Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 060313
Area Forecast Discussion
National Weather Service Raleigh NC
1010 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 1010 PM Monday...
Conditions continue to showly deteriorate as short lived Miller-B
CAD setup progresses pretty much on schedule. Rain coverage will
approach 100 percent of the area by morning as southeast isentropic
flow and attendant lift strengthens on the 290K surface between 09Z
and 12Z. No changes of note are needed except minor timing
adjustments on the temps, which are falling a little more slowly
Previous discussion: 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/...
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.
.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 /00Z TUESDAY THROUGH FRIDAY/...
As of 700 PM TUESDAY...
24-Hour TAF period: Although aviation conditions are VFR as of 00Z
Tuesday, expect lowering cigs over the next few hours. Expect cigs
to reach MVFR between 06Z and 09Z and quickly into IFR and LIFR,
thereafter. VISBYS will generally remain in the 2-5 SM range through
the TAF period, likely lowering after 00Z Wednesday. Dry air will
begin to advect into the upper levels late on Tuesday, but low
clouds/moisture will linger throughout the day/evening. There is a
slight chance for a possible rumble of thunder, mainly across the
south, in the early afternoon Tuesday. The biggest concern will be
the likelihood of low-level wind shear at KFAY, KRWI, and KRDU
throughout the day Tuesday as the CAD wedge airmass and easterly
winds remains in place near the surface and strong southwesterly
winds move into the region aloft. Rain will persist through the TAF
Looking ahead: The passage of the trough axis will also cause
widespread rain to end, and clearing to commence, from SW to NE
throughout the evening hours. The clearing, in conjunction with wet
soil, will result in the development of patchy fog Tue night. Chance
of MVFR ceilings ahead of an arctic cold front Wed night-Thu, and
blustery NW winds behind the front late Thu-Thu night. -MWS