Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 271102

Area Forecast Discussion
National Weather Service Blacksburg VA
702 AM EDT Thu Oct 27 2016

A weak cold front will approach the region from the west this
morning before passing across the area later today into this
evening. High pressure follows the front Friday bringing a return
to drier and milder weather into Saturday. Another weak cold front
will dip south through the Mid-Atlantic region later Sunday into
Sunday night.


As of 300 AM EDT Thursday...

Surface wave passing to the north will gradually propel a weak cold
front into the mountains later this afternoon and across the Blue Ridge
this evening. Moisture ahead of the boundary remains quite limited with
dewpoints in the 30s/40s under westerly flow aloft. This again spells
concern for coverage of showers with the front later today as best
dynamics pass north while much of any initial lift will go to basically
moisten the column. Models remain quite limited in producing much QPF
outside of the far north/northwest with the GFS wetter with a pre-
frontal convergence axis this afternoon before the actual front
arrives this evening. This tied to a stronger lead shortwave rounding
the base of the upper trough which looks overdone. Latest ECMWF on
the other hand quite spotty with showers in having only a few
hundredths mainly east of I-81 and a tenth or two to the west.
However despite limited deep return moisture with only subtle backing
seen aloft today, lapse rates look rather steep and with progged
theta-e ridging and weak diffluence aloft, still appears a couple
bands of broken showers possible. This mainly within a possible
pre- frontal band over the west that will attempt to shift into
southeast sections late, and with the actual front crossing the
western ridges by early evening. Isolated thunder cant be totally
ruled out mainly far north per upper support, and over the far
south where guidance shows some weak late day instability, but
quite iffy given limited moisture recovery at this point.

Thus keeping pops mainly chance while cutting back on thunder and
allowing some sunny breaks espcly east this morning and perhaps at
times over the west if showers are slower to develop. Also leaned a
little more toward the milder Met mos today given warmth aloft and
westerly flow which with some breaks could allow readings to jump well
into the 60s to near 70 southeast.

Front should finally clear the area overnight allowing drying aloft to
kick in as northwest flow aloft increases. This should shut off most
lingering shower chances during the evening with downslope clearing
taking shape out east. However low level moisture within the
northwest trajectory likely to aid low clouds and possibly spotty
drizzle western slopes after midnight with low clouds likely
spilling out toward the Blue Ridge overnight. Thus becoming mostly
clear east to partly cloudy Blue Ridge to remaining mainly cloudy
far west. Cool advection bleeding into the west should allow lows
to drop off into the 40s west of the Blue Ridge with overall low/mid
50s east given best cooling aloft to the north and west.


As of 330 AM EDT Thursday...

After a vigorous short wave exits New England on Friday, the upper
level pattern will trend to a progressive quasi-zonal regime through
the weekend. Anything resembling cold air will remain bottled up to our
north and with high pressure at the surface taking up a position over
the southeast we will have a steady warming trend with temperatures
well above normal through the weekend. By Sunday a low will be sliding
by to our north and slowly pushing a weak frontal boundary into the
region. This may bring a shower to the far north from Greenbrier county
WV through the Alleghany Highlands and down the western slopes of the
Appalachians later on Sunday into Sunday night, but any precipitation
looks to be meager and the majority of the area will see no
precipitation at all. It also looks to be a bit breezy mainly Saturday
night and Sunday.

High temperatures on Friday will generally be in the upper 60s/lower
70s east of the Blue Ridge to low/mid 60s west. However by Sunday highs
will be close to 80 for some locations east of the Ridge with low/mid
70s west, which will be a solid 10 degrees above normal.


As of 300 PM EDT Wednesday...

Above normal temperatures will continue into the medium range with
Southeast ridging. Several shortwaves will rotate across the northern
Tier of the CONUS in the fast upper flow. High pressure will build
south into our region for Monday into Wednesday.


As of 655 AM EDT Thursday...

Upper trough and its associated surface low will pass north of the
area today with a trailing weak cold front approaching from the
west this afternoon. Some pre-frontal showers may develop ahead
of the boundary this morning which will help saturate the air mass
but the surface cold front will not cross the mountains until the
afternoon and into the VA/NC piedmont during the evening.

Increasing mid and high clouds will continue this morning with
some lower strato-cu possible across the west and perhaps patchy
stratus in the KDAN vicinity. However still appears most cigs
will remain just above VFR levels given low level dry air in
place with perhaps brief MVFR/IFR around KDAN. Bases will
gradually lower through this afternoon, but even with the
showers, should remain VFR outside of possibly KBLF/KLWB where
cigs may lower into MVFR at times if showers are a bit more
widespread later in the day. Post frontal sub-VFR cigs are also
likely along the western slopes of the Appalachians into tonight,
but these low clouds are not expected to make it east of the Blue
Ridge including KBCB.

A low level southwest jet will remain strong this morning as winds
in the valleys remain light. Thus have kept in LLWS for KLWB early
this morning where models show the jet aloft a bit stronger.

Extended aviation discussion...

High pressure builds in from the northwest Friday, lingering MVFR
cigs are possible at KBLF/KLWB through daybreak Friday before
clearing. Another cold front will approach from the north on
Saturday and pass through the region Sunday with possible showers
and MVFR ceilings mainly in the mountains. However, models were
still showing differences in the timing of the weekend system with
potential for showers to stay mainly north of the region. High
pressure and dry weather with VFR conditions are expected on




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