Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 200959

Area Forecast Discussion
National Weather Service Boise ID
259 AM MST Mon Nov 20 2017

.SHORT TERM...Today through Tuesday...Soggy conditions expected
through Tuesday. A strong, moist upper level low will continue to
impact the area today with widespread precipitation expected. The
morning hours are expected to be when the most significant
moisture falls, but precipitation will continue through the day.
Models in fair agreement on precipitation amounts, with
indications of 0.25 to over 0.50 inches possible through the
Treasure Valley. For the higher elevations, amounts around or
above an inch are anticipated, especially over the Boise and West
Central Mountains of Idaho. Snow levels over the higher terrain of
central Idaho will start around 4500 ft this morning, and are
expected to rise to around 6000 ft by the afternoon hours.
Therefore, most snowfall should occur this morning, with light
snowfall anticipated through the afternoon. Snow levels across the
remainder of the area will not be conducive for snow production,
including into eastern Oregon. However, a few spots will see an
opportunity for freezing rain, which look to potentially impact
routes in and around Burns, OR this morning. Regarding snow
totals, the central mountains of Idaho are looking to see 2 to 5
inches through today, with locally higher amounts possible. A
building ridge will then move into the area, causing a quick rise
to snow levels and increasing rainfall on Tuesday. Even with
ongoing precipitation on Tuesday, temperatures across the area
will warm 5 to 10 degrees, with values ending up around 10 degrees
above normal.

.LONG TERM...Tuesday night through Sunday...A strong upper level
ridge will build over the southwest Wednesday, ushering in a mild
and moist southwesterly flow aloft. Temperatures ranging in between
15-20 degrees above normal will commence in the wake of a warm
frontal passage Wednesday, behind which temperatures will spike and
conditions will dry. Thus, the bulk of the precipitation will fall
across the mountains both in east-central Oregon and west-central
Idaho, and to the north. Snow levels will reach upwards of 10,000
feet for the duration. The ridge will be temporarily suppressed
Thursday as a wave of moisture pushes through the region, allowing
for late Thursday, early Friday rain showers. Temperatures will
decrease by 5-10 degrees as this wave of moisture pushes through.
Mild southwesterly flow aloft returns Saturday for a chance of
showers over the higher terrain and continued above normal


.AVIATION...Lowering clouds and visibilities from west to east for
low VFR-IFR conditions. Mountain obscuration expected. Showers will
reach southwest Idaho around 11Z. FZRA possible at KBNO 10Z-12Z and
isolated locations nearby. Snow levels 4000-5000 ft will rise to
9000 ft or more after 21/00Z. Surface winds: south to southeast 5-15
kts. Winds aloft near 10 KFT MSL: W-SW 35-45 kts.





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