000
FXUS62 KRAH 162355
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
754 PM EDT Tue Apr 16 2024

.SYNOPSIS...
A weak backdoor cold front stretching across the region today will
lift north as a warm front tonight through early Wednesday. A
weakening cold front will move across the region early Thursday,
followed by a stronger front that will cross the area over the
weekend.

&&

.NEAR TERM /REST OF TODAY AND TONIGHT/...
As of 250 PM Tuesday...

As of the 18Z surface analysis, the backdoor cold front has settled
south through most of central NC, lingering along the NC/SC border.
High pressure continues ridging into the area, with nely winds
advecting slightly cooler, drier air into the northern half of
central NC.

The surface boundary should be quasi-stationary through this aft/eve
before lifting northward as a warm front tonight. A s/w will
progress through the area late this aft/eve. Showers and storms have
already fired along the surface boundary over the mtns/foothills as
of 2 PM (where via SPC the SBCAPE is around 1500 J/Kg, bulk shear is
40-45 kts and low-level lapse rates are 8 deg/Km). As the s/w passes
overhead through this evening, expect showers and storms to continue
developing along the surface boundary, mainly over the western and
southern Piedmont of NC, but possibly drifting north and eastward
into the remainder of the Piedmont and Sandhills late this evening.
Via the SPC mesoanalysis, forecast instability is maximized (about
1000-1500 J/Kg of SBCAPE) and low-level lapse rates are strongest (8
degC/Km) along, south, and west of the surface boundary through
sunset, although the effective bulk shear is forecast to be slightly
lower than over the foothills, 30-35 kts. Immediately north/east of
the boundary the CIN is gently eroding but some could linger through
the evening. An isolated strong storm cannot be ruled out. Timing of
storms over central NC based on the hi-res model guidance is roughly
between 6 PM and midnight.

Quite the range in highs for this afternoon, with mid 70s NE to
mid/upper 80s SW. The front should lift back northward through the
area as a warm front tonight, with winds largely becoming
southerly/swly in its wake Wed morning. Expect cloud cover to
increase from the west through Wed morning. Lows tonight will
largely depend on the progression of the front, but for now expect
low/mid 50s NE to low 60s SW.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 310 PM Tuesday...

Aloft, the sub-tropical ridge will progress eastward through the
area and offshore Wed morning. As a low lifts through the western
Great Lakes Wed/Wed night, some of the s/w energy will move through
the mid-Atlantic and Carolinas. At the surface, in the wake of the
warm front, winds will become more sly/swly over central NC. A
Piedmont trough will develop over the area Wed aft/eve as a surface
low drifts east through the mid-Atlantic through Wed night. Cloud
cover should be plentiful through Wed eve, then clear from the NW
Wed night. There could be two chances for showers Wed, one ahead of
the s/w Wed morning, mainly across the western Piedmont. The second
round of showers and possible storms would be with the decaying
surface boundary as it collapses southeastward through the area Wed
aft/eve. With abundant cloud cover and possible precipitation, highs
should top out in the low to mid 80s. With showers exiting to the SE
and gradual clearing from the NW Wed night, lows should generally
range from upper 50s to mid 60s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 355 PM Tuesday...

A surface low over southern Ontario will weaken and get absorbed by
another low to its NW on Thursday, as a secondary low develops off
the Delmarva/southern NJ coast and slowly drifts east. An associated
decaying cold front will move through central NC in the morning. But
there will be no drop in temperatures behind it. In fact, mostly
sunny skies and shortwave ridging aloft will help bring temperatures
back into the 80s areawide on Thursday, maybe even touching 90 in a
few spots in the far south. Lows Thursday night will also be above
normal, in the mid-50s to lower-60s.

Mid/upper ridging will move offshore on Friday and get replaced by
weak shortwave troughing and height falls. At the surface, a warm
front will lift north through central NC, while a much stronger cold
front begins to approach from the NW and a surface low develops
along it and moves east across the Carolinas. This will bring the
next chance of showers during the afternoon and evening, and
ensemble guidance has trended significantly wetter compared to
yesterday. So POPs are increased to chance across the area. With
models showing CAPE as high as 500-1000 J/kg particularly across the
south, a few storms can`t be ruled out. Mid-level flow around 25-35
kts on the GFS and ECMWF isn`t too impressive and borderline for any
kind of severe threat, but will need to watch over the next few
days. Forecast highs on Friday are a bit cooler than Thursday in
most places, ranging from upper-70s to mid-80s, except still upper-
80s in the far south. Lows Friday night are again expected in the
mid-50s to lower-60s as precipitation chances diminish but some
cloud cover remains.

