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FXUS61 KRNK 232318

Area Forecast Discussion
National Weather Service Blacksburg VA
718 PM EDT Tue Jul 23 2019

A cold front will push south and east of the area tonight
with high pressure building into the region along with cooler 
temperatures and lower humidity for the next several days.


As of 705 PM EDT Tuesday...

Have tapered pops off as rain showers have exited the east.
Cannot rule out an isolated shower along the dewpoint front,
but overall looking at clearing in the west and mostly cloudy in
the east this evening, then mostly clear by late tonight at all
locations. Dropped dewpoints lower than previous forecast as
upstream dewpoints are in the upper 40s to lower 50s. Obviously
we will experience a different airmass when we wake up Wednesday

Previous discussion from early this afternoon...

The focus for significant weather now rapidly shifting to our
southeast as the main area of heavy rain continues to move east.
The southeast counties of the RNK CWA will see several more
hours of moderate rainfall with additional amounts up to 0.50
inches. Scattered light rain will continue from the Blue Ridge
eastward for a few more hours as well. The lingering showers 
this afternoon and this evening will wrap up after about 00Z 
followed by slow clearing overnight. Will see a noticeable 
change in air mass with much lower humidity and temps actually 
below normal in many areas for the first time this month. Lows 
will range from 50s west to low 60s east. Tomorrow will be a 
very pleasant late July day with high from 70s to low 80s.


As of 230 PM EDT Tuesday...

The short term period of the forecast will be dominated by an 
anomalously deep upper level trof on the order of 2-3 standard 
deviations below normal per the GEFS. This trof will begin to relax 
by Friday, and with a slight uptick in PWAT values, perhaps an 
isolated shower or storm could form, but with forecast soundings 
indicating a deep dry layer of air in the mid levels of the 
atmosphere, will keep the forecast dry through this period. 

The primary challenge will be temperatures. Considering a sfc high 
will reside over the region through this period, leaned toward the 
cooler guidance for low temps. Coolest temps during this period will 
likely be on Thursday morning, as by Friday morning, a shift to a 
more easterly low level winds may bring some low level clouds as 
suggested by forecast soundings, especially to areas in the southern 
Blue Ridge.


As of 230 PM EDT Tuesday...

As the Eastern U.S. upper level trof deamplifies, PWAT values and 
850 mb temps begin to return to normal. This will bring a return to 
more typical summer conditions with diurnally driven storms and near 
normal temperatures. The deterministic long range models are in good 
agreement that a weakness in the upper level flow moves over our 
area Monday which may bring an increased risk of showers and storms, 
but with a lack of a low level forcing mechanism precip coverage 
should still be widely scattered. 

Temperatures through this period will gradually increase, but to 
levels near average for late July.


As of 710 PM EDT Tuesday...

Expect VFR through the period as high pressure builds in. At the
moment, some models are showing fog potential, but low
confidence as dry air works in, though not much wind so fog
could form in the typical spots like LWB and BCB, so adjusted a
vsbys a little higher than previous forecast.
.Extended Aviation Discussion...

High pressure will expand across the eastern CONUS with 
generally clear skies and dry weather promoting VFR from 
Wednesday night through Sunday. Cool calm nights will promote 
fog formation withing the mountain valleys. Expect brief periods
of IFR/MVFR in the early morning hours for some of the mountain
terminals such as KLWB and KBCB. May see some mountain showers 
and storms over the weekend.





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