Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 200135
Area Forecast Discussion
National Weather Service Blacksburg VA
935 PM EDT Mon Sep 19 2016
An upper low will remain just to our south through most of the
week, with a trof of low pressure along the coast locking us into
a moist northeasterly flow of air. This will keep unsettled
conditions across our region, with just a chance for showers
mainly east of the Blue Ridge, through the end of the workweek.
.NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --As of 930 PM EDT Monday...
Cluster of showers and isolated thunderstorms that developed in
the Alleghany Highlands and moves south-southwest through the New
River Valley has begun to weaken. Hi-Res Guidance had the
precipitation still moving south-southwest but losing intensity
then eventually dissipating by 1AM. MSAS analysis showed local
environment was becoming more stable. Only minor changes made to
overnight lows based on current trends in observations.
The upper trof moving in from the west will be closing off just to
our south and lingering for a while. This will allow the remnant
surface low off the Carolina coast to spin in place and develop
moist northeast flow across the Appalachians and central mid
Atlantic. There is no change in airmass behind the frontal boundary
that moved through today and this will keep some residual
diurnally driven instability in place through tomorrow. However,
a good discrete forcing mechanism is not apparent and model
guidance seems a bit too robust with POPs. The best chance for
precipitation overnight and through Tuesday will be across
Southside VA and eastern sections of the NC/VA piedmont, tapering
to slight chance west of the Blue Ridge and generally dry for
Expect temperatures to remain mild tonight with upper 60s east of
the Ridge and generally lower 60s to the west. Highs tomorrow will
be seasonable with readings around 80 east to mid/upper 70s west.
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.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 330 PM EDT Monday...
A shortwave trough traveling towards the southern Appalachians will
amplify and close off over the Southeast and during the process will
absorb the remnants of post tropical cyclone Julia east of the
Carolina. A weak frontal zone across the Mid Atlantic coastal plain
along with low pressure wave will remain near the coast during the
period. The forecast challenge is how far west the richest moisture
or heavier rain pushes. The WPC Day 2 and Day 3 excessive indicate
that the marginal to slight chances will be located to our south and
With a northeast flow transporting Atlantic moisture into our region,
increased pops and cloud cover for Tuesday night. Low temperatures
Tuesday night will range from the mid 50s in the mountains to the
mid 60s in the Piedmont.
Increased cloud cover and pops for Wednesday into Wednesday night.
Shaped cloud cover towards ConsAll with its gradient from
northwest to southeast. Allowed for scattered showers across the
southern and eastern portions of the forecast area Wednesday into
Wednesday night. High temperatures on Wednesday will vary from the
lower 70s in the mountains to around 80 degrees in the Piedmont.
Low temperatures Wednesday night will generally be from the mid
50s in the west to the mid 60s in the east. Isolated to scattered
showers will continue east of the Blue Ridge Thursday into
Thursday night. With the richer cloud cover lowered high
temperatures on Thursday to the lower 70s in the mountains to near
80 degrees in the Piedmont. A few showers may linger Thursday
night in the southeast portion of the forecast area. Low
temperatures Thursday night into Friday morning will feature
readings from the mid 50s in the west to the mid 60s in the east.
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 330 PM EDT Monday...
The weak closed 500mb low opens to become absorbed in the general
west to east flow which gradually takes the clouds and rain east and
off the Atlantic coast Friday night.
Upper ridge strengthens by Saturday morning but remains undercut by
low level southeast flow Saturday ahead of a shallow backdoor front
that may slide south into the area by Sunday. This supports isolated
diurnal pops Saturday before deeper upstream moisture ahead of a
stronger Midwest cold front works east along the backdoor boundary
resulting in perhaps more widespread showers by early next week.
Leaned temperatures towards Superblend with cooler readings
especially for Sunday and Monday with moderating High temperatures
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 735 PM EDT Monday...
Low pressure at the surface was off the coast of North Carolina
this evening. Circulation around this low was resulting in
northeast winds across southwest Virginia, northwest North Carolin
and southeast West Virginia. The western edge of the lower clouds
and MVFR ceilings wrapped around this low were moving to the east
and were close to KLYH and KDAN.
Water vapor loops showed a short wave crossing through Virginia
and North Carolina this evening with drier mid level air advancing
across the mountains. This may be enhancing the lift for a cluster
of showers and isolated thunderstorms in southwest Virginia but
expect with the loss of heating as as this wave moves east the
coverage and intensity of showers and thunderstorms will diminish
Areas west of the Blue Ridge will remain VFR this evening. Medium
confidence that lower clouds will spread west overnight bringing
KLYH, KDAN and KBCB down to IFR, and KROA and KBLF back to MVFR.
Enough clearing for fog formation at KLWB. High confidence of LIFR
at KLWB after midnight.
Conditions will improve gradually on Tuesday. Expect VFR west of
the Blue Ridge after 18Z/2PM and for east of the Blue Ridge, not
until at least 20Z 4PM. Medium confidence on this timing.
Extended aviation discussion...
Tuesday night through Friday, outside of late night/early morning
fog/low clouds, expect mainly VFR conditions with the caveat to
this being any lingering slight chance of showers and
thunderstorms from Julia per GFS/EC, mainly affecting areas east
of the Blue Ridge.