Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 120228

Area Forecast Discussion
National Weather Service Raleigh NC
928 PM EST Mon Dec 11 2017

High pressure will move east tonight. A strong upper level
disturbance and associated cold front will move east across the mid-
Atlantic region Tuesday. Much colder conditions will follow for mid
to late week.


As of 925 PM Monday...

Clear skies this evening will give way to increasing cloud cover
overnight as a potent s/w disturbance and associated cold front
approach from the west. In addition to the increasing cloud cover,
expect we`ll see winds stay up overnight (generally light out of the
south to southwest). This will lead to warmer overnight low tonight,
with temps possibly even rising a few degrees after midnight across
the western portion of the area as cloud cover increases. Thus,
expect low temps will generally range from around 30 in the usual
rural cold spots to the mid 30s in the urban areas.


As of 300 PM Monday...

...Gusty NW winds to 25-30 mph with wind chills in the 10-15
degree range Tuesday evening...

The main cold front and upper level feature will move across central
NC between 12z and 18z. This is when the mid and high level moisture
will increase enough for variably cloudy skies. Once the cold front
passes, winds will shift to the WSW and increase to 15-20 mph with
gusts to 30 mph. CAA will be delayed a few hours behind the front
due to the strong westerly downslope component. Guidance is robust
in warming temperatures well into the mid 50s to lower 60s in the
east, with highs 50-55 NW.

Expect a very sharp drop in the temperatures late Tuesday and
Tuesday evening with strong cold dry air advection. Readings will
slip below freezing within a few hours of sunset in the Triad, and
by late evening in the Triangle. Mainly clear skies and diminishing
winds are expected late Tuesday night. Lows will be in the lower to
mid 20s. Wind chill readings of 10-15 are likely from mid evening
through the early morning hours.


As of 230 PM Monday...

Cold air will be advecting into Central NC in northwest flow on
Wednesday in the wake of the dry cold frontal passage. Despite full
sun, highs will be capped in the mid 30s north to low 40s south.
Overnight lows in the mid to upper 20s. Meanwhile, a shortwave will
begin diving south-southeastward from central Canada, through the
High Plains and toward the Mid-Atlantic. The resultant upper level
winds will become briefly more westerly then southwesterly on
Wednesday night. A reflection of this wave will be seen at the
surface as a low moving through the OH Valley region, eastward to
the Atlantic. The winds will become more southwesterly at the
surface late Wednesday/Wednesday night ahead of the aforementioned
low and its attendant cold front. This cold front, which won`t be as
potent as the previous one, will stall over Central NC Thursday into
Friday. A low strengthening along the stalled front over the area
will result in an increase in temperature gradient from WV to SC on
Friday. Persistent west-southwesterly flow into the region will
result in increased warm, moist air advecting into the Carolinas and
thus an increase in precipitation potential, mainly along and ahead
of the front. The front should finally move eastward over the
Atlantic late Friday into Saturday, allowing cold air to advect into
the area from the northwest as high pressure migrates eastward along
the Gulf coast, ridging into the Carolinas. Another frontal system
develops in the Midwest Saturday/Sunday, approaching the Mid-
Atlantic Sunday/Monday. Medium range models are in fairly good
agreement for being so far out in time, so this may be a system of
focus for the next week or so. Highs through Saturday will generally
range from mid 40s to mid 50s, while lows will fluctuate between low
to mid 30s and mid to upper 20s. Ahead of the next frontal system,
temperatures will likely moderate, highs the mid 50s and lows into
the mid


As of 700 PM Monday...

VFR conditions will persist through Tuesday night. While clouds will
increase and thicken nw-se after 04Z across central NC, ceilings, if
they occur, will likely remain above 5000ft. The approach of a cold
front from the northwest will increase the sfc wind later tonight,
with a south-southwest wind 7-10kts, especially across the western
Piedmont and in vicinity of the Triad terminals.

The sfc cold front will cross the Piedmont Tuesday morning, and the
coastal plain and Sandhills Tuesday afternoon. The passage of the
front will be noted by the surface winds veering to the west-nw, and
increasing to around 15 mph with gusts 30-35 mph probable. While sfc
winds will subside a bit after sunset, gusts 20-30 mph will occur
through much of Tuesday night.

VFR parameters are expected to continue Wednesday through Thursday
night, though an upper level disturbances passing overhead Wednesday
night will cause a period of mid-high level clouds. There is a small
threat for sub VFR ceilings friday into Friday night  Saturday, a
series of upper level disturbances will cause periods of cloudiness
Wednesday night, and again Friday into Friday night as another
storm system passes to our north.




SHORT TERM...Badgett
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