Flood in Idaho, May 7, 2022

Area Forecast Discussion
National Weather Service Missoula MT
232 PM MDT Fri May 6 2022

.DISCUSSION...

A broad area of low pressure will be swirling near to and around
the Northern Rockies through at least the middle of next week.
There are several phases of this storm system that will impact the
region in unique ways, including...

PHASE 1: Some of the strong winds aloft will mix to the surface
this afternoon and evening, increasing hazardous crosswinds on
highways, blowing around loose objects, and increasing wave
activity on Flathead Lake. Gusts around 30 mph are possible near
and around Flathead Lake through sunset this evening, with
increased wave activity continuing through the overnight.

PHASE 2: A surge of moisture colocated along a cold front is
anticipated to move across portions of north central Idaho and
west central Montana this afternoon through Saturday midday. Some
of the moisture will be realized as rain (and even thunderstorms
across north central Idaho), further increasing flows in area
small streams and rivers. Exercise caution along river banks, as
the cold and swift water conditions can be hazardous. Snow levels
will drop to near 5000 feet and change much of the precipitation
to snowfall. This introduction of cold air aloft will slow runoff
and moderate area stream and river levels throughout much of
Saturday. However, travel above 5000 feet could be impacted by
several inches of snowfall covering roads and reducing visibility
tonight through Saturday morning (particularly for Lolo and Lost
Trail Passes, as well as high elevation locales near Elk City and
Dixie).

PHASE 3: Cold air aloft and residual moisture will allow high
elevation snow and valley rain/snow showers to continue Saturday
through Monday midday. Additional snow accumulation will mostly be
confined above population centers, however there is a roughly 50
percent chance that Butte will see 1 inch or more snowfall
accumulation (mainly on grass/trees/soil) each overnight Saturday
through Monday. Area mountain passes could have some snow covered
roadways briefly during these overnights as well.

PHASE 4: Monday afternoon through Wednesday, there's a bit of a
question about what the evolution out of the current low pressure
pattern will look like. Despite what models and ensemble have
portrayed over the past several days, the prospects for dry and
warm high pressure in the next 6-10 days appears quite low (about
a 20 percent chance). Many ensemble members portray a secondary
low pressure circulation intensifying over California and swing
northeastward across the Great Basin and Central Rockies Wednesday
through Friday next week. This pattern would create a mixed bag
of mild temperatures, variable cloudiness, and elevated showers.
Not until the following weekend do some models/ensembles start to
depict high pressure.

&&

.AVIATION...Widespread shower activity, with embedded
thunderstorms, have developed across northeast Oregon and
southeast Washington as of 06/2000z. Shower and thunderstorm
activity will shift eastward across north central Idaho and west
central Montana from 06/2100z through at least 07/0600z.
Thunderstorm coverage will focus across Clearwater, Idaho,
Missoula, and Ravalli Counties. Thunderstorms will be capable of
producing brief heavy rain, pea size hail, and gusty winds in
excess of 40 knots. A 30% chance exists for a thunderstorm in the
vicinity of Missoula from 06/2300z to 07/0200z. Snow levels will
drop near 5,000 overnight into Saturday morning, with scattered
showers continuing. Ceilings will lower overnight across western
Montana. /Lukinbeal

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from midnight tonight to 10 AM MDT
     Saturday ABOVE 5000 FEET for the Bitterroot/Sapphire
     Mountains.

ID...Winter Weather Advisory from 11 PM this evening to 9 AM PDT
     Saturday ABOVE 5000 FEET for the Southern Clearwater
     Mountains.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
842 PM MDT FRI MAY 6 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0506 PM     TSTM WND DMG     2 NNW EAST KAMIAH       46.24N 116.02W
05/06/2022                   IDAHO              ID   UTILITY COMPANY

            REPORTS OF TREES AND LINES DOWN NEAR THE
            INTERSECTION OF CARIBEL AND GLENWOOD IN
            KAMIAH.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
914 PM MDT FRI MAY 6 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0510 PM     HAIL             3 NNE EAST KAMIAH       46.25N 115.98W
05/06/2022  E0.50 INCH       IDAHO              ID   TRAINED SPOTTER

            STRONG GUSTY WINDS, ESTIMATED NEAR 40 MPH.
            HEAVY RAIN. TOOK LIMBS OFF SOME OF THE
            TREES.

&&