Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 251503

Area Forecast Discussion
National Weather Service Boise ID
903 AM MDT Sat Mar 25 2017

.DISCUSSION...Patchy valley fog will end by noon.  Otherwise,
current forecast is on track with isolated to scattered showers
developing later today in Oregon and western-most Idaho under
eastward-moving upper trough.  Cloud shield farther east will delay
warming and convective development in south-central Idaho.  Next
Pacific frontal system will begin showers Sunday afternoon but the
main rain will come Sunday night/Monday when the cold front moves
through from west to east.


.AVIATION...Local IFR fog conditions in southwest Idaho should break
up by 18Z, elsewhere VFR. Scattered afternoon showers developing
over Oregon this afternoon, moving east into Idaho late afternoon.
Some stronger cells could produce graupel and gusts to 25 kts.
Otherwise surface winds west 10-15 kts. Winds aloft 15-25 kts at 10k

Sunday...Clouds increase from west-to-east in the morning over
Oregon and afternoon over Idaho. Ceilings probably remain VFR during
day, with some showers producing MVFR by afternoon. More widespread
MVFR ceilings and showers move in from the west Sunday evening and
overnight. South to east winds at surface to 20 kts. Southwest winds
aloft increasing to 25-35 kts at 10k feet.


SHORT TERM...Today through Sunday...Cold front has pushed east of
the area with colder air aloft as an upper level trough moves
overhead. Daytime heating today will generate instability as cold
air aloft provides steep lapse rates. These lapse rates will fuel
isolated to scattered showers across southeast Oregon and the
southwest Idaho highlands, Owyhee and west Central Idaho mountains.
Gusty winds and graupel are possible with showers during the
afternoon. High clouds currently over the region could keep showers
from developing over the Boise Mountains and areas south toward the
Magic Valley as they move east. Expect clearing skies after sunset.
Patchy fog is expected in the mountain valleys on Sunday morning
ahead of the next approaching system. Slightly warmer air moves into
the region on Sunday afternoon, as southwest flow develops and
clouds increase with an approaching system.

LONG TERM...Sunday night through Friday...Upper trough tracks
through the interior NW Sunday night and Monday. A cool rain in the
valleys with snow levels of 4500-5500 feet. Weak ridging brings
drier conditions for Monday night into Wednesday. Some timing
differences have developed between model solutions for late Wed
through Friday though consensus remains that another sharp upper
trough will move through the area late Wed/Thur with more rain and
mountain snow. Snow levels with this system will drop from around 6k
feet late Wed to 4500 feet on Thursday. Will see a drying trend on
Friday as an upper ridge builds in from the Pacific. Temperatures
are near normal through the period with Monday and Thursday the
coolest days of the week.





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