Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 200907

Area Forecast Discussion
National Weather Service Boise ID
307 AM MDT Wed Sep 20 2017

.SHORT TERM...Today through Thursday...Another significant
shortwave trough will move into the area today, setting off
showers and isolated thunderstorms across most of the area. Temps
will remain well-below normal today, and cool down even more
Thursday. Showers will diminish...but not disappear...tonight
through Wed, as enough cold air will remain in place aloft to
continue a chance of showers. A cold front will move through the
area today, entering southeast Oregon this morning and southwest
Idaho this afternoon. This will be the focal point for isolated
thunderstorms this afternoon. We did not put thunderstorms into
the forecast for this evening, as the loss of what little solar
heating occurs will bring them to an end near 6 pm MDT...but
cannot rule out a few storms in the Western Magic Valley or Boise
Mountains through 7 or 8 pm MDT. Winds will be near advisory level
today, but not quite high enough to reach criteria. Snow levels
will drop to around 5000 feet in the north tonight, but only a
dusting is forecast for places like McCall. More noticeable snow
is forecast for the higher elevations of Baker County and the
west- central and Boise Mountains, with 2 to 6 inches possible
above around 7500 feet.

.LONG TERM...Thursday night through Tuesday...A closed upper
level low will remain over the northern Rocky Mountains region
through Friday bringing below normal temperatures and showers
across the forecast area. Snow levels will come down to about 5800
ft MSL for high elevation snow showers on Friday. The upper level
low begins to shift eastward on Saturday for drier conditions yet
the temperatures will still remain well below normal under
northwesterly flow. Lingering showers will be focused across the
west central Idaho mountains and south towards the Nevada border
Saturday afternoon. Upper level ridge starts to build in from the
west on Sunday beginning a drying and warming trend into next
week. Maximum temperatures will be about 15 below normal at the
start of the extended forecast, gradually increasing a few degrees
each day, ending Wednesday within 5 degrees of normal.


.AVIATION...VFR except local brief MVFR conditions in heavier
showers. Snow levels 7K-8K ft MSL. Scattered showers early this
morning will become widespread by 18z this afternoon. Breezy
conditions ahead of a cold frontal passage this afternoon and
evening. Surface winds south to west 10-20 kts increasing to 15-25
kts after 15z Wednesday and shifting to west after 18z then to the
northwest with the frontal passage after 00z. Winds aloft at
10kft msl west 40-50 kts.





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