Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 241756
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
155 PM EDT Mon Apr 24 2017

.SYNOPSIS...
A strong and deep low pressure system will slowly cross the region
through Tuesday, producing wet and unsettled weather. Behind this
low, a ridge of high pressure will extend into the region for mid to
late week.

&&

.NEAR TERM /Today and Tonight/...
As of 910 AM Monday...

Forecast of steady moderate to heavy rain covering central NC
remains valid. Deep mid-upper low pressure wobbling into west
central GA with a negative tilt will continue to draw deep moisture
into the Carolinas, with PW values expected to near 1.5", which
would place values near record highs, according to PW climatology.
Low level moisture transport and convergence are expected to remain
focused over our area, from Laurinburg, Lumberton and Fayetteville
up through SW portions of the Triangle region in particular, and
this is where the primary bands of significant rainfall should line
up. The surge of moisture and precip intensity should increase
through the day as 850 mb onshore-directed flow strengthens to 35 to
45 kts, pumping greater amounts of Atlantic moisture into the area,
north of a shortwave riding from the Bahamas northward off the SE
coast through the day. Have raised storm total rainfall to near 5
inches in the SE (Laurinburg/Raeford/Fayetteville) to 3-4 inches in
the Triad, 2-3 inches in the Triangle, and near 2 inches in the far
NE. Street flooding remains likely, along with rapid creek rises
especially in the Triangle to the south and west. No changes to the
flood watch at this time. It will remain chilly today with
widespread rain and thick clouds, with highs from the lower 50s NW
to the mid-upper 60s in the far eastern Coastal Plain. -GIH

Earlier discussion from 345 AM... Overview: An upper level low
centered over northern AL at 06Z will track SE/ESE to the Southeast
coast this afternoon and evening. An attendant surface low will
track eastward to the GA/SC coast this evening, then lift slowly
northeast along the North Carolina coast late tonight.

Precipitation: With the upper level low /attendant surface low/
expected to track E/SE across GA/SC and an established CAD wedge in
place over central NC, the narrow warm sector in southern GA/SC is
expected to shift N/E through eastern SC to coastal NC this aft/eve.
As such, convection should remain elevated in nature over central
NC. A N-S oriented band of elevated convection over western NC will
shift eastward into central NC today and assume a NW-SE orientation
this afternoon as the upper level low progresses SE from northern AL
to eastern GA and low-level flow strengthens/backs to the Southeast
off the Atlantic. In close vicinity to the warm front (southern
Cumberland and Sampson counties), a narrow window for sfc-based
convection (and an attendant severe weather potential) cannot be
ruled out this afternoon. Otherwise, any threat for severe weather
should remain along/east of Hwy 17 near the Carolina coast. The
primary band of elevated convection will assume a W-E orientation
tonight as the upper low passes to the south and low-level flow over
central/eastern NC backs to an easterly direction. The heaviest rain
will fall where the band of elevated convection pivots as it
transitions from a N-S orientation to a W-E orientation this
afternoon into tonight.

Temperatures: With regard to temperatures, a pronounced CAD wedge is
expected to remain in place across the N/NW Piedmont through
tonight, with little variation in temperature (upper 40s to lower
50s). From the Triangle south and east, the modified CAD wedge
should vary little through the day (except perhaps in the far SE
Coastal Plain for a few hours this afternoon), though temperatures
will likely rise from east to west overnight as surface winds
strengthen from the east and advect a higher theta-e airmass inland
from the coast. -Vincent

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 330 AM Monday...

The vertically stacked/mature low pressure system will track slowly
north across eastern NC Tuesday and Tuesday night and then off the
Delmarva coast on Wednesday.

