Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 250030
Area Forecast Discussion
National Weather Service Raleigh NC
830 PM EDT MON OCT 24 2016
A dry cold front will move across central North Carolina this
evening. High pressure will extend into the region tonight and
persist through late Wednesday. A cold front will drop southeast
across the Mid Atlantic on Thursday.
.NEAR TERM /Tonight/...
As of 650 PM Monday...
The dry cold front was a few hours slow in passing through central
NC. The front extended across TN into southern VA at 630 PM, and was
preceded by a surface trough. Both will push through the region by
midnight. DAA and downslope flow behind the surface trough lowered
the dew points by 10+ degrees (fell from 43 to 30 at Winston-Salem
between 400 PM and 500 PM). However, the temperature remained in the
upper 70s. The true CAA was tied to the cold front and was located
north a few hours behind the surface trough and cold frontal passage.
Therefore, the air will dry out further this evening but most
importantly the actual temperatures will be very slow to fall. The
evening will be very mild, even a few hours after the frontal
passage. The SW wind at 10 mph will shift to the NW at 10 to 15 mph
with the frontal passage. A few gusts to 20 mph will occur this
evening. Expect plenty of 60s through the mid to late evening, finally
cooling from the north later.
The skies were clear ahead, along, and behind the front over the
entire mid-Atlantic region, and are expected to remain so overnight.
Later tonight, winds will diminish to light and finally some
radiational cooling will take over. Lows by daybreak will be in the
40s (lower 40s N to upper 40s S).
.SHORT TERM /Tuesday through Wednesday night/...
As of 330 PM Monday...
Quiet and fairly uneventful through mid week. A portion of the
surface ridge settles over central NC and modifies somewhat on Tue,
then is followed by a weak reinforcing boundary dropping southward
through NC Tue evening, and cool Canadian-rooted high pressure
nosing in from the north through Wed. This ridge axis will be capped
by an 850 mb anticyclone which will drift from the Mid South ESE
across the Southeast states through Tue night before shifting off
the coast late Wed. Further aloft, the mid levels will remain
subsident and warming as a large vortex centered over the Canadian
Maritimes and encompassing much of NE NOAM drifts NE and fills with
weakening flow over our region as a shortwave ridge builds in from
the west through Wed. All of this equates to little or no lift or
moisture and a generally weak surface flow. The only issue of
concern is the presence of the chilly ridge axis overhead Tue night
accompanied by clear skies and light winds, fostering radiational
cooling and bringing about the risk of patchy frost. Statistical
guidance has trended slightly cooler in spots, and with otherwise
favorable conditions, will introduce patchy fog over portions of
north central NC with lows in the upper 30s. Otherwise, expect
somewhat cool highs Tue/Wed in the mid-upper 60s. The surface ridge
will then shift east off the coast Wed night with a light return
flow helping to drive surface dewpoints back up through the 40s Wed
night. Lows in the mid-upper 40s with mostly clear skies. -GIH
.LONG TERM /Thursday through Monday/...
As of 350 PM Monday...
Shortwave troughing will extend from south central Canada through
the Great Lakes to the Mid South early Thu, shifting eastward Thu
into Thu night. This will be accompanied by a strong surface low
crossing the Great Lakes (and culminating in a triple point low over
E PA and NJ) Thu through early Fri, and a trailing cold front that
will drop SE through NC Thu night/early Fri. We will briefly be in
the warm sector Thu, which will help drive up thicknesses to near or
just above normal with temps expected to warm up into the upper 60s
to mid 70s. Moisture depth does improve with PW reaching near 1.25",
with decent mid level DPVA and minor upper divergence, although
along-front mass convergence is apt to be small. Will retain chance
pops Thu afternoon, peaking Thu night before departing early Fri
morning. Projected instability appears minimal, and will keep it at
just showers for now. The active northern stream across the north
central and northeast CONUS/Mid-Atlantic persists through the rest
of the week, with the aforementioned trough strengthening to a
closed mid level low over MI Thu before shifting east and off the
Northeast coast by early Sat, and another closed low close on its
heels over the weekend. Another high pressure ridge builds into NC
and overhead through Sat morning before shifting to our SE Sat
afternoon in response to this fast flow. Expect minimal cooling Fri
as the cooler thicknesses barely work into NC, then a warmup back
into the 70s is anticipated Sat as we again get into return flow on
the back side of the departing surface ridge. The next front pushing
in from the north is likely to drop into or through NC on Sun or Sun
night, but this too should be moisture-starved. Expect highs to cool
back down a bit Sun and a bit more Mon, into the 65-70 range. The
way-too-early outlook for Halloween night appears to be dry, with
seasonable to slightly cooler than normal temps. -GIH
.AVIATION /00Z TUESDAY THROUGH FRIDAY/...
-- Changed Discussion --As of 820 PM Monday...
High confidence of VFR conditions through the TAF period.
A dry cold front will move south across central NC this evening.
High pressure and associated (light) NLY winds will follow later
tonight through Tue. Mainly clear skies will fill with cirrus in NW
upper level flow late in the day Tue.
Outlook: A chance of MVFR ceilings will accompany a warm front
forecast to retreat NWD across NC Wed night-early Thu, followed by a
chance of showers along the trailing cold front Thu-Thu night.
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