Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 242312

Area Forecast Discussion
National Weather Service Blacksburg VA
712 PM EDT Fri Mar 24 2017

High pressure will continue to move off the Virginia and North
Carolina coast this weekend. A strong area of low pressure will
drift east over the southern plains with a trailing cold south
into Texas. A warm front will reside from the Great Lakes region
to Lake Erie into Saturday.


As of 711 PM EDT Friday...Forecast looks to be in pretty good
shape overall with only adjustment made to adjust sky cover to
match current satellite trends, and also to reduce sky cover a
bit after dark. Though I couldn`t rule out low clouds along the
southern Blue Ridge with the increase in moisture, light
southwesterly component to the wind may limit the development.
METARs out of Boone this afternoon have shown 5 mile visibility
haze, which stems from smoke being advected north-northeastward
from a wildfire seen on 3.9 micron infrared imagery as the
hotspot in northwestern Burke County NC. So there may be
periodic instances of smoke in the air at times across Watauga
and Wilkes Counties for the next few hours, though
diminishing/decoupling southerly flow as the night processes
should limit northward extent of residual smoke. No changes

Previous near-term discussion issued at 300 PM follows...

The center of a dry stable high pressure will continue to drift
off the VA/NC coast into this weekend. As this system moves
further to the east, increasing areal coverage of southerly flow
will bring more warm air into the region. Today`s highs were in
the 60s. Tomorrow`s high will range from the upper 60s across
the mountains to mid 70s east of the Blue Ridge.

Even though the center of this stable high will continue to
move offshore, the western edge will remain over VA-NC-SC into
the weekend. Warm moist air will continue to ride over this
lingering insitu wedge with only an increase in cloud cover
expected overnight into Saturday morning. Warm air and afternoon
mixing may produce some breaks in the clouds during the
afternoon. Instabilities increase some outside of the influence
of the wedge, particularly across southeastern West Virginia.
With some orographical lift, a few showers/sprinkles may develop
across the mountains during afternoon heating.


As of 302 PM EDT Friday...

Warmer and moist this period. Models seem in agreement on
getting the cold front west of the Appalachians Sunday, then
weakening it as it crosses over. Still plenty of southwest flow
aloft and southerly low level flow to increase moisture
convergence over the region. Will see best coverage of showers
west of the foothills into WV. Thunder threat depends on the how
quick the clouds/rainfall get into the area. By all accounts,
seems the thunder threat is going to be reduced some as rainfall
happens in the mountains by 8-11am Sunday. Best instability
lies across KY and south into the Carolinas/Georgia. Will have
chance thunder over WV into the NC mountains/foothills.

By Sunday night into Monday we are looking at main lift exiting
north, but still residual low level convergence along pre-
existing frontal zone and enough moisture to allow for showers
to hang around, especially in the mountains. Expect limited
sunshine, but with some breaks and warm air advection still
looking at highs Monday in the mid to upper 60s higher ridges,
with mainly lower to mid 70s elsewhere.

Monday night, next upstream shortwave and front approach, so
increased pops again after midnight in the southwest, but should
see better chances Tuesday.


As of 142 PM EDT Friday...

Active pattern this period.

Upper-level low pressure system will arrive in our region early
Tuesday. Dynamics are marginally favorable for thunderstorms,
but if line of convection moves in sooner, lack of
thermodynamics will limit thunder threat.

High temperatures are expected to be in the 60s to lower 70s.

Wednesday should be dry with upper ridge building again.

Thursday, still dry as upper low slowly edges eastward over the
southern plains keeping us under warm ridge, although could
start see mid/upper level moisture working in from the
southwest. High pressure nosing in from the northeast may keep
it cooler, so kept highs in the 60s.

Friday, the upper low pushes northeast toward the midwest with
strong high situated over the mid atlantic coast. Will start
seeing warm advection precip arriving late Thursday night with
front not moving into the area until later Friday. By then
dynamics weaken over the north.


As of 705 PM EDT Friday...

Generally VFR through the period, though periodic obscured
North Carolina ridgetops due to haze/smoke lofted north-
northeastward, particularly from wildfire in northwestern Burke
County NC.

Earlier persistent mid-level clouds in far western VA/southeast
WV beginning to scatter, with generally FEW-SCT high clouds
elsewhere. Ridge axis positioned to our south will allow for
low-level moisture to increase. With general south-southwest
low- level flow feel that lower ceilings along and east of the
Blue Ridge probably are a remote outcome. Prospects for
radiation fog also are of low-confidence as it is unclear
if crossover temperatures will be met, though presence of
radiation inversion opens the door for that possibility. Since
confidence isn`t all that high in either situation, opted to
keep TAFs VFR. Surface winds south/southwest 6-10 kts become
light southerly overnight.

Continued VFR for Saturday, with at least mid to high- level
cloudiness spilling in from the southwest. Could see some
diurnal Cu along the ridges leading to potential multi- layer
cloud decks at times, but nothing of significance from an
aviation perspective. Light southwest winds increase to 7-10 kts
on Saturday.

Extended Aviation Discussion...

Moisture continues to increase over the weekend ahead of an
upper-level low pressure area moving northeast from the southern
plains. Precipitation is not expected until Sunday when sub-VFR
conditions become more of a possibility. Otherwise looking at
overall VFR to start the weekend with most lower cigs remaining
west of the area until later Sunday at this point. Periods of
unsettled weather will continue into the first half of next week
as a series of upper-level lows track from west to east across
the U.S.




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