Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 261454

Area Forecast Discussion
National Weather Service Boise ID
854 AM MDT Sun Mar 26 2017

.DISCUSSION...Pacific frontal system now onshore and making steady
eastward progress across western WA and OR.  System will bring rain
and mountain snow nearly everywhere this afternoon and tonight. Post-
frontal northwest winds will increase to 20-35 mph Monday afternoon
in the Upper treaasure Valley and western Magic Valley.  The Snake
River at Weiser, and the Boise River at Glenwood in Boise, will
coninue in minor flood through at least Tuesday.  No updates.


.AVIATION...VFR conditions continue this morning...but trending to
MVFR across KBNO 16-18z. KBKE and KMYL should see conditions
lowering to MVFR/IFR around 21z and KBOI and sites east around 00z.
Precip starts as rain across most locations becoming snow above 5000
feet this evening. Surface winds east to southeast 5 to 15 kts across
southwest Idaho and generally south to southwest in eastern Oregon.
winds shifting west to northwest by 27/1200z. 10Kft winds generally
15 to 20 kts from the southwest.


SHORT TERM...Today through Monday...A broad trough of low pressure
is poised to move ashore in the Pacific Northwest today.
The leading edge of the trough and associated moisture and cloud
cover is currently moving overhead in western Washington. No
shower activity is present across much of the interior Pacific
Northwest, however, coastal radars are indicating precipitation is
not far off-shore.

The trough is expected to move into Washington and Oregon today,
and across Idaho overnight and into Sunday. A warm front
associated with the trough will push south to north across the
area today with precipitation favoring northern locations and
higher terrain. Significant precipitation is anticipated when the
systems cold front moves through late today and overnight.
Forecast models are in good agreement that a consolidated band of
precipitation will accompany the cold front, along with dropping
snow levels. Valley locations will generally see between 0.15 and
0.25 inches of precipitation, while mountain locations will see
between 0.33 and 0.75 inches. Snow levels will start out around
6000 feet and drop closer to 5000 feet by early Monday. This will
allow for more whitening of the higher terrain of both SE Oregon
and SW and Central Idaho. Gusty northwest winds are anticipated
behind the front for much of the day Monday. Temperatures will
generally be at to slightly above normal today, then slightly
below normal on Monday.

LONG TERM...Monday night through Saturday...A ridge will transition
across the area on Tuesday, with dry conditions. On Wednesday, a
trough begins to dig along the Pacific NW coast, setting up
southwest flow over eastern Oregon and SW Idaho. As this system
approaches, warmer southwest flow develops bringing in warmer air on
Wednesday. An impressive moisture field develops late Wednesday
night with widespread precipitation across the region. Precipitation
amounts are healthy with this system, as the center of the trough
passes by overhead, with the mountains receiving 1.0 to 1.5 inches
of liquid equivalent. Although snow levels start out at 7000-7500ft
with the onset of precipitation, snow levels begin to fall to around
5000ft midday on Thursday. Significant snow will fall on the peaks
above 8000ft. Ridging builds into the Pacific NW on Friday, bringing
cool north-northeasterly flow through Saturday. Temperatures will
generally be below normal through the extended period, with the
exception of Wednesday.





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