Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 200234
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
834 PM MDT Wed Jun 19 2019

.DISCUSSION...Winds are diminishing slowly this evening, after
peaking out just barely at or below advisory criteria in a few
spots. Should be stronger winds tomorrow, as the strongest
gradient aloft, associated with a shortwave currently off of
Vancouver Island, passes overhead during the afternoon. Thus, a
wind advisory for the Snake River plain from Mountain Home
eastward on Thursday afternoon and evening looks good. That
shortwave also supports a few showers for Thursday afternoon,
mainly over the Idaho mountains. Temperatures will also be down
about 15 degrees from what we saw Wednesday afternoon as the
coolest air aloft moves overhead. All this handled well in current
forecasts.
&&

.AVIATION...VFR with mostly clear skies through the rest of the
night. Increasing cloud cover Thursday afternoon. Isolated showers
developing in northern portions of SE Oregon and SW Idaho early
afternoon with most activity in the central Idaho mountains. Snow
levels lower to around 6K feet MSL with light accumulations,
generally 1 inch or less, through the West Central mountains.
Surface winds, northwest 5-10kts through the night and early
morning then increasing to 15-20kts with gusts of 30-35kts in the
afternoon. Winds aloft to 10k feet MSL, northwest 25-35kts.
&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Friday...Breezy, cooler weather has
already started as H5 heights lower from the northwest and the
nw-se surface pressure gradient tightens.  A deep upper trough
in western Canada will settle over the interior northwest US
Thursday bringing unusually cool and windy weather to our area.
High temps Thursday will only be in the 50s to mid 60s.  The nw-se
surface pressure gradient will tighten further under aligned
northwesterly flow aloft.  Winds are expected to reach advisory
speeds Thursday afternoon and early evening in the Snake Basin
east of Boise through the Magic Valley.  Elsewhere expect west/
northwest winds 20-30 mph Thursday afternoon.  Precipitation
Thursday will be confined to the west Central Idaho mountains,
with up to an inch of snow above 6000 feet MSL.  Instability will
also support a slight chance of thunderstorms in those areas
Thursday afternoon.  Winds will ease Thursday night.  Friday
morning will be quite cool in all areas with lows in the 30s in
the mountains to mid 40s in the valleys.  Later Friday the upper
trough will shift slightly east but high temps will still be only
in the upper 50s through 60s, along with breezy northwest winds.
A chance of showers will continue Friday in the west Central Idaho
mountains through the Boise Mountains and as far south as the Camas
Prairie, but the snow level will rise to near 7500 feet.  Models
also see a slight chance of rain showers in Owyhee County Friday
afternoon.

LONG TERM...Friday night through Monday...A deep trough
propagates eastward out of the region on Friday night, resulting
in northwest flow through Sunday. An upper low then moves
southward from the Gulf of Alaska, as warmer southwest flow
returns on Monday. Temperatures will remain a couple degrees
below normal with possible showers and thunderstorms over the
West Central Idaho Mountains each evening.

Monday night through Wednesday night...Mostly clear and warm,
except afternoon through evening showers and thunderstorms mainly
along the northern mountains. A Pacific low is expected to usher
in moisture and instability required to support the persistent
convective activity. High and low temperatures are expected to
measure in a few degrees below normal.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from 2 PM to 8 PM MDT Thursday IDZ014-016.
OR...None.

&&

$$

www.weather.gov/Boise
www.facebook.com/NWSBoise
www.twitter.com/NWSBoise

DISCUSSION...TB
AVIATION.....JC
PREV SHORT TERM...LC
PREV LONG TERM....AL/WH


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