Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 241938

Area Forecast Discussion
National Weather Service Blacksburg VA
338 PM EDT Mon Oct 24 2016

A cold front from the Delmarva to the mid Mississippi Valley will
continue to move southeast tonight, followed by high pressure. The
high will move across the Great Lakes, Ohio Valley and Mid Atlantic
region tonight through Tuesday night. Low pressure crossing the
Great Lakes will push a cold front through our region on Thursday.


As of 315 PM EDT Monday...

A cold front was approaching Danville at 18Z/2PM and extended west
into Tennessee. This front will continue to move southeast this
evening. Winds behind the front will gradually diminish tonight and
turn from northwest to north. By Tuesday morning surface high
pressure will be centered over the Ohio Valley with the ridge axis
extending into western Virginia. Winds will become calm to light and
variable late tonight in the west. Expecting some upslope lower cloud
on the western slopes of southeast West Virginia this evening, but
as winds weaken, the clouds will dissipate. Valleys west of the Blue
Ridge have a high probability of frost tonight. A Frost Advisory
will be issued for the overnight and early morning hours from Bath
County to Smyth County Virginia. Surface dew points have dropped
into the upper 30s to lower 40s. Haves used the coolest of the suite
of guidance for minimum temperatures tonight.

High, thin clouds begin to spread into the region from the west on
Tuesday afternoon. Used MAV as guidance for maximum temperatures.


As of 310 PM EDT Monday...

High pressure will wedge down south east of the Blue Ridge Tuesday
night into Wednesday. Heights increase over the wedge during the day
Wednesday as a low pressure system enters the midwest. Moisture
profiles are not overly impressive with this wedge, but could see
overcast skies Tuesday night into Wednesday morning, then breaks in
the clouds Wednesday afternoon. Even though overcast conditions are
expected, it does not appear to be thick enough to produce any light
rain or drizzle. However, flow is southeasterly within the wedge and
will keep temperatures cooler than normal along and east of the Blue
Ridge for Wednesday. Models are also hinting at breezy conditions
across southwest Virginia Wednesday with a tight pressure gradient
between the wedge of high pressure over the coastal piedmont and low
pressure in the midwest. Southeasterly downslope flow may also aid
in breezy and gusty conditions, especially if overcast skies break.
At this time, wind speeds will not reach advisory criteria, but may
gust up to 30 mph Wednesday afternoon and night.

Low pressure will move from the midwest to the Ohio Valley Wednesday
night. Pressure falls over the Ohio Valley will erode the wedge over
the area by dawn Thursday. Prefrontal showers will then track over
the mountains during the morning, then over the piedmont early
Thursday afternoon. The cold front associated with this low will
move over the area Thursday night and may produce a few evening
showers across the mountains. Rainfall totals will range from up to
a quarter of an inch /0.25/ along western slopes to a tenth /0.10/
across the rest of the mountains and east to the piedmont.

Temperatures will be cooler than normal Wednesday with the wedge in
play. Temperatures will range from the upper 50s to mid 60s. We will
see slightly warmer temperatures (closer to normal) Thursday as
morning showers exit and temperatures rebound ahead of the
front Thursday night.


As of 300 PM EDT Monday...

Weak high pressure will build over the region following the frontal
passage Thursday night. The center of this surface high will sink
south over the southeastern US Friday. Also stretched along the Gulf
states will be an upper level ridge. Both of these high pressure
systems will block moisture from returning into the region.
Meanwhile, a low pressure system will track from the Great Lakes to
New England Friday into Saturday. The associated front with this
system will slowly move south across the forecast area Saturday and
Saturday night. Since we have a ridge blocking the Gulf and bulk of
the precipitation and energy will be with the parent low to the
north, we are only forecasting scattered light showers north of 460
and sprinkles or just an increase in clouds south. Both the GFS and
ECM are at odds with the forecast for Sunday and Monday. For now, we
will keep conditions dry.

Temperature will warm above normal Friday and Saturday with areas
along the VA/NC border warming into the 70s. Temperatures cool down
behind the front Sunday but are expected to remain above normal into
early next week.


As of 135 PM EDT Monday...

Early this afternoon a dry cold front extended from the Delmarva
peninsula into Tennessee. This front will move slowly southeast
this afternoon and tonight. The pressure will rise behind the
front tonight and Tuesday. By Tuesday morning the center of high
will be over the Ohio Valley.

Winds will be gusty from the northwest early this afternoon.
Higher elevations in the Appalachians will have wind gusts of 15
to 25 knots. A the high builds in this evening winds will
diminish. High confidence that wind speeds across southwest
Virginia, southeast West Virginia and northwest North Carolina
will be less then 10 knots after midnight tonight.

Models were showing some upslope cloud cover this afternoon and
evening on the western slopes of southeast West Virginia. Ceilings
may lower to MVFR at KLWB but confidence is high that these lower
clouds will stay to the north and west of the airport.

Extended aviation discussion...

Tuesday night and Wednesday...Potential for river valley fog in
the mountain valleys with local vsby restrictions between 08-14Z
each morning, otherwise widespread VFR. Patchy frost is likely too
in the colder mountain valleys.

Thursday...Low pressure is forecast to move across the upper
midwest and into the Great lakes with a surface front crossing the
Ohio Valley. Threat for showers and sub-VFR will be possible
along this front which would impact the central Appalachians by
Thursday. Attm, this does not appear that it will have a
significant impact to our region. Biggest impact would be from
Ohio Valley north into Great Lakes closer to the surface low.

High pressure builds in from the northwest Friday, with potential
MVFR ceilings at BLF/LWB before the high arrives. ANother front
will cross through the region on Saturday with the potential for
showers and MVFR ceilings in the mountains. However, models were
still showing differences in the timing of the weekend system.


As of 300 AM EDT Monday...

Little or no rain has fallen across the northwest North
Carolina Piedmont in the last 14 days. Conditions are becoming
increasingly dry for western North Carolina, espcly just east of
the Blue Ridge. Drying conditions will continue for this region
again today, and for much of the upcoming work week. Passage of a
dry cold front by this afternoon may pose control problems for
any fires in the lee of the Blue Ridge, and especially for areas
which have not seen rainfall. Greatest concern would be from Mount
Airy, North Carolina, and areas to the southwest, including Pilot
Mountain. Wind gusts of 15 to 25 mph are possible into this
afternoon, coupled with humidity minimums in the 25 to 35 percent
range which will cause added drying of smaller fuels. Therefore
plan to include a headline for now in the fire weather forecast as
a heads up for low humidity and gusty winds today.




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