Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 271738
Area Forecast Discussion
National Weather Service Raleigh NC
138 PM EDT Mon Mar 27 2017
A warm moist southerly flow will hold over the area through
Wednesday. An upper level trough will cross the region beginning
late tonight through Tuesday, bringing unsettled weather. A backdoor
cold front will drop southward through the area late Wednesday
through Wednesday night. Another storm system will cross the area
Thursday night and Friday.
.NEAR TERM /THROUGH TONIGHT/...
As of 1010 AM Monday...
The band of light showers was slowly weakening and dissipating over
the eastern Piedmont and northern Coastal Plain late morning.
Rainfall this morning has been generally less than a tenth of an
inch with this band. We will update the weather and POP grids to
indicate scattered showers closer to the Interstate 95 corridor with
a few isolated showers possible over the western Piedmont through
around 18Z. This afternoon, it appears that a lull in showers will
occur, supported by current data and by the Hi-Res convection
allowing models, as the focus for storms will shift well to our west
over the Tennessee Valley with the next short wave trough. This
trough will set off strong to severe thunderstorms over TN/AL this
afternoon and evening with weakening storms likely advancing into
the NC mountains tonight. Before that time, a few showers/isolated
thunderstorms may develop this afternoon - with a low chance POP
warranted into the Triad region.
Satellite data indicated some breaks developing over much of the
Piedmont, with stratus confined to the NW Piedmont and Foothills.
This is expected to burn off by early afternoon. Partly sunny skies
will lead to increased mixing with SSW winds 10-15 mph. Highs should
warm into the 70s to near 80 in the Sandhills. Readings in the N and
E Piedmont and N Coastal Plain may be tempered a few degrees due to
the slower clearing.
Tonight, increasing POP later over the western third of the region
with the convective threat increasing. Otherwise, very mild SW flow
and at least partly cloudy skies will lead to lows around 60 (15-20
degrees above normal).
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 330 AM Monday...
Tuesday and Tuesday night low pressure currently over the Arklatex
area will track north of the area through the mid-Atlantic states
and bring a very weak cool front with it. Maybe a bit better chance
for thunder Tuesday afternoon, especially in the central and eastern
portions of the forecast area as instability look a little better
than on Monday afternoon and low-level lapse rates remain very
steep. The proximity of the low to the north will provide upwards of
25-30 kts of bulk shear to work with. As a result SPC, currently has
the forecast area in a marginal risk for severe thunderstorms. While
damaging wind should remain the primary threat, some better CAPE
values aloft could result in some small hail.
Temperatures will continue to be in the upper 70 to low 80s across
the forecast area on Tuesday afternoon with lows in the mid 50s.
.LONG TERM /Wednesday through Tuesday/...
-- Changed Discussion --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
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.AVIATION /15Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --As of 1010 AM Monday...
24 Hour TAF Period: Generally VFR CIGS expected this afternoon, with
MVFR CIGS and VSBYS with showers/isolated thunderstorms expected to
spread eastward into the region after 06Z/tonight. Lower IFR CIGS
with showers likely between 06Z-12z/Tue, especially at
KINT/KGSO/KRDU. This should spread into the KFAY and KRWI areas
Tuesday. A return to VFR conditions is expected Tuesday night and
Wednesday, with the exception of IFR to LIFR fog and stratus
potential during the early morning Wed.
Long term: A storm system is expected to push into the region
Thursday night and Friday with showers, low CIGS, and fog.
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