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000 
FXUS62 KRAH 171943
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
243 PM EST Wed Jan 17 2018

.SYNOPSIS...
In the wake of a strong upper level disturbance and associated 
arctic cold front, a moderating arctic high pressure over the 
Southern US will gradually build east into the area through Thursday 
night. A warm-up will begin Friday and extend into the weekend. 

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 243 PM Wednesday...

...Winter Storm Warning continues for the western Piedmont counties-
west of US Highway 1 through 900 PM tonight...
...East of US Highway 1: Winter Weather Warning and Advisory will be 
extending in time to 1 am Thursday...

F-gen band centered over the heart of central NC will translate 
slowly east across the remainder of the NC Piedmont this afternoon 
and then into the NC Sandhills and Coastal Plain through the 
evening, exiting the coastal plain counties by around 06z. 
Meanwhile, the back-edge of deeper moisture and measurable snow can 
be seen on GOES 16 satellite approaching the far western/Triad 
counties. 

Thus far, we've seen a broad wet snow swath of 4 to 6 inches across 
the western and northern Piedmont counties, with localized higher 
amounts of 7 inches maximized in an axis extending along Randolph, 
Alamance, Orange and Person Counties, where the CSI mesoscale 
banding feature set-up and went on to produce 1.0 to 1.5" hourly 
snow rates and snow ratios on the scale of 18-20:1(outside of this 
band ratios where more like 8-12:1(climo)) 

As this precip band shifts east through the course of the evening, 
we do not expect it to be as efficient snow producer as it was over 
the Piedmont counties, due to much warmer surface temps in the mid 
30s to lower 40s, with a good bit of precip falling as rain before 
both wet-bulb cooling and lost of daytime heating allows for a 
change-over to snow.  

Through the remainder of the afternoon/evening expect additional 
snowfall amounts of 2 to 4 inches from the Triangle north and 
northeast, tapering off to 1 to 2 inches across the Sandhills and 
southern Coastal Plain, and potentially another half inch to an inch 
over the Triad.  

Due to the slower timing, had to extend the Winter storm warning and 
advisory across the eastern half of the forecast area through 06z. 

CAA overnight, along with fresh snow cover and clearing skies will 
help   temperatures fall into the teens, with wind chill values in 
the single digits. 

Given these frigid temperatures, any snow or slush on roads and 
bridges/overpasses will freeze, making for treacherous road 
conditions Thursday morning. 


&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... 
As of 120 PM Wednesday...

H5 west to northwest flow and surface ridging will result in mainly 
clear weather.  Temperatures will start very cold with highs on 
Thursday in the upper 30s to lower 40s. After lows in the teens to 
lower 20s Thursday night, temperatures will moderate to near 
seasonal normals on Friday.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 120 PM Wednesday...

The warmer weather will continue into the weekend as the upper level 
pattern transitions to more ridging in the SE and a trough in the 
western US. 

A storm system will move northeastward from the central plains 
Sunday to the western Great Lakes on Monday.  This system's 
attendant cold front will cross our region Monday night with a 
chance of showers. Temperatures in the 50s Saturday afternoon will 
climb to around 60 on Sunday, and 60 to 65 on Monday. After the cold 
front passage, temperatures Tuesday and Wednesday will fall back 
into the 50s. 

&&

.AVIATION /18z WEDNESDAY THROUGH MONDAY/... 
As of 1247 PM Wednesday...

24-Hour TAF period: The IFR/LIFR conditions will continue as the 
snow continues to fall. KRWI is just now starting to come down 
(currently MVFR) and KFAY is still VFR but should start a downward 
trend as the precipitation moves in. With the snow, visbys are 1/4 
to 3/4 SM and cigs range from 3-8 KFT. Winds in the 8-12 kt range, 
with increasing gustiness in the east will continue into tonight, 
even after the snow ends. Snow should taper off from west to east 
between 00Z and 12Z Thursday, accompanied by a return to VFR 
conditions.

Looking ahead: VFR conditions will persist through Saturday. 
Forecast soundings hint at some low-level moisture Saturday night, 
otherwise the next chance for adverse aviation conditions will occur 
Monday night into Tuesday. 

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 AM EST Thursday for NCZ078-089.
Winter Storm Warning until 9 PM EST this evening for NCZ007-021>025-
038>040-073>076-083-084.
Winter Storm Warning until 1 AM EST Thursday for NCZ008>011-026>028-
041>043-077-085-086-088.

&&

$$ 
SYNOPSIS...CBL 

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