411
FXUS62 KRAH 311510
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
1110 AM EDT Fri May 31 2024

.SYNOPSIS...
Canadian high pressure will build across and offshore the Middle and
South Atlantic through Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1105 AM Friday...

A nrn stream shortwave trough and accompanying reinforcing cold
front and convection have moved offshore this morning. In its wake,
a longwave ridge extending this morning from the TN Valley to Hudson
Bay will progress east and extend from the Carolinas to QC by 12Z
Sat. Accompanying strong height rises, maximized in excess of 150
meters at 300 mb over the lwr Great Lakes in 12Z RAOB data, will
spread sewd and across the srn Middle Atlantic. While associated
mid/upr-level subsidence will result over cntl NC, visible satellite
data depict a veil of convective blowoff cirrus/cirrostratus that
will stream across the NC Piedmont and Sandhills, while probably
thinning.

At the surface, the center of 1027 mb Canadian high pressure over OH
will follow the aforementioned height rises aloft and across the srn
Middle Atlantic and become situated squarely over NC tonight, with
nely surface winds today that will become calm tonight.

The presence and influence of the Canadian high will yield
unseasonably cool temperatures in the 70s (~5-10 F below average)
today and in the middle 40s to lwr 50s (~10-15 F below average)
tonight. Observed mean mixing ratios of 2.5 - 4.5 g/kg evident on
the 12Z GSO and RNK soundings suggest surface dewpoints will mix
well into the 30s F throughout the Piedmont today, as wrn Piedmont
locations already have, with some upr 20s possible in nearby
srn/swrn VA. Associated minimum RH in the 20th percentile will
result throughout cntl NC today, making the 70s degree temperatures
feel even more comfortable.

&&

.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/...
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.

&&

.AVIATION /11Z FRIDAY THROUGH TUESDAY/...
As of 625 AM Friday...

There is high confidence in VFR conditions through the 24-hour TAF
period as cool and dry high pressure builds over the area. 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...MWS
SHORT TERM...CBL
LONG TERM...KC
AVIATION...CBL