163
FXUS62 KRAH 221859
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
300 PM EDT Wed May 22 2024

.SYNOPSIS...
High pressure over the western Atlantic will extend across the
Southeast through tonight. Disturbances in westerly flow aloft will
interact with an underlying surface trough as they track from the
lower MS Valley to the srn Middle Atlantic Thursday through the
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 900 AM Tuesday...

No major changes with this mornings forecast update. Made minor
adjustments to some temperatures and dew points for today, but
otherwise forecast is on track. Mostly cloud free skies today with
high temperatures in the mid to upper 80s.

As of 345 AM Wednesday... A sub-tropical mid-level ridge will extend
from the Gulf of Mexico newd and across the Southeast and Carolinas,
while low amplitude, wswly flow, and embedded convectively-amplified
disturbances, will exist on its northwest periphery from the srn
Plains to the cntl Appalachians and nrn Middle Atlantic.

At the surface,  ~1017 mb high pressure centered just off the Middle
Atlantic coast swwd and along the coast of the Carolinas will
remain, while an Appalachian-lee trough --and axis of weak to
moderate instability-- will develop this afternoon across the srn
Middle Atlantic Foothills/wrn Piedmont.

Sensible weather associated with the pattern described above will
feature warm(er) and dry conditions throughout cntl NC, though with
an isolated shower or storm that may initiate on the surface trough,
then subsequent outflow, and drift toward the far nw Piedmont before
dissipating with nightfall. High temperatures should be a few
degrees higher than those of Tue and generally in the mid-upr 80s,
followed by milder lows mostly in the lwr-mid 60s.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 135 PM Wednesday...

By Thur morning, the ridge axis, both sfc and aloft, will be to our
east.  Meanwhile, a couple short wave troughs will be centered well
to our N and NW, one just north of the Great Lakes and another over
the northern Rockies. SW flow between those features will gradually
increase over our area as this pattern slowly shifts east. Within
that SW flow will be several low-amplitude waves and likely to be
several MCVs from earlier convection, which models suggest will
support a round of showers and thunderstorms crossing our CWA during
the late afternoon and evening hours Thursday.

With the ridge to our east, southerly flow will result in a warmer-
than-average airmass over our region.  High temps Thursday will be a
bit warmer than today...highs from the mid 80`s NW to around 90 east
and southeast.  Given this warm airmass and dwpts in the mid 60s,
there will be plenty of instability for thunderstorm activity. That,
along with increase mid-level flow and resulting shear will support
a risk for isold severe thunderstorms with damaging winds and hail
the main threats.  The latest round of CAMs generally are fairly
close regarding timing... with a line or several clusters of
thunderstorms moving e/se across our CWA from about 21Z through 03Z
tomorrow.  After the storms move east, quiet weather expected the
rest of the night. Low temperatures will be in the 60s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...

The extended will features a series of chances for afternoon/evening
storms, though the main focus periods appear to be Fri/Sat and Mon
into Tue based on the ensemble and probabilistic guidance.
Temperatures will largely hover above normal through the period with
highs in the 80s to low 90s, perhaps cooling off slightly by midweek
in the 70s to mid 80s behind an early week cold front.

On Friday, models still depict a shortwave moving through some
portion of the area in the westerly flow aloft. However, guidance
differs on where the energy tracks, with the GFS the furthest south
over SC, while the ECMWF/CMC are over VA/NC. Convection from Thu may
bring an outflow through the area, which could focus daytime storms
more across our south and east, though instability will still be
high with moisture still elevated in the 1-1.5 inch range of PWs.
Given the lack of model agreement, hard to determine overall storm
coverage. For now, we have highest PoPs over the Sandhills to
Coastal Plain, in proximity to a sea-breeze and residual outflow
from Thu convection. Severe threat is also questionable with weak
shear, though a stronger storm is certainly possible in the
favorable instability.

That shortwave lingers into Sat, though will start to move off
toward the coastal waters of VA/NC in the afternoon, with ridging
trying to build in from the TN valley. Coverage of storms should be
more isolated, with the best chances along the trough axis - Coastal
Plain and Sandhills counties of central NC.

Ridging will start our day Sunday, but we will start to see
influence from a trough over the Midwest and upper MS valley. There,
models show an area of low pressure over MO/IL tracking into the
Great Lakes by early Mon. Increasing WAA and energy east of this
system will favor chances of isolated/scattered storm activity
during the aftn/eve Sun, most favored across the western Piedmont.

A better chance of area-wide showers/storms appears Mon into Tue as
the aforementioned low pressure system tracks up into Canada,
eventually trying to bring a cold front through the region sometime
Tue or Wed. Some guidance lingers the front over the area Tue before
it fully pushes through sometime Wed. Models show high instability
and increasing shear ahead of the front Mon, so this will be
something to watch in the coming days. For now, our PoPs are highest
in the Mon aftn/eve timeframe, with 30-40 percent chances on Tue and
trending drier by Wed.

&&

.AVIATION /18Z WEDNESDAY THROUGH SUNDAY/...
As of 135 PM Wednesday...

High pressure over the region will continue to favor VFR conditions
through the 18z TAF period. Along with VFR conditions expected for
much of the period, light S and SW winds around 5-10 knots are
expected and some some fair weather cumulus clouds. By Thursday
afternoon and early evening, increasing cloud coverage will approach
ahead of an approaching frontal boundary.

Outlook: A chance of SUB VFR conditions are possible with
showers/storms moving through the area through the weekend, mainly
during the afternoon-evening.

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...CA/MWS
SHORT TERM...NP
LONG TERM...Kren
AVIATION...CA