Overall, model guidance has come into better agreement for the
pattern this weekend. Saturday now looks drier and cooler, as the
ECMWF trended toward the GFS in depicting a faster cold frontal
passage through central NC in the morning and afternoon. Forecast
highs are in the mid-70s to lower-80s. POPs are only slight on
Saturday and Saturday night, before increasing to chance areawide on
Sunday and Sunday night (highest SE) as the next wave of low
pressure rides along the front. With models showing the front to our
south, we would be on the cool and stable side which would preclude
any chance of storms and would result in more stratiform rain. But
confidence in these details is still not high until we see more run-
to-run consistency. Confidence on amounts is even lower as the GFS
is more suppressed with the front and largely keeps the rain to our
south, while the ECMWF brings heavier amounts into our region.
Ensemble guidance is all over the place with around half of the GEFS
bringing us measurable rain.

We will largely dry out by Monday as the surface low moves away into
the Atlantic and cool high pressure begins to build in from the
west. High temperatures will only be in the 60s with lows in the
40s. Tuesday will be mostly sunny with temperatures increasing back
to near normal (lower-to-mid-70s).

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 800 PM Tuesday...

Mostly VFR conditions are expected across the region over the next
24 hours. As the weak frontal boundary makes its way across the
region tonight, it has collided with a few storms but they have for
the most part kept their distance from the terminals. These storms
are expected to dissipate in the next couple of hours resulting in
no major aviation issues. Light winds are generally from the east
northeast, but expected to change to SW by Wednesday afternoon.
Cloudy skies will continue tonight and cloud decks could lower
tomorrow as the warm front retreats back to the north. After the
warm front retreats, by Wednesday afternoon a few showers could
develop, especially over the nwern terminals, as a weakening cold
front moves across the region west to east.

As of 150 PM Tuesday...VFR conditions will generally prevail across
central NC for the next 24 hours, with a couple of potential
exceptions. A weak frontal boundary currently stretches NW to SE
across central NC, separating ridges of high pressure to our
northeast and centered off the Southeast coast extending westward.
This is resulting in a light surface wind from the NE or ENE over
northern terminals (INT/GSO/RDU/RWI) and from the ESE across the
south (FAY). Passage of weak disturbances aloft from WNW to ESE is
associated with patchy mid clouds topped with a veil of high clouds,
and this will continue through Wed morning. We`ll also have sct
clouds based at 3500-6000 ft AGL from time to time late this
afternoon through tonight, and an isolated shower or storm can`t be
ruled out, mainly at INT/GSO/RDU this evening, but these should be
very brief and circumnavigable. Late tonight, from 09z-13z, areas of
MVFR stratus expected to form in coastal sections tonight may drift
westward to RWI/FAY with a lower risk of reaching RDU, but
confidence in this being a prevailing conditions for more than an
hour or two at these locations is low. Surface winds will be mostly
light through tonight, then shift to be from the SSW and SW near 10
kts after 14z Wed as the weak frontal boundary lifts back northward
as a warm front and fizzles out.

Looking beyond 18z Wed, VFR conditions are expected to dominate
through much of Fri, although isolated showers and storms are
possible very late Wed afternoon through Wed evening. We`ll have
another chance of showers/storms late Fri, then a risk of sub-VFR
cigs/vsbys in fog Fri night ahead of a cold front. Uncertainty grows
over the weekend with respect to timing of this cold front passage,
but an uptick in shower/storm chances and accompanying sub-VFR
conditions is expected over the weekend just ahead of and with the
front. -GIH

&&

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

&&

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

&&

$$

SYNOPSIS...Blaes/Hartfield
NEAR TERM...KC
SHORT TERM...KC
LONG TERM...Danco
AVIATION...CA/GH