Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 300313

Area Forecast Discussion
National Weather Service Boise ID
913 PM MDT THU SEP 29 2016

.DISCUSSION...Shower and thunderstorm activity on the wane this
evening as atmosphere stabilizes. Most areas are dry the rest of
the night. Southern Twin Falls county (Jackpot area) will be the
exception as weak energy tracking through ne NV keeps isolated
showers/storms into early Friday morning. Winds will stay up
overnight through the Snake Plain and across higher elevation
rangeland. Temperatures are mild again tonight with morning lows
well above normal. Current forecast is on track so no updates.


.AVIATION...VFR. Isolated showers ending by 05Z. Scattered to
broken mid-level clouds tonight, then mostly clear Friday. Surface
winds east to south 5-15 kts increasing to 10-20 kts Friday
afternoon. Winds aloft near 10k ft msl southwest 10-20 kts,
increasing to 20-30 kts Friday.

WEEKEND OUTLOOK...VFR. Friday night through Saturday morning
scattered showers over the west central Idaho and Boise Mountains
and south into Nevada, mainly east of a KMYL-KMUO-KEKO line. Sunday
afternoon showers redeveloping over those areas, and over eastern
Oregon, mainly Baker and Harney Counties.


SHORT TERM...Tonight through Saturday...Isolated showers and
thunderstorms formed across a portion of Southwest Idaho, from
near Fairfield to west of Twin Falls. This area should see further
development through this afternoon and early evening, with the
activity diminishing after sunset. The remainder of SW Idaho and
SE Oregon resides within a drier/stable southwest flow aloft. Most
of the area will remain within the dry slot on Friday, with only a
slight chance of showers and afternoon thunderstorms south of Twin
Falls and north of Fairfield. Shower chances will increase in
Baker County and in SW Idaho Friday night ahead of a cold front.
Drier air will work into the region on Saturday behind the cold
front, which will shift the slight chance of showers to the east
of McCall and Idaho City, and to the south of Twin Falls. The
cooling trend will continue with highs 10-15 degrees lower (close
to normal) on Saturday. Breezy southwest winds of 15-25 mph are
expected in SE Oregon and the higher elevations of SW Idaho on
Friday. Winds are not expected to be strong behind the front as it
moves through the region late Friday night through early Saturday

LONG TERM...Saturday night through Thursday...The forecast area
will be in a dry slot behind a shortwave on Saturday night and
much of Sunday. Still enough moisture over the mountains on Sunday
afternoon to support some showers and thunderstorms. Models are
starting to diverge quite a bit by late Sunday, with the GFS now
taking the approaching upper-level low even further south into
southern Nevada, while the ECMWF is further north, near the
Idaho/Nevada border. Precipitation would be more likely with the
ECMWF solution, but even that solution has much of the
precipitation outside the forecast area. Backed off the precip
chances accordingly for the Sunday and Monday period. Temperatures
will likely not be quite as cool as earlier forecast as the bulk
of the cold air goes south of the forecast area. Nevertheless,
temperatures will be below normal by 5-10 degrees Saturday through
Monday. A weak trailing system may bring a few showers to the
Oregon zones on Tuesday, but models are starting to agree that
ridging will build after that, which supports a slow warming
trend, back to near normal temperatures by Thursday.





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