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000
FXUS62 KRAH 180740
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
340 AM EDT Thu Apr 18 2024

.SYNOPSIS...
A weak cold front will move east across the region this morning
and off the coast this afternoon. A stronger cold front will
move across the area late Friday into Saturday, before stalling
near or just to our south. A wave of low pressure will track
along the front along the southeast coast late in the weekend.
Much cooler conditions are expected this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 320 AM Thursday...

* Mainly sunny and quite warm with highs 12 to 16 degrees above
  average this afternoon.

The latest surface analysis shows a weak area of low pressure across
the northern Chesapeake Bay with a weak cold front extending
southwest into the southern Appalachians. The cold front will move
southeast across VA and the Carolinas this morning and off the
Carolina coast this afternoon. A backdoor cold front will drive into
far northeastern NC near sunset and drive southwest across central
NC tonight. Further aloft, weak troughing extending from the mid-
Atlantic southwest across the southern Appalachians early this
morning will shift east with a modest and short lived period of
northwest flow aloft developing across the region today before short
wave ridging moves across the area tonight. The airmass across the
region will dry out a bit today with PW values dropping from a
little over 1.0 inch to 0.75 inches or so this afternoon. The
developing northwest flow aloft and a northwest low level wind
behind the front today will result in some downslope drying
complimented by mixing up to 5-6kft.

In terms of sensible weather, the band of high clouds extending from
southwest to northeast across the eastern Carolinas early this
morning will shift offshore this morning with mainly sunny skies
today. Some high clouds will move into the region from the west
tonight and thicken overnight as the ridge axis shifts east. In
addition, a layer of lower clouds will advance into the region from
the northeast in the wake of the backdoor cold front across the
northern Coastal Plain and northeast Piedmont toward daybreak. Low
level thickness values will start off the day in the 1378-1388m
range supporting highs in the mid to upper 80s. These highs are
about 12 to 16 degrees above average. Lows tonight will range in the
mid 50s to around 60. -Blaes


&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 340 AM Thursday...

* Challenging forecast with considerable temperature contrast
  and instability that will impact convective coverage and
  severity.

* Trend for a somewhat more limited coverage and intensity to
  storms, greatest threat across the southern areas.

A general west to northwest flow aloft is expected across the
Carolinas on Friday and Friday night as the Carolinas are on the
southern periphery of strong mid and upper level jet across the
Midwest and the Great Lakes. At the surface, a frontal zone will be
in place across southern NC on Friday morning marking the leading
edge of a cooler and more stable airmass that moved into the region
from the northeast on Thursday night. This front will lift northeast
as a warm front on Friday afternoon as a stronger cold front
approaches from the west on Friday afternoon and moves into central
NC late Friday night. The airmass across central NC will vary
considerably with the frontal zone lifting northeast across the
area. Highs across the north will range in the upper 70s to near 80
but south of the front, highs will reach the mid to upper 80s. These
temperatures combined with dew points in the upper 50s to lower 60s
will result in weak to perhaps moderate destablization across the
southern areas with a more stable airmass near the VA border and
northern Coastal Plain.

This pattern will support the development of scattered showers and
thunderstorms on Friday afternoon and Friday night that should shift
east and southeast. Deeper convection is favored across the southern
areas in the region of greater instability and with 0-6 km shear
values of around 25-35 kts, some storms could become organized and
possibly severe. SPC has trimmed the marginal risk southwestward
given the more stable regime to the northeast. The primary threat
will be damaging wind gusts with a secondary threat of large hail.
Limiting factors for severe weather include the amount of
destablization and the presence of a capping inversion that could
linger across much of central NC, including southern areas into the
afternoon and evening. In addition, convection may be limited in
coverage during the afternoon and evening with greater coverage
overnight during a period of reduced instability.

Highs on Friday will be problematic with the presence of the
frontal zone and a good deal of cloudiness. Highs will range from
the upper 70s near the VA border and northern Coastal Plain to the
lower 80s in the Triad and Triangle to the mid and upper 80s across
the southern areas and Sandhills. Lows Friday night will range from
the mid 50s near the VA border to lower 60s near the SC border.
-Blaes

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 231 AM Thursday...

