943
FXUS62 KRAH 291743
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
142 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 1057 AM Saturday...

Water vapor imagery this morning depicted a de-amplified ridge over
the southeast. Further upstream, a developing trough and associated
convection was evident over the Midwest/Great Lakes region. A weak,
convectively-enhanced short-wave currently over Missouri/Illinois
will progress east across the mid-Atlantic today.

The remotely-sensed MMIC-TPW satellite product depicted a pocket of
residual drier air over much of central NC this morning. This drier
air will lift northeast and offshore today, as flow turns more sly
with increasing PWAT expected to stream in from the west late
tonight. Void of upper forcing (shunted to the north), and strong
sfc forcing, showers/storm coverage should be limited and primarily
confined to the higher terrain today. A few showers and isolated
storms could trickle into the far western Piedmont this afternoon,
and perhaps a rogue sea-breeze cell further east, but overall it
should be mostly dry today.

Given the persistent sly flow today, temperatures should once again
reach the mid 90s.  However, given the exiting residual drier air,
think that the dew points could mix out a bit more than previously
thought later this afternoon (upper 60s).  As such, heat indices may
not officially reach Heat Advisory criteria, but should hover in the
100 to 105 range.  Given that these values will be quite close to
advisory criteria, and that the experimental HeatRisk product
depicts the "Major" category over much of central NC, will let the
current Heat Advisory ride this morning.

&&

.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 FRIDAY/...
As of 205 AM Saturday...

Aloft, a trough will progress eastward through the Northeast and mid-
Atlantic Mon/Mon night, while the mid-level anticyclone sits over
the ARKLATEX. As the trough moves away from the East Coast, the high
will once again build into the region from the west, sitting over
the TN Valley/Deep South Tue and Wed. A series of northern stream
s/w disturbances will track eastward through the northern CONUS Tue
through Fri, with each successive s/w slowly suppressing the high
southward. However, the high should generally remain over the
Southeast US through Fri. At the surface, the cold front should be
through NC Mon morning, with high pressure ridging into the area in
its wake from a high moving eastward through the Great Lakes. As the
high continues eastward through the Northeast and offshore Tue/Tue
night, it will continue ridging southward into central NC. Once the
high moves out over the Atlantic, a lee trough will develop, with
swly flow and the advection of warm, moist air into the area taking
over once again. Temperatures may actually be near to slightly below
normal Mon and Tue, but once the warm advection commences on Wed,
they will quickly rise back above normal Wed and remain above to
well above normal through the end of the week. As for rainfall,
aside from some possible lingering showers/storms in the east on
Mon, the next best chance for appreciable rainfall looks to be Fri
night.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
As of 120 PM Saturday...

VFR conditions will prevail through the 24 hour TAF period.
Scattered VFR stratocu (3.5 to 6 kft AGL) will continue to blossom
across the area this afternoon, but should dissipate with loss of
daytime heating this evening. Afternoon convection should mostly be
confined to the mountains and just inland of the coast, however a
stray shower/storm could trickle near KINT/KGSO later this
afternoon. Overall though, the forecast appears dry the next 24
hours.  Overnight sub-VFR stratus should mostly be confined to the
mountains. However, some fleeting MVFR ceilings could migrate near
or at KINT/KGSO early Sunday morning. Confidence in this occurring is
too low at this time to include in the TAFs however.

Beyond 18Z Sunday: Showers and storms are forecast to develop ahead
of an approaching cold front Sunday afternoon and evening. Coverage
could develop as early as 18 to 20Z in the west, pushing 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 showers/storms may be possible
along the passing cold front late Sunday night into Monday morning.
VFR conditions should return Tuesday and Wednesday as dry high
pressure extends into central NC. Diurnal isolated showers and
storms will then be possible Wednesday and 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...Luchetti
SHORT TERM...Kren
LONG TERM...KCP
AVIATION...Luchetti