-- Discussion containing changed information from previous version are highlighted. --
249
FXUS62 KRAH 201730
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
130 PM EDT Mon May 20 2024

.SYNOPSIS...
High pressure will extend across and offshore the Middle Atlantic
through Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 915 AM Monday...

The primary change with the morning update was to tweak fog coverage
along with sky grids. There are still several sites showing
visibilities less than 2 miles (including HNZ, TQV, and RDU), and
have kept fog in the forecast through 10am. In addition, the low
clouds that have plagued the eastern half of the forecast area this
morning have been a little more persistent than expected, so also
updated the timing of when those clouds should scatter out.
Meanwhile, it`s a mostly sunny morning with temperatures in the 60s
across western counties. Did not make any change to today`s highs,
which should range from the upper 70s in the northeast to the low
80s in the southwest. Previous discussion follows.


As of 345 AM Monday...

A mid-level, 700-500 mb anticyclone centered over the mid-South in
00Z RAOB data will drift ewd and become situated over the Carolinas
and srn Middle Atlantic by tonight. Underlying surface high pressure
will continue to extend across the Middle Atlantic and Southeast.

Nely low-level flow and continued radiational cooling this morning
will contribute to the expansion of fog and low overcast over all
but the far nw Piedmont, the latter where multi-layered
stratocumulus and altocumulus will likely persist. The depth of the
associated stratus/fog layer should be much shallower and
consequently disperse more quickly than that of Sun morning, with
partly to mostly sunny conditions expected after ~14Z. Associated
insolation, and modification of the surface ridge and air mass, will
yield high temperatures generally within a couple of degrees either
side of 80F. The presence and proximity of the surface ridge will
favor calm and mainly clear tonight, which will support excellent
radiational cooling into mostly the low-mid 50s and with an
accompanying redevelopment of areas of radiation fog/stratus Tue
morning.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 355 AM Monday...

A weak mid-level trough will move across the cntl Appalachians and
Middle Atlantic through 12Z Wed, while ridging will otherwise extend
across the Southeast. Surface high pressure that will initially
extend along the Middle Atlantic coast will drift offshore and
result in the development of sely/"return" flow Tue afternoon and
mainly calm Tue night. High temperatures should respond and increase
into the lwr-mid 80s, followed by another night of strong
radiational cooling into mostly the mid-upr 50s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 311 AM Monday...

Upper pattern through the extended: Mid-level ridging over the
eastern US will shift offshore through Wednesday evening. A low-
amplitude upper trough will then lift through the Great Lakes
Thursday.  A short wave will then move through the TN Valley and
wash out over central NC Friday into the weekend.

Wednesday: The western ridge of an offshore sfc high will extend
light sswly flow across central NC on Wednesday.  Void of forcing
for ascent and lingering below normal PWAT, Wednesday will remain
dry.  Given the sswly flow, however, temps will begin to steadily
rise reaching the mid 80s Wednesday afternoon. Warm overnight lows
in the lower 60s is expected.

Thursday through Sunday.  Ensembles continue to suggest the
potential for periods of rain over this time as upper forcing from
the aforementioned upper features move overhead. On Thursday, an
upper trough will lift through the Great Lakes. Some mid-level
energy associated with this feature may trickle down into our
northern locations and promote showers/storms later in the day.
However, the better forcing and low-level moisture transport appears
to stay well to our north, and thus continue to maintain just slight
chance to low chance POPs across our central to northern areas
during this time.

From Friday onward, ensembles continue to simulate a potentially
potent short wave riding through the TN Valley and eventually over
central NC through Sunday. Periods of rain look promising over this
temporal period, the details of which are hard to pin down at this
point.  Severe weather parameters are not popping off the charts at
this point, but periods of higher shear could promote some isolated
stronger storms especially Friday afternoon/evening.

There is high probabilities amongst ensembles that temperatures will
exceed the mid 80s both Thursday and Friday.  The quartile spread
widens a bit more over the weekend, likely due to differing
solutions wrt to any sfc boundaries. Regardless, temps will likely
remain in the 80s this upcoming weekend.


&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
-- Changed Discussion --
As of 130 PM Monday...

TAF period: There are some lingering MVFR ceilings in the region,
but expect that all locations should generally have low VFR diurnal
cumulus through the afternoon. Conditions will clear out tonight,
then another round of restrictions are expected late tonight into
Tuesday morning. RWI is favored for restrictions based on
climatology and is the only site with IFR restrictions forecast.
Elsewhere, blended guidance and persistence from observations this
morning, giving a tempo site at other terminals for MVFR fog. Wind
will continue to be out of the northeast through the period,
becoming lighter/calm overnight.

Outlook: Wednesday morning could have yet another round of
restrictions, although most guidance is showing that most
restrictions should be contained to the eastern third of the state,
locally only impacting RWI. Otherwise, the forecast will be dry
through Thursday afternoon, then diurnally driven
showers/thunderstorms are expected into the weekend.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...Green/MWS
SHORT TERM...MWS
LONG TERM...Luchetti
AVIATION...Green