Area Forecast Discussion
Issued by NWS Boise, ID

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000
FXUS65 KBOI 191557
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
957 AM MDT Thu May 19 2022

.DISCUSSION...No updates to the forecast are planned this
morning. A much cooler and windy day is in store today
across the area. Breezy winds were observed overnight behind a
cold front in the lower elevations with strong, gusty winds on
mountain peaks. As daytime heating increases, strong winds aloft
will further mix down into the lower terrain. The strongest winds
will be observed south and east of Boise and into the Magic
Valley, where sustained winds of 25-35 mph and gusts to 50 mph are
expected late this morning through early this evening. A Wind
Advisory remains in effect through 9 PM MDT this evening for these
areas. Although not quite strong enough elsewhere for an
advisory, it will still be windy across the entire area with gusts
30-40 mph common. Winds will subside after sunset. High
temperatures today will be around 20 degrees cooler than
yesterday, with highs only in the 50s in the lower elevations.
Showers will increase this afternoon with daytime heating,
especially in the mountains, although isolated showers may develop
in the Treasure Valley as well. Snow levels will be near
4000-4500 feet, so heavier showers could produce minor, brief snow
accumulations in mountain communities today. Weak instability
this afternoon and early evening will allow for isolated
thunderstorm development across the mountains. Finally,
temperatures tonight will drop into the 30s in the agricultural
valleys, with temperatures dipping below freezing in the Magic
Valley by early Friday morning.

&&

.AVIATION...Mainly VFR, except periods of MVFR in rain and snow
showers over Baker Co., OR and the West Central Mountains through
20/04Z. Thunderstorms possible tomorrow afternoon in Baker Co., OR
and the West Central and Boise Mountains. Surface winds: W-NW 10-20
kt with gusts 20-30 kt and up to 40 kt in the Lower Snake River
Plain, decreasing to W-NW 5-15 kt after 20/12Z. Winds aloft at 10k
feet MSL: W 40-55 kt decreasing to W-NW 15-25 kt.

Weekend Outlook...Scattered rain and snow showers in SE Oregon and
the West Central and Boise Mountains. Otherwise, dry and mostly
clear conditions for the region through Sunday. Breezy winds Sunday
evening.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Saturday night...Strong westerly flow
aloft will be replaced by north to northwest flow later today as
an upper level trough digs into the area. This feature will bring
an unseasonably cold airmass with it, along with enough cold air
aloft to give us a chance of thunderstorms generally in the north
today through Saturday. Showers will also be in the forecast for
the same area overnight when thunderstorms are much less likely.
Snow levels will fall from roughly 5000 ft in the north and 7000
ft in the south early this morning, down to 3500-4000 ft by Friday
morning. A wind advisory will remain in effect today from 9 AM
MDT to 9 PM MDT south and east of Boise, where sustained winds
will average 25 to 35 mph and gusts to 50 mph are forecast. The
strongest gusts will most likely be from the Upper Treasure Valley
near Mountain Home east into the western Magic Valley. Outside
that area, the strongest gusts will likely be associated with
showers that mix down gusty air from several thousand feet up.
Temperatures will be much cooler today - roughly 20 degrees
cooler than yesterday, over most of the area. After today, we will
see gradual warming through Saturday. Highs today will be 15-20
degrees below normal, rising to 10 degrees below normal Friday and
5-10 degrees below normal Saturday. Morning lows Friday will be
near freezing in the western Magic Valley, in the mid 30s through
the Upper Treasure Valley, and in the 20s in the mountains. Due to
the freezing temperatures in the Western Magic Valley zone Friday
morning, we have issued a freeze warning.

LONG TERM...Sunday through Thursday...An upper level trough will
continue to support scattered rain and snow showers and isolated
thunderstorms on Sunday, mainly during the afternoon over the
mountains of Baker County Oregon and central Idaho. Showers will end
Sunday night as the trough exits to the east. Temperatures will
average about 5 degrees below normal Sunday and Monday and slightly
above normal on Tuesday as an upper level ridge builds over our area
from the west. As the ridge axis shifts to the east Wednesday and
Thursday, temperatures will continue to warm under southwest flow
aloft. Although there is still some uncertainty, ensemble blends are
currently showing highs near 10 degrees above normal both days.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Freeze Warning from 3 AM to 9 AM MDT Friday IDZ016.
     Wind Advisory until 9 PM MDT this evening IDZ014>016-028-030.
OR...None.

&&

$$

www.weather.gov/Boise
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DISCUSSION...ST
AVIATION.....SA
PREV SHORT TERM...SP
PREV LONG TERM....JT


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