-- Discussion containing changed information from previous version are highlighted. --
640
FXUS62 KRAH 211327
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
925 AM EDT Tue May 21 2024

.SYNOPSIS...
High pressure over the western Atlantic will extend across the
Southeast ahead of a cold front that will approach from the west and
become quasi-stationary from the Middle Atlantic to the lower MS
Valley Thursday and Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 925 AM Tuesday...

All low clouds have cleared out of northeastern counties, leaving
just a few high clouds around the region. Tweaked some hourly
temperature/dewpoint grids, but more seasonable high temperatures in
the low to mid 80s remained unchanged in the forecast. Previous
discussion follows.


As of 345 AM Tuesday...

A weak mid/upr-level trough will move across the OH Valley today and
cntl Appalachians and Middle Atlantic tonight. Preceding deep
dryness and stability evident on the 00Z/21st GSO RAOB, and neutral
height tendency aloft with the approach/passage of the trough,
suggest the only sensible weather impact may be thin cirrus
overnight.

At the surface, high pressure centered this morning along the Middle
Atlantic coast will continue to extend swwd and across the
Southeast.

Modification of the high and associated air mass will favor
afternoon temperatures about 2-5 F warmer than Mon, or 79 to 85. The
continued proximity and presence of the surface ridge will yield
strong radiational cooling once again, with lows mostly in the mid-
upr 50s and accompanied by a risk of radiation fog over the Coastal
Plain.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 400 AM Tuesday...

A sub-tropical mid-level ridge and the underlying wrn extension of
surface high pressure centered over the wrn Atlantic will remain
over the Southeast, while an Appalachian-lee surface trough will
develop across the srn Middle Atlantic Piedmont. Warmer and dry
conditions will result, with highs in the mid-upr 80s, followed by
milder lows in the mid 50s to lwr 60s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 346 AM Tuesday...

Upper pattern through the extended: A low-amplitude upper trough
will lift through the Great Lakes Thursday.  A series of short waves
will then move through the TN Valley and wash out over the southern
Appalachians Friday through Monday.

Thursday:  On Thursday, a low-amplitude upper trough will lift
through the Great Lakes. Some mid-level energy associated with this
feature may trickle down into our central to northern locations and
promote showers/storms later in the day. While some deterministic
models suggest better coverage over central NC Thursday evening
(e.g. GFS, Canadian, EURO), ensemble guidance has higher
probabilities for precipitation staying north into central VA,
lowering with southeastward extend.  This makes sense conceptually
as the better forcing/low-level moisture still appears to stay to
our north. As such, decided to lean on ensemble guidance and
continue to hold just slight to low chance POPs Thursday
afternoon/evening.

Ensembles continue to simulate a potentially potent short wave
riding through the TN Valley Friday, followed by a secondary vort
signature passing over central NC on Saturday. Deterministic models
are still in a bit of disagreement wrt the evolution of these
features, but overall it still looks like periods of unsettled
weather should occur Friday through Monday. Severe weather
parameters are not popping off the charts at this point during this
period. However, ensembles continue to simulate periods of
relatively higher shear (~30 to 35 kts) and elongated hodographs on
Friday. Thus, a few isolated stronger storms may be possible 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 and continue into early next
week.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
As of 800 AM Tuesday...

A general scattering of 3000 ft AGL stratocumulus over the nrn
Coastal Plain may briefly attain broken coverage at RWI through 14Z.
High pressure will favor VFR conditions otherwise and elsewhere
through early tonight, along with calm to light and variable surface
winds. A risk of fog/stratus will continue mainly over ern NC and as
far west as RWI and perhaps FAY late tonight-Wed morning.

Outlook: A chance of afternoon-evening showers/storms will
exist mainly across the Piedmont Thu and area-wide Fri-Sat.

&&

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

&&

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