-- Discussion containing changed information from previous version are highlighted. --
473
FXUS62 KRAH 211900
AFDRAH

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

.SYNOPSIS...
High pressure aloft will remain in control over the region through
early Sunday. Rain chances will return late Sunday as a northern
stream upper level trough moves into the area. 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 1110 AM 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. Meanwhile an inverted trough
extending from a 1018 mb area of low pressure just east of
Jacksonville will graze our southern areas today. This will help
switch the low-level flow to a S/SE direction, increasing 1000-850
mb thicknesses by around 10 m compared to yesterday. This will
support high temperatures in the lower-to-mid-90s across central NC.
Dew points will also be slightly higher but with good mixing should
still bottom out in the lower-to-mid-60s in most places, keeping
heat indices close to the air temperatures.

Radar depicts a line of showers from enhanced moisture convergence
in the inverted trough currently moving NW to the SE NC coast around
ILM. The latest HREF still shows some upper-60s to lower-70s dew
points and 750-1250 J/kg of CAPE creeping into our far SE in the
afternoon. Some CAMS (including the NSSL and ARW) depict a few of
the showers and storms making it to our far SE, but they quickly
dissipate before moving farther inland. So continue slight to low
chance POPs over just southern Sampson County from this afternoon
through 00z. Any convection would quickly die off after sunset, with
milder lows in the upper-60s to lower-70s as 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 best low-level moisture will be.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 330 AM Friday...

Heights aloft will continue to lower as the upper anticyclone/ridge
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.
Given an expected 6-8 m increase in thicknesses, highs Saturday
should be 2-3 degrees warmer, topping out in the lower to mid 90s.
Very humid and uncomfortable dewpoints in the upper 60s and lower
70s will be prevalent and will propel heat indices in 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 an isolated sea-breeze
convection across the far SE zones.

Warmer overnight lows in the lower to mid 70s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.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 21:
KRDU: 75/1933

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

&&

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

&&

$$

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