Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Blacksburg Virginia
941 PM EDT Tuesday Oct 13 2015
a cold front will move east tonight into the Atlantic Ocean. High
pressure will build in behind the front tonight into Thursday.
Near term /through Wednesday/...
as of 935 PM EDT Tuesday...
Wind gusts have continued to subside across most of the
region...but remain in the 10 to 20 miles per hour range at higher
elevations. Drier dew points at the surface continue to advect
into the region...all the while just a little higher up...there is
still enough moisture for some cloud cover across the mountains.
The challenge tonight will be the impact of the cloud cover
reducing a temperature decrease...all while lowering dew points
will promote a temperature decrease. Have made little if any
adjustments to the ongoing low temperature forecast as the numbers
represent both of these processes.
As of 635 PM EDT Tuesday...
Overall pleasant evening across the region. Lower dewpoints
continue their slow March eastward this evening. As of 6pm...the
line of 40s dewpoints has made it past the Blue Ridge and will
push through the Piedmont overnight. Upslope cloud cover will
continue across southeast WV tonight will some spillover of scattered cumulus out to
the Blue Ridge. West/northwest winds have been gusting 15-25kts at times
across the higher elevations...while they will subside some it
will remain a bit breezy through the night.
As of 235 PM EDT Tuesday...
An upper level trough will remain over the east tonight into
Wednesday. Several shortwaves will drop southeast in the northwest
flow with most of the energy passing to our north. The hiresw-
arw...Canadian...GFS and NAM displayed some upslope cloud cover in
West Virginia tonight...with clear to partly cloudy elsewhere. Low
temperatures tonight will be chilly with readings from around 40 in
the mountains to the upper 40s in the Piedmont.
High pressure will build east into our region Wednesday. An upper
level disturbance will rotate around the base of the upper trough
Wednesday afternoon into Wednesday evening. Because there is
limited moisture with this feature...only anticipating additional
cloud cover. High temperatures will range from the lower 50s in
the northwest mountains to the lower 70s in the Piedmont.
Short term /Wednesday night through Friday/...
as of 300 PM EDT Tuesday...
Dry weather will continue for Wednesday night through Thursday
night. The next significant synoptic scale short wave comes through
the northwest flow and pushes a surface cold front through the
forecast area on Friday. 12z run of the GFS was slower than the NAM
with the deepest moisture crossing the forecast area but even the
GFS had a bulk of any moisture and lift exiting the southeast County
Warning Area by 00z Saturday/8pm Friday. Strong jet maximum with some
lift in the right rear quadrant will aide in lift so have slightly
increased the probability of rain in the far western upslope areas
on Friday. Amount moisture is the most questionable part of the
forecast. The winds at the surface and low levels back to the
southwest ahead of the front but overall flow keeps Gulf shut off
and higher relative humidity confined below 800 mb according to
BUFKIT forecast soundings.
Trended temperatures toward a blend of met/mav guidance.
Long term /Friday night through Tuesday/...
as of 100 PM EDT Tuesday...
Models in decent agreement in this time frame. A large high fills
in behind the front for Saturday through Tuesday. The high will be
centered over Virginia by Sunday morning and with 850 mb temperatures
around zero at that time hazardous weather outlook will highlight
potential for first fall frost/freeze for the County Warning Area.
Aviation /02z Wednesday through Sunday/...
as of 730 PM EDT Tuesday...
VFR conditions expected through the taf valid period...with one
possible minor exception at blf. Initial cold front moved well off
the East Coast with dry west-west-northwest flow established across the region.
West-northwest flow aloft also well established across the region. A weak
short wave...located across the Ohio Valley...will drift east-southeast
overnight and be east of the region by middle-day Wednesday. No
precipitation expected...but upslope clouds can be expected with
this system. The upslope cloud cover should peak in the 06z-14z
time frame and remain west of the Blue Ridge. Ceilings may drop to
below 030 late night/early morning at blf. Otherwise...VFR.
Although model guidance showing LIFR fog at lwb...feel enough dry
west-west-northwest wind will prevent this from occurring. Radiational
conditions are far from ideal tonight with troughing and cyclonic
flow across the region.
Winds...west-northwest 5-7kts overnight...becoming west-southwest-west-northwest 8-12kts with low
end gusts west of the Blue Ridge after 14z Wednesday.
Medium to high confidence in ceilings through the taf valid period.
High confidence in visibilities through the taf valid period...except lwb
medium confidence through 14z.
Medium to high confidence in wind speed/direction through the taf valid
Dry high pressure will remain across the region for middle week
promoting VFR Wednesday night and Thursday. Another cold front
will cross the area late in the week associated with possible
brief showers and a brief period of MVFR.
short term...air mass
long term...air mass