Area Forecast Discussion
Issued by NWS Boise, ID

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385
FXUS65 KBOI 252045
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
245 PM MDT Tue Jul 25 2017

.SHORT TERM...Tonight through Thursday...Isolated showers have
developed in the wake of a weak shortwave. Convective development
had been retarded by cloud cover this morning, but partial clearing
will allow more isolated thunderstorms to develop as convective
temperatures are exceeded. A few lightning strikes are already
showing up in northern Nevada and the Southwest Idaho Highlands.
The Flash Flood Watch for southern Harney and Malheur Counties, and
the higher terrain south of the Snake River Valley, continues
through this evening. PW amounts are still over an inch, and the
upper level flow is light, so storms will be slow moving. We can
expect another round of thunderstorms Wednesday afternoon and
evening as an upper level trough currently centered over the
northern California coast moves inland. Will hold off on a Flash
Flood Watch for that period, as water vapor imagery shows drier non-
monsoon air associated with the trough has already pushed into
western Nevada, and the trajectory of the deeper monsoon moisture
over Utah should keep it east of our area. On Thursday thunderstorms
will be limited to the Southwest Idaho Highlands and Central Idaho
Mountains under drier west-southwest flow aloft. Temperatures will
remain a few degrees above normal.

.LONG TERM...Thursday night through Tuesday. The extended forecast
continues to show uncertainty. The trough passes through the CWA by
Thursday night, however, a second trough is just upstream sitting
off the California coastline. Depending on which model you choose to
look at precipitation potential wavers. High pressure starts to try
and build up over the four corners region once again in the GFS
which then helps to usher in monsoonal moisture from the south,
while the ECMWF pushes this trough a little further inland and
brings the monsoonal moisture into our CWA a tad later. Slight
chances are mentioned in the extended forecast for Thursday night in
the central Idaho mountains. After this, confidence is pretty low
with the variance among the models. At this time, left a slight
mention in the higher elevations of Owyhee and Southern Twin Falls
county Saturday afternoon then dried things out for the remainder of
the forecast. Temperatures will remain above normal throughout the
extended forecast.

&&

.AVIATION...Widespread VFR. Showers and/or thunderstorm activity
has started to increase in coverage and move into the area from the
ID/NV border pressing NE. Most showers/thunderstorms look to remain
south of the Treasure Valley, mostly in SE Oregon. Surface winds,
variable 10 kts or less except in and around thunderstorms with
gusts as high as 40 kts possible. Winds aloft to 10k feet MSL,
variable 5-20 kts

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Flash Flood Watch until midnight MDT tonight IDZ015-029-030.
OR...Red Flag Warning until 11 PM PDT tonight ORZ625.
     Flash Flood Watch until 11 PM PDT tonight ORZ061-063.

&&

$$

www.weather.gov/Boise
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SHORT TERM...JT
LONG TERM....JC
AVIATION.....JC



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