Flash Flood Warning 13, NWS Boise, ID

027 
WGUS75 KBOI 220243
FFSBOI

Flash Flood Statement
National Weather Service Boise ID
843 PM MDT Mon Aug 21 2023

IDC047-220253-
/O.EXP.KBOI.FF.W.0013.000000T0000Z-230822T0245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Gooding ID-
843 PM MDT Mon Aug 21 2023

...FLASH FLOOD WARNING WILL EXPIRE AT 845 PM MDT THIS EVENING FOR 
NORTHWESTERN GOODING COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat.

LAT...LON 4316 11504 4302 11492 4302 11489 4311 11480
      4319 11475 4319 11501 4319 11503

$$

BOI

Area Forecast Discussion
National Weather Service Boise ID
234 PM MDT Mon Aug 21 2023

.SHORT TERM...Tonight through Wednesday night...Heavy rains
shifted into the Weiser Basin/ID and Baker County/OR as the
center of former Hurricane Hilary tracked northeastward to near
Ontario/OR early this afternoon. The track shifted slightly
east of previous forecasts and is now forecast to exit Valley
County/ID around 6 PM MDT, taking the heaviest rain with it.
However, showers will continue through sunset. The Flood Watch
is cancelled as of 1 PM PDT in Harney and Malheur Counties, but
will continue in Baker County until 11 PM PDT. Skies have
partially cleared to the south and east in Idaho, but
thunderstorms were beginning to form there. The strong southeast
winds did develop in the southwest Idaho Highlands late this
morning. Those winds were decreasing this afternoon and the
High Wind Warning and nearby Wind Advisories have been
cancelled as of 2 PM MDT. The thunderstorms, however, will
still occur through the evening, so the Flood Watch will
continue until midnight MDT in Idaho north of the Snake Basin
into Baker County/OR. More thunderstorms are forecast Tuesday
in western Idaho and may bring heavy downpours again, but not
the widespread heavy rain that occurred today from Hilary.
Wednesday will be drier and warmer than Tuesday, but still
slightly cooler than normal.

.LONG TERM...Thursday through Monday...By Thursday, an elongated
low will become established off the West Coast as an Alaskan
low moves south along the coast to merge with a low off the
Californian coast. The positioning of the low will allow a ridge
to amplify over the western U.S. bringing us warmer and drier
south-southwesterly air through Friday morning. The low pressure
will begin to push moisture and energy into our area beginning
Friday through the period, giving us a 20-40% chance of
precipitation in the afternoon/evening periods through Saturday.
Higher terrain will be favored, with a 10-20% chance of
precipitation in the Snake Plain and low terrain. The flow after
Saturday through Monday seems to be drier, reducing chances of
precipitation. Temperatures will steadily warm through the
period.

&&

.AVIATION...Widespread rain and areas of MVFR and mountain
obscuration in Baker County/OR and west-central ID as remnants
of Hilary pass through around 22/00Z. VFR elsewhere. Scattered
thunderstorms in south-central ID moving northward through
22/06Z with local MVFR conditions and mountain obscuration.
Local IFR in valley fog 22/09Z to 22/15Z. Southeast or
southerly surface winds 20-30kt in southern ID until 22/00Z
then decreasing. Winds aloft at 10kft MSL: Sw 20-30kt.

&&

.HYDROLOGY...A Flood Watch for flash flooding remains in effect
across Baker County, Weiser River Valley, West Central
Mountains, and Boise Mountain zones where 1.5 to 2.5 inches of
rain has fallen today. Some additional rain will continue in
these areas this evening. The watch has ended for the rest of
southwestern Idaho and southeastern Oregon where rain has come
to an end. In addition, a Small Stream and Urban Flood Advisory
remains in effect for a portion of northern Malheur and Baker
Counties in Oregon and Washington, and Adams County in Idaho.
USGS stream gages are showing some rises on small streams in the
advisory area and additional rises to bankfull conditions are
possible into the early evening. Ponding of water in low spots
and other poor drainage areas has also been reported in the
advisory area.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Flood Watch until midnight MDT tonight IDZ011-013-033.
OR...Flood Watch until 11 PM PDT this evening ORZ062.

&&

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

SHORT TERM...LC
LONG TERM....JM
AVIATION.....LC
HYDROLOGY....JB