River Flood Warning 10, NWS Raleigh, NC

Area Forecast Discussion
National Weather Service Raleigh NC
335 PM EST Sat Feb 23 2019

.SYNOPSIS...
High pressure will ridge southward and result in continued
Appalachian cold air damming across the middle Atlantic states
through Sunday morning. A cold front will cross the
region Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 PM Saturday...

Classical cold air damming regime firmly established across central
NC this afternoon and will persist into the evening. Mid afternoon
analysis depict the sfc ridge extending SW-NE across the Piedmont,
originating from a parent high (~1030mb) offshore of southern New
England. Aloft, sly flow in the 925-850mb layer continued to pull
warm moist air over the cool stable air at the surface. Decent speed
convergence noted at 850mb with 10kts at GSO and 40kts at
FFC/Atlanta per 12Z upper air analysis. This sly flow veers to a
swly direction later this afternoon and this evening. This action
should push the axis of persistent rainfall over the northern
Piedmont a bit farther north into southern VA by this evening, and
more so overnight. Thus, we should experience a relative lull in the
precip over the northern Piedmont/northern Coastal Plain, aside from
areas of drizzle.

Later this evening and into the overnight, warmer air immediately
above the surface will spread nwd. This warmer air above the cool
surface should promote the development of fog, some of which will be
dense. Model guidance has shifted gears a bit and now suggest the
Piedmont and Sandhills as the favorable region for dense fog, and
less so across the Coastal Plain. Still, expect at least pockets of
dense fog in vicinity of the I-95 corridor. Confidence not quite high
enough to issue a dense fog advisory, though one will likely be
needed later tonight. Evening temperatures will generally hold
steady near 40 north to the low-mid 40s south. After midnight,
temperatures will slowly rise across the far south as the warmer air
slowly makes inroads into our region. By daybreak, expect
temperatures to vary from around 40 NW Piedmont to the upper 40s-
lower 50s south.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 330 PM Saturday...

Sunday, a strong cold front associated with a deep low lifting
northeast across the Great Lakes, will sweep across central NC
Sunday morning, exiting our region by early afternoon. Convergence
along this feature will support a band of moderate-heavy showers
ahead of the front. While kinematics are impressive with bulk shear
around 60kts, the lower levels of the atmosphere appear too stable
to support deep convection, so not expecting any thunder with this
system at this time. Still, the heavier showers able to obtain some
depth will aid to translate some of the strong winds aloft to the
surface. Wind gusts 40-50 mph are a possibility with some of the
heavier showers.

Behind the sfc front, blustery west-northwest winds will usher a
drier air mass into the region. This drier air coupled with
subsidence behind the exiting frontal system should dissipate cloud
cover west-to-east immediately behind the front. The insolation and
the tight pressure gradient associated with the deep low to our NW
will cause west-northwest sfc winds 15-20 mph with frequent gusts 30-
40 mph. Sporadic wind gusts 45 to 50 mph not out of the question
across the northern Piedmont. A wind advisory may be needed in later
forecast issuance. Warmer air over the region Sunday, thanks to the
deep wly flow, will permit temperatures to soar into the 70s across
most of the Sandhills and Coastal Plain. Elsewhere, residual effects
of the CAD may temper the warm up a bit, yielding temperatures
generally in the mid-upper 60s.

Cooler air will overspread central NC Sunday night. Under clear
skies and steady west-NW wind, expect overnight temperatures in the
30s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 240 PM Saturday...

Monday through Tuesday night: Surface high pressure will build into
and through the region behind the front through Tuesday, with dry,
seasonable conditions expected through Tuesday night. The surface
high pushes offshore late Tuesday/Tuesday night. Generally expect
temperatures to moderate through this time frame with highs in the
mid 50s to mid 60s and lows in the 30s to around 40 degrees.

