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FXUS65 KBOU 222057

Area Forecast Discussion
National Weather Service Denver/Boulder CO
257 PM MDT Thu Jun 22 2017

.SHORT TERM...(This evening through Friday)
Issued at 255 PM MDT Thu Jun 22 2017

Storms continues to spread west to east across the forecast area.
With the front now all the way through the area, upslope flow 
continues to increase. However, the better moisture has been slow
to work its way in, so strength of storms are weaker at this point 
than initially thought. More threat right now is strong outflow
winds, with hail threat increasing as the afternoon goes on. 

A shortwave currently in southern Idaho into central Wyoming is 
progged to push south tonight, to push additional moisture and the
cooler air in with an increase in upslope flow. Will see a 
continuation of showers and storms likely through midnight, with a
possibility of seeing convection for a few hours after midnight
with the shortwave. Forecast soundings show lower levels 
moistening up with stratus expected to push in, however upper
levels still remaining unstable. For now will remove mention of
thunder after midnight for the high terrain and after 3am over 
the plains, with stratus spreading across the plains and into the
foothills up to about 10kft. This will create areas of fog along
the foothills and adjacent plains. 

High surface pressure will remain over the Great Plains to keep
upslope into NE Colorado Friday. Clouds will likely remain over
the most of the plains to keep temperatures readings in the 60s, 
a nice respite from the heat of late. Further west of the divide, 
temperatures will still be cooler than today, but some instability
may allow for isolated weak afternoon thunderstorms. 

.LONG TERM...(Friday night through Thursday)
Issued at 255 PM MDT Thu Jun 22 2017

Cooling trend continues through the weekend with a moist and cool
airmass in place on the plains. A cold front will move into NE
Colorado Saturday ushering in cooler air. Easterly winds will 
help to keep moisture pooling into the foothills with clouds 
persisting through the evening into Saturday afternoon. Model air 
soundings show increased mid-level subsidence through the weekend.
Some light precipitation will be possible but expecting more 
showers and closer to the foothills vs convection. The convection 
potential will increase over the higher terrain for Saturday and 
Sunday as conditions will be warmer and more unstable then on the 
plains. Brief heavy rain, deadly lightning and small hail with 
gusty winds will be possible with any convection. Temperatures 
will continue to be below seasonal normals with highs in the 70s 
through the weekend. 

For Monday into mid week the upper level ridge will start to build
back into the Great Basin ushering in a warmer airmass for Monday
and slowly increasing temperatures through the week. With the
warming least for Monday into Tuesday do not expect
much in the way of convection due to a stable mid level. A lee
side trough will help to increase downsloping and warming
temperatures for Monday evening into Tuesday with lows in the 60s
and highs on Tuesday reaching back above normals in the low 90s. 
Chances of convection increase on Wednesday with the possibility 
of breaking the cap and having some isolated storms in the 
afternoon on the plains. By Thursday GFS and EC showing a front 
moving in late Wednesday that could help to destabilize the
atmosphere and increase storm chances for Thursday. Will continue
to monitor to see how models time the incoming front. 


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 255 PM MDT Thu Jun 22 2017

Scattered thunderstorms will continue this afternoon, with
stronger storms possible after 22z and into the early evening,
mainly before 03z. Localized MVFR ceilings, strong outflow winds
and hail are possible with the strongest storms. Multiple wind 
shifts with gusts as high as 40 knots are also likely in this 
period. For tonight, ceilings will lower, with areas of MVFR- IFR 
conditions developing as moist upslope flow continues through the 
night. Ceilings of below 1000 ft AGL may remain through 18z 



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