Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 212351
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
650 PM EST Tue Feb 21 2017

.SYNOPSIS...
High pressure extending along the East Coast will move offshore
tonight. A slow-moving upper level trough will cross the Southeast
and Mid Atlantic states through Wednesday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 650 PM Tuesday...

Partly to mostly cloudy weather this evening across central North
Carolina as low pressure over the lower Mississippi Valley moves
slowly eastward.  Main area of showers remains well to the west
across Georgia this evening.

Rain chances late tonight look pretty small outside of the far W and
NW CWA. The split mid level trough, consisting of a broad low-
amplitude wave crossing the eastern Great Lakes/Quebec/Northeast
states and a prominent deep low moving from NE LA into the NE Gulf,
will bring increasing moisture and forcing for ascent to our area.
But forecast soundings show a notable dry layer in the mid levels,
likely leading to smaller hydrometeors, and DPVA with the
approaching trough will be trending lower given the weakening mid
level winds. Model-generated precip, including from the
SREF/GFS/ECMWF, is generally confined to western NC, where the
better moist upglide and upper divergence will reside, while the
slowly departing low- and mid-level ridges should protect much of
the central and eastern CWA from measurable precip. Will restrict
pops through tonight to just the far W and NW CWA. With gradually
increasing and thickening clouds from the west, expect a trend to
mostly cloudy skies areawide. Lows from the mid 40s NE to the lower
50s SW, with patchy fog in the west.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 650 PM Tuesday...

The light low level flow from the E and SE will keep low level
moisture streaming into the area, banked up against the higher
terrain, resulting in partly (east) to mostly (west) cloudy skies
Wed. Forcing for ascent remains fairly weak, as the weak mid level
flow limits DPVA. Moist isentropic upglide will also be weakening
through the day, confirmed by GFS precip progs showing a batch of
morning precip over the NW Piedmont shifting ENE across VA where
upglide will be deepest. The very weak and shallow moist upglide
will persist through Wed night, with stratus, patchy fog, and a risk
of drizzle or very light showers, particularly over the west. But
models continue to generate very little to no precip over most of
our CWA as the weakening mid level shear axis shifts to our east and
850 mb flow decreases and become more westerly, yielding a stagnant
column with plentiful moisture in the lowest few thousand feet.
Aside from good chance to low-end likely pops in the extreme NW Wed
morning, expect fairly low chances for much of the area from midday
Wed through Wed night. Expect areas of fog to develop late Wed night
as dewpoints steadily climb. With thick cloud cover lodged over the
NW Piedmont Wed and greater sunshine over the east with continued
very warm thicknesses, we`ll see wide-ranging highs Wed, from around
60 NW to the lower 70s SE. Lows Wed night around 50 to 55. -GIH

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...

Thursday is starting to look pretty dry as a low pressure system
moves across the Florida Peninsula and into the Atlantic. A low
pressure system to the west is slower to develop then model
solutions showed over the last several iterations. This leaves
central NC in a moisture gap for much of the end of the work week
with both Thursday and Friday looking drier and fairly warm with
highs in the low to mid 70s on Thursday and in the mid to upper 70s
on Friday.

As the parent low makes its way to the Great Lakes region it will
push a cold front eastward over the Appalachians and into central NC
on Saturday/Saturday evening. The tail end of the moisture moves
across the state with northern areas of the forecast area more
likely to get rain than southern areas. QPF looks very meager on the
raw model output but there will be some instability around and if
some showers or thunderstorms were to form some areas could locally
see up to a half of an inch of rain but this is likely to be the
exception rather than the rule. Thus not as much help to the
abnormally dry situation as we had hoped.

While Saturday will still be warm ahead of the front with temps in
the mid to upper 70s, the airmass does modify on Sunday and high
temps drop back near 60 degrees which is much closer to normal this
time of year. Temperatures will modify back through the 60s on
Monday and back towards the 70s on Tuesday with dry conditions
expected.

&&

.AVIATION /00Z WEDNESDAY THROUGH SATURDAY/...
As of 650 PM Tuesday...

VFR conditions will continue through this evening as mid and high
level clouds increase from the southwest.

Tonight, low pressure will move into the Gulf Coast states,
sending low level moisture northward to the Triad/Triangle and
eventually the coastal plains. Will start to see sub-VFR cigs
and vsbys working to most terminals after 06z with best threat
of any rain over INT/GSO, with drizzle toward RDU and RWI after
08z. With high pressure keeping flow off the Atlantic will see
some fog as well, so vsbys could drop to IFR, though confidence
is not high enough to add in the terminals except INT closer to
the foothills.

As we head into Wednesday will be tough to dislodge the lower
cigs but models favor most sites going to VFR after 15z, though
in-situ damming over the Triad should keep INT/GSO IFR til the
end of this taf period.


Looking ahead: Expect cigs in the MVFR/low end VFR range to persist
through Wednesday afternoon, mainly west of RDU. With continued
southeast flow through Friday, the early-morning sub-VFR cigs
and visbys will likely be a reoccurring theme. Low clouds may
scatter out enough during the daytime hours for a return to VFR.
Winds will slowly veer through the period ahead of the
approaching cold front. Showers and sub-vfr conditions will also
be possible ahead of the front, which is expected to move
through Central NC on late Saturday.

&&

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

&&

$$

SYNOPSIS...Hartfield
NEAR TERM...Hartfield/Franklin
SHORT TERM...Hartfield/Franklin
LONG TERM...ELLIS
AVIATION...KC/WP/Franklin


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