-- Discussion containing changed information from previous version are highlighted. --
381
FXUS62 KRAH 310654
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
254 AM EDT Fri May 31 2024

.SYNOPSIS...
A vigorous mid and upper-level disturbance will pivot across and
offshore the southern Middle Atlantic through early Friday. Canadian
high pressure will otherwise extend across the region through early
Saturday, then drift off the coast of the Carolinas by Saturday
night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 200 AM Friday...

A vigorous shortwave disturbance and an associated strengthening 100-
120kt upper jet diving SEWD through the base of the larger scale
mid/upper level trough will move off the southern mid-Atlantic
coast, including the NC coast later this morning. The glancing shot
shot of lift and moisture is resulting in some scattered mid clouds
across central NC. Otherwise, showers will remain well east of the
area.  In it`s wake, strong synoptic scale subsidence and drying
will overspread the area. PWATs will fall into 0.4-0.5", which is in
the lowest 0-1 percentile of the climatological data set.

The weather headlines will be the seasonably cool/below normal
temperatures and ultra comfortable humidity as Canadian high
pressure settles over much of the Eastern Seaboard. Highs ranging
from lower/mid 70s north to upper 70s/near 80 south, as BL dewpoints
lower to 30s and 40s across the area.

Anyone with outdoor plans this evening may want to bring along a
light sweater or jacket as strong radiational cooling within the dry
airmass in place will allow temps to cool quickly into the upper
50s/lower 60s, with overnight temps expected to bottom out in the
mid to upper 40s north to lower 50s elsewhere.


&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 200 AM Friday...

Canadian high pressure centered over the area will slide eastward
and offshore during the afternoon and evening as transitory
shortwave ridging aloft builds over the area. The cP airmass will
begin to recover as southerly return flow develops over the area.
Warmer, but still slightly below normal for the 1st day of
meteorological summer. Highs 80 to 85 with dewpoints/humidity still
quite comfortable for this time of year.

Upper ridge axis moves offshore Saturday night. Modest moisture
advection associated with a shortwave trough moving east into the
Ohio and TN Valleys will lead to an increase in mid and high clouds
Saturday night, especially across western NC. However, conditions
will remain dry. Not as cool. Lows 55 to 60.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
As of 250 AM Friday...

Sunday and Sunday night: A s/w aloft will progress eastward from the
OH Valley through the mid-Atlantic and offshore, clipping central NC
Sun aft/eve. At the surface, as high pressure off the Carolina coast
drifts eastward out over the Atlantic, a warm front will lift
through the area while a low moves eastward through the OH Valley
and mid-Atlantic. A trough may amplify through central NC as the low
passes to the north. For now it looks like this s/w will be fairly
moisture-starved as it moves east of the Appalachians, however given
the proximity to the s/w and favorable diurnal timing, there is a
slight chance for showers/storms Sun aft/eve. PWATS should gradually
increase during the day/eve to 1.4-1.6 inches Sun eve/night.
Instability will likely be the primary limiting factor in
development/maintenance of any convection, as there is little (GFS)
to none (NAM) forecast at this time. Highs in the low to mid 80s and
lows in the mid 60s are expected.

Monday onward: Still somewhat low confidence given continued model
differences, although there is better agreement for mid-week.

Aloft, there could be another s/w passage Mon/Tue (GFS, not ECMWF),
which would increase chances/coverage of showers storms those days.
The next high amplitude trough should develop over the northern
Plains Tue/Tue night. The GFS is a bit farther northeast than the
ECMWF, with the closed low developing over central Canada versus
over the central US-Canada border Tue night/Wed. The trough should
then amplify sewd toward and through the mid-Atlantic/Carolinas Wed
night through Thu night/Fri, though the exact placement remains
uncertain. At the surface, as the low shifts off the mid-Atlantic
coast Mon/Mon night, a trailing backdoor cold front could drop into
central NC, though the model guidance differs wrt how far into the
area and where the surface front will be for Tue/Tue night.
Regardless, a warm front will again lift through the area lat
Wed/Wed night as a weak surface low tracks through the Southeast and
a cold front approaches from the NW. The medium-range guidance still
varies wrt the timing of the cold front through central NC, Thu
aft/eve (GFS) or Fri aft/eve (EC). Either way, the greatest chances
for showers and storms will be along/ahead of the cold front either
Thu or Fri. Given the uncertainty, will forecast highest chances for
showers/storms during the aft/eve both days (although it will likely
be one or the other). Above normal temperatures should prevail
through mid-week.
-- End Changed Discussion --

&&

.AVIATION /05Z FRIDAY THROUGH TUESDAY/...
As of 100 AM Friday...

Showers and thunderstorms associated with a vigorous upper level
disturbance moving through the southern mid-Atlantic states,
including NC, will remain east of any TAF sites. Otherwise, there is
high confidence in VFR conditions through the 24-hour TAF period.
With the exception of a few gusts of 12 to 15kts, winds will
generally remain light and from the N-NE.

Outlook: Dry VFR conditions will continue through Saturday. Isolated
to scattered chances of mainly diurnal showers/storms returns Sunday
through the middle of next week.

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...KC
AVIATION...CBL