Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 230244

Area Forecast Discussion
National Weather Service Boise ID
844 PM MDT Tue May 22 2018

.DISCUSSION...Showers and thunderstorms continue this evening
across south-central Idaho and southeast Oregon. The stronger
storms are currently across Baker and Northern Malhuer counties
where the airmass remains unstable. These storms will produce
brief heavy rain and small hail. Storms early in the Western
Magic valley produced heavy rainfall and small hail however, the
airmass has since stabilized from rain cooled air. Showers will
persist though in the Western Magic and Upper Treasure Valley
through midnight. Thunderstorms should diminish by 09z across
Southeast oregon. Another round of showers and thunderstorms is
expected Wednesday afternoon. Minor update to pops mostly in
Southeast Oregon tonight. Update will be out shortly.


.AVIATION...Mostly VFR. Showers and thunderstorms will continue into
the late evening. Most activity will end by 05z. Strongest storms as
of 0230Z were near KBKE and east of KBNO, and were moving south.
Surface winds: variable 10kts or less with winds in and around
thunderstorms 15-25kts with gusts 30-40kts. Winds aloft to 10k feet
MSL, variable 10-15kts.


SHORT TERM...Tonight through Friday...Thunderstorms have
developed near the Nevada border as they did yesterday.
Unlike yesterday, thunderstorms are also developing in
the Boise Mountains and to a lesser extent in the west
central Idaho Mountains.  WPC indicates a marginal threat
of flash flooding in the Boise Mountains tonight but 12Z
model QPFs are relatively small.  In any case, we are
forecasting highest PoPs for showers and thunderstorms
tonight in eastern-most Idaho zones, especially southern
Twin Falls County and the western Magic Valley.  These areas
are closest to the expected track of an upper low currently
in eastern Nevada.  The low will pass through southeast Idaho
early Wednesday morning then into Montana.  Short wave upper
ridge will build in behind the low.  Moisture and instability
will continue however, and showers and thunderstorms will
develop Wednesday afternoon in central Idaho and in the
Blue Mountains of Baker County.  A weak impulse will continue
showers and storms in Harney County Wednesday evening.
Thursday looks drier as the upper ridge shifts through and
east of our CWA.  Moist southerly flow will then increase in
Oregon as the next Pacific Upper low approaches the California
coast.  Models agree that a significant surge of moisture will
spread over Harney County late Thursday night, then farther
east into more of our CWA Friday for another round of showers
and thunderstorms.  Temperatures will average 3 to 5 degrees
above normal through Friday.

LONG TERM...Friday night through Tuesday...An upper level low
moving through southern NV through the weekend will bring showers
across the area with afternoon thunderstorms. On Saturday showers
will be mostly throughout SE Oregon then drift eastward to SW Idaho
by Saturday afternoon. SE Oregon begins to dry out by the start of
Memorial Day (Monday) while showers linger in central Idaho.
Temperatures will hover right around normal.





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