Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 271841 RRA
Area Forecast Discussion
National Weather Service Raleigh NC
241 PM EDT Mon Mar 27 2017
-- Changed Discussion --An upper level trough will cross the region Tuesday, along with a
trailing cold front. High pressure will build in from the north on
Wednesday, then shift offshore Thursday. A strong storm system is
expected to affect the region late in the week.
-- End Changed Discussion --
.NEAR TERM /THROUGH TONIGHT/...
As of 241 PM Monday...
The earlier band of light showers really stabilized the boundary
layer and led to a large area of stratus and stratocumulus. This was
centered over the northern and central Piedmont earlier, and has
spread out eastward over the Sandhills and Coastal Plain. Sunshine
was finally breaking out in the western Piedmont and Foothills at
200 PM with continued mixing. The instability was increasing over
upstate SC into the NC Mountains with heating. There was also a
small sliver of instability extending from SC into the southern
Sandhills. With the boundary layer stable over much of central NC,
there is essentially little chance of showers this afternoon into
the early evening, with the exception of near the SC border and over
the Foothills. We will continue to carry a slight chance of showers
in the far south and west, otherwise no POP for the rest of the
region. Highs should eventually reach 80 around Fayetteville, and
mid to upper 70s elsewhere.
The attention for tonight turns to the west with the approaching
mid/upper level trough. This trough, like it`s predecessor, is
forecast to weaken as it crosses the Mountains later tonight and
Tuesday. The severe convection that is expected over TN/AL this
afternoon and evening is forecast to weaken considerably overnight
as it tracks into the Appalachians. The Hi-Res models indicate some
of the weakening convection to arrive in the western Piedmont
between 03z-09z before dying off. Little if any residual convection
is expected to make it to the eastern zones.
We will keep a chance POP for tonight in the western areas only.
Some stratus is also favored in the west, where higher dew points
nearing 60 will be advected in from the SW. Lows generally mid 50s
east to lower 60s SW (a good 15 degrees above normal).
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 235 PM Monday...
The latest Hi-Res convection allowing models suggest that only a few
showers will remain from tonight`s convection that tries to cross
the Piedmont. Regardless, the timing of the approaching mid/upper
trough appears to be during the morning and early afternoon for the
western Piedmont, which is essentially not diurnally favorable for
strong or severe storms in the western zones.
Models do favor redevelop of at least scattered showers and
thunderstorms along the surface wind shift line that is forecast to
move SE into central NC Tuesday afternoon. The favored lift area out
ahead of the mid/upper trough is forecast to reach the eastern
Piedmont into the Coastal Plain and Coastal Areas during the peak
heating period. Convection may blossom as early as late morning or
around noon near the wind shift line, and should spread and develop
ESE during the afternoon.
It appears that the most favored area for optional heating and
destabilization should occur just to the east and south of the
Triangle area, just before the convection develops in the early
afternoon and tracks into the region. The earlier timing of the
front and trough should limit the strong to severe threat in the NW
Piedmont Triad region, with the focus in the eastern zones. Even in
the east where the instability and shear is expected to be higher,
most parameters for severe storms are forecast to be marginal. Highs
in the upper 70s to lower 80s in the east, with dew points nearing
60, should lead to MLCapes near 1000 J/KG. Mid level lapse rates may
still be in question but some subtle warming aloft may be a negative
factor for organized severe storms.
Still, look for at least scattered thunderstorms with the potential
for wind gusts to 40-50 mph and possibly up to 1 inch hail in a few
of the strongest storms. We will highlight areas east of the Triad
area for this potential due to timing in the Hazardous Weather
The convection should be east of the region by around sunset or so,
but the lagging wind shift line may aid in some weaker trailing
storms into the evening in the east. Otherwise, partly cloudy with
lows in the 50s expected.
.LONG TERM /Wednesday through Tuesday/...
As of 145 PM Monday...
