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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 161902
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
302 PM EDT Wed Aug 16 2017

.SYNOPSIS...
A surface trough will extend along the North Carolina coast
southwestward into central South Carolina and Georgia through
Thursday. A back door cold front will approach the region on
Thursday before another cold front approaches from the northwest
on Friday and moves into the region on Saturday.
&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 250 PM Wednesday...

The early afternoon surface analysis shows a surface trough
extending northeast to southwest along the NC coast and then
laying across central SC and GA. A cold front extended from near
Washington DC westward to the Ohio river valley. The air mass
across northern portions of the area has dried out a bit with
dew points in the upper 60s to lower 70s near the VA border
while it remained very humid across the Sandhills and southern
Coastal Plain with dew points in the mid to upper 70s (dew point
was 79 at KGSB at 18Z). GOES-16 satellite imagery shows a
growing cumulus field in an arc from the Triad south across the
western Piedmont and Yadkin valley into the Sandhills. Doppler
radar is showing a couple of isolated showers in the northwest
and southern Piedmont an in a region of enhanced instability
and convergence.

Convection allowing models are consistent in highlighting the
western and southern periphery of the RAH CWA for isolated to
widely scattered showers and thunderstorms this afternoon and
evening with little to no convection from Raleigh northeast. The
convection will drift slowly southeast and should wane by mid
evening with little to no convection overnight. Another period
of late night and early morning fog and stratus is expected to
develop across the northern and central Coastal Plain and the
northeast Piedmont. Lows tonight will range in the lower to mid
70s. -Blaes
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
-- Changed Discussion --
As of 300 PM Wednesday...

A short wave ridge axis over the Carolinas on Thursday morning
will give way to decreasing heights and an increasing
southwesterly flow on Thursday night. An increasing southerly
flow will develop allowing a recovery of moisture with
precipitable water values climbing back to between 2.0 to 2.25
inches by Thursday evening. While the forcing for ascent is
modest, the return of warm advection and increasing moisture
should result in an uptick in showers and thunderstorms over
today. After a period of morning stratus in the Coastal Plain
and northeast Piedmont, expect variably cloudy skies. Low-level
thickness values increase a few meters supporting highs between
89 to 94 with lows in the lower to mid 70s. -Blaes
-- End Changed Discussion --

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 AM Wednesday...

Friday and Friday night: An upper level shortwave trough and surface
cold front will approach the region from the west on Friday, though
it will likely get hung up over the mountains. As a result, strong
southwesterly flow over Central NC will result in warm, humid
conditions and the best chances for convection will be along
differential heating boundaries near the foothills and along the sea
breeze. For now, Friday night appears to be largely dry, although if
enough pre-frontal moisture makes its way into Central NC, some
convection could persist into the night. Highs in the upper 80s to
mid 90s and lows in the low to mid 70s expected.

Saturday and Sunday: A stronger upper level trough and surface cold
front will approach from the west on Saturday, with the upper level
trough swinging through the region and deamplifying as it does so
Saturday night into Sunday. Although the front appears quite strong,
it is expected to stall over Central NC, having a hard time
progressing through the area before getting washed out Sunday night.
Best chances for convection will be in proximity to the stalled
front, lower in its wake, Saturday and Saturday night. Chances for
convection could decrease further on Sunday, again with the highest
chances farther southeast. Southerly to southwesterly flow at the
surface will be enhanced ahead of the front with return flow around
the Bermuda High extending into the region. Highs will generally
remain in the upper 80s to low 90s over the weekend (although if the
front progresses into the region a bit further it will affect temps
to the northwest). Lows generally in the low to mid 70s.

Monday onward: Surface high pressure will build off the Mid-Atlantic
coast, with continued southerly flow over Central NC through mid-
week. Aloft, high pressure will build over the Southeast U.S. with a
trough amplifying over the Midwest Tuesday and progressing east-
southeastward. With the little change in airmass expected, continued
diurnal convection in the favored areas will be most likely. As for
temperatures, expect highs generally in the mid 80s North to low 90s
South and lows in the upper 60s to mid 70s.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --
As of 235 PM Wednesday...

The 24 hour TAF period...widespread VFR conditions early this
afternoon will give way to isolated to widely scattered showers and
storms with local restrictions across the western and southern
portions of the RAH CWA. SCT-BKN cumulus has developed and expanded
in an arc from the Triad south across the western Piedmont and
Yadkin valley into the Sandhills in a region of enhanced instability
and convergence. Expect isolated to scattered showers and
thunderstorms to develop in this region during the mid afternoon
hours and continue into the early evening before dissipating during
the mid to late evening. The greatest chances of convection will be
at the KINT and KGSO terminals with a small threat of a shower at
the KFAY terminal and no precipitation expected at KRDU and KRWI.

Another round of late night stratus and fog is expected to develop
overnight, primarily across the Coastal Plain and the northeast
Piedmont/Sandhills. IFR restrictions are likely to develop in most
locations by the predawn hours with a period of LIFR conditions in
fog and stratus possible across the northern Coastal Plain at KRWI.
Local restrictions will improve during the mid morning hours on
Thursday before scattered showers and storms redevelop toward
early afternoon.


Looking further ahead...A cold front will approach the region on
Thursday into Friday and then settle across the area on Sunday into
Monday. This result in an increase shower and thunderstorms,
primarily during the afternoon and evening on Thursday into Saturday
with a decrease in adverse aviation conditions on Sunday into
Monday. -Blaes
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...BLAES
NEAR TERM...BLAES
SHORT TERM...BLAES
LONG TERM...KCP
AVIATION...BLAES