Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 240206
Area Forecast Discussion
National Weather Service Blacksburg VA
906 PM EST Thu Feb 23 2017
Weak high pressure off the Mid Atlantic coast will cover
Virginia and North Carolina through tonight into Friday. A cold
front will then sweep across the forecast area Friday night into
Saturday, bringing chances for showers and thunderstorms.
Temperatures will be unseasonably mild through Friday and may
near record highs. High pressure returns to the forecast area on
.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --As of 900 PM EST Thursday...
Cloud cover diminishing over the region this evening, but no fog
as of yet with dewpoint depressions in the 5 to 12 degree range.
Appears will still see fog per model soundings and residual low
level moisture and higher dewpoints. However, fog will be not as
dense as last night, but still noticable. Best threat of dense
fog will be toward the piedmont east of Danville and Reidsville
and possible portions of the mountain valleys.
Otherwise, skies should be mostly clear to partly cloudy then
some stratus forms with fog late.
Lows will be in the upper 40s to lower 50s.
Previous afternoon discussion...
Ridge of surface high pressure remains in place across the
forecast area. Sky conditions range from mostly clear to the
east and mostly cloudy well to the west, and is contributing to
a mild, spring-like afternoon. Current temperatures in several
locales are near record highs for the date. Aloft, a positively-
tilted mid-level shortwave ridge axis extends into the VA/NC
piedmont region with a faster belt of mid-level southwest flow
to our northwest in the Ohio Valley.
For Tonight: Subsidence aloft along with stabilizing boundary
layer will allow for diurnal cumulus clouds to erode. Though a
few higher resolution models generate some token light PoPs west
early tonight, I`m dubious about the prospect due to waning and
already marginal surface-based instability, height rises in
mid-levels and the light southerly weakly-convergent low-level
wind field. Maintained a dry forecast, but I have also kept in
the forecast of patchy fog primarily for eastern and central
areas (east of the New River Valley to the Piedmont). Forecast
soundings continue to reveal a developing radiational inversion
along with light winds that are favorable for such development.
I`m not as confident we`ll see fog as dense as last night given
that we`re a day removed from the wetting rain, so we may not
have as good near-surface moisture fluxes like we saw yesterday.
I`ve therefore held on any Dense Fog Advisories with this
package. Given good radiational cooling, lows should be warmest
along the higher elevations (lower 50s) and coolest (mid/upper
40s) in the lower valleys and Piedmont.
For Friday: Areas affected by fog stand to be several degrees
cooler early in the morning but should burn off quickly under
insolation. After that, we`ll be in the warm sector of a
deepening surface low to our northwest over IL/IN. 850 mb
temperatures are in excess of +10C - and off the 12z NAM are in
the +12 to +13C ballpark. Dewpoints should be similar to today,
though BUFKIT soundings show us capped to convection around 700
mb. Only the NAM-based guidance generates any token precip but
given the cap aloft feel this is overdone and have again sided
toward a drier forecast idea. Think we`ll end up seeing clear to
partly cloudy skies with the greatest coverage of cloudiness
more closely tied to orography, though. Will also see some
increase in southerly winds/light breezes later in the day as
pressure gradient starts to increase and low-level flow also
increases. Used the warmer bias-corrected grids for high
temperatures along with the 12z METMOS, which generates highs
from the upper 60s to the upper 70s; a few spot 80 degree
readings would not be out of the question in Charlotte,
Pittsylvania and Caswell Counties. Since projected highs do get
close to daily records in Blacksburg, I have added to the
Climate section the high temperature records for Friday February
-- End Changed Discussion --
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 338 PM EST Thursday...
On Friday night, expect a south-southwest low level jet to be
increasing in advance of an approaching cold front. While no
precipitation is expected for the first half of the night, showers
and some isolated storms in advance of the front will be arriving
across the far western sections of the area by sunrise Saturday. The
latest Day 2 Convective Outlook from the Storm Prediction Center
places a marginal risk of severe weather across our far western
tier of West Virginia and Virginia counties. Temperatures will be
very mild with lows around 50 degrees to the lower 50s across the
mountains, with low to mid 50s across the Piedmont.
The front will cross the region on Saturday. Timing of this crossing
has differed from run-to-run, and continues to demonstrate this with
the latest 12Z/7AM solutions. The general consensus is for a pre-
frontal line of convection to cross the area about three hours in
advance of the actual cold front during the morning into the early
afternoon. The front to cross late morning into the mid afternoon,
and the associated 850 mb front to cross the area late afternoon
into the evening. The latest Day 3 Convective Outlook from the Storm
Prediction Center offers a marginal risk of severe weather across
the central and northeastern sections of the forecast area with the
passage of this front.
Winds will be on the increase in the wake of this front, ushering in
colder air by the afternoon, especially in the west. Anticipate
early high temperatures with temperatures falling off in the
afternoon. Eastern parts of the area will realized their high
temperatures a little closer to the typical afternoon times, but
still experience falling temperatures before sunset. Highs will
range form the mid to upper 50s in the west, with lower 60s to near
70s across the Piedmont, with the warmest readings in this range
across the far southeastern sections of the area.
