Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 071942
Area Forecast Discussion
National Weather Service Raleigh NC
245 PM EST Wed Dec 7 2016
Weak high pressure will settle over the Carolinas today.
An arctic cold front will move through the area Thursday.
.NEAR TERM /THROUGH TONIGHT/...
As of 940 AM Wednesday...
Mostly clear skies across central NC this morning, except for in the
southern Piedmont where fog has been slow to disperse, though
visible satellite imagery is finally showing signs of improvement.
High pressure will settle over the area today between a low
departing tot he northeast and an arctic cold front moving through
the Midwest. Skies will remain clear for most of the day in most
areas, but some of the low-level moisture in the Coastal Plain may
result in scattered cur this afternoon, while abundant moisture over
SC will inevitably return north across the western Piedmont this
evening as the flow veers to southerly ahead of the cold front. None
of this will have an impact on afternoon highs, which MAV/MET MOS
suggest will be in the mid to upper 50s in relatively hallow mixing
below the subsidence inversion. -BS
Tonight...Models have been pretty consistent in showing some
isolated showers/sprinkles accompanying the front, with the front
expected to approach the Triad right around daybreak Thursday.
Uniform lows in the upper 30s to lower 40s.
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 320 AM Wednesday...
Shallow moist upglide ahead of the leading edge of the Arctic
intrusion spreading west to east through the area on Thursday will
support a broken band of very light rain showers/or sprinkles with
abrupt clearing in it`s wake owing to the strong cold dry air
advection. In fact, we could see temperatures falling across the
western piedmont by the afternoon. Highs ranging from lower 50s NW
to upper 50s southeast.
Strong CAA will continue Thursday as expansive Arctic high begins
east into the region. Overnight lows in the mid 20s to upper 20s
with a steady wind 7kt breeze resulting in chill values in the teens.
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --As of 245 PM Wednesday...
Cold air tap will be turned on Thu night as an Arctic ridge builds
south and east out of the central plains. The leading cold front
will be offshore with clear skies and dew points falling into the
teens on Friday. It will be brisk, with northwest winds gusting up
to 20 mph coincident with highs struggling to reach the lower 40s,
with upper 30s more likely across the northwest. Associated wind
chills will top out in the upper 30s in the afternoon. Near ideal
radiational conditions are expected Friday night, and we will see
our coldest temperatures thus far this season, with most areas
falling to the low 20s by sunrise Saturday, and some outlying areas
will see mins bottom out in the upper teens. The high pressure will
be overhead and the cold airmass in place will be hard to warm up
due to the low sun angle, and highs Saturday will again be mostly in
the lower 40s.
The surface high will be edging off the mid Atlantic on Sunday, and
ensuing return flow will begin to moderate temperatures as well as
spread moisture progressively north and west into the area during
the late day. Should see increasing clouds throughout the day and
maybe some patchy light showers in the west by evening, with chance
PoPs across the entire area after midnight. Highs will edge into the
mid to upper 40s.
There are significant timing and feature detail inconsistencies
concerning our next system approaching from the west early in the
work week, with a weaker but faster frontal passage Sunday night per
GFS vs. a stronger, sharper frontal passage later Monday per the
ECMWF. As such, will maintain chance PoPs from Sunday night through
Monday afternoon, with dry weather and near-seasonable temperatures
Tuesday into Wednesday in faster zonal flow. Highs Monday through
Wednesday will be mostly in the 50s with morning lows in the 30s.
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.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
As of 115 PM WEDNESDAY...
Clear skies and VFR through early evening. The main forecast issue
overnight will how quickly sub-VFR conditions return, and given wide
ranging solution from our models, this is a rather low confidence
forecast. Brief clearing this morning has resulted in clear skies
and VFR this afternoon, but there is ample low-level moisture south
and east of the area to support the return of low clouds tonight as
weak warm advection develops ahead of a cold front in the Midwest.
There are starkS differences between the NAM/GFS and RAP/HRRR, with
the RAP and HRRR indicating IFR and LIFR stratus as early as 03Z.
However, with light wind, its possible some fog may develop, and
this would make more sense around KRWI. In general, expect A mix of
LIFR, IFR, and MVFR conditions areawide by 06-08Z, with some patchy
light rain also possible.
The aforementioned cold front will cross the area between 12Z and
18Z Thursday, clearing out the low clouds and possibly consolidated
the precip into a few showers that will exit to the east by midday.
West-northwest winds will increase to 8-12kt, with gusts into the
upper teens during the afternoon.
Outlook: VFR conditions are expected through the weekend. The next
chance of sub-VFR conditions will be early next week.