Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 230242
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
842 PM MDT Sat Jul 22 2017

.DISCUSSION...No updates this evening.  Broad upper ridge over the
Intermountain region with dry westerly flow aloft. Clear but locally
smoky skies.  Convective potential will gradually increase the next
several days as flow aloft backs to southwesterly and draws monsoon
moisture northward into our CWA.

&&

.AVIATION...VFR with mostly clear skies and smoke layers through
Sunday. Variable surface winds up to 10 kts. Winds aloft near 10kft
MSL: westerly 5-15kt. Thunderstorms expected at times Monday through
Wednesday with heavy rain and gusty winds.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Monday...Very dry conditions over
the area today will modify through Monday as moisture is drawn
northward in advance of an upper level low off the CA coast. Late
Sunday afternoon into Sunday evening shower/thunderstorm chances
become high enough to warrant mention in the forecast in southwest
Harney County. Overnight moisture continues to increase as the low
moves onto the CA coast, and the chance of convection spreads
slowly north and east. By Monday afternoon, the threat encompasses
almost the entire CWA. The only areas without a mention of
showers/thunderstorms will be the lower elevations of the
Treasure Valley and north into the Weiser River Basin where the
chance will be just below 15 percent. Temperatures will warm each
day, with highs in the lower elevations in the upper 90s Sunday
and near 100 Monday. Lows will warm to 5 to 10 degrees above
normal by Monday morning.

LONG TERM...Monday night through Saturday...Monsoon moisture
from the south ahead of a weakening upper level low will bring
thunderstorms Monday night through Wednesday. Latest models have
trended the greatest instability along the Nevada border
(especially on Tuesday) which looks to be the best area for
thunderstorms. The upper level low weakens early Wednesday and
lifts northeast Wednesday afternoon for at least a slight chance
of thunderstorms across much of the forecast area. The
thunderstorms may produce heavy rain due to high precipitable
water values of over an inch. Although drier air will follow the
passage of the low, residual moisture and instability will allow
for a slight chance of thunderstorms for the remainder of the
week, mainly in SW Idaho. Temperatures will be slightly above
normal.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Fire Weather Watch from Monday afternoon through Monday evening
     IDZ423-426.
OR...Fire Weather Watch from Monday afternoon through Monday evening
     ORZ636-637.

&&

$$

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DISCUSSION...LC
AVIATION.....KA
PREV SHORT TERM...SP
PREV LONG TERM....JDS/WH



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