Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 271406
Area Forecast Discussion
National Weather Service Blacksburg VA
Issued by National Weather Service Raleigh NC
1005 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.
.NEAR TERM /THROUGH TONIGHT/...
As of 1005 AM EDT Monday...
Showers have moved east of the area and a light east to southeast
wind has kept low clouds in the mountains. Hi-res models develop
more showers over the southwest mountains after midday with an
uptick in showers and some thunderstorms after 18z regionwide as
upper shortwave and sfc low moves 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.
.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
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 50s.
.LONG TERM /FRIDAY THROUGH SUNDAY/...
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.
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
As of 1005 AM EDT Monday...
East to southeast flow and a retreating front keeping ceilings under
1K ft in ROA/LYH. As the front lifts northeast, ceilings will
increase to MVFR then VFR by 18z. Still should have ceilings all day
with some breaks in clouds from time to time.
Showers will be isolated to scattered over the mountains this
afternoon, but not enough for predominant in the tafs. Better
rain threat later tonight ahead of the front, with cigs dropping
to MVFR toward 12z Tuesday.
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.