Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 270225

Area Forecast Discussion
National Weather Service Boise ID
825 PM MDT Mon Jun 26 2017

.DISCUSSION...At 8 PM MDT showers and thunderstorms extended from
northeast Oregon through the west central Idaho mountains and Boise
Mountains, to Twin Falls County.  A strong solitary thunderstorm
was in northern Owyhee County moving toward Mountain Home but it
was weakening.  Late this afternoon thunderstorms were in Harney
and Malheur Counties and most of southwestern Idaho, but conditions
have improved in those areas this evening.  The air mass has been
exceptionally humid with some dew points in the 60s during and just
after local heavy rains.  Forecast shows clearing from the southwest
overnight, then sunny and cooler Tuesday as a Pacific upper trough
replaces today`s ridge.  No updates planned.


.AVIATION...Mainly VFR. Scattered locally strong thunderstorms
continue to move northeast this evening. Best chance before 06z will
be east of a line from La Grande, OR, to Wells, NV. Strong outflow
winds and local visibility restrictions in blowing dust have been
observed with these storms. After 06z isolated thunderstorms will be
confined to Baker County and the west central Idaho mountains, with
clearing skies elsewhere. Surface winds west to northwest 5-15 kts,
except variable near thunderstorms with gusts 30-40 kts and locally
over 50 kts. Winds aloft at 10k ft msl west 15-25 kts.


SHORT TERM...Tonight through Wednesday...As of 2:00 MDT,
convection has initiated in southeast Oregon associated with a
shortwave currently located in southwest Oregon and moving
east/northeast. Surface heating and moisture transport ahead of
the shortwave are aiding in thunderstorms. Most models are showing
convection continuing to progress eastward through the evening
hours, and the forecast matches this solution. The inverted-V
profile for the afternoon and evening hours suggests downdraft
gusty winds up to 50 mph are possible near the stronger storms.
Overnight tonight, the surface cold front, then upper level axis
will pass overhead and shift the convection to the north and
east, leaving chances for thunderstorms only in the Idaho Central
Mountains for Tuesday. Where most valley locations will be
approaching 100F this afternoon, high temperatures tomorrow are
expected to be 10-15 degrees cooler than today. By Wednesday, a
drier northwest flow will set up under a broader trough pattern,
keeping temperatures near normal, but conditions dry.

LONG TERM...Wednesday night through Monday...The upper level
trough begins to exit the region Wednesday night into Thursday
making way for an upper level ridge to begin building over the
Pacific Northwest. Temperatures begin to climb back above normal by
the weekend. A disturbance in the flow pushes through Saturday night
which will give the West Central Mountains a slight chance of
afternoon showers/thunderstorms. Models are in disagreement after
this with the ECMWF wanting to keep zonal flow in the region while
the GFS begins to build in another ridge. Kept the forecast dry
after Saturday night for now because of these differences.





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