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000
FXUS62 KRAH 221144
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
645 AM EST Tue Jan 22 2019

.SYNOPSIS...
Arctic high pressure overhead this morning will drift offshore later
today. This will allow a slightly warmer air mass to overspread the
region. An approaching storm system will bring unsettled weather to
central NC Wednesday into Thursday. Drier and colder weather
anticipated for the end of the week.


&&

.NEAR TERM /TODAY/...
As of 325 AM Tuesday...

Arctic high pressure will extend overhead today, maintaining a cold
and dry air mass over central NC. The abnormally dry air is noted in
the sfc dewpoints which vary early this morning from the single
digits across the north, and between 10 and 15 above across the
south. Aside from patchy cirrus floating overhead, skies will be
mostly clear. With the sfc high in our proximity, expect winds to be
lighter compared to the past few days, mainly light from the east-
northeast.

With many locations starting out in the middle teens, a diurnal
temperature recovery of 20-25 degrees will yield afternoon high
temperatures in the upper 30s to lower 40s.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
As of 325 AM Tuesday...

...Light ice accrual possible overnight across the NW Piedmont...

The center of the Arctic high will drift offshore tonight, though a
sfc extension of the high will extend back into central NC. A return
sely flow at the sfc will aid in modest moisture advection into
central NC. Sfc dewpoints in the teens at sunset will slowly recover
into the 20s, and possibly into the lower 30s across the Sandhills
and southern Coastal Plain.

A few thousand feet above the surface, sly flow will strengthen in
response to the area of high pressure offshore and a s/w crossing
the southern Plains. this will result in increasing isentropic
upglide, especially after 06Z. Moistening in the 925mb-700mb layer
coupled with isentropic upglide/lift should generate patchy light
precip overnight in vicinity of the Yadkin/Pee Dee River Valley.
With sfc dewpoints in the 20s, and dry bulb temps near or slightly
below freezing across the NW Piedmont (and initially across the
southern Piedmont), expect spotty light freezing rain or freezing
drizzle to occur. This freezing precip, though light, may persistent
long enough across portions of the NW Piedmont to result in a trace
of ice on elevated surfaces such as bridges/overpasses. This
probability appears highest in the 09Z (4AM) to 14Z (9 AM) time
frame. Plan to issue a winter weather advisory for the NW Piedmont
counties of Guilford, Forsyth and Davidson from midnight to 10 AM.
There is the potential that the advisory may need to be expanded a
little farther to the south and east, if it appears that precip will
start sooner or is more extensive.  While not anticipating
widespread travel problems, the random nature of the precip will
play havoc with early morning commuters as slick spots expected to
be random, catching motorists offguard.

As the s/w progresses east into the lower MS Valley Wednesday,
strengthening sly flow over the SE U.S. will induce a coastal
trough/warm front to advance northwestward into central NC. This
feature will create a wide disparity in temperatures as portions of
the Sandhills and Coastal Plain will warm into the low-mid 60s.
Meanwhile patchy light precip across the NW Piedmont will likely
initiate an in-situ or hybrid cold air damming, keeping temperatures
in this region in the 30s for most of the morning, recovering into
the mid-upper 40s by late afternoon.

Due to the random nature of the expected rain coverage, will have
PoPs no higher than chance or low end likely. Expected precip
amounts will be light, totaling no more than a few hundredths
throughout the day.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY NIGHT/...
As of 235 AM Tuesday...

Wednesday Night and Thursday: The lingering wedge airmass will
likely be eroded by midnight Thursday and temperatures are expected
to increase through the overnight hours as the front approaches from
the west. As such, the "morning" low will likely occur around
midnight, mid 40s NW to around 60 degrees SE. The deep southwesterly
flow will pump the warm moist air into the region, with increasing
temperatures and precipitation chances from west to east through
Thursday morning. Despite the precipitation, temperatures will top
out around 50 degrees NW to mid 60s SE. The parent surface low is
expected to move through the Great Lakes and into Canada before the
front pushes into the region. However, a secondary low, strengthened
by a developing shortwave aloft, will develop along the front over
the southern Appalachians/northern Gulf Coast. The surface low will
lift northeast along the mountains and eastward through the
Carolinas/Virginia through Thursday morning. The cold front will
likely move through central NC Thursday aft/eve, resulting in both
an end to precipitation and decreasing temperatures behind it. As a
result, temperatures may actually fall through the evening. Largely
expect the front to be through the area by midnight Friday.
Overnight lows in the upper 20s NW to low 30s SE.

Friday through Monday night: Expect a return of cooler, drier
weather in the wake of the cold front, with highs in the 40s on
Friday and Saturday. Lows Friday night in the generally in the mid
20s, increasing slightly for Saturday night, upper 20s to around 30
degrees. Forecast confidence decreases significantly beyond Sunday.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
As of 645 AM Tuesday...

There is a high probability that VFR parameters will occur across
central NC through 06Z Wednesday. Sfc winds will slowly veer from a
northeasterly direction this morning to an east-southeast direction
this evening, then sly by early Wednesday. A developing low level
jet will bring a threat for low level wind shear conditions to the
region early Wednesday morning.

Ceilings are expected to lower after 06Z Wednesday with IFR/LIFR
ceilings probable across the Piedmont and Sandhills prior to 12Z
Wed. Spotty light precip expected to develop and with sfc
temperatures below freezing, patchy light freezing rain/freezing
drizzle possible in vicinity of the Triad terminals between 08Z-14Z.

Rain is expected to expand in coverage and intensity Wednesday night
into Thursday morning as a frontal system approaches and crosses the
region. Improving weather conditions expected late Thursday with VFR
parameters expected Thursday night into Saturday.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to 10 AM EST
Wednesday for NCZ021-022-038.

&&

$$
SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...KC
AVIATION...WSS