Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 211001
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
401 AM MDT Mon May 21 2018

.SHORT TERM...Today through Tuesday...Upper level low continues to
move south and east into NV and AZ this morning and is cutting
off from the parent flow. As this trough cuts off, storm motion
winds will weaken to under 5kt which will keep showers and
thunderstorms over the higher terrain this afternoon. Lack of
steering winds should keep the Treasure and Magic Valleys in Idaho
and the basins of SE Oregon dry today. The upper level trough
over southern NV will slowly move north on Tuesday and steering
winds will pick up from the east to southeast 5-10kt on Tuesday
afternoon. Showers and thunderstorms will develop over the higher
terrain during the afternoon and slowly drift east, with the best
chances of storms in the Idaho zones. Temperatures remain around 5
degrees above normal, with overnight lows around 10 degrees above
normal.

.LONG TERM...Tuesday night through Friday...The upper level trough
will slowly move northwest and weaken over our area before being
absorbed into the southwesterly flow. This will allow
temperatures to warm a few degrees on Wednesday and Thursday with
continued unsettled conditions. Precipitable water values will
also increase to near the 95th percentile during this time,
keeping the heavy rain threat with storms. Will need to monitor
the flash flooding threat for Wednesday and Thursday. By Friday,
the upper level flow shifts to the south, bringing warmer
temperatures to the region(around 15 degrees above normal). A
trough will move onto the CA coast on Friday afternoon, keeping a
threat of thunderstorms in the Oregon zones on Friday, while the
Idaho zones are generally dry.

Friday night through Monday...Showery, unsettled conditions are
in store as a strong, moist upper low makes its way into and
across the CWA. Models in fairly good agreement that inclement
weather will persist most of the period, blanketing a huge portion
of the area with showers until improving conditions take hold
Monday afternoon. Widespread afternoon through late evening
thunderstorms are also a likely possibility with coverage
gradually diminishing to the northeastern corner of the CWA by
Monday evening. High and low temperatures will gradually cool down
from around ten degrees above normal to near normal.

&&

.AVIATION...Isolated showers with areas of MVFR ceilings and
mountain obscuration this morning. Partial clearing by midday.
Scattered showers and thunderstorms developing across the
mountains this afternoon, with highest chances of storms near the
NV/ID border. Surface winds generally northerly 5-10kt, except
gusty erratic winds to 30kt near storms this afternoon. Winds
aloft at 10kft MSL: E-NE 5-10kt.

&&

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

&&

$$

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

SHORT TERM...KA
LONG TERM....KA/WH
AVIATION.....KA



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