851 
FXUS65 KBOI 050317
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
917 PM MDT Fri Oct 4 2019

.DISCUSSION...Clearing skies and lighter winds setting up for
tonight as an upper trough exits the region. Areas that saw
precipitation earlier today will have the best chance for fog
development overnight, to include portions of the lower Treasure
Valley. No update planned for the current forecast which is on 
track for tonight.

&&

.AVIATION...Mainly VFR except in patchy mountain valley
fog/stratus through Sat morning. Then, local MVFR/IFR and 
mountain obscuration in scattered snow showers over west-central 
Idaho Sat afternoon. Snow levels: 5k-6k feet MSL. Surface winds: 
variable less than 10 kts, becoming W-NW 5-15 kts with gusts to 
around 20 kts Sat afternoon. Winds aloft at 10k feet MSL: W-NW 
15-25 kts. 

Sunday Outlook...Patchy morning fog Sunday. Light easterly or 
variable surface winds.

&&

.PREV DISCUSSION...
SHORT TERM... Tonight through Monday...At 1 PM MDT the back edge
of showers extended from near Hells Canyon through Boise to Elko,
NV, and shifting east.  West/northwest winds have increased to 
20 mph with gusts 30 to 35 mph in the Snake Basin east of Boise,
and should reach 25 to 30 mph with gusts to 40 mph late this
afternoon, just below advisory levels.  As of 1 PM MDT wet snow
had accumulated about 1/2 inch at the McCall, ID snow stake.  
Higher mountains in central Idaho will get up to 6 inches total
snowfall before ending this evening.  Gradual clearing west
to east overnight, but fog is expected in the valleys later 
tonight and Saturday morning due to damp ground, clearing skies,
and light winds.  Fog is likely again the following two nights/
mornings.  After the fog Saturday will become mostly sunny
except in the west central Idaho mountains where a weak upper
trough will bring a chance of rain/snow showers in the afternoon.
Sunday and Monday look sunny and gradually warmer in all areas.
Highs Monday will be 55 to 65 in the mountains and 65 to 72 in 
the lower southern valleys under dry northwesterly flow aloft.

LONG TERM...Monday night through Friday...Temperatures will be
near normal on Tuesday ahead of another unseasonably cold low 
pressure trough from northern Alaska. Models agree on timing the
cold front through our area Tuesday night. Following the front,
snow levels will lower to 3000-4000 feet by Wednesday morning.
Precipitation is still expected to be confined mainly to Baker
County/Oregon and the central Idaho mountains Tuesday and Tuesday
night and continue over the central Idaho mountains through 
Wednesday. The trough is forecast to move east of our area 
Wednesday night. Temperatures will be 10-15 degrees below normal
Wednesday and Thursday. Lows Wednesday night will likely be below
freezing in all areas. On Friday a transitory high pressure ridge
will warm temperatures to 5-10 degrees below normal. 

AVIATION...Mainly VFR in southeast Oregon. In southwest Idaho 
mountains obscured, with areas of MVFR and local IFR/LIFR conditions 
in rain and snow. Mainly VFR after 00z except for patchy fog.
Snow levels 5k-6k ft MSL. Surface winds west-northwest 10-20 kts 
except 15-25 kts southeast of KMUO before 05/03z, becoming light and 
variable after 03z. Winds aloft at 10k feet MSL west-northwest 20-30 
kts. 

Weekend Outlook...Mostly VFR. Scattered snow showers over the west 
central Idaho mountains Saturday afternoon and evening. Patchy late 
night and morning fog Saturday and Sunday.

&&

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

&&

$$

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DISCUSSION...DG
AVIATION.....SH
PREV SHORT TERM...LC
PREV LONG TERM....JT