Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 251010

Area Forecast Discussion
National Weather Service Blacksburg VA
510 AM EST Sat Feb 25 2017

An intense cold front will cross through the Mid Atlantic region
today, triggering showers and thunderstorms and leading in much
colder air and strong gusty winds tonight. High pressure will
cover much of the eastern United States on Sunday then will move
off the southeast coast on Monday. A low pressure system will
develop in the southern plains on Monday and track into the
Tennessee Valley by Wednesday.


As of 430 AM EST Saturday...

At 4AM a strong cold front extended from Lake Erie to eastern
Kentucky to southwest Alabama. A pre-frontal band of showers
and thunderstorms was just ahead of the front with the eastern
edge of this line just reaching Smyth and Tazwell Counties.
Winds will temporarily turn to the west behind the line then
resume a southwest direction until the main front comes through.

Models were in very close agreement with the timing of the
front. Expecting the boundary to move through southeast West
Virginia and far southwest Virginia this morning. The front
will continue to move east during the day and will be exiting
the area east of Danville and Lynchburg between 4PM and 6PM late
this afternoon.

A general weakening trend is expected in the band of showers and
thunderstorms as it crosses the Appalachians then more showers
and stronger thunderstorms will redevelop east of the Blue Ridge
this afternoon.

Temperatures will be in the 50s and 60s ahead of the front and
will be falling behind the front. GLAMP and blend of other short
range guidance was used for the non-diurnal trend. Between
12Z/7AM this morning and 12Z/7AM Sunday morning 850mb
temperatures drop from around +10 to a range of -10 to -2. This
strong cold aid advection will combine with decent pressure
rises of +5 to +10MB/6hrs to produce gusty winds behind the
front. For now do not have any advisory (40kt/46mph)gusts in the
forecast but day shift will have a chance to re-evaluate. Threat
for higher wind gusts will continue to be highlighted in the
Hazardous Weather Outlook.

Air mass gets cold enough for snow in the western upslope area
of southeast West Virginia after 00Z/7PM. No change needed to
snowfall amounts/liquid equivalent based on the latest


As of 330 AM EST Saturday...

High pressure over eastern Kentucky Sunday morning will move east
across the region and push off the Atlantic coast by Sunday night.
Gusty westerly winds Sunday morning will diminish Sunday afternoon
as the high builds east. High temperatures Sunday will range from
the mid 30s in the lower 50s in the Piedmont. Light southwest winds
are expected Sunday night under increasing clouds. Low temperatures
Sunday night will vary from the mid 20s in the mountains to the mid
30s in the Piedmont.

Zonal flow aloft will develop across the CONUS Monday. Southwest
winds will result in warm air advection, increasing moisture and
threat for showers. Kept the highest pops in the southwest portion
of forecast area. High temperatures Monday will warm into the mid
40s in the mountains to near 60 degrees in the southeast.

Shortwaves rotating eastward in the upper flow will create the
potential for scattered rain showers Monday night. Low temperatures
Monday night will generally be from the upper 30s in the northern
mountains to the upper 40s in the Piedmont.


As of 330 AM EST Saturday...

Zonal flow will promote warming temperatures for mid week with main
focus for precipitation centered around noisy southern stream short
wave energy which models are having difficulty timing.

Through Wednesday, the region is expected to remain in a deep
southwest flow in advance of a developing trough across the
Central Plains states. The GFS continues to be more progressive
in depicting pieces of energy streaming across the area, each
with the potential for additional rounds of precipitation,
especially on Wednesday. CAPE is also forecast to peak on
Wednesday, and with trough generally forecast to come through
during the day this suggest potential for thunderstorms. Since
models have not quite nailed down the timing will list the
threat as slight chance attm.

Cold front will push off the Atlantic coast Wednesday night. The
timing is a little slower on ECMWF compared to GFS. Northwest flow
upslope rain and snow showers are possible Thursday, supported by
both GFS and ECMWF. Drier weather returns for Friday into Saturday.

Temperatures will peak by Wednesday followed by lowering numbers for
Thursday behind the trough, dry weather and near seasonal
temperatures returning Thursday night into Saturday.


As of 1130 PM EST Friday...

Expecting overall VFR to prevail over the next few hours with
ocnl MVFR cigs possible with a swath of strato-cu currently
traversing southern/central sections. However appears cigs will
lower late from west to east as a band of pre-frontal showers
heads east into the mountains by daybreak. The biggest
challenge will be timing the cold frontal passage west to east
across the region tomorrow. Expect fropa early morning at KLWB
and KBLF, mid/late morning at KBCB and KROA, then early
afternoon KLYH and KDAN. While best dynamic forcing will be
shearing off to our north, expect there will still could be
isolated thunder with the pre-frontal band of precip so
including a brief TEMPO for tsra far west early. Otherwise using
prevailing MVFR vsby for a period of showers most spots
excluding KDAN where a bit more removed from deeper moisture.
Showers and isolated thunderstorms will be east of KLYH and
KDAN by 00Z/7PM if not sooner. Winds behind the front become
west to northwest and quite gusty as cold air advection
generates good downward momentum transfer and the low level wind
field amplifies late Saturday through at least midday on

High pressure will cover the region behind the front for late
Sunday into Monday with VFR expected under lighter winds.

Extended Aviation Discussion...

A warm front is expected to stay near us Monday night into
Tuesday keeping a threat of showers around with sub-VFR
possible. Another wave of low pressure will likely prolong the
sub-VFR conditions with the next round of heavier showers
possible on Wednesday.




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