Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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034
FXUS62 KRAH 131955
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
255 PM EST Wed Dec 13 2017

.SYNOPSIS...
A fast moving upper level disturbance will move just north of the
region tonight, and will be followed by a weak surface cold front
that is expected to pass across central North Carolina Thursday
morning. High pressure will then build into the area by late
Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 248 PM Wednesday...

Latest water vapor shows the next short wave trough crossing the
Midwest and western Great Lakes regions.  This wave will continue
tracking to the SE then E, passing by to the north of our area later
this evening and overnight. The attendant sfc cold front will lag a
bit behind...not expected to cross central NC (uneventfully) until
just after sunrise Thursday morning.  Other than a brief increase in
mid and high clouds on the southern tail end of the system, and
perhaps a bit of a light breeze (rather than the typical calm or
light winds that we usually see overnight)...we`re not expecting any
notable weather or impacts from this system.  In terms of
temps...look for a subtle warming trend ahead of the cold front,
thus lows tonight will likely be several degrees warmer than last
night, but still falling below freezing across most if not all of
our zones. Lows in the upper 20s.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 248 PM Wednesday...

Fair weather is in store for Thursday in the wake of tonight`s
departing short wave trough and the sfc cold front continuing to
push south of our area. With the upper flow becoming westerly, look
for the high clouds currently located over the central Plains to
gradually move eastward and across our area.  Otherwise, with low
level thicknesses remaining close to their pre-frontal values (some
30-40m higher than today), we should see highs at least 8-10 degrees
warmer than today. Overall, Thursday will be partly cloudy with
highs in the lower 50s.

Thursday evening the low level wind field will shift to the N/NE as
high pressure over the Ohio Valley moves east.  Although low level
thicknesses may drop a few meters on this N/NE flow...increasing
high clouds from the southwest should offset the cooler airmass.
Lows in the upper 20s to around 30 under partly cloudy skies.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 255 PM Wednesday...

A strong upper short wave moving across the Ohio Valley will nudge a
reinforcing surge of cold air into the area. Surface high pressure
will then build across the area, resulting in plenty of sun, but
suppressing high temperatures to the 40s Friday and Saturday.
Morning lows Saturday will be mostly upper 20s, with some areas
across the south only falling to near freezing. Short wave ridging
will be amplifying north into the Eastern Conus by Saturday night,
with increasing heights and initiation of warm air advection in
return flow as the surface high moves offshore. Cloudiness will be
on the increase by later Sunday with highs reaching mostly low and
mid 50s after a morning low near freezing.

By Monday, a low pressure area will be lifing northeast out of the
Gulf of Mexico. There is a good deal of uncertainty as to how the
details will play out, with model timing issues as the ECMWF has a
strong fast moving short wave race across the Ohio Valley to kick
the system offshore quickly, resulting in precip pretty much limited
to the southeast, while the GFS`s slower short wave allows for a
couple of waves to ride up the upper ridge into the area to produce
more widespread precip and prolonging the duration of precip chances
into Tuesday. Will maintain our ongoing forecast of chance PoPs from
Sunday night through Tuesday and allow details to emerge from later
model consensus. That said, precipitation type will be no problem
with southern stream flow into the area allowing highs Monday and
Tuesday to reach the 50s after morning lows in the low to mid 40s.
Wednesday looks to be a dry and a bit cooler, but still near
seasonable in the 50 to 55 range.

&&

.AVIATION /12Z WEDNESDAY THROUGH MONDAY/...
As of 1232 PM Wednesday...

Through 14/18z:  Mainly clear skies will persist through the rest of
the afternoon, then mid and high clouds will briefly cross north-
central NC between 14/00z-14/07z, associated with the the next short
wave passing by to our north.  HRRR forecast soundings hint that a
brief period of LLWS is possible during those evening and early
overnight hours, thus have included it at all TAF sites.  Otherwise,
VFR conditions through the TAF period.

After 14/18Z:  VFR conditions expected through the rest of the week.
A southern stream system may bring increased moisture and risk for
reduced flight conditions early next week.

&&

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

&&

$$
SYNOPSIS...np
NEAR TERM...np
SHORT TERM...np
LONG TERM...mlm
AVIATION...np



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