Area Forecast Discussion
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FXUS62 KRAH 251817
Area Forecast Discussion
National Weather Service Raleigh NC
215 PM EDT Tue Apr 25 2017
Low pressure will move slowly northeastward over eastern North
Carolina this afternoon, and then push off the Mid Atlantic coast
tonight. High pressure will extend from the Atlantic westward into
the Southeast states Wednesday through Thursday.
.NEAR TERM /through tonight/...
As of 215 PM Tuesday...
Lingering high water on many area roads and in creeks necessitated
an areal flood warning through this evening for a large chunk of
central NC. However, the heavy rain threat is done, and water should
continue to recede on roads and in creeks. Flooding will
persist, though, on many mainstem rivers (see hydro section below).
The mid level low, stacked nearly atop the surface low, will move to
the NE over coastal areas of NC through early evening, before
passing off the Delmarva coast tonight. Confluent cyclonic low level
flow acting on residual moisture favors a lingering threat of
scattered showers on the W/SW side of the low into the evening as it
pulls away slowly. A storm or two also remains possible over the far
NE CWA, where observed mid level lapse rates are around 6-6.5 C/km,
low level lapse rates are nearing 7 C/km, and MUCAPE is 500-1000
J/kg, thanks to some sunshine. Vorticity lobes pivoting around the
low may also contribute to ascent. Will hold onto areas of chance
pops into early evening. Drier air eventually building in from the
WSW in the wake of the low overnight will lead to a clearing trend
from SW to NE, with NE sections the last to see the benefits of
downslope flow and falling dewpoints. Expect lows tonight in the
lower 50s west ranging to around 60 in the far E. -GIH
.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 400 AM Tuesday...
In the wake of the low pressure lifting up the Mid-Atlantic coast,
low-level southerly winds and short wave ridging aloft will mark the
return of sunshine and warming temperatures. Highs ranging from
upper 70s NE to lower 80s south. Lows Wednesday night in the upper
50s to lower 60s.
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 400 AM EDT Tuesday...
Lead short wave trough will lift from the Mid MS/TN Valley NE into
the Great Lakes on Thulate rsday with trailing sfc cold front
expected to stall out west/northwest of the mtns.
Associated convection is expected to be ongoing Thursday morning
across Tn, Al, and Ga Thursday morning. However with the better
trough dynamics/forcing lifting off well to the north Thursday
afternoon and evening, the showers and storms should exhibit a
steady decline/weakening trend as they cross the mtns Thursday
afternoon/evening. Will leave isolated chances across the far
western zones Thursday afternoon, otherwise it should remain dry
with temperatures steadily rising in the SWLY WAA regime. Highs in
the lower to mid 80s west to upper 80s central and eastern areas.
The synoptic pattern will favor near record heat by Saturday, owing
to a 590+dm H5 ridge, Bermuda highs and H7 anticyclone over SC.
Thickness are progged at 1410m Saturday, 50m above normal and
indicative of upper 80s to lower 90s. The main question is how
quickly another shortwave ejecting out of the Central/Southern
Plains, this one potentially stronger, will cause the ridge to
retreat offshore a bit. Heights are forecast to lower slightly on
Sunday, more so across western NC. Highs in the mid 80s west to near
90 central and eastern area.
A cold front will bring the next chance for rain/storms to the area
on Monday with cooler temps following on Tuesday.
.AVIATION /18Z Tuesday through Sunday/...
As of 135 PM Tuesday...
MVFR cigs and patchy showers (yielding brief MVFR vsbys) will
dominate central NC terminals this afternoon, followed by gradual
SW-to-NE improvement to VFR areawide late tonight.
A strong and slow moving upper level low will track toward the NE
over eastern NC for the rest of today, before shifting to our NE and
off the Delmarva coast tonight. Low level moisture continues to
rotate around this low this afternoon, with MVFR cigs over all but
RWI, where dry air wrapping around the low has progressed inland
from the coast, leading to VFR cigs there, although a period of MVFR
cigs remains possible as the moisture over the Piedmont shifts to
the NE behind the departing low. Cigs should lift to VFR by 00z at
INT/GSO as surface winds become light from the NW, although the
moisture circulating around the exiting low will keep a threat of
MVFR to IFR cigs at RDU/FAY/RWI into the overnight hours, with RWI
potentially not reaching VFR until 10-12z Wed morning. VFR
conditions will prevail after 12z Wed areawide as a weak high
pressure ridge noses in from the Atlantic. Surface winds will be
mostly light and becoming W or NW through tonight.
Looking beyond 18z Wed, shallow fog is possible early Thu morning
within a light moist flow from the SW, followed by a better chance
of MVFR/IFR fog/stratus each late-night through morning, Fri through
Sun. A few storms with sub-VFR conditions are possible Sat and Sun
As of 140 PM Tuesday...
The flood watch expired this morning, with no threat for additional
heavy rain. However, ongoing high water on area roads and in
numerous creeks has prompted an areal flood warning for much of
central NC through this evening. In addition, river flood warnings
are in effect for several mainstem rivers across the area. See
water.weather.gov/ahps2/index.php?wfo=rah for additional information.