Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
FXUS62 KRAH 110608
Area Forecast Discussion
National Weather Service Raleigh NC
105 AM EST Sun Dec 11 2016
High pressure overhead will drift offshore later this morning. A
warm front will push northward through the area tonight, followed by
the approach of a cold front Monday and Monday night. This front
will stall across the Carolinas Tuesday and Wednesday.
.NEAR TERM /THROUGH TONIGHT/...
As of 845 PM Saturday...
Cold, clear, and calm overnight. Lows 15-20 in the Piedmont
to lower 20s SE.
1035 MB surface high pressure was centered over the mid-Atlantic
states into NC/SC this evening. Data indicates that central NC is on
target to be just as cold, if not a degree or two colder than last
night. The mid evening temperatures were already 25-30 with dew
points in the teens/20s across the Piedmont/Coastal Plain.
Conditions were calm.
.SHORT TERM /Sunday through Sunday night/...
As of 235 PM Saturday...
The surface high will shift off the Mid Atlantic coast Sunday with
frontogenesis taking place along the Carolina coast. Moist
overrunning flow focused on the 285-290K layer will surge northward
through the area Sun afternoon, resulting in a south-to-north trend
to mostly cloudy skies, which will last through Sun night. The
precip details are tough to resolve, given the lack of agreement
among the large scale models as to the coverage and amounts through
Sun night. The NAM brings very light precip into the NC Foothills
Sun afternoon, whereas the GFS has patchy light rain over the
Sandhills, and the ECMWF is dry. Heading through Sun night, the
ECMWF remains mostly dry (sandwiched between showers and the coast
and light rain in the NC/VA Foothills), while the GFS brushes light
precip over our far eastern sections and the NAM -- which has much
deeper saturation -- drops heavier rain farther west to Highway 1.
The SREF QPF plumes show most members have no precip or just very
light amounts, around 0.01". Given the expected presence of dry air
above the freezing level and fairly shallow nature of the moist
upglide, have kept pops mostly in the slight chance range, for light
rain or drizzle, although I have retained a period of 25-30% pop in
the east for a portion of Sun night. Expect highs of 45-51 Sun,
coolest NW and warmest SE, followed by a "low" of 39-47 Sun night,
with temps dipping early in the evening then holding steady or
rising slightly overnight as the warm air just aloft spreads in. -GIH
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 325 PM SATURDAY...
Not a lot of confidence in the long term forecaster this afternoon.
Monday will begin with a low pressure system over the Great Lakes
with a cold front stretching southward through the Mississippi
Valley. Temperatures will warm with southwesterly flow ahead of this
front and so Monday and Tuesday will both see temperatures in the
mid 50s to mid 60s NW to SE. Frontal passage should actually occur
Monday night early Tuesday with some light rain associated with it.
On Tuesday we could see another chance for rain with a wave coming
up from the south but accumulations for this event will not be very
high for either event and are expected to be all liquid as low temps
as temperatures Monday night and Tuesday night should stay mostly in
the 40s with some upper 30s across the NW Piedmont.
A couple more southern waves may affect southern counties on
Wednesday and Wednesday night again with minimal all liquid
accumulations. Temps on Wednesday will be in the 50s with lows in
the upper 20s to mid 30s with the sub-freezing temperatures occurring
in the NW after the precipitation has already moved out. Thursday
and Friday will be dry and cold with temps in the upper 30s to low
Very low confidence forecast for Friday night into Saturday morning
however, there is a slight chance that there will be a short window
for some freezing rain across the northern counties early Saturday
morning if freezing temperatures and precipitation overlap. Right
now there is a huge spread in the models in both temperature and
precipitation values. The only thing that is fairly high confidence
is that if, and that is a big if, we have any precipitation type
problems, it will most likely be freezing rain. Stay tuned.
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
As of 105 AM Sunday...
High confidence that VFR parameters will persist across central NC
through 18Z today as high pressure at the surface will be drifting
offshore. The return flow on the backside of the retreating high
will advect low level moisture into central NC this afternoon
through tonight, resulting in lowering ceilings into the MVFR/IFR
categories by this evening. In addition, expect patches of light
rain and/or drizzle to develop in vicinity of KFAY late this
afternoon, and elsewhere tonight. Also, an increasing low level jet
may produce marginal low level wind shear parameters overnight into
early Monday morning, mainly in the form of speed shear, as wind
speed 35-40kts probable between 1500-2000ft.
Mostly sub VFR conditions expected Monday through Monday night as a
cold front drifts slowly east across the region. A brief intrusion
of drier air may lead to a period of VFR conditions, mainly across
the northern terminals, on Tuesday. Another round of sub VFR
ceilings anticipated Tuesday night through Wednesday night with the
approach/passage of another low pressure system. VFR conditions
expected by Thursday as cold high pressure builds into central NC.