Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 271750
Area Forecast Discussion
National Weather Service Raleigh NC
1250 PM EST Mon Feb 27 2017
High pressure will move offshore today, followed by a warm front
lifting through the area tonight. Meanwhile, warm southwesterly
flow will continue ahead of a cold front approaching from the
west through midweek.
.NEAR TERM /THROUGH TONIGHT/...
As of 1015 AM Monday...
Little change to the near term forecast. Adjusted hourly
temperatures through early afternoon to reflect observed trends.
A relatively dry air mass and a developing low level south-southwest
flow will aid to boost temperatures through the 50s this morning,
and into the 60s this afternoon. Potential for a few spots in the
far south to top out around 70.
The approach of a weakening low amplitude wave in the lower half of
the atmosphere will lead to an increase in mid-high level clouds
from the west later this afternoon and tonight. Increasing
isentropic upglide in the low level warm air advection pattern (as
depicted by the GFS and the NAM) support the idea of a few light
rain showers tonight across the western and southern Piedmont.
The abundant cloudiness and warming air mass will support overnight
temperatures a solid 10-13 degrees warmer than last night.
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 340 AM Monday...
West-southwest flow will ensue on Tuesday as a surface warm
front lifts north of the area. Morning stratus will likely hold
longest across the west but full heating is expected for a large
portion of the area as period of high clouds spread east in
relatively low amplitude flow. 1000-850mb thicknesses support
highs in the lower 70s west to near 80 east. Dewpoints creeping
into the upper 50s and modest 6.5-7 C/KM mid level lapse rates
will lead to weak instability, but forcing is largely lacking
outside of warm advection. Currently think showers and a few
storms will be widely scattered across the Piedmont and coastal
plain. Tuesday will be rather mild in the warm sector of a
stronger low pressure system moving through the Midwest, with
lows in the upper 50s and lower 60s.
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 400 AM Monday...
Wed-Wed night: A complex mid-upper level trough compromised of
multiple embedded shortwave perturbations will move E from the
Plains states early Wed to the Northeast by Thu morning. At the same
time and at the surface, related waves of low pressure will migrate
from the mid MS Valley to New England, while the trailing cold front
will move from the Appalachians late Wed-Wed evening to the Atlantic
coast by Thu morning.
It will be warm and windy, but dry for most of the day Wed, owing to
a stout capping inversion. Strong SWly flow in the warm sector will
yield sustained 15-20 kt winds, with gusts up to 30-35 kts during
the afternoon. Morning stratus, trapped beneath the aforementioned
inversion, will disperse by midday or early afternoon, so
temperatures should consequently rise rapidly into the upper 70s to
lower 80s. Pre-frontal showers and storms will be possible over the
far wrn Piedmont, as mid level height falls related to the
approaching trough aloft move overhead and fully lift and erode the
preceding capping inversion there by sunset.
The better chance of showers and storms will occur Wed evening and
Wed night, as the surface front sweeps Ewd. Strong SWly deep layer
flow, oriented mainly parallel to the frontal zone, will favor
linear convection that would pose primarily a damaging wind threat
given a relative lack of more robust low level moistening, and
associated instability. Blustery post- frontal NWly winds will
follow in strong CAA late Wed night- early Thu, with lows in the low-
mid 40s west to middle 50s east.
Thu-Sun: A following clipper shortwave trough in NW flow aloft will
amplify across the Middle Atlantic states Thu night-Fri, with an
associated re-enforcing, but dry, cold frontal passage on Fri.
Temperatures will nadir in the middle 20s to around 30 degrees Sat
morning, but a moderating trend will follow as the flow aloft
becomes more zonal by the weekend.
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
-- Changed Discussion --As of 1250 PM Monday...
There is a high likelihood of VFR conditions across central NC
through 03Z Tuesday. An area of high pressure at the surface will be
positioned offshore by tonight while an area of low pressure drifts
slowly west. The resultant circulation around these two weather
systems will yield a sly flow. This flow will lead to moisture
increasing across the region overnight into Tuesday. This will
increase the chance for low end VFR/MVFR ceilings, primarily across
the western counties including the Triad terminals after 06Z
Tuesday. In addition, there is a chance for a few showers overnight
into the first half of Tuesday morning.
An unsettled weather pattern across central NC through Wednesday
night will lead to an increased risk for sub VFR conditions.
Additionally, a tightening pressure gradient will lead to windy
conditions Wednesday with gusts 30-40kts highly probable. Prior to
that, there is a chance for low level wind shear conditions
overnight Tuesday night, more so speed shear rather than directional
The approach and passage of a cold front late Wednesday and
Wednesday night will also increase the risk for a few thunderstorms.
At this time, VFR parameters appear highly probable Thursday through
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