FXUS61 KRNK 261143

Area Forecast Discussion
National Weather Service Blacksburg VA
743 AM EDT Mon Jun 26 2017

Weak high pressure will linger over the area today. An upper
trough and associated cold front will move through the area
Tuesday. A large area of high pressure will build over the area
behind the front for Wednesday, then move east of the area
Thursday through Friday. Mostly dry conditions with below normal
temperatures are expected through Wednesday with warmer, more
humid conditions and returning chances for showers and
thunderstorms are expected during the later half of the week.


As of 400 AM EDT Monday...

Little change expected in the weather across the region today
from what was observed on Sunday. 850mb temperatures will change
little from around +8C on the northern end of the CWA to around
+12C in the southern areas. Broad troughing, anchored across
the Great Lakes will continue leaving the area with below normal
heights and temperatures as noted above. With the air mass
fairly dry, only expecting scattered CU development today with
limited cirrus. Slightly breezy west to northwest winds, but
otherwise an extremely pleasant day for late June with high
temperatures mostly in the 70s west to the lower and mid 80s
east after a cool morning with lows in the 50s to lower 60s. Not
really very June like, but nice!

Overnight into early Tuesday, a stronger short wave embedded
within the Great Lakes upper trough will move toward the region,
then is slated to sweep through the area Tuesday. Mid clouds
will be on the increase overnight in advance of this feature.
Not very excited about precipitation with this system,
especially prior to 12Z given the limited moisture it has to
work with, e.g., PWATS less than 1 inch. However, dynamics may
be strong enough to overcome the lack of deep moisture and some
light rain showers or more likely sprinkles may begin to
develop across eastern KY/TN/WV before daybreak Tuesday, so have
introduced some slight chance pops into the
Richlands/Bluefield/Independence areas before daybreak Tue. Low
temperatures overnight might be a tad warmer in the west than
this morning thanks to increased cloud cover, but will still be
below normal for late June, mostly in the 50s across the CWA.
Radiational cooling will be more effective across the Piedmont
Tuesday morning.


As of 330 AM EDT Monday...

An upper level trough will pivot over the Ohio and Mid Atlantic
region Tuesday. Short waves coming across the area will use all
available moisture to produce scattered showers through the day. The
best coverage will be across the mountains in the morning. Models
are wanting to push these showers east of the Blue Ridge, however
with a northwest transport wind of 15 to 25 mph and cloud bases at
or above 7 kft, sprinkles may be the best bet in the early
afternoon. Drier air moves in quickly as high pressure builds in
from the west to end the threat for rain Tuesday evening. With
abundant cloud cover and rain in northwest flow, Tuesday's
temperatures may run 10F cooler than normal.

Cool dry high pressure will drift over the region Wednesday. With
plenty of sunshine and a dry air mass, afternoon temperatures will
warm into the 70s across the mountains to the lower 80s east of the
Blue Ridge. This high will slide off the VA/NC coast Wednesday night
and Thursday. Southerly flow on the back side of this ridge will
bring temperatures back to seasonal levels. Dew points will also
return back to the 60s by Thursday afternoon.


As of 230 PM EDT Sunday...

Trough lifts out and 5h ridge works in ahead of the next upstream
trough over the northern tier of the U.S. Will see return flow
around southeast high with temps/dewpoints returning to typical late
June/early July numbers. Also with differential heating and some
weak upper impulse should expect to see more storms Friday-and as
front across the midwest edges closer to the Ohio Valley, should see
a better chance into the weekend especially over the mountains.


As of 740 AM EDT Monday...

VFR conditions expected to continue through the TAF valid
period. A broad upper trough remains over the Great Lakes. An
embedded short wave will deepen on the southwest side of this
upper trough and move southeast through our region late tonight
and Tuesday. Low-level moisture is limited, but dynamics are
strong so expect a period of mainly mid clouds and a few showers
or sprinkles, mainly west of the Blue Ridge after 12Z Tue.
Ceilings through this TAF valid period are expected to be mainly
at or above 100, with a brief period of BKN cigs possible in
some areas this afternoon in the 050-060 range, clearly still
VFR. Fog failed to develop this morning as air mass has dried
out and increased clouds should prevent fog development
overnight into Tuesday morning. The exception could be the
Piedmont, such as KLYH and KDAN, but have not advertised for now
because confidence is too low. Given expected thick mid/high
clouds have left fog out of KLWB for Tue morning, despite
indication from several MOS guidance packages of LIFR at KLWB
around 12Z Tue. That appears to much driven by climatology at
this point, not meteorology.

Winds will remain W to WNW through the TAF valid period at
speeds of 6-12kts daytime with low end gusts at most stations
during the late morning/early afternoon mostly < 20kts. Winds
will diminish to 5kts or less after 23Z.

High confidence in VFR cigs through the TAF valid period.
High confidence in VFR vsbys through 08Z Tue, then medium to high
Medium to high confidence in wind speed/direction through the
TAF valid period.

Extended Aviation Discussion...

A weak disturbance dropping in from the northwest may bring a
period of MVFR cigs along with a few showers to the mountains
Tuesday, mainly during the first half of the day. Otherwise
expecting overall VFR for Monday through Thursday with some
brief late night/early morning mountain and river valley fog

By Friday, a large area of high pressure will drift to the
southeast of the area and be located off the SC/NC coast into
the weekend. This will allow a warm/moist southwest flow to
return to the area. As a result look for increasing diurnally
driven convection into the weekend, most numerous over the
mountains. This will increase the threat for brief periods of
sub-VFR cigs/vsbys in afternoon/evening thunderstorms. It will
also increase the likelihood of late night/early morning
fog/low clouds, especially west of the Blue ridge with sub-VFR
cigs at times during these hours.




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