492 
FXUS65 KBOI 081528
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
928 AM MDT Fri Oct 8 2021

.DISCUSSION...Showers are underway this morning in most of 
southwest Idaho and in Malheur County/OR, and thunderstorms have 
already started along the Owyhee County/NV border. Rain has been 
slow to get into the Treasure Valley and radar suggests shadowing 
by the Owyhee Mountains. But hi-res models overcome the shadowing 
and bring rain into the Treasure Valley by 11 AM MDT and continue 
it for several hours. SPC still has south-central and southeast 
Idaho under a marginal risk of strong winds and large hail, and 
it has expanded the area of general thunderstorms westward to 
include Malheur and southeast Baker Counties in Oregon. Our 
forecast already has isolated thunderstorms in eastern Oregon. 
Current forecast decreases pcpn tonight from west to east but 
latest hi-res models show showers again late tonight on the Idaho
side, more than in the current forecast. PoPs will be increased 
for tonight if other models and ensembles support the hi-res 
models. Saturday still looks mostly sunny but we are considering 
including morning fog in the Oregon valleys.

&&

.AVIATION...Generally VFR in OR, with MVFR to IFR at times 
in ID. Scattered showers and isolated thunderstorms. Areas of 
mountain obscuration. LIFR conditions possible near KTWF KJER 
after 00z/Sat. Surface winds: SW-SE 5-15kt, becoming NW 10-20kt 
after 21z/Fri. Gusts up to 35kt in vicinity of thunderstorms. 
Winds aloft at 10k feet MSL: SW 10-20 kt, becoming NW 15-25kt by 
03z/Sat.

Weekend Outlook...Areas of mountain obscuration and patchy fog 
on Saturday morning. LIFR conditions possible near KJER KTWF 
with low stratus. Showers tapering off by Saturday afternoon with
clearing and becoming VFR. Northwest surface winds 10-20kt with 
local gusts up to 35kt Sat afternoon and evening. Increasing 
clouds Sunday with showers spreading southeast across the area 
Sunday evening. Widespread precipitation by Sunday night with 
mountain obscuration, MVFR/IFR conditions, and gusty NW surface 
winds. Snow levels 6k-7k feet MSL Sunday lowering to 3k-4k feet 
MSL Monday morning.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Sunday night...Southwest flow remains
across the area today as the upper trough axis approaches eastern
Oregon. Widespread shower activity is favored across much of the
region, with enough instability to bring isolated thunderstorms
as well. Thunderstorm coverage will dissipate with the loss of 
daylight this evening, though showers will continue. The trough 
axis will move through the region tonight and Saturday, producing 
a drier northwest flow. Slightly warmer conditions expected 
Saturday. The next cold front is anticipated to reach the western 
border of the forecast area on Sunday morning, and mostly exit the
area on Sunday evening. Showers and gusty to breezy wind will 
accompany the frontal passage. Temperatures will generally remain 
around 5 degrees below normal through the forecast period. 

LONG TERM...Monday through Friday...Widespread showers and gusty 
winds will continue into Monday as a deep trough axis swings across 
the Intermountain West. Snow levels will lower to 3000-4000 ft MSL 
as temperatures fall roughly 20 degrees below normal. Valley rain 
and mountain snow will linger across south central Idaho through 
Tuesday evening as the upper trough propagates to the east. The 
first freezing temperatures of the season will be possible in 
sheltered locations in the lower valleys Tuesday morning, but 
chances will be much better by Wednesday morning as winds decrease. 
A weak shortwave trough will cross the region on Wednesday, stirring 
up light snow showers over the northern mountains. Temperatures mid-
week will remain roughly 15 degrees below normal, then warm slightly 
on Friday as conditions dry out and an upper ridge begins to set up 
over the Pacific Northwest.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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DISCUSSION...LC
AVIATION.....KA
PREV SHORT TERM...KB
PREV LONG TERM....AL