Area Forecast Discussion
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FXUS62 KRAH 181142
Area Forecast Discussion
National Weather Service Raleigh NC
645 AM EST Sat Feb 18 2017
An upper level trough will approach from the west and cross the
southeastern U.S. tonight through early Sunday. High pressure will
build into our region behind the exiting low pressure system Sunday
night and Monday.
.NEAR TERM /THROUGH TONIGHT/...
As of 255 AM Saturday...
S/W ridge over the Carolinas early this morning will scoot quickly
east and offshore in advance of an upper low pressure system that
will cross the lower MS Valley today. Diffluent upper flow ahead of
this system will result in increasing and thickening mid/upper level
clouds later today, spreading sw-ne across the area. The arrival of
this thicker cloud cover will play a role in how warm it will be
this afternoon. Based on satellite trends, the broken/overcast skies
will spread into our southern counties during the late morning/mid
day hours, and over the northern counties during the afternoon.
Thus, appears to be some potential for warming, especially across
the northeast half of the forecast area. Will lean high temps toward
the full sun values from the low level thickness scheme which favors
highs in the upper 60sw-lower 70s, warmest along our eastern
The low pressure system will be weakening as it approaches from the
west. Thus, little if any moisture advection expected in the low
levels which remain quite dry this afternoon. While some forcing
noted aloft, any precipitation that develop will likely evaporate
before reaching the surface. Thus have opted to mention a chance of
sprinkles rather than slight/chance measurable rain.
Variably cloudy skies and a threat for a few sprinkles will linger
into tonight as the weakening upper level low passes overhead. The
variably cloudy skies and light sfc wind regime will maintain
relatively mild nighttime temps for mid-February. Overnight
temperatures in the mid-upper 40s.
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 255 AM Saturday...
Our stretch of mild/warm temperatures will persist Sunday and
Monday. The upper level low, which will reside overhead early
Sunday, will depart by afternoon. Subsidence behind this system and
developing nw flow in its wake will aid to diminish the cloud cover
leading to mostly sunny skies during the afternoon. Considering the
mild start to the day and the potential for increasing sun in the
afternoon, temperatures should recover back into the upper 60s-lower
70s Sunday afternoon.
An amplified upper ridge will extend from the eastern Gulf into the
Great Lakes Monday. The resultant nw flow aloft will drive a dry sfc
cold front across our region Monday afternoon. Warmer air ahead of
this system will yield highs temps in the 70-75 degree range across
much of central NC. The exception will be the far northeast where
the earlier arrival of the sfc front may result in cooler
temperatures in the upper 60s.
Low level easterly flow Monday night may cause in patchy low-mid
level clouds to form in the upslope region of the Foothills,
possibly spilling into our far western Piedmont. Otherwise expect
mostly clear skies Monday night. It should be slightly cooler with
min temps in the 40-45 degree range.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 205 AM Saturday...
The surface high that had been ridging into the region will lift off
to the northeast on Tuesday, with a more southeasterly then
southerly return flow setting up over Central NC by Wednesday
morning as a subsequent warm front slides north through the area.
Aloft, the ridge over the eastern U.S. will shift off the coast and
weaken as the next weather system approaches. A closed low will
break away from the northern stream trough late Tuesday, then slide
slowly east-southeast over the Gulf of Mexico on Wednesday (well
south of the North Carolina). Meanwhile, the northern stream energy
will largely pass to the north of Central NC. Some light rain is
possible over the area Wednesday/Wednesday Night, but accumulations
should be minimal as the best moisture will be well south of the
area. A better chance for descent rainfall will come Friday or
Saturday a low pressure system develops over the northern high
plains and progresses east. The parent low will track northeast
through the Great Lakes as the attendant cold front extends south
into the Gulf. The strongest warm advection into the Carolinas will
be just ahead of the front Friday/Friday night, with the frontal
passage on Saturday. Expect moderating temperatures through Friday
Night (highs maxing out in the mid 70s Friday and lows in the low to
mid 50s Friday Night), decreasing thereafter.
.AVIATION /12Z Saturday through Wednesday/...
As of 645 AM Saturday...
There is a high likelihood that VFR conditions will persist across
central NC through 12Z Sunday. Mostly clear skies early this morning
will give way to thickening mid-high level clouds this afternoon.
Enough forcing aloft will cause some precip to develop, though the
dry sub-cloud layer will cause most of the precipitation to
evaporate before reaching the surface. Southwest surface winds will
increase after 18Z Saturday to near 10kts with infrequent gusts
between 15-18kts probable at KRDU, KRWI, and KFAY.
Ceilings tonight will mostly vary between 7000-12000ft. Gradual
clearing expected to occur Sunday morning-early afternoon as an area
of low pressure pulls away from our region. Mostly clear skies
anticipated Sunday night into Monday.
There is a high probability of VFR conditions Monday through
Tuesday. The approach of a low pressure system Tuesday night into
Wednesday will increase the chance for sub-VFR ceilings.