Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 180007
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
707 PM EST Sun Feb 17 2019

.SYNOPSIS...
Cold air damming high pressure will extend across central NC through
early Monday, while Miller-B low pressure will track west of the
Appalachians and along the middle Atlantic coast, respectively. A
trailing cold front will cross central NC Monday afternoon. Cold
high pressure will then build from the northern Plains to the
Northeast, while extending southward across the middle Atlantic and
Carolinas, through the middle of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 200 PM Sunday...

Embedded in the energetic SW flow aloft, the next batch of shortwave
impulses embedded will lift NE along the northern periphery of the
subtropical ridge in place across the SE US. With the bulk of DPVA
skirting just north/northwest of the area, the steadier-more
persistent rain will remain across the far northern Piedmont
and coastal plain counties. Meanwhile, across central and southern
portions of the forecast area, overrunning lift atop a shallow but
strong CAD airmass in place across central NC will generate
intermittent light rain and/or drizzle through the late
afternoon/early evening.

A SW to NE oriented band of deep frontogenesis, maximized over the
heart of the CAD airmass across the NC Piedmont; and on the cool
side of a warm front lifting into the eastern Sandhills and southern
coastal plain counties will overspread the area this evening and
overnight. Very similar to what we saw this past Friday
night/Saturday morning, expect precipitation to fill in during that
time with an area/band of moderate rain setting up across the
Piedmont counties with rainfall amounts of 0.50 to 1.0".

Expect nearly steady temps till around midnight, followed by
rising temps and the high likelihood of a very sharp temp gradient
INVOF the eastern Sandhills and southern coastal plain counties
overnight as a warm/wedge front lifts north into SE NC.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
As of 250 PM Sunday...

Lead cold front and associated band of rain/showers bisecting central
NC Monday morning will progress east and will exit the coastal
plain counties during the late morning hours. NWLY downslope flow
will lead to west to east clearing through the afternoon. The
compressional warming and afternoon sunshine will initially help to
offset the weak CAA. Highs Monday ranging from upper 50s NW to
mid 60s SE with some periodic gust of 20 to 25 mph.

A secondary cold front; the leading edge of a ~1040 mb surface
high building into the area from the upper MS Valley will move
through the area Monday evening/night. CAA will drive
temps overnight. Lows ranging from near 30 north to mid/upper 30s
south.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 325 PM Sunday...

An already active weather pattern looks to persist throughout the
long term period as a series of fronts, weather systems, and CAD
events jockey for position over the Carolinas. Temperatures are
expected to alternate around normal (50s/30s) throughout the period
with high bust potential thanks to uncertainty into CAD erosion
efficiency. Clouds and POPs will be plentiful through the entire
period, with relief likely not arriving until next Sun/Mon. QPF
values range from several inches (along the VA/NC border) to around
an inch across the SE on average.

Tuesday through Wednesday: Early Tuesday, high pressure to our north
will slide east of the Appalachians sending colder and more dense
air southward along the lee side of the ridges. To our southwest, a
southern stream surface low will begin to organize and strengthen
over the MS river delta before progressing northeast through the TN
Plateau through midweek. Compared to previous runs, a bit stronger
of a high to our north should help slow the precipitation arrival
times by a factor of 6 hours or so, with highest POPs arriving
across the southwestern zones a little after sunset Tuesday evening.
With the CAD event well underway, boundary layer moisture continuing
to increase overnight, and models trending a degree or so cooler
compared to previous runs, have introduced a rain/freezing rain
mixture across the northern/western Piedmont zones early Wednesday
morning. Still plenty of uncertainty here as wet bulb temps should
remain at freezing at worse, however, any wintry precip that does
fall should have little to no impact at the surface. Precipitation
should transition to all rain by mid morning, likely to persist
through most of the day Wednesday and into Wednesday night as a weak
surface wave progresses northeast along the I-95 corridor,
attempting to erode the CAD a bit from the SW.

Remainder of the period: A cold front approaches the area on
Thursday before stalling across the area into the weekend. This will
allow numerous weather features to track from SW to NE across
central NC, introducing rather persistent POPs. Model QPF through
this period continues to increase, with 2 - 3 inch amounts plausible
across the northern Piedmont with lesser amounts likely as you
progress south through central NC. The persistent rainy pattern
looks to come to an end on Sunday/Sunday evening as a cold front
slides across the area allowing high pressure to take over.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 700 PM Sunday...

Widespread LIFR-IFR conditions are expected tonight, with periods of
rain and drizzle increasing in intensity and becoming moderate to
heavy at times near and just northwest of RDU and RWI, most notably
at INT/GSO. Additionally, a 40 to 50 kt, swly low level jet will
develop across east-central NC and produce a period of LLWS at KRDU,
KFAY, and KRWI between 06-12z Monday.

Outlook: Developing wnwly low level flow will cause early morning
rain and widespread LIFR-IFR conditions to scour, lift, and scatter
to VFR through midday Monday. A wavy frontal zone will move into and
become quasi-stationary over the Carolinas Tue night through Fri,
when a prolonged period of rain, sub-VFR conditions, and episodes of
low level wind shear, are expected. The rain may begin as a period
of freezing rain at INT and GSO between 09Z-18Z Wed.

&&

.EQUIPMENT...

After electronic technicians performed a hard restart earlier today,
KRAX is still suffering from poor data quality issues in the 0.5 and
0.9 degree elevation slices. This will impact several radar
products, including rainfall estimates. Users should use the data
with caution. We appreciate your patience as our engineers and
technicians solve the problem. We will provide updates when they are
received.

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...JJM
AVIATION...MWS
EQUIPMENT...RAH


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