Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 230256

Area Forecast Discussion
National Weather Service Boise ID
856 PM MDT Tue Jun 22 2021

.DISCUSSION...Severe thunderstorms formed this afternoon and
evening, resulting in a large area of rain-cooled air that then
led to strong and damaging winds over much of the area. Dust storm
warnings have been issued, and just recently high wind warnings
were issued. We have received multiple reports of trees and power
lines down, visibilities below 1/4 mile in dust, and high winds.
As of 8:45 pm MDT, one strong thunderstorm was moving north just
to the southwest of Smiths Ferry. This area is currently under a
dust storm warning due to the likelihood of low visibilities due
to strong winds. We expect the strong winds to move north and
east through the West Central and Boise Mountains, Upper Weiser
River Basin, and into the Western Magic Valley, through the
evening. This was well forecast by the previous shift, and no
updates are needed at this time.


.AVIATION...VFR, except IFR to MVFR near thunderstorms and blowing
dust. Isolated to scattered showers and thunderstorms will end after
06z/Wed. Gusty outflow winds 40-50 kt and blowing dust will continue
to move through the Magic Valley this evening, as well as near any
thunderstorms this evening. Thunderstorms will develop once again
across eastern Oregon and southern Idaho Wednesday afternoon.
Surface winds: decreasing to variable 10 kt or less after 06Z/Wed.
Winds aloft at 10k ft MSL: west 15-25 kt. Hot temperatures this week
will lead to increased density altitude.


SHORT TERM...Tonight through Thursday night...A vigorous
shortwave over NW NV and southcentral OR will move into SW Idaho
this evening. Showers and storms have been going all morning in
south central OR and will slowly move northeastward over the day.
A cold pool has developed over east-central Oregon near Burns with
temperatures currently in the 70s. This cold pool combined with
the hot conditions in extreme eastern OR and southwest Idaho will
enhance a pressure gradient over the region this afternoon and
evening. There is enough CAPE and shear to support thunderstorms
this afternoon and evening. The stronger storms in Oregon will
produce hail but the lower atmospheric levels will be so warm that
large hail is unlikely to reach the ground. Where temperatures
have reached into the 90s this afternoon, inverted-V soundings and
DCAPE values of 1500-2000j/kg have developed, which will be
favorable for wind gusts up to 60 mph with showers and storms that
do form. A high wind watch remains in effect from 5pm to 10pm
MDT to highlight the wind gust potential this afternoon and
evening. Blowing dust, wind gusts up to 60 mph possible across
much of southwest Idaho and extreme eastern OR this evening. Things
quiet down after midnight tonight. More showers and thunderstorms
expected on Wednesday and again on Thursday, mainly along the NV
border to the Owyhee Mountains with gusty winds possible during
the afternoons.

LONG TERM...Friday through Tuesday...Hot and dry. A large and very
warm upper level high pressure ridge centered over the B.C. coast on
Friday will remain over southwest Canada and the northwest U.S.
through Tuesday. Many locations will see near-record to record heat
over the weekend and into early next week, with highs around 20
degrees above normal.


ID...High Wind Warning until midnight MDT tonight IDZ011-013-033.
     High Wind Warning until 10 PM MDT this evening
     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening IDZ423-426.
OR...High Wind Warning until 10 PM MDT /9 PM PDT/ this evening ORZ064.
     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening ORZ637.
     Red Flag Warning until midnight MDT /11 PM PDT/ tonight



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