Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 200723

Area Forecast Discussion
National Weather Service Blacksburg VA
223 AM EST Mon Nov 20 2017

High pressure over the Lower Mississippi valley will move east
and off the southeast coast tonight. A cold front will move
through the eastern United States Tuesday night, followed by
high pressure on Wednesday and Thursday. Another cold front will
cross the region this weekend.


As of 210 AM EDT Monday...

Upper trough and colder air aloft over the northeast United
States move east today. 500 mb pattern over the Mid Atlantic
region gradually becomes southwest ahead of the next northern
stream trough. Colder air at 850MB is retreating too. by Tuesday
morning 850MB temperatures will be in the +6 to +8 range over
southeast West Virginia, southwest Virginia and northwest North

At the surface high pressure moves from the Tennessee Valley to
off the Carolina coast by this evening. Expect the high to be
far enough offshore tonight that winds will slowly increase from
the southwest over the ridges overnight. Even surface winds in
the foothills and piedmont may not decouple.

Clouds and moisture along the western slopes all below 850MB.
Model show clearing before 9AM then little to no clouds for the
rest of the day and tonight. Will be staying close to National
Blend and bias corrected MAV for highs today and lows tonight.


As of 145 PM EST Monday...

Shortwave ridging will slowly weaken Tuesday as surface high
pressure slides offshore in advance of both northern/southern
stream shortwaves within the split flow regime. These features
still remain just out of phase with only a couple solutions
pulling enough moisture north for showers Tuesday night as the
southern surface low passes off the Carolinas. Since the latest
ensembles show a few showers both across the east, and also
northwest with the northern piece of energy will keep in some
low pops in spots Tuesday night. High pressure following these
systems to bring drier weather including a quick punch of cooler
air on brief gusty winds Wednesday before the gradient
diminishes by Wednesday night. We will see another short wave
trough track a disturbance off the Carolina coast Thursday and
Thursday night. Rain with this system will remain along the
coast with only an increase in high clouds for the area.

Highs mid 50s to lower 60 Tuesday before cooling back to 40s
mountains and 50s east per cool advection Wednesday and
Thursday. Cold air slow to come in Tuesday night with most areas
staying above freezing (mid 30s to lower 40s). Temperatures
fall into the 20s across the mountains and 30s east Wednesday
and Thursday night.


As of 200 PM EST Sunday...

Overall upper troffiness to prevail through the period with
reinforcing energy arriving next week that looks to carve out
an even deeper 500 mb cold pool. Will see low pressure develop
offshore the Carolinas later on Thanksgiving within split upper
flow early on but appears too far offshore for any showers at
this point. Otherwise should see mainly dry weather under weak
high pressure and overall below seasonal temps until a strong
cold front arrives Saturday. This front will again be followed
by colder temperatures next Sunday similar to this weekend.
Appears a few western rain showers possible ahead of the front
Saturday night, followed by western snow showers early Sunday,
but little more than low pops for now.


As of 1215 am EST Monday...

Mainly MVFR conditions west of the Blue Ridge to VFR conditions
east of the Blue Ridge tonight, becoming VFR all areas by

In the wake of the strong cold front that moved through the area
yesterday, a large area of surface high pressure will slide
across the southern central and southeast states through
Tuesday. This will keep a dry westerly flow in place across our
region through the TAF valid period.

MVFR level upslope clouds (020-030 ceilings) across the
Alleghanys will gradually diminish overnight, especially by 10Z
and all TAF sites should be VFR by or shortly after daybreak, if
not sooner. The Piedmont areas, including ROA, LYH, and DAN,
are expected to be VFR through the TAF valid period. No
restrictions to visibility are expected at any TAF site through
the period. Any -SHSN across the Alleghanys have also ended now.

West to northwest winds will continue overnight, with speeds
continuing to diminish as the surface high slides east across
the Mid South and into the Southeast U.S. Sustained winds of
8-12 kts with gusts of to around 20 kts can be anticipated
through the next few hours, but winds speeds are expected to be
10 kts or less all areas by 12Z. Winds will continue to diminish
during the day Monday as the surface high draws closer to the
area. Speeds will be mostly 10kts or less with the direction
trending more toward the west or west-southwest through the day.

Medium to high confidence in ceilings through 14Z, then high
confidence in VFR ceilings all TAF sites through the TAF valid
High confidence in VFR visibilities throughout the TAF valid
Medium to high confidence in wind speed and direction throughout
the TAF valid period.

Extended Discussion...

Mainly VFR conditions are expected Monday night into Friday.
Exceptions would be some lower cigs with a front/trough Tue
night-Wed in the mountains, and again Thanksgiving. With the
flow aloft mainly northwest, no appreciable amounts of moisture
or expected through the Thanksgiving week.




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