Area Forecast Discussion
Issued by NWS Boise, ID

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
FXUS65 KBOI 201634

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

.DISCUSSION...As of 9 AM MST light rain was as far east as
Boise and advancing steadily east.  All models show western
Idaho and eastern Oregon wet by 11 AM MST with widespread
pcpn amounts of .10 to .25 inch by then, and more this
afternoon.  Models seem a little fast so far.  The pcpn is
coming in with a warm front.  Tuesday will be warmer than
today with rising snow levels.  Another warm front and
more light rain Tuesday night then very warm Wednesday.
New MET guidance has highs in the upper 40s and 50s in the
mountains, and 60s in all of southern Idaho and southeast
Oregon Wednesday.  Our forecast is slightly cooler than that.
Awaiting rest of 12Z model data before making changes.  No
updates for now.


.AVIATION...Widespread low VFR to MVFR precipitation expected across
SE OR and SW ID today with mountain obscuration. IFR conditions
expected near KMYL and other mountain locales. Snow levels 5000ft
MSL this morning then rising to 7500-9000ft MSL by 00Z/Tue. Surface
winds generally SW-SE 5-15kt. Winds aloft near 10 KFT MSL: Westerly
35-50kt easing to 15-25kt by 12z/Tue and becoming SW 30-40kt by


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





PREV LONG TERM....AB is the U.S. government's official web portal to all federal, state and local government web resources and services.