Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 271517
Area Forecast Discussion
National Weather Service Raleigh NC
1015 AM 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/...
-- Changed Discussion --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.
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.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 /12Z MONDAY THROUGH FRIDAY/...
As of 645 AM Monday...
High confidence in VFR today under influence of high pressure. A
light south-southwest wind will develop today as the high moves
east. Mid and high level clouds will increase this evening as a
weakening upper level disturbance moves overhead and a warm
front lifts north into the Carolinas. More substantial MVFR stratus,
will likely come after 06Z and be most prevalent at GSO and
INT, with a low end chance of a few showers as the warm front
lift through through central NC. Some IFR stratus is possible,
though the lowest ceilings should remain west of INT.
Outlook: Stratus developing early Tuesday will burn off prior to
midday, with scattered showers and storms possible during the
afternoon and evening. A more substantial threat of sub-VFR is
expected late Wednesday and early Thursday a cold front crosses
the region. VFR will then return for the end of the week.