Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 252038
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
438 PM EDT Thu May 25 2017

.SYNOPSIS...
An upper level trough will move off the mid-Atlantic coast this
evening. Weak high pressure will build into the Southeast on
Friday and Friday night. A warm front will develop across the
Appalachians and extend into North Carolina and Virginia
through the weekend.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 110 PM Thursday...

A mid-upper low over western Appalachians is pivoting east southeast
this afternoon.  Cold air aloft associated with the upper low
combined with solar heating is supporting convection in central
North Carolina with small hail. Isolated stronger cells have the
potential to produce up to 1 inch diameter hail.

There will be a related conditional threat of severe hail,
particularly east of U.S. Hwy 1, where both instability and SSWly
mid level flow/bulk shear will be relatively maximized in a brief
window from 17Z-21Z. Strong to damaging straight line winds, driven
by both the background mid level flow and sub-cloud
evaporational/diabatic cooling, may also result.

After about 21Z, the passage of the trough axis will cause the mid
level flow to weaken and veer and consequently mitigate an earlier
severe threat, while small hail will remain possible through early
evening.

Lastly, mixed character precipitation (Ie. a stratiform shield of
light rain with some convective elements) will likely pivot across
the nrn piedmont as the parent mid level moist axis swings around
the base and wrn side of the upper trough; and this may result in a
few sprinkles there this evening, until the moist axis lifts away
after 03Z.

Lows tonight in the 50s, with a light but steady Swly breeze in the
MSL pressure gradient between sub-1000 mb low pressure that will be
lifting away from the Middle Atlantic coast, and incoming 1015 mb
high pressure from the nrn GOM and Gulf coast.  Ridging and drier
airmass on Friday will support clear to scattered clouds with max
temperatures 80 to 85.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 430 PM Thursday...

The mid and upper level low over new England at the start of the
period will depart as the upper level flow over the mid-Atlantic
becomes more westerly Friday night as an upper level ridge
develops across the northern Gulf of Mexico. Increasing mid and
and high level moisture will result in some high cloudiness.
Lows will range in the lower to mid 60s.

A general westerly to west-northwesterly flow aloft is expected
for Saturday and Saturday night across the mid-Atlantic. A good
warm advection pattern will develop across the deep south and
Southeast. This will result in the development of a warm front
that extends from the southern Appalachians into the VA and NC
and subsequent scattered convection. The best chance of
thunderstorms will be across the northeast half of the CWA,
primarily Saturday afternoon and evening. It will be noticeably
warmer and a bit more humid with highs in the mid 80s to lower
90s across the southeast. Lows will range in the mid 60s to near
70.
&&

.LONG TERM /Sunday through Thursday/...
As of 430 PM Thursday...

A ridge aloft across the northern Gulf of Mexico will shift east
and off the Southeast coast by Wednesday and Thursday. A mid and
upper level closed low over central Canada will slowly move
southeast into the Great Lakes region by the middle of the week
with a trough axis pushing east toward the coast. A weak cold
front will approach the region late Sunday and drop into the
region on Monday supporting scattered, mainly afternoon or
evening convection. It will be muggy with highs will range in
the mid 80s to near 80 both days with lows in mid 60s to lower
70s.

Another cold front will approach the region on Tuesday, move
across the region on Wednesday and linger around the area on
Thursday. This should result in a trend toward slightly cooler
and less humid conditions as we head toward the middle of the
work week. Scattered storms expected on Tuesday afternoon and
evening will lead to drier conditions on Wednesday and perhaps
Thursday too. Highs will range in the lower to mid 80s with lows
in the 60s. &&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
As of 110 PM Thursday...

Convection continues to intensify at 17Z from Albemarle to Chapel
Hill to Roxboro.  Isolated hail up to 1 inch diameter with stronger
cells. Convective cells moving east northeast at 25 knots and will
pass through RDU vicinity 1745-1830Z. Afternoon solar heating will
support additional convection mainly northern half of area as an
upper level trough and associated very cold temperatures aloft pivot
northeastward across the forecast area.

Outlook: At least a couple of clusters of showers and storms, some
strong to severe, and with gusty outflow winds surging well away
from them, will return to portions of central and/or northern NC for
Sat afternoon through Sunday. The approach and stall of a couple of
cold fronts east of the Appalachians may result in a band of MVFR
ceilings over central NC Mon night, and also a small chance of
diurnal convection both Mon and Tue.

&&

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

&&

$$
SYNOPSIS...BLAES
NEAR TERM...JF
SHORT TERM...BLAES
LONG TERM...BLAES
AVIATION...JF


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