Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 241823

Area Forecast Discussion
National Weather Service Blacksburg VA
223 PM EDT Mon Jul 24 2017

A weak cold front will slide southeast through the area tonight
before stalling over the Carolinas Tuesday into Wednesday. High
pressure builds north of the region behind the front bringing a
return to more seasonal temperatures later tonight through mid
or late week. Another cold front approaches from the northwest
on Friday and works slowly through the area by the weekend.

As of 210 PM EDT Monday...

Convection continues at a minimum this afternoon as the region
remains in a somewhat drier westerly flow between the exiting
surface trough to the east and the cold front along the Ohio
River. This front should finally slide southeast and across the
region later this evening as the upper trough to the north
swings by to the northeast. Latest guidance still showing some
degree of at least shallow convection just ahead of the boundary
with the Nam quite agressive, while other solutions only show
widely scattered coverage within the instability axis along our
northwest slopes. Since some potential for a band of broken
convection to move into the northwest sections, have included
low to isolated pops later this afternoon into early evening for
locations mainly west of the New River Valley. Otherwise should
see clearing take shape overnight as the front sags to the
south allowing for a bit more comfortable air to advect into the
mountains where expect lows well into the 60s. Moisture may
linger across the south/east so kept lows mainly upper 60s to
lower 70s there. Also despite good drying today, appears some
fog/stratus development possible espcly valleys given heavy
rain from last night and better radiational cooling west

High pressure builds in from the north on Tuesday with weak
northerly flow resulting in enough dry advection to limit most
convection to across far southern sections at best. This seen
via model lowering of PWATS from north to south and axis of
deeper moisture well to the south closer to the residual surface
front. Therefore reduced pops to slight chance mainly across
northwest NC where perhaps enough low level moisture/instability
may linger to pop a shower or two but iffy. Otherwise enough
subsidence for overall mostly sunny skies and not quite as
hot/humid with highs low/mid 80s mountains to 87-92 east of the
Blue Ridge.

As of 1245 PM EDT Monday...

Little change in the weather pattern and no synoptic scale forcing
Wednesday and Thursday. Will keep minimal probability of
precipitation, mainly in southern Virginia and northern North
Carolina each afternoon and evening. Persistence combined with bias
corrected MET/MAV guidance will be reasonable for daily highs and

As of 1245 PM EDT Monday...

Upper pattern amplifies starting on Friday with the upper ridge over
the western United States slightly retrograding and a trof digging
in the east. An upper low may eventually close off somewhere over
the Tennessee Valley or Mid Atlantic region by Sunday or Monday.
This closed low solution was not supported by a majority of the
extended guidance. Probability of showers and thunderstorms will
increase on Friday and Saturday with some vorticity advection and
lowering heights. Air mass ahead of the trough stays in the +16 to
+20 range for temperatures at 850MB and will be a little cooler on
Sunday and Monday.

As of 1245 PM EDT Monday...

Overall conditions have returned to VFR across the region with
only KBLF holding onto some lower MVFR cigs under upslope flow.
Expect those lower cigs to finally scatter out shortly resulting
in mainly cumulus VFR cigs beneath some high clouds above into
early this evening. Cant totally rule out isolated convection
developing mainly west of the KBLF-KLWB corridor after mid
afternoon with an isolated storm or two possible around KDAN.
However given uncertainty will leave out any mention with best
potential over the western sites late this afternoon. Winds
will be turning more west/northwest through the rest of the
afternoon with speeds mainly 5-15 kts except for a few gusts
above 20 kts over the ridges.

Weak front drops southeast through the area overnight with any
lingering convection over the west fading this evening. Looks
like enough of a threat to include a VCSH mention perhaps at
KLWB or KBLF early this evening but quite iffy in whether or not
any shra/tsra to the west will actually make it to any of the
terminals. Otherwise expecting VFR under clearing this evening
before possibly seeing some filling in of low clouds/fog across
parts of the mountains, and espcly around KBLF given continued
weak upslope flow. Also appears with slightly lower dewpoints
that temperatures fall enough to help develop dense fog across
the valleys. Thus including a IFR/LIFR mention at KLWB late as
well as brief MVFR to IFR late at KBCB/KLYH and perhaps KBLF.

Any sub-VFR due to low clouds/fog will gradually improve
Tuesday morning as drier air mixes out low level moisture under
high pressure. Convective chances again appear quite low Tuesday
afternoon with any threat mainly south of the taf locations so
running with overall VFR under cumulus/cirrus for now.

Aviation Extended Discussion...

A frontal boundary should stall to the south, with high
pressure wedging southward on Wednesday. Overall VFR but with
flow turning more east, this could bring some MVFR/IFR
ceilings, which should quickly dissipate by Thursday. Any
convection also likely to remain isolated and south of the taf
sites again later Wednesday. Next best threat for showers and
storms arrives with another front Friday with perhaps some of
this coverage lingering over southern/western sections into




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