Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 091912
Area Forecast Discussion
National Weather Service Raleigh NC
210 PM EST Fri Dec 9 2016
Arctic high pressure will build across the area through Saturday. A
cold front will approach from the west late Sunday and move through
the area on Monday.
.NEAR TERM /THROUGH TONIGHT/...
As of 950 AM Friday...
Forecast is in good shape. A large area of arctic high pressure
continues to build in from the NW today, with fast mid level flow
from the WNW and a dry column. A weak wave passing by to our north
is responsible for the sporadic snow showers on the western slopes,
but neither these nor the associated cloud cover will survive
crossing the mountains. The observed thickness at GSO this morning
was 1278 m, well below the seasonal normal, and steady cold air
advection today will not afford much of a rise, even with ample
sunshine. Temps so far this morning are running a degree or so above
the forecast pace, so have nudged up temps accordingly this
afternoon by a degree or so, peaking at 40-46. -GIH
The expansive arctic high pressure currently centered over nation`s
mid-section will build slowly eastward into the area through the
weekend. Aloft, trailing channeled shortwave energy, associated with
the closed low moving out over the Canadian Maritimes will traverse
the Mid-Atlantic region today. However, it will prove of little
consequence as the cP airmass in place(PWATS ~ 0.10") is just too
dry to support any clouds.
With H8 temps -10 Celsius(2 to 3 standard deviations below normal)
and low-level thicknesses bottoming around 1275 meters(45 meters
below normal), temperatures will will run a good 10 to 15 degrees
below normal. Highs in the upper 30s to lower 40s. Lows in upper
teens to lower 20s.
.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 200 AM Friday...
Flow aloft transitions to zonal on Saturday. Otherwise, very little
little change as the modified arctic high pressure migrates east
atop the region. Temperatures Saturday and Saturday night will be
very similar to today and tonight. Highs 40 to 45.
Lows 20 to 25.
.LONG TERM /MONDAY THROUGH FRIDAY/...
-- Changed Discussion --As of 210 PM Friday...
Initial low amplitude long wave troffing will produce fast and near-
zonal flow across the central and southern tiers of the Conus
through mid week. Return flow ahead of an initial front on Monday
will produce a strong surge of warm air advection with highs ranging
from upper 50s across the north to mid 60s in the south...5 to 10
degrees above normal. Moisture advection will cut off pretty quickly
as low level flow turns westerly across the Gulf states...with
chance PoPs during the day shifting to the east and diminishing
post-fropa on Monday night.
The frontal zone aligns parallel to the flow and forecast details
are murkier heading towards midweek with considerable variablity in
model solutions. The frontal zone looks to remain south of the
area...with small chance PoPs mainly across the southern tier...
both Tue and Wed as surface high pressure races across the Ohio
Valley. Highs will be on a gradual fall as the upper trof amplifies
a bit and we should be in a predominantly cloudy regime. Highs
Tuesday in the mid to upper 50s will fall to the low and mid 50s on
Confidence in model solutions for the late week is even lower
although colder air will continue edging southward. The upper flow
is not highly amplified, however, which will block off the really
frigid airmass north of the area. Regardless, highs will probably
top out in the mid 40s after morning lows in the mid to upper
20s both Thu and Fri.
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.AVIATION /18Z Friday through Wednesday/...
As of 120 PM FRIDAY...
High confidence in chilly but tranquil aviation conditions for the
next 24 hours. Skies will be virtually cloud-free with unrestricted
vsbys for the rest of today through tonight and into Saturday as
high pressure builds in from the NW. Only a few high clouds tonight
are expected as a weak mid level wave passes by within a fast flow
Looking beyond 18z Saturday, VFR conditions should hold through the
first half of Sunday as high pressure builds overhead. As a warm
front approaches from the south, moisture will increase, and cigs
will trend to MVFR then IFR Sunday afternoon from south to north.
Adverse aviation conditions, including sub-VFR cigs and vsbys, are
expected to dominate from late Sunday through at least Monday night
-- and perhaps into Wednesday -- as waves of low pressure track
along the frontal zone as it holds over or just south of the area. -