Heavy Rain in Oregon, June 9, 2023

Area Forecast Discussion
National Weather Service Boise ID
327 AM MDT Fri Jun 9 2023

.SHORT TERM...Today through Sunday night...Models have consistently
predicted that today would be the wettest day of the week in our
CWA as an upper low in northern Nevada moves into southeast Oregon.
The main moisture is forecast to wrap around the low's northern
and western flanks, i.e., directly over Baker and Harney Counties
where widespread amounts of .50 to .75 inch of rain will fall.
Amounts up to 1.25 inch are forecast for the mountains of western
Baker County, with a 20% chance of as much as two inches under
the heaviest showers and thunderstorms. Similarly heavy rainfall
is also forecast for the Owyhee Mountains and nearby parts of the
southwest Idaho Highlands, Lower Treasure Valley, and Malheur
County. All these areas are under a Flood Watch from mid morning
until sunset today. Precipitation will decrease late tonight
through Saturday as the low continues northward into Washington,
but on Sunday another Pacific upper low will come inland across
central California, close enough to increase showers and
thunderstorms along our Nevada border zones Sunday night.
Continued relatively cool again today, then about 5 degrees
warmer Saturday and another 5 degrees Sunday as the first upper
low moves away.

.LONG TERM...Monday through Friday...Long range models depict a
closed upper low located over California and Nevada will track
eastward Monday and Tuesday. Afternoon and evening showers and
thunderstorms, mainly over southwest Idaho, can be expected both
days as instability and moisture continues to impact the area with
this low. Stronger storms that develop will be capable of heavy
rainfall and gusty outflow winds. As the upper low exits the region,
ensemble guidance suggests the upper pattern will transition to
drier northwest flow and reduce the threat of shower/thunderstorm
activity Wednesday through Friday. Temperatures are forecast to be
slightly above normal through the week.

&&

.AVIATION...Isolated, slow-moving rain showers over E Oregon and SW
Idaho this morning, capable of brief MVFR conditions and mountain
obscurations. Expect VFR conditions outside of showers. Numerous
showers and thunderstorms by Fri/18z across E Oregon and SW Idaho.
Heavy rain and erratic outflow winds up to around 35 kt in storms.
Activity weakening/decreasing after Sat/03z. Surface winds outside
of storms: mainly SW to SE 5-15 kt. Winds aloft at 10k feet MSL:
S to W 10-20 kt.

Weekend Outlook...Mainly VFR, except scattered MVFR due to
afternoon/evening showers and thunderstorms. Storm development will
favor the mountains of SW Idaho. Mountains obscured at times. Gusty
outflow winds and heavy rain with thunderstorms, otherwise light and
variable winds.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Flood Watch from 10 AM MDT this morning through this evening
     IDZ012-015-029.
OR...Flood Watch from 10 AM MDT /9 AM PDT/ this morning through this
     evening ORZ061>064.

&&

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SHORT TERM...LC
LONG TERM....SH
AVIATION.....SH