Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus65 kboi 190843 

Area forecast discussion
National Weather Service Boise Idaho
243 am MDT Sat Oct 19 2019

Short through Monday night...a strong, and
strengthening, upper level trough will move directly over the
area today, bringing strong winds, a potent cold front,
convection, and snow above around 5000 feet. The Winter Weather
Advisory issued yday for snow in portions of the west-central
mountains will be kept in place, along with the Wind Advisory for
southeast Idaho and the Owyhee Mountains. Two zones were added to
the Wind Advisory - southwest Highlands and southern Twin Falls
County - effective from 21z to 02z. The front will works its way
from west to east across the cwa, crossing eastern Oregon between
6 am and 11 am local time and southwest Idaho between 8 am and 3
PM MDT. It will spread showers and isolated thunderstorms, along
with wind gusts 40-50 mph in the advisory area and 30-40 mph
elsewhere, as it rapidly moves east. Showers and thunderstorms
will have the potential for wind gusts to 50 mph *regardless* of
where they form because they may "tap into", and "mix down",
winds around 10000 feet ranging from 40 to 60 mph. They will also
be capable of brief heavy downpours and graupel. Thunderstorms
should end by 6 PM MDT. Winds will decrease through the evening
and overnight hours, as snow levels fall behind the cold front and
showers move mainly into the mountains by dawn Sunday.
Temperatures will be cool today, around 10 degrees below normal,
owing to the precipitation and cold front, and then reach about
the same numbers Sunday. Monday will be 5 to 10 degrees warmer.

Ridging aloft will build in behind the departing trough beginning
tonight. Snow levels will fall to 3500-4500 feet. Moisture aloft
moving southeast down the eastern side of the ridge will help keep
a chance of showers going in the higher elevations all the way
through Monday night. In addition, a disturbance also moving down
the east side of the ridge will bring a "slight chance" to
"chance" of showers to most of the area Sunday afternoon and
evening. This disturbance will move out late Sunday night, leaving
a chance of showers Monday and Monday night only in the northern
and northeast part of the County Warning Area.

Long term...Tuesday through Saturday...snow showers will
continue across over Baker County Oregon and the west central
Idaho and Boise Mountains on Tuesday under moist northwesterly
flow aloft. Showers will retreat to the west central Idaho
mountains Tuesday night and Wednesday and end Wednesday night as
an upper level high pressure ridge centered off the California
coast expands inland. The chance of precipitation will increase
for the west central Idaho mountains Friday night and Saturday as
a weak upper low pressure trough from the Gulf of Alaska crosses
northern Idaho. Temperatures will be near normal Tuesday and
Wednesday, then around 5 degrees below normal in the valleys
starting Thursday as a temperature inversion develops due to
warming aloft.


Aviation...conditions will deteriorate this morning as a deep
upper level trough from the North Pacific spreads rain and snow
across the area. Expect widespread mountain obscuration and areas of
MVFR and local IFR/LIFR conditions. Isolated thunderstorms are
possible this afternoon. Conditions will improve tonight as
precipitation ends across southeast Oregon and lower elevations of
southwest Idaho. Snow levels 5k-6k ft mean sea level lowering to 3500-4500 ft
mean sea level tonight. Surface winds southeast to southwest 10-20 kts this
morning becoming west to northwest 15-25 kts this afternoon. Winds
aloft at 10k ft mean sea level west 40-50 kts this morning and northwest 40-50
kts this afternoon.

Sunday outlook...mainly VFR. Scattered showers with local MVFR/IFR
conditions and mountain obscuration. Snow levels 3k-4k ft mean sea level.
Surface winds west to northwest 5-15 kts.


Boi watches/warnings/advisories...
Idaho...Wind Advisory from 3 PM this afternoon to 8 PM MDT this evening
Wind Advisory from noon today to 8 PM MDT this evening idz029.
Winter Weather Advisory from 6 am this morning to midnight MDT
tonight idz011.
Or...Wind Advisory from noon MDT /11 am PDT/ today to 8 PM MDT /7 PM
PDT/ this evening orz061-063.




National Weather Service Glossary of Abbreviations