Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 231442

Area Forecast Discussion
National Weather Service Blacksburg VA
942 AM EST Fri Feb 23 2018

A weak backdoor cold front moved through the area last night.
This front will stall over the Carolinas this morning and
return as a warm front this evening. A stronger front will move
through the region from the Ohio Valley this weekend.


As of 935 AM EST Friday...

satellite imagery and surface obs show that the wedge is now
firmly in place with low clouds, fog, drizzle, and much cooler
temperatures for most locations. The exception is far west
that remains outside of the wedge and has some sun and
temperatures into the lower 60s. Expect only gradual erosion
along the periphery of the wedge today and have lowered temps a
bit in the piedmont. Also expect differential heating along the
wedge boundary to couple with some short wave energy and weak
instability to generate some showers this afternoon along/west
of the Blue Ridge, possibly with a rumble of thunder.

...Previous discussion...

Wow factor from the above seasonal warmth will be tempered today
per the passage of last night`s backdoor cool front. Front has
made its way into NC, nearing the SC border. Winds in its wake
are out of the ENE with the relatively cool airmass lacking
enough depth to push it over the Appalachian Divide, leaving
our western CWA from Bluefield into the headwaters of the TN
Valley, west of Marion and Tazewell and including the NC High
Country unaffected. As such, todays forecast will reflect warmer
numbers in the west compared to the east.

Shallow wedge of cool air is forecast to stall this morning near
the SC/NC border, then begin to retreat back to the north
this afternoon and evening. Little to no precipitation with or
behind the wedge has been observed, however expect some drizzle
vicinity of the Blue Ridge and VA highlands this morning where
there is favorable uplift from the shallow ENE flow. Chance for
measurable precipitation today will be mainly limited to areas
along and north of I-64 where some instability will exist

Even though the wedge will begin to erode from the southwest
this afternoon, low-level moisture may remained trapped along
and east of the Blue Ridge for much of the afternoon/evening.
This will impact the temperature rise in those locations with
readings only rising back to near 60, compared to yesterdays
80+. For the upper TN valley and into the Bluefield area,
another record breaking day expected with temperatures reaching
the mid 70s. Areas that manage to break out of the wedge, such
as the western New River Valley and NW NC may also make a run
for the upper 60s or test 70 degrees before the end of the day.

For tonight...erosion of wedge will continue with only some
remnant stratus/fog along the eastern slopes of the Blue Ridge.
Southwesterly winds are forecast to increase aloft, so breezy
conditions likely along the ridges with temperatures remaining
AOA 50. Shower threat will primarily resided north of I-64 and
west of I-77.


As of 230 AM EST Friday...

The region will continue to be under the influence of a very
unseasonably mild ridge of high pressure heading into the weekend.
Anticipate temperatures to continue to average 20 to 25 degrees
above normal. Showers are still forecast in advance of an
approaching cold front within the unseasonably warm and moist air
across the region. Chances will be greatest across southeast West
Virginia and neighboring counties of southwest Virginia. Chances
will decrease along an gradient heading southeast into eastern
portions of the forecast area.

This will change on Sunday. Anticipate the front to cross the area
with all locations likely to have showers. Afternoon instability
across the southeast parts of the area may yield some isolated
thunderstorms coincident to the frontal passage.

Sunday night into Monday, model guidance varies significantly. The
GFS is robust in having the frontal boundary easily exit the
forecast area with precipitation not an issue Sunday night through
Monday night. Most of the other operational model offer solutions of
a disturbance along the Gulf Coast riding northeast along the front,
and thus stalling it, just south of the forecast area. The
disturbance would then buckle the front north again Sunday night
into Monday with showers impacting at least the southern half of the
area, if not the entire area to some degree.

Our forecast during the Sunday night into Monday time frame will
reflect the impact of the disturbance, but also weigh in the null
solution of the GFS with overall probability of perception no higher
than 40 percent across the southeast sections of the region with
values closer to 20 percent over southeast West Virginia.

All guidance show the region clear of precipitation by Monday night
with the disturbance to our northeast and northwest winds ushering
the front southeast of the region.

Temperatures behind the front will trend cooler, but still above
normal for this time of year. Even the more progressive GFS
solutions still has readings around 10 degrees above normal Monday


As of 300 PM EST Thursday...

Models show high pressure overhead Monday night before sliding to
the coast on Tuesday. This should bring somewhat cooler and drier
weather into Tuesday night with highs in the 50s/low 60s, which
remains a good 10 degrees or so above normal.

Fast west/southwest flow aloft looks to bring pieces of upper energy
out of the southwest states by Wednesday with a couple waves ahead
of a parent mid level system that will eject out into the upper
Midwest by Thursday. This should result in an axis of deeper
moisture lifting back north through the TN valley by early
Wednesday and into our region Wednesday afternoon/night as a warm
front edges north. Moisture remains in place well ahead of the
trailing cold front that will approach Thursday with at least added
showers around. Thus running with decent chance to low likely pops
for mid week at this point. Highs again mostly 50s/60s with cooler
values mountains Wednesday, and warmer readings possible Thursday
east well ahead of the cold front.


As of 700 AM EST Friday...

Cool wedge resides on the east side of the Appalachians with
widespread IFR Cigs and MVFR vsbys...ridges obscured. There is
a sharp line between IFR/VFR along the crest of the Appalachian
Divide from BLF-TNB. Low stratus cloud deck was confined to
areas east of the Divide.

Little change is expected today with only gradual improvement
this afternoon and evening as the stratus begins to erode. It
may take until sunrise Saturday before deep enough mixing takes
place to rid the low cloud layer completely.

Winds will favor an easterly direction today, then trend back to
southerly for Saturday.

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

Extended Aviation Discussion...

VFR conditions are expected to return for Saturday afternoon
into early Sunday. Shower coverage and increasing likelihood for
sub-VFR conditions can be expected later Sunday into Monday as
a cold front crosses the Mountains from the west. Sub-VFR
conditions may persist into Monday as the front stalls to our
south and an upper-level disturbance in the southern stream
tracks across the southeast states along the front Monday.


Plethora of records yesterday. Please reference past Record
Event Reports for details.

Records still possible at Bluefield today, and within the realm
of possibility at Blacksburg, pending erosion of the wedge.

Thursday 2/23/2018
Site MaxT/Year HiMin/Year
BLF    74/1975    51/1975
DAN    73/2017    50/1981
LYH    74/1943    52/1925
ROA    76/1943    54/1925
RNK    69/1980    46/1990




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