Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 251600

Area Forecast Discussion
National Weather Service Boise ID
1000 AM MDT Sun Jun 25 2017

.DISCUSSION...Moisture over Northern California moving up into
Oregon today will produce thunderstorms over Central Oregon. Some
of these may drift into Harney County in the evening with some
lightning, and minimal precipitation. But more confident that
wind gusts to 40 mph will push across Harney County, even if the
storms themselves stay further to the west. Updated the forecast
this evening for these details. Still expecting a hot day
everywhere today as the upper level ridge pushes overhead. Monday
still looks like the more active thunderstorm day as there is a
short wave riding up the west side of the ridge to help focus the
convection. Storms start out fairly dry with gusty winds, but
moisten up quickly as the moisture over Oregon spreads to the
east. Some cooling on Monday for the Oregon zones, but still as
warm, or warmer, on Monday for most of the Idaho zones.

.AVIATION...VFR. Increase in mid-upper level cloud cover Monday
afternoon into the evening. Slight chance of thunderstorms
developing Monday afternoon in and around KBNO and KBKE. Surface
winds, variable 10 kts or less. Thunderstorm development in SW
Oregon Sunday afternoon/evening could produce some gusty surface
winds after 03z in the higher elevations of Harney County of 15-25
kts. Winds aloft to 10k feet MSL, southeast thru 01z then southwest
10-20 kts.

SHORT TERM...Today through Monday...High pressure remains in firm
control across the west this morning. Satellite imagery indicates
some mid/upper level moisture is migrating northward through the
ridge. This moisture set of some thunderstorm activity over the
Sierra Nevada range in California yesterday afternoon. At the
surface high pressure is parked over the Pacific Northwest, with a
pronounced thermal trough draped over the west coast from southern
California to southwest Oregon. The ridge of high pressure is
expected to slide eastward today and tomorrow in response to an
approaching trough. This eastward progression will cause the
surface thermal trough to move into the area as well. The
combination of the thermal trough and the ridge of high pressure
will lead to much above normal temperatures. Widespread areas of
mid to upper 90s are anticipated both today and Monday.

The approaching trough is expected to interact with the mid/upper
level moisture migrating under the ridge leading to thunderstorm
activity Monday and Monday evening. Current projections indicate
the best chance of convection will be over the higher terrain of
eastern Oregon and central Idaho. There are strong indications
that the lower levels of the atmosphere will remain on the dry
side as the trough swings through. This means that any storms
that develop will likely produce gusty winds at the surface. These
gusty winds could kick up dust impacting visibility and air
quality late Monday.

LONG TERM...Monday night through Saturday...Upper level trough
moves across Central Oregon and into Northern Idaho Monday night.
Trough will be bring a chance of thunderstorms with gusty surface
winds throughout SE Oregon and the West Central Mountains. Lingering
moisture Tuesday will be enough for afternoon/evening thunderstorms
in the Central Idaho Mountains. Northwest flow through Wednesday
will bring temperatures just below normal. Another upper level ridge
begins to build over the Pacific Northwest Thursday with
temperatures climbing above normal on Friday ahead of another
trough. The upper level trough moves through the region on Saturday
cooling temperatures back below normal and bring a slight change of
thunderstorms the West Central Mountains.





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