Scientific Forecaster Discussion
fxus65 kboi 202026 cca
Area forecast discussion
National Weather Service Boise Idaho
226 PM MDT sun may 20 2018
Short term...tonight through Tuesday...strong thunderstorms with
heavy rain and small hail were developing early this afternoon in
Owyhee and Twin Falls counties. These storms were moving NNE
around 15 mph. Meanwhile, showers and storms have been slower to
develop in eastern Oregon where models say the flash flood threat
should be greater due to high precipitable water and slower storm movement.
Based on model consensus we will continue current Flash Flood Watch
into this evening. Late tonight the threat will diminish in all
areas. Upper trough in Nevada will close off a low in Southern
California Monday which will allow drying in eastern Oregon. In
Idaho moisture and instability will continue, and showers and
thunderstorms will develop again especially along the Idaho/Nevada border
and in the Boise Mountains. The upper low will turn north in
Nevada Tuesday bringing strong instability to southern Idaho
Tuesday afternoon and renewed thunderstorm activity. Slightly
warmer Monday and warmer again Tuesday with high temps 5-10 above
Long term...Tuesday night through Sunday...the upper level trough
over the intermountain region will exit to the northeast Wednesday
night, replaced by an upper level ridge which will remain over our
area Thursday and Friday, bringing a drying and warming trend.
Models move the next upper level trough onshore over California
Saturday night, while the ridge shifts east of Idaho. The trough is
expected to move north over Oregon and Washington Saturday night and
Sunday, increasing the chances of showers and thunderstorms for
southeast Oregon and southwest Idaho. Temperatures will average
around 10 degrees above normal, with Friday and Saturday the warmest
Aviation...mostly VFR. Widespread rain showers and scattered
thunderstorms will continue through this evening, with local heavy
rain, hail, and brief MVFR conditions. Thunderstorms will mostly
end by 04z, but scattered showers and isolated thunderstorms will
continue overnight. Showers and thunderstorms will redevelop over
the higher terrain Monday afternoon. Surface winds variable 5-15 kts
except gusts to 30 kts possible near showers and thunderstorms.
Winds aloft through 10k feet mean sea level south 10-20 kts.
Idaho...Flash Flood Watch until midnight MDT tonight idz015-029.
Or...Flash Flood Watch until midnight MDT /11 PM PDT/ tonight