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fxus62 krah 111141 
afdrah

Area forecast discussion
National Weather Service Raleigh NC
640 am EST Mon Dec 11 2017

Synopsis...
high pressure will extend over the Gulf of Mexico and southeast
states today through tonight. A dry cold front will cross North
Carolina Tuesday, ushering in even colder air for mid week.

&&

Near term /today through tonight/...
as of 240 am Monday...

Calls to counties in the northwest part of the forecast area, where some
snow lingered on grassy areas, reveals that the roads dried out
considerably with the sunshine and breeze yesterday. While some
isolated icy spots likely remain this morning, widespread travel
problems are not anticipated, so a black ice advisory will not be
needed.

Within a stable column featuring fast west-northwest flow, the passage of a
band of elevated moisture aloft -- along a 700 mb trough axis now
crossing the area -- has kicked off some orographically enhanced mid
clouds over the north Piedmont early this morning. Once this moisture
band passes to our east closer to daybreak, we should see these
clouds dwindle, leaving generally sunny skies today. Surface high
pressure will continue to span the Gulf of Mexico and FL, with south-southwest
to SW surface winds over NC. Latest model runs show thicknesses just
a bit below normal this morning but rising nicely through the day
within warm air advection, although cooler air may hang in longer
across the far northern County Warning Area. Expect highs from the upper 40s north to
the mid 50s S. Our attention then turns to the potent mid level
clipper diving southeast over the upper Midwest this morning. This wave,
and its accompanying surface cold front, will drop southeast then east into
the mid miss valley and Ohio Valley through tonight. As it
approaches, we're likely to see increasing mid clouds late this
afternoon through tonight, especially across the northwest and N, with weak
moist upglide noted on the 310k surface. Improving low level
moisture, especially over the northwest cwa, may induce patchy stratus as
well overnight. The trend to partly to mostly cloudy skies and the
light SW breeze holding up overnight should temper cooling somewhat,
yielding lows of 30-36, not far from normal but much milder than the
last couple of nights. -Gih

&&

Short term /Tuesday through Tuesday night/...
as of 310 am Monday...

The upper level shear axis and corresponding dry surface cold front
will traverse the area Tuesday, arriving in the mid morning W, and
shifting east of the area during the mid afternoon. Skies should
remain partly to mostly cloudy through the morning, with a gradual
improving trend to fair to partly cloudy skies in the afternoon,
with a combination of thin mid and high clouds along with flat cu as
moisture is trapped near the top of an increasing boundary layer
mixed depth. The cooler air mass will be building in from the west,
such that it appears that the mountains will initially block the
coldest air, and we should still reach highs from the upper 40s northwest
to the mid 50s se, although a Stout breeze with frequent gusts
around 20 kts will make it feel chillier, especially late in the day
as the dewpoints plummet. While the initial cold front will be
moving to our east by mid afternoon, the more prominent cold/dry air
surge will arrive late Tue afternoon through the evening, as a
strong vorticity Max dives through the trough base across NC, with
the dynamic trop dropping to around 650 mb. Some enhanced cloudiness
and perhaps a burst of stronger wind gusts may accompany this trough
passage. Otherwise, skies will clear out Tue night, and temps are
expected to bottom out in the 20-25 range. These readings with a
steady northwest breeze will bring the wind chill down into the low teens
over much of the area. -Gih

&&

Long term /Wednesday through Sunday/...
as of 230 am Sunday...

The quieter weather pattern continues mid week, as general troughing
in the east gives way to a more zonal pattern toward the end of the
period. Wednesday looks to be the coldest day across central North
Carolina, with afternoon highs failing to reach the 40 degree mark
under a brisk northwest wind. Southerly to southwesterly flow
returns early Thursday, allowing a brief warmup to more seasonable
temperatures to take place. Around this same time, an area of low
pressure looks to develop off of the Carolinas, introducing shower
chances into the forecast Friday afternoon and evening. Model
differences take hold at this point, with a much wetter and more
amplified GFS model introducing an additional wave or two of
precipitation to the region before the end of the weekend, while a
much drier European model (ecmwf) keeps US under high pressure. For now, have limited
shower activity at the end of the period until better consensus is
observed.

&&

Aviation /12z Monday through Friday/...
as of 640 am Monday...

With one exception, VFR conditions are a near certainty for the next
24 hours, as a surface high pressure ridge extends into the area
from the west-southwest. Vsbys will be unrestricted through this evening, with
no cigs. Starting soon after midnight, an approaching front will
bring scattered mid clouds based above 12,000 ft agl, as well as a
risk for cigs below 1,000 ft above ground level at int/gso after 08z. In addition,
a low level jet from the southwest may bring low level wind shear conditions to Fay
late in the period (after 09z). Otherwise, surface winds will be
light, under 8 kts, from the W, shifting to SW then S late today
into tonight.

Looking beyond 12z Tue: a dry cold front will move through the area
on Tue, but VFR conditions should hold. Winds will shift back to
northwesterly after frontal passage Tue, and gusts up to 20-25 kts
are possible from late Tue morning through much of Tue night. VFR
conditions will dominate through at least Thu night. Sub-VFR
conditions are possible with rain chances increasing Fri as an upper
trough approaches. -Gih

&&

Rah watches/warnings/advisories...
none.

&&

$$

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