Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 240523

Area Forecast Discussion
National Weather Service Blacksburg VA
1223 AM EST Fri Nov 24 2017

High pressure will continue to control our weather pattern through
Friday. A cold front will cross the area this weekend, with only
isolated showers expected. High pressure rebuilds over the area by
early next week and remains through the middle of the week.


As of 1215 AM EST Friday...

Adjusted temperatures down somewhat in most areas, on average
2-3 degrees F. Do not expect it to be as cold as last night as
850mb temps have warmed slightly, but radiational cooling is
excellent in the dry air. All other grids are in good shape at
this time.

As of 650 PM EST Thursday...

No significant changes needed the the grids at this time. Will
need a bit more time to see how the min temperature is tracking
for tonight. Suspicious that the dewpoint at KBLF is too low,
but otherwise grids are in good shape. Made only minor
adjustments to T, Td, and Sky grids.

As of 200 PM EST Thursday...

A ridge of high pressure was oriented from eastern Texas, northeast
to Pennsylvania.  Aloft, a shortwave trough was heading eastward
through the Great Lakes region, and low pressure was centered near
Jacksonville, FL.  Tonight into Friday, the Florida low pressure is
expected to progress northeast around 100 miles off the coast of the
Carolinas. Any associated precipitation is progged to remain well
southeast of the forecast area. The shortwave trough moving the
Great Lakes region will progress into and east of New England, with
its associated precipitation staying well north of the area. At
best, the area may see an increase in some thin high level cloud
cove by this time tomorrow.

At the surface, high pressure will remain over the area, with its
axis shifting east of the region by Friday afternoon. This will
result in light and variable or calm winds tonight through Friday
morning. By Friday afternoon, a prevailing weak south wind is

Low temperatures tonight will be on the cold side.  Will continue to
favor values below the coldest guidance. Anticipate low to mid 20s
across the mountains with primarily mid 20s across the Piedmont. On
Friday, as geopotential heights rise and likewise with 850mb
temperatures, high temperatures are expected to be some 5 to 10
degrees warmer than those realized today. Expect low to mid 50s
across the mountains with mid to upper 50s across the Piedmont.


As of 110 PM EDT Thursday...

Cold front by Saturday morning will extend from Ontario to northern
Texas. Models similar with the timing of the front. Deeper moisture
along and just behind the front clears east out of the piedmont by
late Saturday evening. Upslope winds will prolong cloud cover on the
western slopes of the Appalachains until Sunday morning. May
increase wind speeds at higher elevations behind the front Saturday
and Saturday night to account for low level jet, cold air
advection and modest pressure rises.

Warm air advection and increasing cloud cover Friday night will
limit drop in temperatures. By Sunday morning 850mb temperatures
back below zero over the mountains.  Will lean toward cooler
guidance with high overhead on Monday morning.


As of 110 PM EDT Thursday...

Split flow pattern remains through Day 7, Thursday. Upper long wave
trough will dig into the western United States Monday and Tuesday
with a strong short wave separating from the southern end of the
trough over the southeast United States on Wednesday. As
typical, GFS is faster with this feature. Prefer the timing of
the ECMWF which brings the short wave across the Mid Atlantic
region on Thursday. Expecting dry weather and seasonal
temperatures MOnday through Wednesday, then a chance of
precipitation and cooler temperatures Thursday. At the surface a
northern stream cold front will cross the area on Wednesday,
then low pressure associated with the southern stream short wave
tracks into the Tennessee Valley on Thursday. Will be slowing
down better probability of precipitation until Thursday.


As of 1215 AM EST Friday...

A progressive semi-zonal flow will remain in place across the
U.S. with a series of dry northwest flow short waves. The
northern stream will continue to dominate the Mid-Atlantic
region with a dry west-northwest to northwest flow aloft.

A series of mainly dry upper troughs and associated cold front
will continue to pass through the area every few days with
little or no moisture return in advance of these systems. Thus,
a dry/VFR forecast will remain in place through this TAF valid
period and beyond. Still feel that the air mass overnight will
be too dry for any radiational fog development, although it
cannot be 100% ruled out in favorable locations. Weak high
pressure will provide mostly calm winds overnight, trending
toward the SSE-SSW Friday afternoon as the high slides to the
east of the area. Speeds will remain mostly 5kts or less through
the TAF valid period.

High confidence in ceilings and visibilities through the TAF
valid period.
Medium confidence in wind direction, high confidence in wind
speed through the TAF valid period.

Extended Discussion...
On Saturday a cold front will cross the area. It will be
moisture starved for the most part, with at best some isolated
showers across the area and some patchy of MVFR ceilings, with
the greatest potential across southeast West Virginia, south
into the Northern Mountains of North Carolina.

High pressure regains control of our weather pattern Sunday into
Monday with a return to VFR for the entire region.

Gusty winds are expected Saturday into Saturday night in the
wake of the cold front passage. Surface gusts of 15 to 25 mph
will be possible at the higher elevations.




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