Flood in Oregon, January 4 to 7, 2022

Area Forecast Discussion
National Weather Service Medford OR
1015 AM PST Tue Jan 4 2022

Updated AVIATION Section

.UPDATE...

A few changes to the forecast this morning with rain continuing
along the coast with snow in the Cascades. Latest road cameras
don't show snow falling over Siskiyou Pass this morning, which
was expected with a snow level around 4500 feet under deeper
westerly flow. Otherwise, a mix of some strong winds and snow will
continue to impact the Cascades and locations east of the
Cascades through this evening. We've received a storm report of 17
inches of snow near Crescent over the last 24 hours and another 4
to 7 inches should be on the way through today.

We also upgraded the river flood watch for the Coquille River at
Coquille to a river flood warning. Flooding should remain minor
and the only impacts will be some flooding of farmland and low
lying areas around the Coquille.

-Smith

&&

.DISCUSSION.../Issued 424 AM PST Tue Jan 4 2022/

Current radar has shown the widespread precipitation
become more showery in nature. Many of these showers remain
focused on higher terrain, especially along the Cascades. This is
indicative of moisture from an atmospheric river that has
separated from its upper-level trough. We also see this with winds
east of the Cascades which are still blowing at advisory levels
with a few locations seeing gusts near 50 mph. West of the
Cascades, winds are still breezy; but much lower than they were
earlier in the day. Still, the showers still seem focused in the
Cascades and Coast Range dominated by orographics which support
the aforementioned separation.

That being said, these breezy to gusty winds will continue
through the morning and increase later today. This could create
additional periods of blowing snow and reduced visibilities. The
increase in winds will signify our next disturbance, a surface
low, which is expected to spin up and come onshore this
afternoon. Ample moisture will likely remain from the previous
atmospheric river for this low to tap into to provide additional
periods of moderate to heavy rain and mountain snow. Snow levels
will rise today starting around 3000 feet this morning and ending
around 6000 feet late tonight. Although most of our winter
headlines were allowed to expire at 4 AM, Winter Storm Warnings
remain in effect along the Cascades and for portions of the East
Side. The big thing with these winter storm warnings is that they
combine effects from the wind and blowing snow this morning before
the hazard transitions to be caused more by falling snow. Still,
this system looks to be poised to dump another foot of snow across
portions of the Cascades. Please see the WSWMFR for more details.

Additionally, periods of moderate to heavy rain will continue to
fall on additional areas of snowmelt (with the higher snow
levels). The good news is that these higher elevations have a good
chance of seeing significant enough snowpack to absorb the rain
like a sponge instead of washing and completely melting the
snowpack into runoff for rivers. Where this transition line will
occur is largely beyond our science at this point, we do recognize
that it happens which is why the additional moderate to heavy
rainfall along the coast and the Umpqua basin will fuel greater
possibility for small stream and creek troubles instead of main
stem river issues for most rivers. Will need to coordinate with
the Northwest River Forecast center, but conditions appear as if
the Coquille River at Coquille in the winter lake area has reached
bankfull and may come relatively close to reaching minor flood
stage--but this is the only river that appears to be moving in
this direction with the other main stem rivers with flood watches
seeing lower crests with this forecast cycle. Still, an areal
flood watch seems necessary for today considering we've had a
trained spotter report flooding along Brummett creek as well as a
few rock falls/debris flows along roadways in the Umpqua Basin.
It is worth noting that the current threat of flooding seems to
have decreased due to the lightening of precipitation and it
turning to showers so allowed the flood advisory for these areas
expire. However, this area will need to be monitored, and am
looking forward to our spotter's next call for this area.
Precipitation will weaken overnight tonight, but showers should
continue into Wednesday morning.

Previous Long Term Discussion...(Issued Monday 1/3 for Wednesday
1/5 - Monday 1/10, 2022) Long Term...Wednesday through Monday,
January 5-10, 2022... A warm front will lift northward through
the area on Wednesday and this will result in a surge in snow
level from 5000-5500 feet in the morning to above 7000 feet by
evening. While the warm front is expected to bring a little light
warm advection precipitation, especially along and west of the
Cascades, amounts aren't expected to be excessive with the main
corridor of moisture lifting to the north and impacting NW Oregon
and Washington. With the surge in snow levels, there will still be
some inflows into area streams/creeks/rivers, primarily due to
snow melt. We're not expecting any main stem river flooding, but a
continuation of higher flows (at least compared to where they
have been most of this wet season) can be expected.

Flat ridging will move into the area on Thursday and this should
allow areas south and east of the Cascades to dry out (even though
there's still a slight chance of rain). Areas west of the Cascades
will also largely get a break from the rain, though onshore flow
will keep rain chances pretty high, especially along the coast and
into the coast ranges.

