Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KRNK 172013
Area Forecast Discussion
National Weather Service Blacksburg VA
413 PM EDT Mon Apr 17 2017
-- Changed Discussion --A cold front will move into eastern Virginia and North Caroline
this evening and off the southeast North Carolina coast by
Tuesday morning. In the wake of this front, a wedge of high
pressure will build over the Mid-Atlantic region bringing
noticeably cooler temperatures for Tuesday and Wednesday.
Overrunning moisture will bring a threat of rain back to the
southern part of the area on Tuesday and spread northward
Tuesday night into Wednesday.
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.NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --As of 415 PM EDT Monday...
Cold front has shifted to just east and south of the Blacksburg
forecast area this afternoon with a line of broken convection
near the boundary moving into southeastern Virginia and north-
central and northeast North Carolina. Scattered lingering
showers behind the front, closer to where the boundary likely
is at 850mb, are expected to fade through the late afternoon
into evening hours. Have moved out showers and storms much more
quickly next few hours so that the tonight forecast should have
no mention of thunder in for any locations, and even chances for
showers are fairly low.
Late tonight, an upper level wave currently over western KY will
approach and bring an increasing chance for light rain back into
the southwestern part of the forecast area, especially NW NC and
far SW VA. Light rain could continue at times into Tuesday
across parts of the far southwest and south overspreading the
wedge, but think this will have a hard time getting much past
the NC/VA border.
Only partial clearing expected across the far north well behind
the front, but most locations will remain overcast. Winds shift
northeast overnight as high pressure center moves east across
Great Lakes and noses southward through NY/PA and northern VA.
Temperatures will be cooler tonight behind the front and with
shallow wedge building in, but most noticeably tomorrow
compared to the highs today. However, even with wedge firmly in
place, the air advecting in from the northeast is fairly dry and
some sunshine is expected at times across the northeast. In
locations where is remains overcast, and additionally there is
rain continue into some of the day, temperatures will be well
below normal and went as much as 5 degree below coolest MAV
guidance. Might have trouble getting out of the 40s in places
like Boone, but most locations will remain in the 50s in the
mountains, with a few low 60s in Mountain Empire, perhaps toward
Bluefield, and then mid to upper 60s in the Piedmont of VA.
Tricky temperature forecast and suspect some areas across the
south we may need to go even cooler, while others may end up
being warmer farther north.
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.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 230 PM EDT Monday...
A strong surface wedge will be draped across the region and
stretching south into Georgia Tuesday night and Wednesday. A
short wave axis over the Tennessee Valley will push moisture
over this wedge starting from the southern Appalachian mountains
Tuesday, then northward over southwestern Virginia Tuesday
night. A surface reflection is expected to form off the North
Carolina coast late Tuesday night into Wednesday. This coastal
reflection and the short wave axis, moving over the southern
Appalachians, will nudge precipitation east off the Blue Ridge
Wednesday afternoon and east of the piedmont Wednesday evening.
The best isentropic lift and upslope flow is across all of the
North Carolina mountains into southwestern Virgina Blue Ridge
(Floyd and Patrick counties) Tuesday night into Wednesday
morning. This lift and moderate rain will track along the NC/VA
border Wednesday into Wednesday evening. Rainfall amounts,
especially along the eastern slopes of the Blue Ridge will range
from a half to one inch. Foothill and piedmont counties along
the VA/NC border should see up to half an inch. Rainfall amounts
north of 460 will range from a few hundredth towards the
Southern Shenandoah Valley to a quarter of an inch in the
Roanoke and New River Valleys. Rainfall intensity will also vary
greatly from moderate to possibly heavy rain south of highway
460 to light rain and drizzle north. Low clouds and fog will
also be present Tuesday night and Wednesday morning. Saturated
soils and warm moist air from a passing warm front will bring
areas of fog to the area again Wednesday night.
Diurnal temperatures ranges will remain small while this wedge
hangs over the region. Overnight lows will be in the upper 40s
to lower 50s Tuesday night and Wednesday night. High
temperatures Wednesday may warm into the upper 50s to lower 60s.
Areas that see the wedge erode Wednesday (Mountain Empire and
Bluefield) could see temperatures warm into the upper 60s to
lower 70s Wednesday afternoon.
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 240 PM EDT Monday...
A warm front will move north of the region on Thursday. With
the wedge gone, temperatures will warm into the mid to upper 70s
across the mountains and lower 80s east of the Blue Ridge. A
cold front slides across the region Thursday night into Friday
morning. Mostly showers will accompany the front, but a few
rumbles of thunder are possible. Temperatures Friday afternoon
will be slight warmer than normal, mid to upper 60s west to mid
to upper 70s east. High pressure builds in Friday afternoon and
will keep the area dry until Sunday. A closed low tracking east
from the Midwest is expected to bring strong to severe storms to
the area Sunday. Models differ on the track of the upper low
but agree on timing for Sunday. This weekend`s temperatures will
depend on the timing and track of the low. For now, we will
keep temperatures near guidance which is near normal.
.AVIATION /20Z MONDAY THROUGH SATURDAY/...
As of 225 PM EDT Monday...
Weak surface front moving through the Appalachians this
afternoon with light showers in the mountains resulting in MVFR
CIGs at times and perhaps briefly IFR. Scattered thunderstorms
forming in the Piedmont but most likely to impact KDAN with
temporary MVFR conditions through about 4 or 5pm, but could
move through even quicker. Also included VCTS at KLYH but this
threat may be over soon as so far all storms forming east of
that site. Winds shifting to NW behind the line of scattered
storms in Piedmont but may switch back to SW or W briefly, and
eventually will shift again NW but lighter by this evening and
then eventually east to southeast overnight.
A small potential exists for IFR ceilings to develop
overnight/early Tuesday at KROA and KBCB, and maybe KBLF, with
low level northeast to east flow developing, but confidence
remains low so continuing with MVFR for now. Low CIGs are likely
along the Blue Ridge southwest of KROA but the worst conditions
are not likely at the TAF sites.
Extended Aviation Discussion...
Surface high pressure will wedge southwest into the area later
Tue-Wed resulting in a more stable air mass and allowing the
front to be pushed a little further south, thus no threat for
convection during the Tue-Wed period with the possible exception
of KBLF late Wed. Some showers could get as far north as KDAN
late Tues perhaps resulting in MVFR conditions but at this time
they appear more likely to remain to the south.
By Thursday, the front will return north as a warm front as a
new front approaches from the northwest once again. Showers and
thunderstorms will be on the increase Thu-Fri as this front also
drifts into the area and stalls. This front will return to the
north as a warm front Saturday as a much stronger weather system
moves into the southeast U.S. Between the wedge Tue-Wed and the
frontal systems in/near the area through the week, multiple and
extended periods of sub-VFR aviation conditions are expected
through the week, but most likely by later in the weekend.