Area Forecast Discussion
Issued by NWS Boise, ID

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS65 KBOI 241648

Area Forecast Discussion
National Weather Service Boise ID
948 AM MST Sat Feb 24 2018

.DISCUSSION...Radar demonstrating a decent swath of moisture
moving through the Treasure Valley producing snowfall. This looks
to be the beginning of a period of heavier snow which could last
into early afternoon hours. As the snowfall moves east, it is
anticipated to move into the Western Magic Valley by the mid-
afternoon hours with significant snowfall possible through the
early evening hours. Brief periods of clearing across the Treasure
Valley this afternoon will increase instability, potentially
promoting additional shower development. With these afternoon
showers, graupel will be possible along with a few lightning
strikes. No changes to highlights or snowfall accumulations needed
at this stage.


.AVIATION...Mountains obscured. Areas of snow this morning with IFR
and local LIFR conditions, except generally VFR this morning
southeast of KMUO. Snow reaching the KTWF/KJER area by 20z.
Conditions improving to mainly VFR at KBNO and KBKE after 19z, KBOI
after 21z, and KTWF/KJER after 00z, except for brief IFR conditions
in scattered snow showers. Snow ending at valley locations by about
03z, but snow showers continuing overnight in the mountains. Surface
winds southeast to southwest 10-20 kts except 15-25 kts over the
higher terrain. Gusts to 35 kts possible near snow showers this
afternoon. Winds aloft at 10k ft MSL west 25-35 kts becoming
northwest 30-40 kts after 21z.

Sunday outlook...Deteriorating conditions. Snow becoming widespread
over the mountains and a chance of snow at lower elevations by 18z.
Widespread snow across the entire area after 26/00z.


SHORT TERM...Today through Sunday...The next winter storm is upon
us, and we made some small changes to the warning and advisories
that were previously posted. The latest timing brings the storm
in a little slower, and we now expect temperatures to allow for
accumulating snows in some of the lower elevations into the early
afternoon. This necessitated some changes in the timing of some
of the advisories. We have also added blowing snow to the forecast
in areas where wind gusts are forecast to be 25 mph or greater
and temperatures less than 28 degrees. Blowing snow will be common
in the mountains and in the Southwest Highlands. Snow is expected
to begin in eastern Oregon before 12Z, then moving into southwest
Idaho. There will be a sharp north-south gradient in snowfall
across the Treasure Valley due to downsloping in the lee of the
Owyhees, with less than an inch expected in the southern part of
the valley, then 1 to 3 inches as you move north toward I-84, and
then 3 to 5 inches north of I-84 (generally speaking). Instability
will be sufficient for very vigorous showers this afternoon, and
even a chance for thunderstorms. Graupel, often confused for hail,
will be present with many of these showers and any thunderstorms
that form. Generally, the morning will bring steady snows, while
the afternoon becomes showery/stormy. This is not true for the
western Magic Valley, where steady snows will not begin until
afternoon, with showers/storms coming late in the afternoon and
into the evening. Tonight will bring a drying trend, and yet
another system begins to move in Sunday. Snows will move into
Baker County and the mountains of southwest Idaho during the
afternoon, and expand south and east overnight. Additional
advisories and/or warnings will most likely be needed for this
system, once today`s system clears the area. Temps will be a few
degrees warmer Sunday than today.

LONG TERM...Sunday night through Friday...Unseasonably cool and
unsettled weather will continue in the extended period, with below
normal temperatures and above normal precipitation. A vigorous cold
front will move through the region on Sunday night into Monday
morning. Westerly flow will favor moderate to heavy snow
accumulations across the central Idaho mountains; with snow amounts
approaching warning criteria. The system will quickly move south on
Monday afternoon, with snow showers lingering across the higher
terrain through Monday evening. Tuesday will be generally dry and
cool in between systems. A system will move into the Pacific NW late
Wednesday into Thursday, bringing more precipitation into the region
through the weekend, although forecast details and timing are
unclear at this point.


ID...Winter Weather Advisory until 8 PM MST this evening IDZ013-015.
     Winter Storm Warning until 5 PM MST this afternoon IDZ029.
     Winter Weather Advisory until 2 PM MST this afternoon
     Winter Weather Advisory from 2 PM this afternoon to 8 PM MST
     this evening IDZ016-030.
OR...Winter Weather Advisory until 2 PM MST /1 PM PST/ this afternoon



PREV LONG TERM....KA is the U.S. government's official web portal to all federal, state and local government web resources and services.