-- Discussion containing changed information from previous version are highlighted. --
087
FXUS62 KRAH 302235
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
635 PM EDT Thu May 30 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 300 PM Thursday...

A shortwave trough comprised of a couple of perturbations now over
wrn PA and Lake Erie will dig sewd and across and offshore the
Middle Atlantic through tonight. A combination of associated 30-50
meter/12 hr height falls mb and 3-5 C cooling at 500 mb will
contribute to the development of generally shallow convection across
sern VA/nern NC this evening-early tonight. A few, associated
showers may result over the far ne Piedmont and nrn Coastal Plain
generally between 00-06Z. After otherwise diurnally-enhanced cumulus
dissipates, it will be mainly clear and unseasonably cool, with low
temperatures ranging from mid 40s in the rural nrn Piedmont to mid
50s in the Sandhills and srn Coastal Plain (~5-10 F below average).

&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 235 PM Thursday...

Canadian cool and dry.

A longwave ridge extending from the MS Valley to cntl Canada today
will progress east and extend from QC to the South Atlantic states
by 12Z Sat. Accompanying strong, 100-120 meter/12 hr mid-level
height rises --and the center of an underlying, ~1025-1026 mb
Canadian high --will spread from the lwr Great Lakes to the srn
Middle Atlantic, with associated tropospheric-deep subsidence over
cntl NC.

The influence of the Canadian ridge will yield cooler than average
temperatures in the 70s (~5-10 F below average) Fri and in the
middle 40s to lwr 50s (~10-15 F below average) Fri night, the latter
still about 5-8 F shy of record lows (GSO: 42, RDU: 42, FAY: 45).

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 340 PM Thursday...

A mid/upper ridge will move east across the Mid-Atlantic on Saturday
and Saturday night, downstream of a shortwave across the lower-mid
MS and TN Valleys. At the surface, high pressure centered over
central NC on Saturday morning will move offshore in the afternoon
and evening. This pattern will bring mostly sunny skies and dry
weather. As return flow around the high turns winds southerly,
temperatures will begin to increase back to near normal with
Saturday`s highs in the lower-to-mid-80s and lows Saturday night in
the upper-50s to lower-60s.

The following few days look to have potential for diurnally-focused
convection as a series of shortwaves moves over or near our region.
However, they look pretty weak and trying to ascertain their exact
timing this far out is difficult. Furthermore, the prevailing flow
looks fairly weak and zonal, and PW values in the guidance are
pretty close to normal. So only carry slight to low chance POPs each
afternoon and evening from Sunday through Tuesday. Instability could
still be sufficient for a few storms, but not concerned about an
organized severe threat and convection will likely be of the pulse
variety.

A closed mid/upper low will then dive SE from the Northern Plains on
Wednesday and Thursday, dragging a cold front to its south. This
will potentially bring central NC a better chance of showers and
storms as upper forcing with it is much stronger. However, timing
uncertainties remain as the ECMWF hangs it back over the Upper
Midwest significantly longer compared to the GFS, with the CMC
somewhere in between. The ECMWF solution would continue just
isolated convection at best on these days. So only have chance POPs
at this time, highest on Thursday.

After another day of near-normal highs in the lower-to-mid-80s on
Sunday, temperatures should warm to slightly above normal for the
workweek as a Bermuda High sets up and brings us continuous S/SW
flow. The operational GFS tries to bring in a backdoor cold front
with highs only in the 60s and 70s on Wednesday and Thursday, but
this solution is an outlier even compared to its own ensembles, so
not taking it too seriously at this time. Forecast highs from Monday
through Thursday are in the mid-80s to 90 with lows in the mid-to-
upper-60s.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
As of 635 PM Thursday...

There is high confidence in VFR conditions through the 24-hour TAF
period. A strong mid-level trough will move through tonight and
warrant a low-end chance of a few spotty showers at RWI, roughly
between 02-05z. However, most high-res guidance keeps any activity
east of the RWI terminal. Thus, confidence was too low to mention
any potential restrictions with any showers. A boundary moving
through overnight will increase low-level winds just below LLWS
criteria. If the winds are higher than expected, some brief LLWS
could occur at RDU/FAY but most guidance is below the wind shear
threshold. Otherwise, N to NE winds will prevail through the
period, briefly gusting at RDU/FAY/RWI to 18 kt Fri morning.

Outlook: Return flow warmth and moisture, combined with a lee trough
or weak surface front, will result in a chance of mainly diurnal
showers/storms Sunday through the middle of next week.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...Danco
AVIATION...Kren/MWS