Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 270739

Area Forecast Discussion
National Weather Service Blacksburg VA
339 AM EDT Mon Mar 27 2017

Low pressure moving out of the Mississippi valley will keep warm
temperatures and a good chance of showers and thunderstorms in
our forecast through Tuesday. A large area of high pressure
will wedge down the east side of the Appalachians behind the low
and bring much cooler temperatures with some drizzle for the
middle of the workweek.


As of 335 AM EDT Monday...

The backdoor front situated from near EKN-FVX should lift back north
as a warm front today. Showers will be mainly isolated to scattered
mainly this morning, with best coverage in the piedmont thru 12z.

A little fog and lower clouds out there as well this morning thanks
to the showers/wet ground and east/southeast wind. Should see any
fog dissipate after 9am.

Will see a lull in the coverage between 12-18z, then should start to
see uptick in showers and some thunderstorms after 18z as upper
shortwave and sfc low moving toward the lower Ohio and mid MS
valleys. Our area will be in southwest flow in the low and mid
levels, however, best lift stays along and west of the Appalachians.
There is some better low level convergence closer to the southern
Blue Ridge so may see better coverage here this afternoon.

Temperatures will be affected by cloud cover, but just enough sun
should send readings into the 70s, except 60s in the higher

Tonight, the sfc low and front move to the Central Appalachians,
with the 00z GFS slightly faster than the 00z ECMWF, in terms of
rainfall coverage. The 00z NAM showed more agreement to the GFS.

Both of these models enhance lift across the Blue Ridge into the
foothills after midnight, with frontal convection moving into KY/WV.
There is a minimum of rain depicted by these models along/west of
the Blue Ride into the New River Valley and far southwest VA. Think
coverage is enough for any light QPF to have higher pops toward the
mountains, with low likelys near the southern Blue Ridge from
Buffalo Mountain to Boone, and in the far western areas from
Chilhowie to McRoss WV. Am a little skeptical in the far eastern CWA
and kept pops here in the 40 percent range.

As far as any strong or severe storms, not expecting any as main
dynamics and energy stay west of the Appalachians over the Ohio/TN
valleys and mid MS Valley today into this evening.


As of 335 AM EDT Monday...

A shallow upper level trof will drive a weak surface low along a
frontal boundary through the region on Tuesday. This will bring a good
chance of showers and thunderstorms to the Appalachians and central mid
Atlantic region, especially through the first part of the day. Guidance
indicates that there will be enough instability with modestly steep
mid/upper level lapse rates to support some thunderstorms, but best
shear is out of phase with instability and does not arrive until
dynamic forcing is pushing off to the east. It is possible that there
may be a window for parameters to come together to support development
of some strong storms mainly east of the Blue Ridge as indicated by SPC
day 2 marginal risk, but all in all the set up is not very impressive.

After the frontal boundary pushes to our east, a large area of high
pressure will move out of central Canada and wedge strongly down the
east side of the mountains. This will cool our temperatures down
considerably but some warm readings will still be found along the
western and southern periphery of the wedge. There will also be a layer
of shallow moisture in the wedge that looks to keep a good amount of
clouds and some sprinkles/drizzle around Wednesday and Wednesday night
mainly along and just east of the Blue Ridge.

By Thursday the axis of the upper ridge will move to our east and allow
an opening closed low to approach from the west. This will bring an
increasing chance of showers to the region as we go through Thursday
into Thursday night.

Temperatures will start the period well above normal with low/mid 70s
east of the Ridge and mid 60s/around 70 to the west, but once the wedge
becomes fully established temperatures on Thursday look to be 10 to 15
degrees cooler with many locations remaining in the low to mid


As of 300 PM EDT Sunday...

On Friday, showers will be likely across most of the region with
isolated thunderstorm possible across the western and southern parts
of the area. The main system will track north of the area Friday
night into Saturday, with its associated cold front across our
region early Friday night. Look for an end of the shower activity
for much of the area by Saturday morning. Lingering upslope showers
on the backside of the system will be possible across southeast West
Virginia and neighboring counties of southwest Virginia.

Saturday night into Sunday, an upper level ridge will build over the
area, allowing for a gradual decrease in the upslope showers in the
west, and limited cloud cover in the east.

Temperatures during this portion of the forecast will be around or
slightly above normal Friday, but trend to readings about ten
degrees above normal for Saturday and Sunday.


As of 119 AM EDT Monday...

There is a backdoor boundary situated from eastern WV north of
LWB to FVX and this has allowed for some low level clouds in
the IFR range to move as far south as ROA/LYH. At the same time,
isolated to scattered showers continue to move northeast with
best coverage approaching DAN/BLF/LWB as of 0515z. Satellite
and high-res models favor a mix of VFR to IFR cigs and at times
vsbys this morning. Usually a backdoor front will not retreat
back to the north at night, and should keep places like ROA/LYH
stuck in the IFR or lower cigs through at least 10-13z.

Given the scattered/isolated nature to showers there will be
some tempo groups in for these through 12z, then as we head into
Monday the flow should increase out of the southwest taking the
warm front north and seeing all sites go to VFR cigs. Appears
next threat of showers and isolated storms will arrive late this
afternoon but should be isolated with best chance in the
mountains near BLF. Better threat overnight, with one wave
moving toward DAN but this after this taf period. Still looking
at VFR through Monday evening.

Extended Aviation Discussion...

Front moves into the mountains after 12z Tuesday with best
threat of showers/some thunder and sub-VFR in the 09z-18z
Tuesday time frame. Cold front exits the piedmont by 00z
Wednesday with lingering sub-VFR cigs in BLF/LWB with VFR east.

High pressure builds in from the north Wednesday into Thursday
with next storm system moving into the MS Valley. A threat for
sub-VFR cigs appears likely as the high wedges southwest Wed
night-Thursday for most sites. Better chance of rain Thursday
night into Friday.




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