Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 052123
Area Forecast Discussion
National Weather Service Raleigh NC
423 PM EST Mon Dec 5 2016
High pressure will build across the Middle Atlantic states through
tonight, ahead of a Miller B low pressure system and associated cold
air damming, which will result in the development and deepening of
an area of low pressure through the eastern Carolinas on Tue.
Another area of high pressure will build overhead for the middle of
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 355 PM Monday...
The weather will be quiet through early evening, as surface high
pressure continues to ridge across the Middle Atlantic states.
Clouds will then quickly thicken and lower, with light rain
having already been observed at 21Z as far E as Wrn SC and SWrn
NC, in association with a lead deamplifying perturbation now
lifting across the Lower MS Valley. This light rain, from mid
level ceilings, will overspread our region overnight, with
temperatures expected to wet-bulb into the lower to middle 40s by
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.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --As of 415 PM Monday...
WV imagery indicates the primary mid-upper low has already begun
to lift more quickly across TX today, and this associated
shortwave trough is forecast to pivot NEwd through the Central
Appalachians Tue and reach the Chesapeake Bay region by 00Z Wed.
Associated forcing for ascent will strengthen and deepen, the
latter as isentropic upglide/WAA rapidly increase from S to N
across central NC Tue morning. A few rumbles of thunder will be
possible around midday, when both deep layer lift and lapse rates
aloft become maximized with the passage of the shortwave trough
and associated cold pool aloft. Widespread rain and overcast will
result in cold air damming and temperatures that are likely to
only rise a few degrees throughout the Piedmont, while a few 50s
will be possible in the far S and E as a secondary low migrates
through the Ern part of the state.
The passage of the trough axis aloft will cause the widespread
rain to end, and clearing to commence, from SW to NE throughout
the afternoon and early evening hours. Storm total precipitation
amounts are expected to range from three quarters of an inch to
one inch. The clearing, in conjunction with wet soil, will then
result in the development of patchy fog Tue night. Lows upper 30s
to lower 40s.
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.LONG TERM /Wednesday through Monday/...
As of 350 PM Monday...
In the wake of the departing low pressure on Tuesday, and preceding
a strong arctic front moving through the Midwest, the flow will be
weak over central NC on Wednesday. Forecast soundings show enough
drying to erode the lingering low clouds and/or fog early Wednesday,
with daytime heat into the mid 50s (per statistical guidance) likely
to result in a cu field, mainly east. Weak but moist southerly flow
should redevelop late Wednesday in response to weak height falls and
an intense upper jet associated with the aforementioned cold front
and result stratus Wednesday night. Lows 39-44.
The cold front, progged to be just west of the Yadkin early Thursday
morning, will will cross the area during the first half of the day,
with strong cold advection behind it Thursday evening and
overnight. The front itself is not expected to produce much precip,
if any, though the GFS cranks out some light qpf, owing likely to a
period of strong low-level FGEN and sufficiently deep moisture
across the northern half of the area. The current slight chance POP
will be maintained. Highs in the upper 40s to mid 50s.
Strong cold advection Thursday night should result in gusts to 15-
20kt and wind chills in the upper teens, as lows drop into the mid
to upper 20s. Arctic high pressure will then build in over the
weekend, with forecast thicknesses progged to approach 1270m Sat/Sun
morning. Lows should have little problem hitting the upper teens
and lower 20s. The high then quickly moves offshore and the
synoptic front return north with the next chance of rain early next
.AVIATION /21Z MONDAY THROUGH SATURDAY/...
As of 330 PM Monday...
Initially VFR conditions through this evening will yield to
progressively lowering ceilings tonight, into IFR-MVFR range late
tonight-early Tue, as lift and moisture increase downstream of a
complex low pressure system approaching from the SW. Patchy light
rain will also begin to fall from the VFR ceilings this evening,
then increase in coverage and intensity through early Tue. A few
rumbles of (elevated) thunder, whose cloud bases would be rooted
around 5000 ft owing to a cold and stable low level air mass, will
be possible roughly between 14-18Z Tue, as lapse rates aloft briefly
steepen with the passage of a mid-upper level trough. The passage of
the trough axis will also cause widespread rain to end, and
clearing to commence, from SW to NE throughout the afternoon and
early evening hours. The clearing, in conjunction with wet soil,
will result in the development of patchy fog Tue night.
Outlook: Chance of MVFR ceilings ahead of an arctic cold front Wed
night-Thu, and blustery NW winds behind the front late Thu-Thu