Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 230246
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
846 PM MDT Fri Mar 22 2019

.DISCUSSION...At 8 PM MDT satellite showed a band of clouds and
showers in central Oregon moving eastward into Harney County.
Models spread showers across all of eastern Oregon during the
night but keep them out of western Idaho until Saturday afternoon
when a second Pacific trough moves onshore.  The wettest period
looks like Saturday night.  Our forecast agrees with this timing.
See previous discussion for more details.  Max temps will be
cooler this weekend with the trough and showers around.  No
updates at this time.

&&

.AVIATION...VFR. Isolated to scattered showers becoming widespread
Saturday then decreasing late Saturday night. Areas of mountain
obscuration and MVFR/local IFR ceilings. Snow level 5k-6k ft MSL.
Surface winds variable 10 kts or less. Winds aloft near 10k ft MSL
west-southwest 10-20 kts.

Sunday Outlook...Mainly VFR. Showers ending in southeast Oregon in
the morning and southwest Idaho in the afternoon, except showers
continuing over the central Idaho mountains. Snow level near 5k ft
MSL.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Sunday...Light precipitation will
spread into southeast Oregon this evening ahead of an advancing
short wave trough. The initial wave lifts north with much of the
shower activity dissipating before reaching southwest Idaho
overnight. The main trough swings into the Pacific NW on Saturday
increasing the chance of precipitation across the region. The
better moisture and dynamics with this system will bring moderate
precipitation amounts to southeast Oregon and mountains of
southwest Idaho with liquid totals of 0.25-0.50 inches. Lesser
amounts in the valleys with up to 0.20 inches in the Snake Plain
through Sunday. Snow levels will fall from 5500-6500 feet on
Saturday to 4500-5500 feet on Sunday as the upper trough lifts
northeastward. Showers taper off from south to north on Sunday
with activity lingering in the west-central Idaho mountains
through the afternoon. Elevations above 6500 feet could see 3-6
inches of snow by Sunday afternoon.Temperatures both days will run
several degrees below normal.

LONG TERM...Sunday night through Friday...A brief dry period of
ridging on Sunday night allows temperatures to rise several
degrees before a trough deepens on Monday night. Temperatures
will fall back to right around normal as a Pacific low pressure
system eases towards the coast Monday night into Tuesday, ushering
in stronger winds. Model consensus is still low in terms of
placement and intensity of precipitation, so a blend of many
models and climatology was used for PoPs. Snow levels will fall
between 4000-5000 ft MSL on Tuesday afternoon, causing widespread
rain with a wintry mix or snow in higher elevations. Showers will
linger through Wednesday, though confidence remains somewhat low
of where rain showers will set up.

Wednesday night through Friday night...Showery and breezy
conditions with a slight cool-down are expected throughout the
period as moist, unsettled air is steered into the region in
advance of an approaching upper low. Rain showers are expected
across the lower valleys with snow showers in the mountains and a
mix along the foothills. These conditions are expected to persist
as moist, unsettled conditions continue to move in with the
approach of the upper low. As snow levels rise some toward the
end of the period, look for rain shower coverage to broaden
and spread throughout the region.  Expect high and low temperatures
to measure in a few degrees below normal.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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DISCUSSION...LC
AVIATION.....JT
PREV SHORT TERM...DG
PREV LONG TERM....AL/WH/LC



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