With the mid-level dry slot encompassing the area Tuesday morning,
there could be a lull/minimum in precip/pops across central NC to
start the day. However, diurnal heating and resultant weak
destabilization(at least across the eastern and possibly central
zones) as the wrap-around moisture band pivots NE through the area,
is expected to lead to convective re-development Tuesday afternoon
and evening. The threat for severe storms will be muted by the lack
of greater instability but given the presence of an occluded front
draped somewhere across eastern/east-central NC, cannot rule out an
isolated severe threat. Additionally, with the potential for slow-
moving/training convection with the wrap-around band, isolated
flooding, especially in low-lying or poor drainage areas will be
possible.

Highs Tuesday afternoon will be challenging, complicated by multiple
boundaries draped across the area. Expect one sharp temperature
gradient invof of where the aforementioned occluded front sets up
across eastern NC, with another tight temp gradient along the
lingering CAD airmass across the western Piedmont. Highs ranging
from upper 50s NW to mid/upper 70s east.

Rain chances will slowly taper off from SW to NE Tuesday night,
finally coming to an end across the NE zones early Wednesday morning
as the mature cyclone lifts away from the area. Lows Tuesday night
in the mid to upper 50s Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 330 AM EDT Monday...

In the wake of the low lifting up the Mid-Atlantic coast, low-level
swly flow and short wave ridging aloft will mark the return of
sunshine and warming temperatures. Highs in the upper 70s to lower
80s Wednesday, warming into the lower and mid 80s by Thursday.

On the southern periphery of dampening short wave energy lifting
through the MS and Ohio Valleys NE into the Great Lakes, we could
see isolated/slight chance of showers and storms Thursday night and
Friday. Otherwise, it will remain mostly dry with the main weather
headlines being the hot temperatures associated with the dominate
subtropical ridge building across the SE US.
Highs Saturday and Sunday in the upper 80s to lower 90s.

&&

.AVIATION /18Z Monday through Saturday/...
As of 155 PM Monday...

High confidence in poor aviation conditions through at least 06z
tonight. Thick IFR and occasionally LIFR based clouds will persist
over central NC as a deep and strong low pressure system slowly
crosses the area through Tue, exiting to our northeast Tue night.
Periods of rain through 06z will affect all sites with occasional
MVFR to IFR vsbys, along with the mainly IFR cigs. Cigs will slowly
lift Tue morning to MVFR with decreasing vertical extent as drier
air just off the ground arrives from the S. The rain will decrease
in coverage and intensity later tonight, although scattered showers
will persist after sunrise Tue as the core of the upper low passes
overhead. Surface winds will be mainly from the NE at 7-12 kts
through tonight, occasionally gusting to 15-20 kts during the
evening and overnight hours, especially at GSO/RDU/RWI as an
easterly low level jet at 1000-2000 ft AGL extends into the area.
This low level jet may lead to a risk of low level wind shear at
INT/GSO/RDU/RWI from late evening into the overnight hours. Surface
winds will then decrease late tonight (after 09z) and become more
from the N or NW Tue.

Looking beyond 18z Tue, cigs should remain MVFR through Tue night,
with infrequent MVFR vsbys in scattered showers, although cigs may
drop back to IFR through Tue night especially at INT/GSO as a cool
stable air mass persists there. After the low shift to our NE Tue
night, high pressure ridging will take over, and we`ll see cigs rise
to MVFR then VFR through Wed morning. VFR conditions will then
dominate through Sat. -GIH

&&

.HYDROLOGY...
As of 330 AM Monday...

...Flood Watch remains in effect through 12Z Tuesday...

Widespread heavy rain is expected to develop over central NC today
into tonight. Storm total rainfall amounts of 3-5" are expected,
with locally heavier amounts possible where the primary band of
elevated convection pivots /persists the longest/. Flooding of local
creeks and streams can be expected. Main stem rivers will experience
significant rises in water levels this afternoon into tonight,
particularly the Yadkin, Haw, Neuse, Tar, Roanoke, and Cape Fear.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Tuesday morning for NCZ007>011-021>028-038>043-
073>078-083>086-088-089.

&&

$$

SYNOPSIS...Hartfield
NEAR TERM...Hartfield/Vincent
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...Hartfield
HYDROLOGY...Vincent/RAH


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