Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 190259
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
955 PM EST Thu Jan 18 2018

.SYNOPSIS...
Arctic high pressure will continue to build into the area tonight
through Friday morning. This high pressure will shift to our south
over the weekend, bringing a milder southwest flow to the area.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 955 PM Thursday...

Primary change was to nudge low temps upward slightly, based on the
current dewpoints and recent pace of temps. The surface ridge
continues to extend through central NC from the SW, capped by deep
ridging up through the mid levels over the Deep South and into the
Southeast. The 00z GSO sounding is quite dry, with dry air upshear
at all levels, and highly stable in the lowest 3 km. Dewpoints are
in the mid teens to mid 20s in most spots, a bit higher than those
indicated by earlier guidance, although recent hi-res runs have
caught up to reality. Still expect the coldest temps over the
snowpack areas (where dewpoints are lowest). Lows 17-27 under clear
skies and with very light winds. -GIH

Earlier discussion from 200 pm: Winter Weather Advisory EXTENDED
through Noon Friday... Cold high pressure will remain the dominant
weather feature through tonight, as the region continues its first
attempt to thaw after the snowstorm. Mostly sunny skies and a light
to moderate westerly breeze has aided in some melting and
evaporation today on low albedo surfaces. However, temperatures have
ultimately struggled to surge above freezing, topping out mainly in
the low to mid thirties by the early afternoon hours.

Looking at latest observation trends, temperatures still seem to be
on track to fall short of most guidance this afternoon. Have held
steady with our previous forecast, keeping highs near to below 40
degrees. This still may end up being a smudge too high thanks to the
modified airmass at the surface.

Tonight, expect any improvement on the roadways to quickly revert,
with black ice formation likely across much of the areas roadways.
Temperatures are expected to plummet below freezing shortly after
nightfall, dipping into the upper teens across the northern and
western Piedmont Counties with lower twenties prevalent across the
Coastal Plains, where there is limited snow pack aiding in low
temperature potential. Thus, have extended the Winter Weather
Advisory across the majority of central North Carolina through
Friday afternoon to account for leftover snow covered roadways
Thursday evening along with the expected refreeze tonight.

&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 240 PM Thursday...

Underneath strong subsidence/rising heights aloft, the antecedent cP
airmass will continue to modify as the parent high over the Deep
South Friday morning will further moderate/weaken as it shifts east
over the SE US Friday-Friday night.

After a chilly start in the teens to lower 20s, high temperatures
Friday will rebound to near normal, ranging from mid to upper 40
north to lower 50s south. Another day of full sun combined with
these warmer temps will go a long way in helping to thaw/melt snow
off the roads and sidewalks. However, good radiational cooling
conditions Friday night and antecedent dry air/low dew points in the
teens and lower 20s will result in overnights once again down into
the 20s, which will cause black ice conditions again on sidewalks,
bridges and overpasses.


&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 240 PM EDT Thursday...

Southern stream shortwave trough traversing the Deep South will stay
south of the area, providing little more in the way of mid/upper
level cloudiness across the area Saturday night and into the day on
Sunday. Otherwise, afternoon temperatures will continue to moderate
through the 50s through the weekend, and even some lower 60s across
the southern counties. Depending on just how much cloud cover we see
Saturday night, Piedmont counties should see sub-freezing temps once
again, ranging from mid/upper 20s NW to lower/mid 30s SE.

A deepening storm system will track NE from the Central Plains late
Sunday thru the Upper Great Lakes and into Southern Canada by late
Monday and into the day on Tuesday, which is coincident with the
trailing cold frontal passage through the region. Models currently
indicate a band of showers will accompany the frontal passage, but
given how far removed central NC is from the better forcing, expect
precipitation amounts to be on the light side. Temps are expected to
remain above-normal for a majority of the upcoming work week, with
the warmest day over next 7 coming on Monday, just ahead of the
front. Highs in the upper 50s NW to mid 60s SE. These mild
temperatures will then be followed by a brief cool done behind the
cold front Wednesday and Thursday.

.AVIATION /00z FRIDAY THROUGH TUESDAY/...
As of 630 PM Thursday...

24 Hour TAF Period: VFR conditions through the TAF period. An
outside chance of some MVFR visibilities overnight, mainly in the
Triad but confidence in this is very low. Otherwise, westerly winds
will continue through the TAF period at 5-10 kts. Earlier gusts have
subsided and are not expected to return on Friday.

Long Term: VFR conditions through much of the long term with the
next system not expected to affect the area until Monday night into
Tuesday.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon EST Friday for NCZ007>011-021>028-
038>043-073>077-083-084-086-088-089.

&&

$$
SYNOPSIS...JJM/GIH
NEAR TERM...Hartfield/JJM
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...Ellis


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