Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 201812
Area Forecast Discussion
National Weather Service Raleigh NC
112 PM EST Mon Feb 20 2017
-- Changed Discussion --High pressure will extend along the East Coast through early
Tuesday. A weakening upper-level disturbance will cross the
Southeast states Tuesday night into Wednesday.
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.NEAR TERM /THROUGH TONIGHT/...
As of 950 AM Monday...
Forecast is on track. Plentiful sunshine is a near certainty beneath
dry high pressure at the surface and deep ridging and stable/warm
air aloft. Observed thicknesses are higher than yesterday morning by
around 10 m, although they shouldn`t rise quite as high through the
afternoon as they did yesterday, given that the surface ridge will
be building down the Eastern Seaboard. Temps are already in the mid
50s to lower 60s, comparable to yesterday`s pace, so still expect
highs from around 70 NE to the low-mid 70s elsewhere, with light
winds veering from NE to E then SE through the day. -GIH
Earlier discussion from 315 AM: A narrow upper level ridge extending
from the eastern Gulf into southern Ontario coupled with a dry air
surface ridge building southward along the East Coast will maintain
mostly clear skies, and very mild conditions for this time of year.
While the low level flow is northerly, it`s a neutral flow, meaning
little if any cold air advection. Thus, afternoon temperatures
should be fairly comparable to Sunday`s, in the 70-75 degree range.
Tonight, the low level flow becomes ely as the parent high to our
north moves a little farther to the east. This ely flow will advect
moisture off the Atlantic and into central NC. Due to the upslope
component of the flow, the rising/lifting of the moisture should
cause a layer of stratus clouds to develop late tonight/early
Tuesday morning in vicinity of the Yadkin River Valley, possibly
spreading into our western counties including the Triad region. This
moisture band is fairly narrow so no precipitation should be
generated from these clouds. Elsewhere, expect mostly clear-partly
cloudy skies, with patchy fog possible. Overnight temperatures will
vary from the upper 30s-around 40 northeast to the mid 40s over the
far south and west. -WSS
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 315 AM Monday...
Tuesday, the low level ely flow will advect a cooler air mass into
central NC, resulting in afternoon temperatures 4-6 degrees cooler
than today`s high temperatures. In addition, expect to see more
clouds, though still partly sunny.
Tuesday night, the low level flow will continue to slowly veer to a
south-southeast direction in response to the departure of the high
pressure system and the approach of an area of low pressure from the
southwest. The tightening pressure gradient will enhance the low
level sly flow and attendant warm air advection, leading to increase
isentropic lift/upglide and the possibility of a few showers
breaking out overnight night across the western Piedmont. Additional
lift may be supplied by increasing divergence aloft. Thus, have
tweaked PoPs up 10-15 percent from the previous forecast with chance
PoPs covering portions of the western/southern Piedmont after 06Z
Wednesday. If model trends continue or remain consistent, solid
chance/low end likely PoPs may be warranted. At this time, not
anticipating rainfall amounts of any significance, with amounts of
just a few hundredths expected. Overnight temperatures near 50-lower
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 230 AM Monday...
A closed low aloft will move east-southeast into the Gulf of Mexico
on Wednesday (well south of the North Carolina). Meanwhile, the weak
remnant northern stream trough will move over Central NC. There is a
slight chance for light rain on Wednesday as the trough passes
overhead. However, accumulations should be minimal as the best
moisture will be well south of the area. At the surface, the
southerly return flow will increase over Central NC on Wednesday,
resulting advection of warm, moist air into the region. A moderating
temperature trend is expected through Friday night. With the
continued surge of warm air and the frontal passage not expected
until the weekend, temperatures will remain well above normal
through Friday night (highs in the low to mid 70s Wednesday,
increasing into the upper 70s by Friday. Lows will follow a similar
trend, low to mid 50s Wednesday night into the mid to upper 50s by
Friday night). The models continue to differ with respect to rain
chances through this part of the forecast, though a slight chance
for rain cannot be ruled out, mainly across the west, Thursday
The best chance for any significant rainfall will come ahead of the
fropa late Friday night through Saturday. The cold front is expected
to move through Central NC on late Saturday. Cold air will advect in
behind the front for Saturday night into Sunday as the surface high
builds over/moves through the region. Expect a dry forecast on
Sunday given the current timing of the front. Temperatures behind
the front will be much closer to, but still slightly above, normal.
.AVIATION /18Z Monday through Saturday/...
-- Changed Discussion --As of 112 PM Monday...
High confidence in VFR conditions areawide through at least this
evening, as high pressure builds in from the north, topped by warm
and stable air aloft. Mostly just high clouds based above 18000 ft
AGL are expected through tonight and Tuesday across the area,
however at INT/GSO, increasing low level moisture within stable low
levels late tonight may result in a few low clouds based below 900
ft AGL and perhaps shallow MVFR fog 08z-12z tonight. Elsewhere, no
low clouds/fog are expected tonight. Winds will stay light from the
NE, trending to ESE areawide over the next 24 hours, but speeds will
be a bit stronger at RWI/FAY this afternoon.
Looking beyond 18z Tue, VFR conditions will hold through Tue
evening. We will see a chance for late-night and early-morning sub-
VFR fog/stratus repeat areawide each day through the remainder of
the week. MVFR to IFR conditions with a few showers are possible
late Tue night through Wed as an upper trough crosses the region. A
cold front will cross the area Sat, bringing a chance for showers
and MVFR cigs. -GIH
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