Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 182358
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
655 PM EST Wed Jan 18 2017

.SYNOPSIS...
High pressure will build over the region tonight and Thursday. A
wave of low pressure is expected to move in from the southwest
Thursday night and Friday. This will be followed by a strong
storm system for late in the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Wednesday...

Sunny and warm conditions will prevail this afternoon with delayed
CAA behind the front. The cold air advection will gradually
win out this evening allowing from cooling from the readings in the
60s/70s this afternoon. Lows tonight will be driven by a combination
of cold advection and radiational cooling, in the 40-45 range,
with clear skies.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 300 PM Wednesday...

An upper level ridge and associated surface high building into the
region from the west tonight will be situated directly over the
Carolinas/Mid-Atlantic on Thursday. As such, expect a pleasant/
sunny day with above normal highs in the upper 50s to lower 60s.
Widespread precipitation is expected to develop upstream over the
Deep South/TN Valley during the day Thursday as a potent upper level
low lifts NE through the Central Plains toward the Upper Great
Lakes. As a result, clear skies will quickly give way to increasing
cloud cover by sunset as mid/upper level ceilings advect downstream
of the mountains. Southerly return flow will quickly strengthen over
western portions of the Carolinas as shortwave energy rounding the
base of the upper low in the Central Plains Thu afternoon ejects
E/NE through the Deep South into the Carolinas Thursday night.
Expect a further increase in cloud cover overnight as mid/upper
level ceilings are complimented by low ceilings assoc/w
strengthening warm advection. In fact, light rain will be possible
by sunrise (09-12Z) Friday morning in the Western Piedmont as
moisture deepens via warm advection in the presence of DPVA (assoc/w
the aforementioned shortwave energy). Low temps Thu night may be met
by Thu evening, particularly in the west, as a result of warm
advection and thickening cloud cover. Expect temps ranging from the
low/mid 40s E/NE to upper 40s W/SW. -Vincent

&&

.LONG TERM /Friday through Wednesday/...
As of 350 PM Wednesday...

The first wave of low pressure in the strengthening jet aloft
is forecast to dampen out Thursday night and Friday as it tracks
NE across the TN Valley to the mid-Atlantic coast. Likely POP
for rain expected, especially in the west and north for a period
late Thursday night and early Friday, with lesser chance POP in the
SE. QPF with the weakening system should be 0.25 or less in the NW,
with 0.10 or less SE. Skies should return to variably cloudy
Friday afternoon and evening between systems. Mild temperatures
will continue with lows in the 40s. Highs Friday in the 60s, except
upper 50s NW.

Friday night through Saturday...

The next system is forecast to approach from the SW late Friday
night and Saturday. The Gulf of Mexico is forecast to be wide
open as the flow between the high pressure off the SE coast and
the deepening upper storm out west increases from the south. A
leading warm front is expected to lift from the Gulf Coast states
northward into our region Saturday. Strong WAA and overrunning
will result in a large shield of rain that is expected to over-
spread much of our region late Friday night and Saturday. The
highest POP and QPF for now will be across the west and south
portions of the Piedmont Friday night, gradually spreading north
Saturday. Mild temperatures will become warmer in the SE later
Saturday as the warm front tries to lift into the region. It
appears it will have some In-Situ Damming resistance over
the Piedmont; however, there should be rather minimal damming
this time due to the lack of a strong enough high pressure
and/or dry air for evaporative cooling to support anything more
than some weak In-Situ Damming in the Piedmont Saturday.
There should still be some highs holding in the 50s NW, ranging
to 60s SE Saturday with rain likely.

Saturday night through Monday...

Heavy rain and the chance of thunderstorms the main hazards
for this period. Severe storms possible in the warm sector
by late Sunday.

The very potent mid/upper level system is expected to have the
potential to produce fairly wild weather conditions (warm and
stormy) for our region (for January standards). The main storm is
expected to strengthen as it lifts out of the FL Panhandle Sunday
toward our region Sunday night. A stronger warm front is forecast to
lift into our southeastern counties Sunday afternoon/night as the
surface low deepens. Widespread rain, some heavy is expected
Saturday night and Sunday. Temperatures should hold in the 50s
Saturday night, then reach into the 60s Sunday. The readings may
hold or come up even more Sunday night depending on the warm front
timing.

The main low pressure track is still uncertain and this will
play a role in our severe storms threat late Sunday and Sunday
night/Monday morning. Widespread rain should hold down the
instability. However, dew points are forecast to surge into the 60s
in the warm sector Sunday night. If this warm sector does surge into
the region (or a portion of the region), the likelihood of severe
weather will increase dramatically. There is still much uncertainty
with these details and they will be hashed out in later model runs.
For now, we will continue to carry periods of rain Sunday and Sunday
night. There will be a chance of thunderstorms, and severe weather
is possible. The timing would be late Sunday afternoon into Monday
morning (with the triple point low and cold frontal passage expected
Monday morning) ending the storminess.

We will broad brush the heavy rain and thunderstorm potential hazards
in the entire region - until the details become more certain in
later forecasts.

Behind the front Monday, we will keep slight chance POP Monday,
with partly sunny skies returning. Very mild to warm air will
lead to some 70s for highs as CAA will be blocked by the Appalachians
(negatively tilted storm system lifts north of the region).

True CAA will likely lag the front until Monday night and Tuesday.
Even so, lows will be in the 40s. Highs are expected in the 60s
Tuesday (Pacific origin air mass).

A turn to colder weather is anticipated by recent model trends by
late next week.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 655 PM Wednesday...

VFR conditions expected to persist across central NC through
Thursday evening. Surface winds will be less than 10 kts through
Thursday evening.

Aviation conditions will deteriorate by Friday morning as
circulation around an area of high pressure to our east and an area
of low pressure to our west pumps moisture into central NC. Expect
widespread MVFR ceilings to overspread the area Friday morning along
with areas of rain. The sub VFR ceilings along with periods of
showers will occur Friday night through Monday. In addition, a few
thunderstorms may occur Sunday afternoon and Sunday night.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Badgett/Vincent
NEAR TERM...Badgett/Vincent
SHORT TERM...Vincent
LONG TERM...Badgett
AVIATION...WSS



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