Wednesday through Friday: Forecast confidence for Wednesday onward
is quite low at this time. Though the medium-range models show
similar upper level patterns, the GFS is much wetter than the ECMWF.
In fact, the EC keeps most of the area dry through the end of the
work week. Expect a series of weak but amplifying shortwaves to pass
through the region. The surface high over the Atlantic will allow
southeasterly return flow to advect moisture into the region. This
supports increasing chances for rain, primarily across the south, on
Wednesday should the shortwaves provide enough forcing to generate
precipitation. Several weak surface lows will develop in response to
the shortwaves aloft, but where, when and how strong they will be is
still in question. The other difference between the GFS and ECMWF is
in regard to the surface boundary location with respect to central
NC. The EC keeps high pressure wedged into the area through Friday
while the GFS keeps central NC in the warm sector Wednesday and
Thursday, with the wedge building into the area on Friday. These
differences are the reason for the low confidence forecast but the
trend is for a possible return to wet weather by the end of the work
week.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
As of 105 PM Saturday...

Adverse aviation conditions expected to persist across central NC
through 12Z Sunday. Widespread IFR/low end MVFR ceilings will occur
this afternoon with widespread IFR/LIFR expected tonight. Rain will
occur through 22Z across the northern half of the forecast area,
affecting flight operations at KINT, KGSO, KRDU, and KRWI. In
vicinity of KFAY, just spotty light rain expected though
visibilities will be restricted in the MFR/IFR categories due to
fog.

After 05Z, just spotty light rain/drizzle expected across the region
though IFR/LIFR ceilings and MVFR/IFR visibilities will persist. A
strengthening low level jet will induce low level wind shear
conditions across the region with wind speeds 35-45kts expected at
1500 ft AGL. These wind shear conditions expected to abate after 14Z
Sunday as the stronger winds aloft begin to mix to the surface.

A strong cold front will cross central NC Sunday morning through
early afternoon. SW winds ahead of the front may gusts around 40kts
over portions of the Sandhills and Coastal Plain. Behind the front,
west-northwest winds expected to gusts 35-40kts. Along the front,
expect a band of heavy showers, producing visibilities at or below 2
miles and wind gusts around 40kts.

Strong subsidence coupled with a downslope component to the low
level wind will aid to dissipate the cloud coverage, with mostly
clear/partly cloudy skies expected areawide by early-mid afternoon.

VFR parameters expected Sunday afternoon through mid week. There is
potential for sub VFR parameters due to ceilings toward the later
half of the work week.

&&

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

&&

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

Hazardous Weather Outlook
National Weather Service Raleigh NC
750 PM EST Sat Feb 23 2019

NCZ009>011-026>028-042-043-073>078-083>086-088-089-250100-
Vance-Warren-Halifax-Franklin-Nash-Edgecombe-Johnston-Wilson-Stanly-
Montgomery-Moore-Lee-Harnett-Wayne-Anson-Richmond-Scotland-Hoke-
Cumberland-Sampson-
750 PM EST Sat Feb 23 2019

This Hazardous Weather Outlook is for central North Carolina.

.DAY ONE...Tonight.

Areas of fog tonight will become dense at times through Sunday
morning.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Areas of dense fog will disperse through mid to late morning Sunday. Windy
conditions will follow, with wind gusts between 35 and 40 mph likely
through early Sunday evening. Locally stronger wind gusts between 40
and 50 mph may occur in a broken line of fast-moving showers that
will cross the area from midday to mid afternoon Sunday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

NCZ007-008-021>025-038>041-250100-
Person-Granville-Forsyth-Guilford-Alamance-Orange-Durham-Davidson-
Randolph-Chatham-Wake-
750 PM EST Sat Feb 23 2019

...WIND ADVISORY IN EFFECT FROM NOON SUNDAY TO MIDNIGHT EST SUNDAY
NIGHT...

This Hazardous Weather Outlook is for central North Carolina.

.DAY ONE...Tonight.

Areas of fog tonight will become dense at times through Sunday
morning.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Areas of dense fog will disperse through mid to late morning Sunday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Wind Advisory.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.