday...

...Hot with Heat Indices Topping Out In the Upper 90s to Lower
100s...

...Continued Dry...

Though weakening, central NC will remain under the influence of the
upper anticyclone/ridge as it retrogrades further west to the lower
MS Valley and srn Plains by early Sunday. The Atlantic surface high
will push farther east out into the Atlantic, with a pre-frontal
trough developing in the lee of the Appalachians. Low-level
thicknesses and humidity will steadily rise as the low-level flow
becomes increasingly southerly. Low-level thicknesses are forecast
to increase 5-7m from yesterday`s observed 1426m, which should yield
in max temps being ~2 degrees warmer than yesterday. Highs generally
in the mid 90s, which is 7-10 degrees above normal.

Afternoon humidity levels east of the Triangle will be higher than
recent days, with upper 60s to lower 70 dewpoints expected. This is
where heat indices are expected to top out into the upper 90s to
lower 100s. This level of heat, this early in the season when most
are not acclimated will pose a moderate risk for heat related
illnesses, especially those without effective cooling and those with
chronic diseases.

Rain chances will once again be limited to isolated sea-breeze
convection across the far SE zones. Dry elsewhere.

Warmer overnight lows in the lower to mid 70s.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
-- Changed Discussion --
As of 325 AM Saturday...

...Second Consecutive Day of Heat Indices Topping Out In the Upper
90s to Lower 100s...

...Rain chances return...


Broad upper level troughing will develop and extend south into the
area as the parent shortwave dives SEwd through the Great Lakes and
into the Northeast by Sunday night. Embedded disturbances are
progged to move through the mid-Atlantic, including NC, during the
afternoon and evening, with the convectively enhanced cold front
expected to move into the area overnight.

Isolated to scattered showers and storms possible from the afternoon
on, with chance PoPs continuing overnight, mainly across the
northern half of the forecast area. Given weak shear, severe storms
are not anticipated. Additionally, rainfall amounts are expected to
be light and/or fairly scattered. Thus, expect little to no relief
from the rapidly developing drought.

Low-level thicknesses level out, with high very comparable and in
some locations a few degrees cooler, owing to increasing
PWATs/moisture and associated rain chances. Highs in the lower to
mid 90s. The upper 60 to lower 70 dewpoints will be a little more
widespread, with heat indices again in the upper 90s NW to lower
100s along and east of US 1. It is strongly recommended to avoid
outdoor activities during the warmest part of the day and if
possible, stay in an air conditioned location. Additionally, elderly
are especially vulnerable to heat. Check on elderly often and make
sure they hydrate.

Lows generally in the mid 70s, which will provide little relief at
night.
-- End Changed Discussion --

&&

.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 /06Z SATURDAY THROUGH WEDNESDAY/...
As of 120 AM Friday...

24-hour TAF period: Increasing low-level moisture in the form of +70
dewpoints into the coastal plain, sandhills, and now the eastern
Piedmont counties will support a chance for IFR to MVFR restrictions
in stratus and/or fog at KFAY and KRWI, and possibly KRDU.
Meanwhile, KGSO and KINT should remain VFR overnight.

The stratus/fog should scour out relatively quickly, between 12-14z,
with scattered VFR cumulus clouds again this afternoon.

Outlook:  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...CBL
SHORT TERM...CBL
LONG TERM...Leins
AVIATION...CBL/Danco
CLIMATE...RAH