Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 222102

Area Forecast Discussion
National Weather Service Boise ID
302 PM MDT Wed Mar 22 2017

.SHORT TERM...Tonight through Friday...Clear conditions noted
across much of western Idaho, and portions of eastern Oregon. The
next Pacific moisture push associated with a trough axis is moving
into central Oregon this afternoon, and will begin to bring
shower activity across the area. Instability with these showers is
anticipated to be weaker than that experienced with showers on
Tuesday, leaving a diminished thunderstorm threat across the area.
Additionally, models indicate instability moving off quickly this
evening, with most potential ending just around sunset. A few
showers will linger across western Idaho into the overnight hours,
though activity will simultaneously weaken as it progresses
eastward. Building northwest flow expected with the passage of the
trough axis, helping to dissipate shower activity.

Dry northwest flow associated with a transitory ridge will leave
benign conditions across the area on Thursday. Temperatures will be
slightly cooler tomorrow in response to the trough passage, but will
still be seasonably mild. These conditions will provide some
hydrologic relief across the area. The ridge axis will move through
the area through Friday evening, with a return of a southwesterly
flow. An Alaskan area of low pressure will spread moisture across
the area Friday morning, with showers moving into eastern Oregon
before sunrise Friday morning. Shower activity will spread through
Friday, with widespread shower activity possible by Friday
afternoon. Instability with this next push is negligible, with
thunderstorms not anticipated. Regardless, moisture with this system
may be plentiful to cause rivers across the area to rise.

.LONG TERM...Friday night through Wednesday...The unsettled
pattern will continue through Monday. The first of two Pacific
weather systems will cross the Intermountain Region Friday night and
Saturday. The second system is forecast for Sunday night and Monday.
Models have been agreeing well on timing. A drying trend is
indicated for Tuesday and Wednesday as an upper level ridge builds
over the area. Temperatures will average a few degrees above normal,
with overnight lows showing the the greatest departure due to cloud


.AVIATION...VFR. Clouds decreasing tonight, and mostly clear skies
on Thursday. Patchy late night/early morning fog is possible in
mountain valleys, including the KBKE and KMYL areas. However
confidence is low due to increasing winds. Surface winds will be
mainly northwest 5-10 kts increasing after 09z to 10-20 kts with
local gusts to 30 kts through the Snake Rover Valley southeast of


.HYDROLOGY...Showers and thunderstorms remain possible this
afternoon, though coverage is expected to weaken through the early
evening hours. River systems underneath any of the convective
showers may see another brief increase in river levels as a result
of the sudden burst of rain. Otherwise, cooler temperatures across
the area should promoted rivers to recede overall during the next
day or so. The next potent system will begin to impact the area
Friday morning, with widespread moisture expected by Friday
afternoon. This may again result in rises in area rivers, streams,
and creeks into the weekend.





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