-- Discussion containing changed information from previous version are highlighted. --
999
FXUS62 KRAH 042017
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
417 PM EDT Sat May 4 2024

.SYNOPSIS...
A series of upper level disturbances will move through the area
through Sunday. Meanwhile, a backdoor cold front will stall across
the area through tonight, before lifting north into Virginia early
Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 235 PM Saturday...

Latest sfc analysis this afternoon depicts the synoptic front
stretching from just north of KRWI, west-northwest just through to
the south of KINT/KGSO.  Those in the far western Piedmont are
largely under the influence of rain-cooled outflow, with primarily
lingering stratiform rain. Further east in the warm sector,
scattered showers and a few storms continue to stream north across
the southern Piedmont/Sandhills regions.  Additional scattered
showers and storms have developed further south across south-central
SC heading northward towards our southern Piedmont.

Aloft, a stronger MCV continues to spiral over northern GA. This
feature will migrate through our southern and western Piedmont later
tonight.  As such, additional showers and storms will continue into
the overnight period, with highest chances continuing for those west
of US-1.  Showers and storms will continue to be slow-moving, and
given the chance for some training, along with an anomalous moisture
profile to tap into, sudden bursts of up to 1 to 1.5 inches will be
possible with any heavier downpour.  As such, isolated instances of
flash flooding will be possible through Sunday morning (WPC has
introduced a Marginal Risk for excessive rainfall generally for
those west of US-1). However, shear will remain weak through the
period, and thus severe thunderstorm chances are low tonight.

It`s not as clear if locations along the NC/VA border will see any
re-development of storms tonight. Forecast soundings highlight some
fleeting stability, but given the approach of the wave aloft, would
not be surprised if some thunder is heard even that far north.

Warm overnight lows in the mid 60s is expected.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 215 PM Saturday...

Aloft, the sub-tropical ridge will shift offshore and breakdown
Sun/Sun night as the increasingly sheared shortwave disturbance
moves through the mid-Atlantic and Northeast US. Another southern
stream s/w will strengthen over the southern Plains on Sun, then
move eastward into the lower/mid-MS Valley through Sun night. At the
surface, high pressure will move off the New England coast and
eastward over the northern Atlantic as a low moves through the Great
Lakes and into the Northeast Sun/Sun night. An attendant cold front
draped swwd from the low will become more W-E oriented through the
OH Valley by Sun night. Meanwhile over central NC, the quasi-
stationary front that had lingered over the area will lift northward
as a warm front, with warm, moist southerly return flow over the are
in its wake.

Precipitation/Convection: Showers and storms will likely still be
ongoing Sun morning, most prevalent over the Piedmont. PWATs will
remain anomalously high, in the 1.6 to 1.8 inch range, through the
afternoon. Surface-based instability should increase with daytime
heating, although the latter may be somewhat inhibited by the
ongoing convection and extensive cloud cover. Bulk shear is also
expected to be weak again on Sun. As a result, slow-moving, widely
scattered showers and storms will be possible through the aft/eve
Sun, with the main threat of some isolated heavy rainfall and
localized flooding, although most locations may only receive a few
hundredths of an inch of rain.

Temperatures: Widespread overcast skies and ongoing convection
should somewhat limit heating early, but temps could recover during
the afternoon. For now expect highs to range from the mid 70s along
the NC/VA border to around 80 degrees SE. Lows Sun night mainly in
the low to mid 60s expected.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
-- Changed Discussion --
As of 415 PM Saturday...

The extended forecast will feature a continued chance of unsettled
weather to start the week Mon, followed by somewhat drier and hot
temperatures by the middle of the week. Energetic wswly flow aloft
will increase shower/storm chances again mid-late week, followed by
milder, stable, and less humid conditions by Sat.

The models remain in relatively good agreement regarding a srn
stream shortwave trough forecast to pivot across the TN Valley and
srn Appalachians Monday and srn Middle Atlantic and Carolinas Monday
night-early Tuesday, during which time above average chances of
showers/storms will result over cntl NC. Shortwave ridging will
follow and migrate across and offshore the South Atlantic with drier
conditions favored Tue-Wed. Associated subsidence, on the wrn
periphery of sub-tropical high pressure that will extend across the
swrn N. Atlantic, will also result in unseasonably hot and humid
conditions extending over cntl NC Wed-Thu. Increasingly-energetic
wswly flow, and at or above climatological chances of convection,
will otherwise prevail across the Southeast, within closely-spaced
srn and nrn stream branches of the westerlies, through early next
weekend. An associated synoptic cold front will move across cntl NC
Fri or Sat.

While the models are in relatively good agreement regarding the
pattern described above, they also depict the development of a
couple of rex blocks over n-cntl NOAM during the middle of the week
and over wrn NOAM late week into next weekend. With those blocking
developments in mind, model guidance may trend slower with the
progression of the cold front and following milder and more stable
conditions by early next weekend.
-- End Changed Discussion --

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
As of 127 PM Saturday...

Under anomalously moist conditions, LIFR ceilings persist at
KINT/KGSO this afternoon. Elsewhere, terminals have largely
scattered to VFR with some clearing of the cloud shield.  Scattered
showers and a few storms will continue to stream from south to north
through early Sunday morning. If any heavier cells interact with our
terminals, brief periods of gustiness and sub-VFR conditions are
likely.  As we progress into early Sunday, additional scattered
showers and a few isolated storms will be possible as well.  LIFR to
IFR ceilings are then likely to sock back in across central NC
starting around 03Z and persisting through early to mid Sunday
morning.

Outlook: MVFR to IFR ceilings are likely to sock back in Sunday and
monday night with additional scattered showers/storms possible.
Drier conditions are expected mid-week.

&&

.CLIMATE...

Record High Minimum Temperatures:

May 4:
KGSO: 65/2022
KRDU: 68/1938
KFAY: 68/1942

&&

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

&&

$$
SYNOPSIS...CBL/Green
NEAR TERM...Luchetti
SHORT TERM...KC
LONG TERM...MWS
AVIATION...Luchetti