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Area Forecast Discussion (AFD)

Issued by Boise, ID (BOI)

FXUS65 KBOI 150828

Area Forecast Discussion
National Weather Service Boise ID
228 AM MDT Wed Aug 15 2018

.SHORT TERM...Today through Thursday...No significant forecast
changes.  Monsoon moisture will increase clouds from the southwest
today in Oregon and tonight in Idaho.  Models continue a chance
of showers along the Nevada/Idaho border this afternoon with just
enough instability for a slight chance of thunderstorms.  In eastern
Oregon clouds will hold Max temps down slightly in Harney County, 
but the low levels of the atmosphere look too dry for showers to
reach the ground.  For tonight skies in our CWA will be partly 
cloudy in the south and mostly cloudy in the north.  The clouds
will keep nighttime temps warmer.   On Thursday a Pacific trough
will reach the coast for a slight chance of showers and afternoon 
thunderstorms in the mountains on the Idaho side and mountains 
of Baker County on the Oregon side.  High temps Friday will 
change little from today.  No significant winds through Thursday
except near thunderstorms.

.LONG TERM...Thursday night through Wednesday...A weak upper level 
trough approaching from the coast Thursday night and crossing our 
area Friday and Friday night will interact with monsoon moisture to 
trigger isolated to scattered showers and thunderstorms, mainly over 
the mountains of central Idaho and Baker County, Oregon. Models show 
the best chance of thunderstorms Friday afternoon and evening, 
corresponding to maximum instability. Drier more stable air moves 
into eastern Oregon late Friday night as the trough begins to exit. 
On Saturday showers are expected to be confined to the west central 
Idaho Mountains. Skies will be mostly clear Saturday night and 
Sunday. Models agree on bringing another weak upper level trough 
over our area from the northwest Sunday night and Monday, but with 
monsoon moisture cut off, there will be no more than a slight chance 
of showers over the central Idaho mountains. Temperatures will be 
near normal Friday and Saturday, then warm to around 5 degrees above 
normal Tuesday and Wednesday as the upper level ridge over the 
desert southwest expands northward. 


.AVIATION...Mainly VFR. Smoke layers with local MVFR due to wildfire 
smoke. Isolated afternoon and evening thunderstorms along the Idaho-
Nevada border. Surface winds variable 10 kts or less. Winds aloft 
near 10k feet MSL south to west around 10 kts.