Wed-Wed Night: With shortwave ridging aloft, expect mostly sunny to
partly cloudy skies and above normal temps in the mid/upper 70s Wed
afternoon. Subsidence in the wake of an upper level low moving
offshore New England Wed evening will result in pressure rises along
the eastern seaboard as an inverted sfc ridge extends southward
through the Mid-Atlantic into the Carolinas, the leading edge of
which will be marked by a backdoor cold frontal passage /wind shift
to the NE at ~15 mph/. Lows Wed night will be determined by the
precise timing of fropa. At this time, expect temps ranging from the
mid 40s NE Coastal Plain to lower 50s in the SW Piedmont.
Thu: NE low-level flow in the wake of the back door cold front early
Thu morning will gradually veer to the E/ESE during the day,
allowing temperatures to recover into the mid 60s across the
Sandhills and SE Coastal Plain Thu afternoon. A cold air damming
wedge is expected to develop across portions of the N/NW Piedmont
where broken/overcast cloud cover (and possibly evap cooling
attendant intermittent light rain or sprinkles in the foothills) are
largely expected to offset diurnal heating, keeping highs in the mid
50s, coolest in Forsyth/Person county.
Thu night: Expect an increasing potential for showers across the
western half of the state (primarily along/west of Highway 1)
between midnight and sunrise Fri as an upper level low progresses
into the OH valley and low-level warm advection strengthens
downstream over the Carolinas. Expect lows Fri morning ranging from
the mid/upper 40s to lower 50s, coolest in the W/NW Piedmont where
precipitation /evap cooling/ is more likely.
Fri-Fri Night: Confidence in the evolution of the aforementioned
upper level low, attendant sfc cyclone and associated fronts
(warm/cold/wedge) remains below normal for several reasons, ranging
from antecedent conditions (CAD wedge in place across portions of
central NC Fri morning) to significant disagreement amongst the
GFS/ECMWF. The 12Z GFS suggests the upper level low over the central
MS river valley on Thu will track east across the Carolinas/VA late
Friday/Friday night. In stark contrast, the 00Z ECMWF shows the
upper level low deamplifying and lifting NE through the lower Great
Lakes into New England late Fri/Fri night. While the precipitation
forecast appears to remain on track (e.g. a solid potential for
showers across the entire area during the day Friday), significant
uncertainty is present w/regard to the intensity of convection/
amount of precipitation. From a hazardous weather standpoint, the
12Z GFS solution would favor a potential for severe storms whereas
the 00Z ECMWF solution would not. The temperature forecast on
Fri/Fri night is challenging to say the least. At this time will
show the coolest temps in the Triad (highs in the lower 60s) and
warmest temps in the Sandhills and SE Coastal Plain (lower 70s). A
clearing trend from SW-NE is expected in the wake of a cold frontal
passage late Fri night, though the timing thereof remains in
question. At this time anticipate lows in the lower/mid 50s, coolest
Sat-Sun night: Confidence in the forecast for Sat has decreased,
with the 12Z GFS guidance now showing a potential for showers
assoc/w DPVA digging SE on the western periphery of the upper level
low tracking offshore the Mid-Atlantic/Carolinas. The 00Z ECMWF
suggests dry conditions and a warm-up with the upper low
deamplifying/lifting into New England and clear skies in the wake of
the cold front on Sat. Dry conditions and further warming are
expected on Sun as a shortwave ridge aloft tracks across the region
from the west.
Mon-Tue Night: Expect increasing cloud cover during the day Monday
and a chance for convection by Tue as the next upper level low
/attendant sfc cyclone/ approach from the west. -Vincent
.AVIATION /18Z MONDAY THROUGH FRIDAY/...
As of 110 PM Monday...
24 Hour TAF Period: Generally VFR CIGS expected this afternoon and
this evening with only isolated showers. IFR Stratus and a chance of
showers will arrive late tonight in the KGSO/KINT areas, lasting
Tuesday morning. Scattered thunderstorms, some with gusty wind and
hail, may affect the eastern Terminals between 18z/Tue and 01z/Wed.
Otherwise, a return to VFR conditions is expected Tuesday evening and
Long term: A storm system is expected to push into the region
Thursday night and Friday with showers, low CIGS, and fog.