622
FXUS62 KRAH 300143
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
943 PM EDT Sat Jun 29 2024

.SYNOPSIS...
Bermuda high pressure will remain locked in over central NC this
weekend. A cold front will push through the area Sunday night into
Monday.  Post-frontal high pressure will extend into the southeast
Monday and Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 940 PM Saturday...

A Heat Advisory remains in effect through Sunday for all but the nw
Piedmont and part of the srn Piedmont in cntl NC.

Afternoon-evening satellite data depict a couple of areas of
concentrated and persistent cumulus along 1) a quasi-stationary lee
trough/convergence axis from near CAE in SC nwd to near and just
west of AFP, VUJ, and EXX in cntl NC and 2) a nwwd-retreating sea
breeze evident in regional radar data from PTB in srn VA to RDU to
TTA in cntl NC. Each may continue to focus isolated to widely
scattered showers/storms until the sea breeze and following clearing
move nwwd and through the wrn/nwrn NC Piedmont through 05-06Z, based
on an extrapolation of its current speed of ~12-14 kts.

A prominent inversion evident around 15 thousand ft AGL on the GSO
and MHX RAOBs this evening seems to be limiting updraft depth and
intensity, given that 45-50 dbz or greater reflectivity has been
confined at and below that inversion level. So while no strong to
severe storms are expected, isolated locations may receive 0.5"-
1.00" of rain, as has been the case over cntl Moore Co. in the past
90 minutes, per MRMS data.

It will otherwise be quite warm and muggy overnight, with
temperatures slow to fall below 80 F and likely to only reach 75-80
by sunrise. In fact, temperatures even at 01Z were still at or above
90 F across the Triangle (90 at TQV and 91 at RDU) and in the upr
80s in the nw Piedmont/Triad (88 at INT and 87 at BUY).

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 142 PM Saturday...

The Heat Advisory has been extended for Sunday and to include the
southern/northeast Piedmont. Heat indices could be as high as 108 in
portions of the advisory area.

A shortwave trough over eastern Canada is forecast to reach the
northern Mid-Atlantic by early Mon. At the surface, a pre-frontal
lee trough will setup along the southern Appalachians during the
day. A cold front will then approach from the north and west
overnight Sun night into early Mon morning as high pressure builds
into the OH valley.

Prior to the onset of showers and storms, a very warm and humid
airmass will be entrenched over the area with broad southerly flow.
This should result in higher dewpoints with low to mid 70s. Combined
with highs in the low to mid 90s, and perhaps some upper 90s over
the Triangle, will result in heat indices between 103 and 109. As a
result, we expanded the advisory to cover much of the region
along/east of US-1.

As for the shower/storm potential, most of the models and high-res
guidance is indicating two potential waves of activity. The first
chance would come along the lee trough and become an effective
front, generating showers and storms during peak heating. These
storms would then track ESE from the NW Piedmont into the Coastal
Plain between about 2 PM and 8 PM. This first wave has the best
potential to be severe, with damaging winds the main threat,
resultant of high instability, 20-25 kts of shear, and the potential
for wet microbursts. The highest severe risk would appear along the
northern sections of central NC, where shear is highest along the
mid-level trough axis.

CAMs are showing a secondary wave of showers/storms late Sun night
along the actual cold front, that could produce additional activity
mainly from the Triangle/Sandills and points east. This wave should
not be severe given the time of day it will be moving through.

On top of the heat and severe risk, there is also a marginal risk
for excessive rainfall. While we have been very dry the past several
weeks, several factors are lining up where isolated flash flooding
is a concern. Precipitable water values range from 2.2 to 2.5
inches, well above the maximum for the end of June. Additionally,
slow storm motion and a deep warm cloud layer exists, favorable for
high rainfall rates in slow moving storms. The latest probability
matched mean from the HREF suggests the potential for 2+ inches for
some areas along/east of US-1. While this will not be widespread,
the potential is there given the above factors, especially over
urban areas. Overnight lows Sun night are expected to be in the mid
60s NE to low 70s SW.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 300 PM Saturday...

Upper level trough over New England will progress eastwards and a
strong ridge will move into the Mid-Atlantic region for the
remaining portion of the long term period. At the surface as the
cold front exits the region Monday afternoon the Triad  region is
expected to be dry while the rest of the area clears from NW to SE.
While isolated showers and storms are possible, QPF amounts remain
less than half an inch for Monday afternoon. Tuesday a surface high
centered over the Lower Great Lakes region will filter in to NC from
the north bringing a short relief from the heat. Temperatures on
Monday and Tuesday will be in the mid to upper 80s with tolerable
dew points in the 60s, maybe even dropping into the 50s Monday night
across the north. Lows will range from low to mid 60s.

On Wednesday high pressure moves off the New England coast and a lee
trough develops to our west. While Wednesday is expected to be dry,
temperatures begin to increase and moisture in the low levels begin
to creep back into the region.  As the lee trough lingers across the
Mid-Atlantic region showers and isolated storms are possible in the
afternoon/early evening Thursday especially across the Piedmont
Region. As time gets closer more Hi-Res model solutions will give a
better idea on time and coverage. Another chance for isolated
afternoon storms are possible Friday and again on Saturday.

Temperatures Thursday through Saturday will be very hot. Highs are
expected to be in the mid to upper 90s each day with dew points in
the low to id 70s. Heat index values will range from 100-110 degrees
each day.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 820 PM Saturday...

Scattered VFR stratocumulus around 5-8 kft will continue to diminish
this evening with loss of daytime heating. VFR will mostly prevail
through tomorrow morning, but some guidance shows potential for low
stratus late tonight and early tomorrow morning in the south and
east. The best chance is at FAY, so added a TEMPO group there for
IFR conditions. Tomorrow afternoon from about 17z to 00z, showers
and storms are likely to develop ahead of a cold front and move E/SE
from the NW Piedmont into the Coastal Plain. Brief gusty winds,
heavy rain and sub-VFR ceilings and visibilities are possible with
any storm. Outside of storms, winds will generally be around 5-10
kts, veering slightly from southerly tonight to more southwesterly
tomorrow.

Beyond 00Z Monday: Showers and storms will continue to push east
through central NC into the evening hours. A few storms could be
strong to severe and cause strong downdrafts near or at our
terminals. A secondary surge of weaker showers/storms with
associated sub-VFR ceilings and visibilities will be possible along
the passing cold front late Sunday night into Monday morning,
especially south and east. VFR conditions should return Tuesday and
Wednesday as dry high pressure extends into central NC. Diurnal
isolated showers and storms will then be possible on Thursday.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Sunday for NCZ008>011-024>028-
040>043-075>078-083>086-088-089.

&&

$$
SYNOPSIS...Luchetti
NEAR TERM...MWS
SHORT TERM...Kren
LONG TERM...CA
AVIATION...Danco/Luchetti