Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 010752

Area Forecast Discussion
National Weather Service Blacksburg VA
352 AM EDT Sat Oct 1 2016

A strong upper level area of low pressure in the southern Ohio
Valley will continue to drift slowly to the north today and
tonight. This will finally allow drier air to the southwest to
punch into the region through tonight. Weak high pressure follows
this system on Sunday with overall dry weather into early next

As of 240 AM EDT Saturday...

Upper low in the southern Ohio Valley region will finally lift
slowly north over the next 24 hours with its associated complex
occluded surface system also shifting off to the northeast. This
should initially allow drier air aloft seen on water vapor to the
south to advect in this morning followed by a gradual turning of
the low level flow to the south/southwest this afternoon in the
wake of the occlusion. Expecting this combination to dry things
out with any early showers northeast sections fading after sunrise
if not sooner. Low level moisture within the lingering wedge out
east may be slower to exit given weak flow but overall expecting a
return to sunshine this afternoon under weak subsidence. Cant
totally rule out an isolated shower redeveloping given slower
exodus of near surface moisture espcly north/east early this
afternoon, although guidance showing little instability given
lowering dewpoints later on. Thus basically leaving out pops after
early this morning with clouds/fog to start then increasing
sunshine. Expect quite a mild afternoon to start October with 850
mb temps of +13C on average combining with southwest flow to push
highs into the 70s and perhaps low 80s southeast.

Area will remain in the dry slot under the departing upper low overnight
making for continued mainly clear skies. Increasing southwest jet
aloft may tap into some high level moisture overnight so some high/mid
clouds possible late along with patchy fog. Otherwise should be
quite comfortable with lows mostly 50s with some 40s across the
western valleys. Thus went below Mos given good radiational cooling
but not as cool as the coop values per wet soil conditions/fog.

As of 230 AM EDT Saturday...

The upper level low that has been wobbling over the Ohio Valley the
past several days will lift north and track over Lake Erie Sunday
then moves off the New England shore Monday night. By Tuesday, high
pressure will wedge south across the Mid Atlantic region bringing
cooler temperatures.

We will remain under the influence of the upper level low Sunday
with passing short waves and a few clouds producing some sprinkles
over the mountains. For the most part, subsidence and dry air
wrapping around the low will limit any shower activity as these
waves pass over the area. With more clouds and cool northwesterly
flow, afternoon highs across the mountains will range in the lower
to mid 70s. Downsloping flow and more sunshine east of the Blue
Ridge, temperatures Sunday afternoon will warm into the upper 70s
and lower 80s. As the low begins to exit offshore Monday, heights
will increase giving a bump to afternoon temperatures. Temperatures
Monday will be a degree or two warmer than Sunday. High pressure
wedges south across the Mid Atlantic Monday night into Tuesday.
Uniform afternoon temperatures in the mid 70s are expected Tuesday.
Some clouds will accompany the wedge, but no precipitation is
expected to fall Tuesday.

As of 330 PM EDT Friday...

The big variable mid to late week lies with the potential track of
Matthew as it is expected to turn north and move up the Atlantic
coast. The latest guidance indicates the tropical system will
remain far enough to our east to keep direct effects of this
system out of our region. However, the wedge will remain in place
and the squeeze between the wedge and the tropical system will
create enough overrunning to generate precipitation by late
Tuesday/Tuesday night especially in the east and continuing
through the end of the period.

Temperatures in the wedge will remain cool and generally several
degrees below normal.


As of 102 AM EDT Saturday...

Isolated showers/storms still lingering in spots across the east
and may stick around a few more hours along a KHSP-KLYH-KDAN
corridor. Otherwise the main concern heading into late tonight
will be fog and low clouds. Already seeing lower cigs at most
locations, and with drier air aloft working in from the south
combined with very moist ground and light winds, should see fog
develop as well. Think most sites will drop to MVFR/IFR or worse
by daybreak, which will vary between fog and/or low stratus.

Saturday, winds stay light but turn southwest. Fog and low clouds
will be slow to lift but overall should be VFR everywhere by
midday into early afternoon. Exodus of the upper low and
associated surface occlusion should lead to little more than
scattered-broken cumulus during the afternoon and without any

VFR to continue Saturday night with fog formation again likely
under clear skies and lights winds over moist ground conditions.
This mainly across the valley locations and less elsewhere.

Extended aviation discussion...

The deep upper level low will finally shift farther to the north
and away from the region on Sunday. The weather will trend back
into a dry pattern with mainly VFR conditions next week, aside for
river valley fog in the mountains resulting in brief period of
late night early morning LIFR conditions at some of the mountain
valley airports through Wednesday.




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