Lingering upslope showers across southeast West Virgina, south into
the Northern Mountains of North Carolina will persist through the
afternoon. Enough colder air will reach the highest peaks in this
region for a mix with, or change over to, light now. This upslope
activity will continue into Saturday night, but transition to more
snow showers. Given how mild conditions will be prior to the arrival
of snow showers, little if any accumulation is expected. Western
Greenbrier County in West Virginia has the best chance for any
measurable snowfall, with one-half inch possible. Low temperatures
Saturday night will range from the mid to upper 20s across the
mountains to the lower 30s across the Piedmont.
The wind gusts at higher elevations may approach wind advisory
levels at the highest elevations during the Saturday afternoon and
evening time frame. However, most gusts across the mountains will be
more in the 25 to 40 mph range with 20 to 30 mph across the Piedmont.
Sunday into Sunday night, high pressure will build over the area,
and shift east to the Atlantic coast. Expect no precipitation and
limited cloud cover on Sunday. Sunday night, south to southwest
winds will be on the increase again as the influence of the high
pressure wanes, and another potential shortwave trough approaches
from the west.
Sunday, high temperatures will range from the mid 40s to near 50
across the mountains with low to mid 50s across the Piedmont. Low
temperatures Sunday night will range from the upper 20s to around 30
across the mountains to the lower 30s across the Piedmont.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 338 PM EST Thursday...
The biggest difference in the model guidance regards the
precipitation potential on Monday. The GFS is agressive with a
southern stream system heading northeast into the area on Monday,
and impacting the entire area. The ECMWF is about 18 hours slower
regarding this feature, with precipitation not arriving until after
midnight Monday night. Our consensus forecast will continue to be
just that. While it will reflect the quicker timing of the GFS, the
magnitude will be downplayed a bit, and reflect guidance provided in
the superblend solution. The onset of this precipitation has the
potential for being a light wintry mix if the arrival is early
Monday morning when surface temperatures are still at or below
freezing over parts of the region. For now, will keep it simple with
a rain versus snow forecast based upon surface temperatures below or
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. Our
forecast will continue to reflect the superblend solution that
accounts for these features, but on a diluted magnitude.
Wednesday afternoon into Wednesday evening, the main upper trough
and associated cold front are expected to race across the area. Look
for another a line of convection to move through the region, with
the potential for isolated thunderstorms. Gusty winds from the
northwest are again forecast to develop in the wake of the cold
front. Anticipate upslope rain and snow showers across portions of
southeast West Virginia, south into the northern Mountains of North
Carolina late Wednesday night, into and through the day on Thursday.
Temperatures during this portion of the forecast will trend from
near normal on Monday to around 10 to 15 degrees above normal for
Tuesday and Wednesday. Thursday will be slightly cooler with
readings around five degrees above normal.
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 700 PM EST Thursday...
Medium confidence in development of IFR/LIFR conditions toward
The region will remain under a lingering wedge remnant while
one area of low pressure moves through the upper midwest, and
another spins off the southeast coast. This pattern will keep a
good amount of moisture in the boundary layer with a southerly
wind flow. Expect diurnal convective clouds will wane and allow
for a period of modest clearing, triggering development of low
clouds and fog. Additional support for clouds will be advection
of moisture up from the south and orographic lift along the Blue
Ridge. This should all make for widespread IFR/LIFR in stratus
and fog by daybreak at all sites, with the notable exception of
KBLF as they are not a favored location for IFR/LIFR conditions
in such a regime. This is a nuanced forecast largely dependent
on behavior of lingering convective clouds early in the period
so adjustments to forecast philosophy will be made as necessary.
Any low clouds/fog will dissipate Friday morning followed by
redevelopment of MVFR to VFR convective clouds by the
afternoon. Precipitation chances tomorrow appear limited with a
cap evident on model soundings. Winds will generally be light
through the period with no significant gusts expected.
Will continue to indicate AMD NOT SKED at KLYH due to
persistent ASOS equipment issues.
Extended Aviation Discussion...
Band of showers and isolated thunderstorms with MVFR conditions
arrive late Friday night into early Saturday along and ahead of
a strong cold front. Drier weather and increasing northwest
winds follow behind the front on Saturday afternoon through
Approach of another front Monday will provide increasing clouds
and possibly showers and MVFR cigs to BLF/LWB late in the day.
As of 340 PM EST Thursday...
Mostly sunny skies Friday may result in warm temperatures
Thursday Night 2/23/17 Record Warm Lows:
Bluefield 51 (1975)
Danville 50 (1981)
Lynchburg 52 (1925)
Roanoke 54 (1925)
Blacksburg 46 (1990)
Friday 2/24/17 Record Highs:
Bluefield 71 (1961)
Danville 79 (2012)
Lynchburg 79 (2012)
Roanoke 80 (1985)
Blacksburg 73 (1975)
As of 700 PM EST Thursday...
The automated observation system at Lynchburg (LYH) continues to
experience problems. Electronics technicians will investigate
further on Friday.