Area Forecast Discussion
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FXUS61 KRNK 211523
Area Forecast Discussion
National Weather Service Blacksburg VA
1123 AM EDT SAT MAY 21 2016
Low pressure off the North Carolina coast will deepen and move
northeast today through Sunday as a weaker low over the Ohio
Valley tracks southeast and dissipates. High pressure over the
central United States will move east Monday and Tuesday, then off
the East Coast on Wednesday.
.NEAR TERM /THROUGH TONIGHT/...
As of 1120 AM EDT Saturday...
Have adjusted pops to keep less coverage in the Piedmont through
early afternoon. Will see more breaks in the cloud cover as we
head through early afternoon, though with upper trough moving
across later there should be more clouds building up. Still looks
like best threat of showers and isolated storms will be over the
mountains and into the foothills of NC.
Previous valid discussion...
The coastal low will move northeast and continue to deepen today
with northwest winds in the eastern county warning area around
this system. The low in the Ohio Valley will drift southeast today
with winds over the mountains from the southwest. By the end of
the day the coastal low will be deep enough to turn the winds
across the forecast area to the northwest.
More questionable in the extreme northeast county warning area
when and if the more stable air and low clouds will erode. Much of
the guidance keeps Amherst, Appomattox and Buckingham counties in
the cooler air through most of the day. Where there are breaks in
the clouds today, temperatures will have a decent chance of
getting into the lower 70s. Where the stable air remains in place,
highs may only be in the lower to middle 60s.
Any thunderstorms and some of the showers will dissipate with
loss of heating this evening. Have held onto a chance of showers
mainly in the northwest and eastern county warning area. Lows will
be near normal.
.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
As of 330 AM EDT Saturday...
The persistent blocky pattern will keep a closed low spinning off the
mid Atlantic coast into the first part of next week. Cold temperatures
aloft will create steep lapse rates and combine with diurnally driven
instability along with short wave impulses to bring a good chance of
showers and some thunder to our forecast on sunday. The low will still
be close enough to us on Monday to keep some showers/thunder in the
forecast mainly east of the Blue Ridge but by Tuesday we can expect
some low amplitude ridging aloft to move in as the surface low moves up
the coast towards Cape Cod. This should finally allow us to dry out a
bit as we head towards midweek.
Temperatures will start the period well below normal with highs on
Sunday only in the low/mid 60s west of the Blue Ridge and in the upper
60s/near 70 to the east. But by Tuesday as the closed low loses its
influence over our weather and temperatures moderate we will see
readings return to normal levels with low/mid 70s west and upper
70s/around 80 east.
.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
As of 330 AM EDT Saturday...
Broad low amplitude ridging will continue our moderating trend with
temperatures well above normal Wednesday through Friday. However with
the warmer temperatures will come moisture and a better chance for
showers and thunderstorms each afternoon and evening...especially from
the Blue Ridge westward. The pattern does not favor organized
convection so any storms are expected to be of the pulse variety.
.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
As of 740 AM EDT Saturday...
Area radar indicated moderate rain was east of KLYH and KDAN as of
11Z/7AM. Isolated light showers were over the mountains.
Low pressure off the North Carolina coast will continue to deepen
and move northeast today. This will help erode the wedge east of
the Appalachians as surface and low level winds come around to the
As the upper low and associated cold pool aloft move southeast out
of the Ohio Valley today, scattered showers and isolated
thunderstorms will develop outside of the wedge. Large lapse rates
will add to instability this afternoon as seen on the NAM and GFS
Bufkit forecast soundings. Medium confidence on the areal coverage
of any thunderstorms this afternoon. For now have left any
thunder out of the TAFs. Expecting IFR to MVFR clouds to fill back
in after sunset. Locations that have rain this afternoon may have
MVFR to IFR fog overnight.
High confidence in the evolution of events today, but low
confidence on the timing. KLYH may stay in the wedge and stable
air well into the afternoon.
Sunday and Sunday night, cigs look to remain quite variable under
the passing upper low with periods of mainly MVFR cloud bases
during the daylight hours and VFR cigs at night. Isolated to
scattered showers will also occur, espcly across the east Sunday
into Sunday evening making for MVFR vsbys or worse at times.
Isolated thunder will also be possible along with patchy sub-VFR
vsbys overnight in fog where earlier rainfall occurred. Northwest
upslope flow may maintain some IFR ceilings at times in the west
espcly around KBLF. Surface gusts of 20 to 25 kts will be possible
across the mountains Sunday and Sunday night. 850 mb winds are
progged to increase to 25 to 35 kts, and gradually veer northwest
On Monday, winds will start to decrease as the center of the upper
low continues to exit the region. Isolated showers will still be
possible, especially in the east, related to this feature.
Monday night through Wednesday, expect mainly VFR conditions as
high pressure settles offshore with southwest flow in place.