Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 241020

Area Forecast Discussion
National Weather Service Boise ID
420 AM MDT Fri Mar 24 2017

.SHORT TERM...Today through Saturday...Southwest flow aloft ahead
of an impressive upper level trough is visible off the Pacific NW
coast this morning. Precipitation associated with this frontal
system will spread across southeast Oregon this morning, and into
southwest Idaho by this afternoon. Strong southwest flow should
keep the Snake Plain dry south and east of Boise through late this
afternoon, before filling in across the Snake Plain and spreading
into the Magic Valley this evening. Temperatures will be a tricky
forecast today, with lower 60s expected in the Magic Valley, and
much cooler temperatures across the north and west in the rain
cooled air. Significant precipitation is expected across the
central Idaho mountains this afternoon and evening, with snow
levels around 5500-6500 feet, with light accumulations in the
mountain valleys. The higher peaks above 7500 feet will see
significant snow accumulations of 6-10 inches with this system.
Precipitation is expected to taper off in SE Oregon late tonight
and southwest Idaho early Saturday morning. With cooler air aloft
on Saturday, scattered showers are expected to develop across the
entire region on Saturday afternoon with daytime heating creating

.LONG TERM...Saturday night through Thursday...The area sees a brief
break in the precipitation Saturday night and early Sunday before
the next upper wave moves into the Pac NW Sunday afternoon with rain
and snow. Precipitation continues into Monday night as this system
digs towards the Four Corners. Tuesday is drier under a passing
shortwave ridge, but the storm systems keep coming as yet another
upper trough tracks across the region Wednesday with more rain and
mountain snow. Models remain in good agreement on the progression of
this pattern through the period so confidence remains high. With
each passing trough snow levels will range between 4500 and 5500
feet and moderate snow accumulations are expected at elevations
above 6k feet. Temperatures will be close to normal with Monday and
Thursday being the coldest days.


.AVIATION...VFR this morning with lowering ceilings through
the day. Low VFR conditions and rain showers develop this afternoon
in the valleys with widespread mtn obscuration in MVFR and local IFR
in the mountains as snow develops above 5500 feet MSL. Lower
conditions continue into early Saturday morning. Southeast to
southwest surface winds to 25 kts today. Southwest winds aloft of 20-
40 kts at 10k feet.

Weekend Outlook...Saturday will see low-VFR in scattered showers
continue across east-central Oregon and the west-central ID
mountains, obscuring higher terrain. Valleys will remain VFR,
drying by afternoon. All areas dry and VFR Saturday night to
midday Sunday. Ceilings lower through the day Sunday with more
rain and snow to the OR/ID border by evening. Saturday will see
northwest surface winds to 20 kts with a shift to the southeast
and increase in speeds on Sunday.


.HYDROLOGY...Rivers and streams will generally lower through
Friday then rise slightly again Saturday in response to Friday`s
rain in the lower elevations. Snow will fall at the higher
elevations above 6000 feet, keeping river levels from rising too
much. The Snake River at Weiser is forecast to continue above
flood stage through next week, as will the Boise River at Glenwood
Bridge. An areal flood warning continues for northern Harney
County, OR and a flood advisory across the Camas Prairie.





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