-- Discussion containing changed information from previous version are highlighted. --
406
FXUS62 KRAH 210631
AFDRAH

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

.SYNOPSIS...
High pressure will remain along the East Coast through Wednesday
before a cold front approaches the region Thursday and brings
unsettled weather into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 855 PM Monday...

Central NC will remain under the influence of weak high pressure
from the north and associated NELY low-level flow. An expansive
layer of marine stratus clouds that extends along much the mid-
Atlantic Seaboard is expected to advect inland into the coastal
plain/I-95 corridor overnight. Elsewhere, mostly clear skies will
prevail, with some areas of fog likely, potentially dense in some
locations, as overnight temperatures are expected to cool to near or
a few degrees lower than this afternoon`s crossover temperature.
Lows tonight in the lower/mid 50s north to mid/upper 50s elsewhere.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 220 PM Monday...

Mid-level ridging will extend NE from the western Gulf of Mexico
into the Mid-Atlantic on Tuesday, in between a weak shortwave over
the Appalachians and stronger, broader troughing off the Southeast
US coast. At the surface, high pressure nosing down from the Mid-
Atlantic coast will slowly push east, helping turn the flow more
southeasterly during the day which will warm temperatures into the
lower-to-mid-80s (near to 5 degrees above normal). The weak
shortwave will move across central NC on Tuesday night, but with dry
air in place no impacts on sensible weather are expected. High-res
guidance including the RAP and HRRR is showing potential for enough
low-level moisture from the SE flow to result in some fog across
eastern NC, which may reach into our far eastern counties early
Wednesday morning. Otherwise it will be mostly clear with lows in
the mid-50s to lower-60s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 152 PM Monday...

The extended continues to favor increasing chances of showers and
storms as we end the week and go into the weekend. Temperatures will
be on the rise, as will humidity levels Thu-Sat.

Ridging aloft over the region Wed will transition to a WSW flow Thu
into Sat as a trough over the upper Midwest slowly tracks into
eastern Canada by the start of the weekend. Southwesterly surface
flow will return Wed and persist through at least Fri as high
pressure slides offshore. Temperatures Wed into Fri will range from
the upper 80s to low 90s, some 5-10 degrees above normal.

As the aforementioned trough moves east, shortwave energy will start
to spread south from the TN/OH valleys and skirt across NC/VA as
early as Thu evening. We retained the chance of showers/storms
during this period, with highest chances across the north, in closer
proximity to a slowly moving boundary. Instability does not appear
that high but could see a strong storm or two with increasing shear
aloft.

Deterministic and probabilistic data appear in at least moderate
agreement for a late-week convective complex initially forming over
the southern Plains reaching our area late Fri and lingering into
Sat. The GFS/ECMWF/CMC all show this MCS/shortwave moving through
during peak heating Fri. This would potentially be the better chance
of strong to severe storms given 30-40 kts of 0-6 km shear and
upwards of 1500 J/kg of CAPE. The storm chance should linger into
Sat as the system remains overhead. Thus, our highest rain chances
are Fri-Sat. There could be a heavy rain threat as well given PW`s
near the 90th percentile at 1.5 inches.

It would appear models and their ensembles show some degree of drier
westerly flow building back in Sun as the shortwave moves offshore,
but lingering instability should warrant at least a chance of
diurnally driven storms Sun. Another system could approach early
next week, but there is more spread in the guidance at this time
frame such that we kept storm chances mainly during peak heating.
Temperatures should remain in the 80s through the remainder of the
period.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
As of 230 AM Tuesday...

The latest satellite trends suggest the area of LIFR-IFR stratus and
fog now over ern VA/NC will probably not bodily move wwd fast enough
to reach RWI prior to ~12Z, by which time diurnal heating will cause
the moist layer to erode and disperse to VFR. More likely will be
the development of patchier and more shallow radiation mist/fog at
RWI and more briefly around RDU and FAY through 12Z. High pressure
will favor VFR conditions otherwise and elsewhere through 06Z Wed,
along with calm to light and variable surface winds.

Outlook: A risk of fog/stratus will continue especially over ern and
e-cntl NC late tonight-Wed morning, followed by a chance of
afternoon-evening showers/storms mainly across the Piedmont Thu and
area-wide Fri-Sat.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...Green
NEAR TERM...CBL
SHORT TERM...Danco
LONG TERM...Kren
AVIATION...MWS