Upper pattern through the extended: An upper trough will move across
the Great Lakes/northeast Saturday into Sunday promoting primarily
wnwly flow over central NC Saturday.  Flow will turn more swly over
central NC Sunday into Monday as a low-amplitude short-wave moves
through the deep south.  A more vigorous short-wave will drive
through the southeast Monday into Tuesday. Wnwly flow will then
persist into Wednesday.

Saturday: A sfc cold front will sag south into our area on Saturday.
The NAM and GFS move the front south of our area by Saturday
afternoon. The Euro and NBM are a bit slower and allow some decent
warming to occur across our southern areas Saturday afternoon. The
latter scenario would suggest some instability could develop ahead
of the advancing cold front. This would promote the potential for
some showers/storms to potentially form Saturday afternoon/evening.
Decided to lean on the slower solutions and maintain chance POPs
across southern areas (where dew points may reach the lower 60s)
Saturday afternoon and evening. Temps on Saturday will largely
depend on the evolution of the front, but generally expecting mid
70s to lower 80s from north to south.

Sunday through Tuesday: Flow aloft turns swly Sunday and Monday
increasing low-level moisture advection into the southeast. While
guidance is in good consensus generally pinning the cold front along
the coast (and shunting most instability to our south), ensembles
are suggesting a decent soaking may still be possible for some of
our southern areas Sunday evening. The highest QPF amongst ensembles
(GEFS/EPS), some deterministic guidance (ECMWF, CMC), and machine
learning guidance (EC-AIFS) is generally from our Sandhills
southeast across the Coastal Plain/Coastline. Alternatively, the
deterministic GFS and GEPS ensemble suggest some higher QPF
spreading further north into our Piedmont.  Regardless, it looks wet
in this period, especially across our southern areas. Thunder
chances should be minimal as temps cool off into the lower to mid
60s and dew points drop into the mid to upper 40s. However, some
instability could develop over the southern Coastal Plain and
perhaps support some higher rain rates in these areas Sunday
evening. It`s worth noting that WPC has introduced a marginal risk
for excessive rainfall over the southern two thirds of our CWA for
Sunday into Monday.  However, unless instability can indeed promote
higher rain rates in these areas, the current QPF would likely
negate much of a flash flooding threat.

Any lingering rain Monday morning should largely pull off to our
north by early afternoon.  A few additional scattered showers may be
possible Monday afternoon/evening with the passing of the upper
feature, but overall Monday should largely be dry. Tuesday will
follow suit under nwly flow aloft.

Temperatures Sunday and Monday will be cool in the mid 60s. Temps
will rise into the mid 70s Tuesday and Wednesday.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
As of 235 AM Thursday...

24 hour TAF period: VFR conditions are generally expected through
the 24-hr TAF period. A lingering shower is still possible across
the eastern Coastal Plain near KRWI through 08Z. A shield of mid and
high clouds extending from southwest to northeast across the eastern
Carolinas will shift east this morning with generally clear skies
after mid morning through tonight. A couple of exceptions include
the potential for a brief period of MVFR stratus to develop near the
far western Foothills and possibly the Triad area near daybreak this
morning before rapidly dissipating. In addition, an area of
MVFR stratus will move into central NC from the northeast very
late tonight into Friday morning impacting the KRWI and KRDU
terminals toward and especially after 06Z.

Light southwest to west winds at 3 to 7 kts this morning will
gradually veer around to westerly to northwesterly by daybreak.
Northwest winds at 8 to 12 kts with a few gusts of 20 kts are
expected later this morning into this afternoon. Winds will
decrease late this afternoon with winds becoming northeast at 4
to 8 kts between 03 and 09Z tonight. A brief period of marginal
LLWS is possible early this morning from KRDU northeast through
09Z, but confidence was too low to include in the TAF.

Outlook: A period of MVFR cigs are expected around daybreak Friday
morning across the northeast including KRWI and perhaps KRDU. An
approaching cold front will trigger scattered showers and
thunderstorms Friday afternoon into Saturday morning with sub-
VFR cigs/vsbys. Another round of sub-VFR conditions is possible
Sunday into Monday as a wave of low pressure travels along the
front that will stall to our south. -Blaes

&&

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

&&

$$

SYNOPSIS...Blaes
NEAR TERM...Blaes
SHORT TERM...Blaes
LONG TERM...Luchetti
AVIATION...Blaes