Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 050052
Area Forecast Discussion
National Weather Service Blacksburg VA
752 PM EST Sun Dec 4 2016
A combination of low pressure cross the Great Lakes region and one
progressing northeast along the coast of the Carolinas, will
continue to provide precipitation across the area overnight. After a
brief break in the weather on Monday, our next weather system will
approach and then cross the area Monday night into Tuesday. Again,
after another break in the activity on Wednesday, a strong cold
front will cross the region on Thursday.
.NEAR TERM /THROUGH MONDAY/...
-- Changed Discussion --As of 730 PM EST Sunday...
The evening update will reflect two notable adjustments.
Temperatures have cooled a couple more degrees across parts of
the area and placed ridge tops along parts of the Blue Ridge at or
a little below freezing. We still expect a gradual increase in
temperatures overnight, but until these figures start to climb,
expect some light freezing rain at these locations. Also, northern
parts of the region will have a bit more coverage of light sleet.
As of 330 PM EST Sunday...
We continue to watch both an area of low pressure moving northeast
along the coast of the Carolinas, and an approaching negatively
tilted shortwave trough heading through the Great Lakes region. Both
of these systems will contribute to precipitation across the region
into tonight. The greatest coverage will be near the VA/NC through
the evening hours with the least coverage across the northern
quarter of the forecast area. There is enough of a warm nose aloft
for the production of some light sleet tonight, mainly along and
north of Interstate 64 in Virginia. The remainder of the region is
expected to receive rain.
Temperatures will hold nearly steady this evening, and then begin a
slow rise from roughly midnight through sunrise Tuesday. So, most
locations will experience their low temperature tonight this evening
will be close to the temperatures at sunset. By sunrise,
temperatures are expected have increased to the lower 40s across the
southwest parts of the forecast area and the mid to upper 30s across
the northeast parts.
The axis of the Great Lakes shortwave trough will cross the area
between midnight and sunrise. Winds will shift west to northwest,
allowing for the potential for some upslope precipitation to
conclude the evening late tonight into early Tuesday morning between
Bluefield and just west of Lewisburg, WV. The bulk of the
precipitation elsewhere will end by sunrise Monday.
On Monday, clouds will be on the decrease east of the crest of the
Blue Ridge as northwest flow prevails and drier air begins entering
the region. The upslope showers in the far western parts of the area
will wane by mid-day with a trend towards decreasing cloud cover.
Late Monday afternoon, look for clouds to start increasing across
the area again in advance of our next weather maker that will be
moving through the Gulf Coast states. Precipitation on the
northeast edge of the system may reach the far southwest portion of
the region very late in the afternoon. Currently, the confidence is
a slight chance.
Highs on Monday will range from around 50 to the lower 50s across
the mountains with mid to upper 50s across the Piedmont.
-- End Changed Discussion --
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 300 PM EST Sunday...
Upper low finally ejecting out of the southwest will give rise to
surface low pressure across the lower Mississippi Valley Monday night
that will track just west of the mountains Tuesday. Secondary low
likely to develop with convection closer to the coastal front making
for an arc of widespread rainfall between the two that will overspread
the region from southwest to northeast later Monday night into Tuesday
before exiting Tuesday night. Expecting heaviest amounts across the
west with the primary wave into Tuesday with a secondary area over the
piedmont closer to the coastal low. May also see another max along the
southern Blue Ridge per upslope early on. Will have to watch for some
cutoff in moisture advection to the south as the second wave forms
while the upper jet tends to dry slot from the southwest between the
two systems. However appears enough lift over the very strong wedge to
support a good soaker with an inch or more espcly south/west with
perhaps a bit less to the north.
Other concerns with increasing southeast flow into the Mountain Empire
region early Tuesday and with possible icing across parts of
Bath/Greenbrier ctys as well. Since forecast soundings show the
stronger winds aloft not mixing down much due to a saturated column,
appears will stay below advisory criteria for now. Latest model
soundings also prog a decent warm nose over the north by Tuesday with
only the ridges near freezing for a period early on. Latest EC/Nam also
continue to indicate the potential for some light icing in spots so
included a freezing rain mention, but quite isolated at this point.
