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fxus62 krah 271125 

Area forecast discussion
National Weather Service Raleigh NC
725 am EDT Mon Mar 27 2017

a warm moist southerly flow will hold over the area through
Wednesday. An upper level trough will cross the region tonight
through Tuesday, bringing unsettled weather. A backdoor cold front
will drop southward through the area late Wednesday through
Wednesday night, followed by cooler high pressure pushing in from
the north on Thursday. Another storm system will cross the area
Thursday night through Friday night.


Near term /through tonight/...
as of 330 am Monday...

The western edge of surface high pressure will remain over central
NC today as a few shortwave disturbances track across the area in
between two larger systems, one moving through New England and the
second back across Arkansas and southern Missouri. These shortwave
disturbances could supply the area with periodic showers and
potentially thunderstorms later in the day as forecast soundings
show tall skinny cape resulting in 700-1000 j/kg across the
northwest Piedmont where forcing will be best, and lesser amounts to
the south and east. With little cape in the hail growth zone,
damaging winds would be the most likely threat from storms but not
expecting storms to be severe at this time. Storm Prediction Center outlook has the area
in general thunder only.

With that in mind attention turns to temperatures which will once
again be warm under southerly return flow as highs expected to soar
into the upper 70s to near 80 degrees. Without a frontal passage,
lows on Tuesday morning only expected to drop into the upper 50s.
Some gusts are possible up to 15 knots or so this afternoon.


Short term /Tuesday and Tuesday night/...
as of 330 am Monday...

Tuesday and Tuesday night low pressure currently over the arklatex
area will track north of the area through the mid-Atlantic states
and bring a very weak cool front with it. Maybe a bit better chance
for thunder Tuesday afternoon, especially in the central and eastern
portions of the forecast area as instability look a little better
than on Monday afternoon and low-level lapse rates remain very
steep. The proximity of the low to the north will provide upwards of
25-30 kts of bulk shear to work with. As a result spc, currently has
the forecast area in a marginal risk for severe thunderstorms. While
damaging wind should remain the primary threat, some better cape
values aloft could result in some small hail.

Temperatures will continue to be in the upper 70 to low 80s across
the forecast area on Tuesday afternoon with lows in the mid 50s.


Long term /Wednesday through Sunday/...
as of 205 am Monday...

Wed-Thu: behind the departing shortwave through, the mid level ridge
axis will shift eastward over the southeast through Thu, although by
Thu it will be deamplifying as the next mid level low tracks through
the central Continental U.S.. NC will remain in the warm sector for much of
Wed, as the backdoor front holds to our north until late in the day,
when energy dropping into the polar low southeast of the Canadian Maritimes
helps drive the cool dense surface high pressure area southward into
NC, with the front dropping through NC north-northeast to south-southwest Wed evening/night
and settling south of the forecast area by Thu morning. Expect
partly to mostly sunny skies Wed with flat cumulus beneath the warm
layer focused around 700 mb. The low levels will cool/stabilize Wed
night with increased moisture pooling around 900-800 mb, so expect
cloudy skies, thickest in the west where moist isentropic upglide
will be deepest. While a uniform northeasterly low level flow into
the area will set up behind the front, the 850 mb anticyclone will
shift off the Carolina coast, resulting in increasing 850 mb winds
and strengthening moist overrunning atop the cool stable pool Thu,
most evident over the northwest County Warning Area. Will keep skies mostly cloudy to
cloudy with a chance of light rain or drizzle in the west from late Wed
night through Thu. Highs Wed from lower 70s NE to around 80 SW. Lows
45-55 NE-SW Wed night as cooler air pushes into the NE. Highs Thu
from mid 50s northwest to the mid 60s southeast within a wedge regime.

Thu night through Fri night: a volatile period as another strong mid
level shortwave moves from the Central Plains through the miss
valley and Ohio Valley before crossing the mid Atlantic region. At
the surface, models depict the primary surface low tracking NE over
or just south of Southeast Michigan through Fri, while the front to our south
shifts back northward as a warm front, and a triple-point low forms
over SW Virginia. While we would normally be skeptical about the complete
passage of a warm front through NC immediately following a wedge
regime, the parent high is rather weak and progressive and may be
unlikely to put up much of a fight, so will depict a northward surge
of higher dewpoints through much of the forecast area (excluding the
far nw) on Fri. The primary low will then track up the St. Lawrence
Valley Fri night while filling, as the triple-point low crosses WV
and north Virginia and becomes the primary low near or just off the Delmarva
Peninsula, with west-to-E cold frontal passage through central NC. In
terms of sensible weather, given the improving mechanisms to force
ascent including mid level DPVA, strengthening upper divergence, and
increasing 850 mb moisture transport, expect numerous showers and
thunderstorms starting Thu night, peaking in coverage and intensity
Fri, then exiting to our east Fri night as the mid level trough
moves off the coast. A few strong storms are possible Fri, although
the DPVA will have weakened a bit by the time the trough gets here,
and we're lacking the instability and strong kinematics that might
prompt greater concern. Lows Thu night mid 40s to low 50s, highs Fri
62-72, and lows Fri night 49-55.

Sat-Sun: weak modified surface high pressure builds in behind the
front with another rough of shortwave ridging in the wake of
friday's trough and ahead of the next system moving from The Four
Corners into the S plains. Expect dry weather and partly cloudy to
mostly clear skies. Thicknesses are projected to stay a bit above
normal through the weekend, so expect highs from around 70 to the
mid 70s. -Gih


Aviation /12z Monday through Friday/...
as of 730 am Monday...

24 hour taf period: line of showers has hung on through the early
morning hours and will continue to push eastward this morning.
Southernmost portion of the band may just clip kfay but not yet sure
if it will hold together all the way to krwi but expect at least a
few light showers. Any decreased visibilities have been mainly with
the line of showers except for at kgww. Otherwise no real fog
problem spots. Expect southerly winds today near 10 kts gusting just
over 15 kts. Chances for rain will increase late in the taf period
with ceilings expected to drop down to at least IFR at most taf
sites if not LIFR by the very end of the taf period. A non-zero
chance for thunder but have left it out of the taf with this package.

Long term: a low pressure system will move through the mid-Atlantic
states on Tuesday brining a chance for rain Tuesday evening. A more
potent system will cross the area on Friday through Friday night
with the potential for showers and thunderstorms. Otherwise, some
potential for some fog/low stratus in The Triad on Tuesday morning.


Rah watches/warnings/advisories...



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