Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 201137

Area Forecast Discussion
National Weather Service Raleigh NC
640 AM EST Mon Feb 20 2017

High pressure will build into the region tonight, then move offshore
on Tuesday. A low pressure system will cross to our south on


As of 315 AM Monday...

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.


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


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
through Friday.

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.


As of 640 AM Monday...

There is a high likelihood of VFR conditions across central NC
through 06Z Tuesday. An area of high pressure at the surface will
build in from the north today. This system will maintain mostly
clear skies and light surface winds through tonight.

With high pressure to our north-northeast later tonight, a low level
ely flow will develop. This flow will transport moisture off the
Atlantic, and into the Piedmont. As the moisture meets the upslope
region of the foothills and the higher terrain of western NC, areas
of stratus will develop. This stratus layer may spread into the
western Piedmont after 06Z Tuesday, increasing the risk for sub VFR
ceilings. The risk for sub VFR ceilings appear higher late Tuesday
night into Wednesday morning.

There will be a chance for sub VFR ceilings Wednesday through Friday
across central NC as a moderately moist air mass and an unsettled
weather pattern is expected.





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