Otherwise slowed pops down a few hours given dry air aloft to start
Monday night with clouds increasing, but still expecting most to see
likely/categorical pops by morning. Then widespread high pops Tuesday
as the core of the deeper lift/moisture crosses through the wedge
making for quite a chilly/raw day with highs mainly upper 30s to mid
System exits to the northeast Tuesday night with only residual evening
pops northeast and across the mountains as a weak trailing boundary
crosses the west with a bit of upslope induced shower coverage. High
pressure to follow from the west on Wednesday as the upper flow turns
zonal making for more sunshine east and overall partly cloudy west but
dry. This should also help push highs back into the 50s east of the
mountains with upper 40s to lower 50s west by Wednesday afternoon.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 230 PM EST Sunday...
Main concern with cold air arriving by the end of the week as brief
zonal flow gives way to a digging upper trough and subsequent
associated Arctic front on Thursday. Models continue to differ a bit on
timing with the ECMWF slower per having a wave along the boundary,
while consensus suggests more in the way of a drier frontal passage
given westerly flow. This would bring the boundary across the mountains
by midday Thursday and across the rest of the region during the
afternoon. Band of moisture just ahead of the front should allow for a
rain to snow shower changeover western mountains Thursday morning
with a few showers east if any moisture makes it over the ridges.
Strong cold advection following the front should make for mainly
upslope snow showers overnight into Friday but amounts/coverage
limited by very dry air. Otherwise will turn windy and much colder
espcly Thursday night and Friday although appears speeds still
below advisory levels with wind chills zero/single digits. Arctic
high finally builds overhead by Saturday allowing for the coldest
temps by early morning before the trough starts to lift out
allowing some moderation Saturday afternoon into Sunday in
response to return warm advection. Next weak system coming out of
the Rockies may tap enough return moisture to bring a band of
light mix to the far west by late Sunday. However without much
southern connection appears precip limited given residual dry air
and could be just clouds and spotty rain if things slow up more so
only low pops for now Sunday.
Expect temps to fall from west to east Thursday followed by highs only
in the 20s mountains to 30s east under a blustery northwest wind
Friday. Lows Friday night mostly teens unless high clouds invade more
late, then warming to highs in the 30s and 40s for the weekend.
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --As of 630 PM EST Sunday...
Precipitation, mainly in the form of light to moderate rain, will
continue progressing across the area this evening. Ceilings are
continuing to trend downward, with most locations now in the MVFR
range, with some pockets of IFR across southwestern parts of the
area. Visibilities have also trended to MVFR across much of the
region. Pockets of sleet and light freezing rain will be be
possible at some of the higher elevations, especially between
KLWB-KHSP before roughly 08Z/3AM.
A cold front will cross the region late tonight into early Monday
morning. Look for winds to increase from the northwest around or
little after sunrise. The northwest winds will bring drier air to
the region. Ceilings east of the crest of the Blue Ridge should
scatter by the mid-morning. Cloud cover will last longer across
the mountains thanks to an upslope component working with
residual low level moisture.
By the late afternoon, VFR conditions are expected across the
Extended aviation discussion...
VFR conditions are expected Monday evening.
Our next weather system looks to bring rain to the region staring
late Monday night, and continue through the day Tuesday. IFR/MVFR
ceilings are probably late Monday night through the day Tuesday.
Likewise, sub-VFR visibilities will accompany the precipitation.
Another cold front will head through the area Tuesday evening.
Look for improvement to VFR east of the Blue Ridge, with lingering
sub-VFR ceilings across the mountains, and perhaps some scattered
upslope rain/snow showers between KBLF-KLWB later Tuesday night
into early Wednesday morning.
Anticipate another break in the activity on Wednesday before yet
another cold front crosses the region on Thursday. Look for a
return of sub-VFR conditions and better chance of snow showers in
the west Thursday night into early Friday.
Friday, expect a gusty day across the region with lingering
upslope cloud and snow showers between KBLF-KLWB. East of the Blue
Ridge, VFR is expected.
-- End Changed Discussion --
As of 345 PM EST Sunday...
NOAA Weather Radio, All Hazards, WZ2500 in Wythe County continues
to be off the air. Technicians will be examining the system
tomorrow to explore a possible power failure.