Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 142341

Area Forecast Discussion
National Weather Service Blacksburg VA
641 PM EST Sat Jan 14 2017

A weak cold front has drifted south of the region and will remain
south of the area tonight into Sunday and will drift back north of
the area Monday. Meanwhile, a series of disturbances aloft will
track over the region keeping clouds and periods of precipitation
across the region for several days. Finally, a stronger cold front
is slated to move through the region by the middle of next week.


As of 300 PM EST Saturday...

Arctic high pressure to our north will slide east tonight into
Sunday. The high center pushed colder air pushing into our region.
The frontal boundary has moved south of us and was located across
Georgia and South Carolina this afternoon. A wave of low pressure
will ride east tonight into Sunday. Regional WSR-88d images showed
an area of rain off to our west mainly north of the Ohio River.
This feature will rotate east tonight into Sunday. Utilized a blend
of the HRRR and Hiresw arw-east for this afternoon into tonight
because they capture this precipitation best. Then, blended in the
nam for pops overnight into Sunday. In general, the Models seem to
focus more activity west in the Tennessee valley overnight/early
Sunday. At any rate, there will likely be patchy of fog and drizzle
when it is not raining with low level moisture. With a non diurnal
temperature curve, low temperatures range from the lower 30s in the
northwest Greenbrier county to the mid 50s in the southwest
mountains. With temperatures close to freezing in western Greenbrier
county, there is a slight chance for freezing rain late tonight
into early Sunday morning.

The low level wedge across the region Sunday morning will weaken as
the flow turns more northwest behind a weak exiting wave offshore.
This may result in some drying especially across central and eastern
portions of the forecast area Sunday before another transient but
weaker surface high starts to build in from the north. Another Mid
level shortwave will rotate east returning precipitation to the west
and spreadings east by late Sunday. High temperatures Sunday will
vary from around 40 degrees in the northern mountains to the
lower to mid 50s along the southern Blue Ridge mountains.


As of 330 PM EST Saturday...

Split flow pattern over North America will persist through
Tuesday. This will keep our forecast area pinned between the
colder northern stream westerlies to our north and subtropical
warmth along the Gulf Coast. Closed southern stream low over the
southwestern CONUS will be the focus for pieces of short wave
energy which will eject east, resulting in period lift along a
wavy surface front which bisects the Mid-Atlantic from west to
east, dividing the colder air associated with the northern
stream from the warmer subtropical air to our south. Result will
be abundant cloud cover with the potential for rain and/or

Highest potential for rain during this time frame will be
Sunday night and again Tuesday night, with widely scattered
showers in between. Sunday night, models indicate about a 6-8
hour period of isentropic lift promoting 60-80 percent chance of
rain, the highest pops vicinity of the blue ridge where lift
will be maximized from the easterly low level wind field. Can`t
rule out an hour or two of freezing rain/drizzle early Monday
morning at the highest elevations along the Blue Ridge (Peaks of
Otter and points north along the Blue Ridge Parkway) where
temperatures will test 32 degrees. Elsewhere, just looking at a
cold rain.

Surface front will get a nudged north Monday into Tuesday, so
temperature trend Monday into Tuesday should be up, with steady
or increasing temperatures, from 40s Monday, steady or rising
Monday night (40s/50s), testing 60 on Tuesday.

Closed low over the southwest is expected to eject northeast
into the upper Mid-West by Wednesday. This will send a surface
front east bound, this feature approaching our area Tuesday
night. Convergence along the front will likely result in another
period of rain or rain showers, beginning as early as Tuesday
evening in the mountains, then spreading east across the
forecast Tuesday night.


As of 345 PM EST Saturday...

Surface front is forecast to cross the forecast area early
Wednesday. Attm, models do not indicate much in the way of cool
air behind the front, a few degrees drop at 850 mb, so once we
dry out behind this feature Wednesday, the afternoon should be
fairly nice with Temperatures once again testing 60.

Beyond Wednesday, the weather pattern still looks mild. A new
cutoff low is forecast to take up residence within the southern
stream over the southwestern CONUS with ridging over the
southeast States and Gulf Coast. There are some model
differences with respect to how far east the southern stream
trough will progress next weekend. This results in timing
differences with respect to precipitation. Per the mild
pattern, there should not be any P-type issues for our forecast
area with any precipitation falling in the form of rain.
Forecast high temperatures will run about 10- 20 degrees above
normal Wednesday through Saturday.


As of 636 PM EST Saturday...

Overall poor flying conditions will continue tonight as a
wedge of high pressure locks in along and east of the mountains.
Low clouds with patchy light rain and drizzle will combine to
produce IFR/LIFR cigs and MVFR/IFR vsbys in the mountains and
MVFR out east where cloud bases should remain higher and
rainfall less. Pilots should prepare for Mountain Obscurations
into Sunday.

Medium to low confidence with cigs and vsbys through Sunday
given varying conditions in and out of the wedge through the
weekend. Spotty nature of fog and drizzle is also problematic.
Higher confidences that east to southeast winds will prevail on

Extended Aviation Discussion...

A baroclinic zone will remain anchored across the region
sandwiched between a strong upper ridge over the southeast
states and an active jet stream from the southwest U.S. into the
northeast U.S. Thus, an unsettled, wet weather pattern is
expected to remain in place Monday into Tuesday. The frontal
boundary may lift north enough by Monday night for a brief
period of mainly VFR, but a stronger front will arrive By
Tuesday with more showers including widespread sub-VFR.
Generally looking at MVFR much of the period, although periods
of VFR as well as IFR- LIFR can be expected at times. Passing
cold front from later Tuesday should clear the region on
Wednesday allowing for a return to VFR across the region for
midweek. Moisture may return from the southwest Thursday
afternoon into Thursday night.




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