642
FXUS62 KRAH 090015
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
816 PM EDT Wed May 8 2024

.SYNOPSIS...
A series of upper level disturbances will interact with an
unseasonably moist airmass over North Carolina through early Friday,
bringing unsettled weather. A cold front will move across the region
on Friday, ushering in drier and less humid air for the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 816 PM Wednesday...

The SVR Watch has been cancelled for the area. Thunderstorms are
exiting Sampson and moving through the Coastal Area.

We are watching upstream for the next potential for later this
evening and overnight in which the guidance continues mixed on
whether anything significant reaches our region.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 652 pm Wednesday...

* Slight/Level 2 Threat continues into Thursday...

The chance for severe storms on Thursday hinges highly on how
convection evolves tonight. A couple rounds of storms are possible
tonight, the latter of which is expected to be a larger MCS moving
into NC overnight.  That deep convection should overturn the
atmosphere and reduce the currently steep lapse rates aloft and
ultimately reduce updraft strength on Thursday.  However, guidance
isn`t exactly consist on how far east the line will track or how far
north it will extend.  The 12z NAM suggests the storms may weaken
significantly before reaching the coastal plain, and thus forecast
soundings from FAY to RDU and east still show a solid 2000 MLCAPE on
Thursday afternoon.  GFS soundings show a similar profile.

In the wake of the MCS, dying or not, there should also be some
subsidence to subdue convection, but otherwise the trailing outflow
effective front may end up across the southern CWA and serves as a
focus for development, along with lee troughing ahead of the
approaching synoptic front and perhaps even another disturbance
approaching from the Deep South (which models tend to take south
into the Southeast state along with an MCS).

Deep layer shear will continue to be strong as the upper jet edges
eastward along with the upper trough and 500mb winds increase to 40-
50kt.

There is a big discrepancy between the CAMS and the coarser
NAM/GFS/ECMWF.  Most HREF members show every little redevelopment of
convection on Thursday and focus activity across SC and further
southwest, while the NAM/GFS/ECMWF suggest quite a bit of convection
in their QPF.  Tend to lean toward less coverage but with a
conditional severe threat where convection does develop.

Highs should range from the mid 80s nW to around 90 SE.  Lows in the
low to mid 80s.

Friday is another tricky forecast day, as multiple days of possible
convection should continue modify the local airmass, but larger
scale forcing will be better as the positively tilted trough over
the Midwest and Mid-Miss valley today swing east toward the Mid-
Atlantic states.  The limiting factor will be instability given that
the cold front is expected to have shifted across the southern CWA,
with highs dipping back into the mid 70s to lower 80s and lower
dewpoints infiltrating the Piedmont. Again, and conditional threat
for severe storms seems possible but confined to areas closer to the
SC border.

Cooler and drier air is expected behind the front as it finally
pushes through the area Friday, but favor the warmer side of low
temp guidance in the lower 50s for Friday night.


&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 215 PM Wednesday...

Sat begins with broad troughing over generally the Northeast CONUS
characterized mainly by two embedded shortwaves, one of which is
shifting out over the western Atlantic while the second dives ESE
out of Upper Great Lakes and into the Ohio Valley by Sat afternoon.
The former will have shifted the axis of deep, rich moisture (PWAT
~1.6 inches) well offshore and usher in PWAT values around 0.5 of an
inch (near the 10th percentile for GSO, RNK, MHX RAOB) driven by
briefly strong subsidence and downsloping flow WNW flow. The latter
shortwave will pivot across Mid-Atlantic Sat afternoon and evening,
but central NC may only see glancing synoptic forcing from this
feature as the better DPVA remains north of the VA border. Point
soundings suggest shallow afternoon cumulus development to the base
of the subsidence inversion with better 700mb moisture (deepening
the moisture layer) moving into the area late Sat afternoon into the
evening hours. This may be enough to squeeze out some sprinkles over
central NC with better chance for very light rain closer to the
NC/VA border.

Surface high pressure and a secondary area of subsidence on the
backside of the departing trough will lead to dry conditions Sun
through Mon with temperatures in the 70s to low 80s. The next system
will move towards the area Mon night into Wed as a closed low near
the Four Corners Region Sun morning slowly drifts eastward. Closed
lows situated in between a split-flow regime often have timing
issues, and this one is no exception. Latest forecast gradually
brings in precipitation early Tues morning with chances lingering
into Wed with greatest chances diurnally favored during the
afternoon/evening. It would not be surprising to see the quicker
GEFS trend towards the slower EPS and precipitation onset becoming
12 hours later than is currently forecast. Temperatures will trend
back towards above normal mid-level height rises and the 850mb anti-
cyclone shifts offshore.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 652 PM Wednesday...

The first round of storms is currently passing mostly from FAY
south and east. Generally VFR conditions are expected elsewhere
through late evening into the overnight. There is the potential for
another round of storms overnight. In addition, stratus is
expected to develop across much of the region between 09z and 13z.

Looking beyond 13z Thu, high uncertainty in the details of showers
and storms and their impacts lingers through Thu. Generally VFR
conditions should develop after the stratus burns off mid
to late morning. Otherwise, a chance of showers/storms into Friday
as the cold front moves through. Then VFR conditions expected
this weekend.

&&

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

&&

$$

SYNOPSIS...Hartfield
NEAR TERM...Badgett
SHORT TERM...BLS
LONG TERM...Swiggett
AVIATION...Badgett


Correction to time of issuance.