The next upper trough and cold front will approach the coast
Thursday night and move onshore Friday morning. This one will bring
another round of wind and rain, with snow in the mountains. It won't
be nearly as vigorous as the early week storm. Snow amounts of 5-10
inches are a good bet above 5000 feet in the Cascades. Snow levels
will gradually lower Friday night to around 3000 feet by Saturday
morning. By then, however, the vast majority of the ensembles
indicate the upper trough shifting eastward and being replaced by an
upper ridge. This would bring a period of drier weather this
weekend. With all the moisture left behind from recent rainfall,
we'll likely be dealing with lots of low clouds, fog and freezing
fog.

The period of drier weather could extend into next week as models
are hinting at a split flow developing. This would mean Pacific
systems will struggle to penetrate very far inland with some
providing glancing blows over the top and others heading into
California. -Spilde

&&

.AVIATION...04/18Z TAFs...From the Cascades west...Higher terrain
will remain obscured through Wednesday morning. Under the
obscuration, mostly MVFR cigs/vsbys with areas of IFR cigs/vsbys in
rain/snow/fog will persist. South to southwest winds have increased
along the coast at North Bend with occasional gusts of 20-30kt. Low-
level wind shear is less likely since winds have surface, but some
turbulence should be expected.

East of the Cascades...Higher terrain will remain obscured through
Wednesday morning. Under the obscuration, areas of mixed IFR and
MVFR vsbys and ceilings in snow and blowing snow will persist.
Increasing snow levels will result in a rain/snow mix a
lower elevations today and tonight, evenutally becoming mostly rain
except at the highest elevations on Wednesday. Gusty winds will
persist through today, strongest over the higher terrain, but these
should ease this evening. -Spilde

&&

.MARINE...Updated 830 AM PST Tuesday 4 January 2022...Seas will
remain high and steep today as heavy westerly swell moves into the
waters.

Another front is expected this afternoon into tonight, which will
bring gusty south winds and steep seas. Occasional gale force gusts
are possible. Winds will diminish tonight, but seas remain high and
steep into Wednesday.

More fronts will follow Wednesday through Friday, including possible
gales Thursday night into Friday. High pressure will build offshore
Saturday. This will bring a break in the stormy pattern over the
weekend. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 10 PM PST this evening for
     ORZ029>031.
     Flood Watch through Wednesday morning for ORZ021>024.
     High Surf Advisory until 10 AM PST this morning for ORZ021-022.
     Winter Storm Warning until 10 PM PST this evening for
     ORZ027-028.

CA...Flood Watch through Wednesday morning for CAZ080.

Pacific Coastal Waters...Small Craft Advisory until 10 AM PST
     Wednesday for PZZ350-356-370-376.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
736 AM PST TUE JAN 4 2022

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

0700 AM     HEAVY RAIN       BROOKINGS               42.06N 124.29W
01/04/2022  M0.75 INCH       CURRY              OR   TRAINED SPOTTER

            24 HOURS ENDING AT 7 AM PST.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
738 AM PST TUE JAN 4 2022

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

0700 AM     HEAVY SNOW       1 W CRESCENT            43.46N 121.71W
01/04/2022  M17.2 INCH       KLAMATH            OR   TRAINED SPOTTER

            24 HOUR TOTAL ENDING AT 7 AM PST. SNOW WATER
            EQUIVALENT OF 1.19 INCHES AND 28 INCHES OF
            SNOW DEPTH AT 7 AM PST.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
845 AM PST TUE JAN 4 2022

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

0700 AM     HEAVY RAIN       7 NNW ROGUE RIVER       42.53N 123.20W
01/04/2022  M2.13 INCH       JACKSON            OR   TRAINED SPOTTER

            24 HOURS ENDING AT 7 AM PST.

0730 AM     HEAVY RAIN       10 NNW GOLD HILL        42.57N 123.09W
01/04/2022  M1.10 INCH       JACKSON            OR   TRAINED SPOTTER

            24 HOURS ENDING AT 730 AM PST.

0800 AM     HEAVY RAIN       6 E GOLD BEACH          42.42N 124.31W
01/04/2022  M1.12 INCH       CURRY              OR   TRAINED SPOTTER

            24 HOURS ENDING AT 8 AM PST.

0800 AM     HEAVY RAIN       4 WSW KLAMATH FALLS     42.19N 121.84W
01/04/2022  M0.56 INCH       KLAMATH            OR   TRAINED SPOTTER

            24 HOUR TOTAL ENDING AT 8 AM PST. SPOTTER
            REPORTS LESS THAN 1 INCH OF SNOW LEFT ON
            GROUND.

&&