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000
FXUS62 KRAH 152016
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
415 PM EDT Mon Apr 15 2024

.SYNOPSIS...
A backdoor cold front will slide southward into central NC tonight
and stall across the area through Tuesday. The front will then lift
northward through the area as a warm front Tuesday night.

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 230 PM Monday...

A conditional threat for isolated severe storms across the northern
Piedmont and northern Coastal Plain counties this evening continues.

The 18Z surface analysis shows a lee trough over the Foothills of NC
and VA, with mainly southwesterly flow across central NC. The
backdoor cold front expected to slide south into the area tonight
was draped across southern PA and into central OH and central IN.
Bermuda high pressure extends into the Southeast US. Temperatures
across central NC have risen into the mid/upper 80s, while dewpoints
are generally in the upper 40s to low 50s.

The Bermuda high will continue to ridge into the Southeast through
and tonight. A surface trough will likely remain in place over
central NC until the backdoor cold front slides southward into the
area tonight. Aloft, a disturbance will progress eastward through
the mid-Atlantic late this aft through this eve, clipping northeast
NC along the NC/VA border. With low level thicknesses still expected
to rise to around 1405m by 00Z, highs are still forecast to top out
in the mid 80s to around 90 degrees.

Showers and storms continue to fire ahead of the cold front over
northern VA/WV and MD. Many of the hi-res models continue to
simulate the showers and storms blossoming over srn/sern VA as the
front advances southward through the remainder of the aft/early eve.
The big question remains whether the storms will be able to overcome
the loss of heating/increasing CIN and lower shear and instability
over central NC to continue into nrn/nern NC this evening. Any
storms that do persist/develop over the area later this eve/tonight
will have the capability of producing some locally strong/severe
wind gusts and/or hail. The shower/storm activity should dissipate
after 06Z or so. with the backdoor front settling W-E across the
area through daybreak Tue. Lows still expected to be well above
normal, upper 50s to low 60s.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 200 PM Monday...

A weak stationary front should remain across the forecast area, with
cooler air generally northeast of the Triangle with warmer air to
the south and west. While the morning should remain dry, an upper
level shortwave is forecast to move across the state Tuesday
afternoon into the evening, which should help trigger another round
of showers and thunderstorms along the front. The GFS/GEFS is
currently the most aggressive with coverage of showers and
thunderstorms, although the HREF/SREF also show a decent amount of
coverage, while the 00Z ECMWF/12Z NAM both show a relatively dry
forecast. Only made minor tweaks to the pops, generally keeping
chance pops north of US-64. With the mid-day update, SPC also added
a marginal (level 1 of 5) severe risk generally north and west of
Raleigh, with steepening low-level lapse rates favoring the
potential for damaging wind gusts. As the front pulls north Tuesday
night, the chance for precipitation will come to an end. With the
front bisecting the forecast area, there should be more of a
gradient in high temperatures for Tuesday - locations near the VA/NC
border will stay around 80 degrees while locations across the south
should rise into the upper 80s once again. Low temperatures should
not have quite as much of a spread, ranging from the mid 50s to the
low 60s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 400 PM Monday...

As a low pressure system moves into Wisconsin and Lake Michigan on
Wednesday and the backdoor front lifts NE and away from our region,
it will turn dry but widespread mid and high clouds should remain.
This will somewhat limit temperatures, but with strong S/SW flow
between this low and a high west of Bermuda, it will still be warmer
than average with Wednesday`s highs in the upper-70s to mid-80s.
S/SW winds may also gust to 20-30 mph in the late morning and
afternoon. As the primary low weakens and moves into Canada, it will
transfer energy to a secondary low that develops over VA and the
Delmarva on Wednesday night. While the best upper forcing will be
well to our NW, an associated weak mid/upper trough will also move
overhead. So there could be enough moisture and forcing to eek out a
few showers (and maybe a storm early) on Wednesday evening and
Wednesday night. This is supported by the ECMWF as well as a
minority of GFS/ECMWF ensemble members. The best chance should be in
northeastern locations, and any amounts will be light (around a
tenth of an inch or less). Lows Wednesday night will be very mild,
in the lower-to-mid-60s.

The primary low will also drag a decaying cold front that moves
through central NC Thursday morning, but it should be a dry passage
and 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. Another upper disturbance may bring
another chance of isolated showers and storms on Friday,
particularly if the GFS verifies, but the heavier amounts it shows
in the SE are not supported by its ensembles and appear to be an
outlier. So only have slight to low chance POPs at this time.
Forecast highs on Friday are again in the 80s, but slightly cooler
than Thursday.

A wetter pattern looks to be in store for the weekend. The next
mid/upper low will move east across southern Canada from mid to late
week, which will drag a much stronger cold front that sinks SE and
slowly moves through central NC this weekend, with multiple waves of
low pressure riding along it. Guidance is still in disagreement on
exact timing, with the GFS depicting the frontal passage on Saturday
night while on the ECMWF it isn`t until Sunday/Sunday night. POPs
increase to low chance on Saturday/Saturday night and high chance on
Sunday, when deterministic models and a majority of ensemble members
have precipitation. There could be enough instability for some
storms, particularly in the SE and if the front is slower to move
through as the ECMWF depicts. We should largely dry out by Monday as
high pressure builds in behind the front. The temperature forecast
this weekend is also low confidence and depends on the timing of the
front. The GFS is much cooler than the ECMWF as it drops the front
through the area faster, and the temperature forecast leans towards
their ensemble means which are somewhere in between. Temperatures
will drop significantly when the front does pass through, and by
Monday forecast highs are only in the 60s, which is well below
normal.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 220 PM Monday...

24 hour TAF period: Fairly high confidence VFR conditions will
prevail through the 24-hr TAF period. The exception continues to be
the conditional chance for showers/storms, mainly invof KRWI and
possibly KRDU between 03Z and 06Z this evening. Where showers do
occur, there could be some high end-MVFR vsbys early Tue morn. Given
the conditional nature and lower confidence of occurrence at a
specific terminal, will leave mention out for now. Otherwise, mainly
swly winds of 8-10 kts with intermittent gusts of 15-20 kts will
prevail through sunset, with gusts abating and winds becoming light
and variable through the remainder of the TAF period. -KC

Outlook: A quasi-stationary front will bisect the area through Tue
before moving back north Wed as a warm front Tue night. This
boundary will bring the threat of scattered showers and storms
Tuesday afternoon/early evening, especially across the northern TAF
sites. Sub-VFR fog/stratus may also be possible in rain-cooled air.
VFR is expected to prevail Wed into Fri, although showers are
possible with another boundary approaching later in the week. -CBL

&&

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

&&

$$
SYNOPSIS...KC
NEAR TERM...KC
SHORT TERM...Green
LONG TERM...Danco
AVIATION...KC/CBL