River Flood Warning 14, NWS Boise, ID

Area Forecast Discussion
National Weather Service Boise ID
949 AM MDT Sun Mar 19 2017

.DISCUSSION...Stalled frontal boundary across southeast Oregon and
southwest Idaho will be focus of shower activity the rest of
today. A weak short wave tracking along the front will help
enhance shower development this afternoon. Best chance remains
along an area from central Harney and northern Malhuer counties
into the lower Snake Plain and west-central and northern Boise
mountains. Isolated showers in the warm sector south of the front
will develop this afternoon over the southwest Idaho highlands
and Snake Plain from Mountain Home to Twin Falls. Have updated
chance of precipitation and removed thunderstorms from southeast
Oregon and lower elevations of southwest Idaho as best overlap of
dynamics and weak instability favors the higher terrain this
afternoon, though don't expect many strikes.

&&

.AVIATION...Mostly VFR with rain and high elevations snow for brief
MVFR/IFR conditions. Snow levels 7500-8500 ft. A few lightning
strikes are possible this afternoon. Surface winds: Generally 10-15
kts with gusts to 30 kts in the afternoon. Winds aloft near 10 KFT
MSL: Southwest 30-40 kts.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Monday...Moist southwest flow will
continue through the short term, even as a weak ridge axis moves
through late tonight. A cold front is located roughly from Adams
County southwest to southeast Baker County to near Burns.
Showers, and possibly thunderstorms in the afternoon and early
evening, will continue over the area. QPF totals in the short term
range from around a tenth of an inch in the lower elevations of
the Snake River Plain, to between a quarter and three-quarters of
an inch in the mountains. As this rain falls on already saturated
soil, further flooding problems are likely. See the hydrology
section below for a discussion of those factors. Temps will remain
above normal despite the cloud cover and precipitation due to the
warm air advection associated with the southwest flow aloft. The
best chance for thunderstorms appears to be Monday after the weak
ridge axis moves north.

LONG TERM...Monday night through Saturday...Two successive upper
level troughs through the long term will keep the area in an
active pattern. The CWA will remain in the warm sector of the
first on Monday night through early Tuesday, before a cold front
moves through. Models continue to show Tuesday being a day for
widespread showers and isolated thunderstorms with snow levels
7000-8000 ft then gradually lowering to 5000-6000 by Wednesday
morning. A brief break in showers is expected on Wednesday
morning, but a shortwave moving through the flow will be enough to
spark more showers and possibly thunderstorms Wednesday
afternoon. By Thursday the upper level axis will be off to the
east, and a brief reprieve from precipitation will give way to the
next upper low moving into the PACNW on Friday. Model agreement
continues to be relatively good for this system to impact the area
during next weekend. Temperatures remain right at or above normal
through the period.

&&

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

&&

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DISCUSSION...DG
AVIATION.....JS
PREV SHORT TERM...SP
PREV LONG TERM....EP