High Wind in Oregon, May 6 to 7, 2022

Area Forecast Discussion
National Weather Service Medford OR
445 AM PDT Fri May 6 2022

.DISCUSSION...A very active pattern will continue today. We're
currently in a relative break between yesterday's front and
another potent disturbance located near 45N and about 135W. The
low pressure system is supported by a 150+ kt upper jet max. This
will send a cold front quickly toward the coast late this morning,
then onshore this afternoon, reaching the Cascades by around 00z.
Mid-level (850-700mb) winds are already significant and will
increase (45-55kt) as this system approaches mid-late morning.
We are expecting some of these winds to surface in the valleys
west of the Cascades as the front moves in. And, with some low-
topped convective showers developing this afternoon, much of the
area will be quite gusty with peak gusts in the 40-50 mph range,
perhaps 55 mph over the East Side. For this reason, we have added
a wind advisory for the west side, including most valleys from
the Shasta/Scott Valleys in NorCal to the Rogue/Illinois/Umpqua
Valleys (NPWMFR). We also added a wind advisory for the Klamath
Basin in addition to the one that was already out for the far east
side and Modoc County. Showers that develop will be most
persistent in the coast ranges of Curry County, but also in the
Cascades. There is enough instability (MUCAPE about 100-300J/KG)
this afternoon that there could be a few lightning flashes across
northern Douglas, northeast Jackson and into Klamath, Lake and
northern Modoc counties. Any thunderstorms will have the ability
to produce strong, gusty winds as well. Snow levels are very high
currently, but once the front moves through this evening, they'll
drop fast. This will bring some snow to the mountains, but
especially above 5000 feet in the Cascades. Since the snow will be
coming mostly at night and into the morning Saturday, we have
added a winter weather advisory for the higher passes in the
Cascades (north of Highway 140) for 4-8 inches of snow. There
could be some slippery snow-covered roads during this time
periods, so if traveling through the Cascades, be prepared for
hazardous winter conditions. Much like earlier this week, however,
since it's early May, snow that falls during the midday and
afternoon Saturday will mostly melt on roads.

Moist, onshore flow will continue right through the weekend with
yet another disturbance arriving in NW flow aloft on Sunday. This
system will cause the long wave trough to settle in over the PacNW
into early next week. It will already be cold in advance of this
system and snow levels will be around 2500 feet -- that's pretty
low for early May! This is the kind of pattern that will lead to
numerous showers area wide and additional snowfall in the
mountains. Given the state of our drought and the deficits built
up during the ridiculously dry period from January to March,
moisture like this in May certainly is welcome. As mentioned by
previous shifts, this is the time of year climatologically that we
see a marked increase in the amount of lightning and this system
will present at least a slight chance of thunderstorms beginning
at the coast in the morning, then inland during the afternoon. Any
stronger cells that manage to get going could contain gusty
winds, graupel and perhaps small hail. This air mass is forecast
to be one of the coldest air masses to settle in over the area at
this time of the year and temperatures on Sunday will struggle to
get out of the 40s. Some of the climate sites are expected to
flirt with daily record lowest maximums, including here in Medford
(our lowest maximum for the date is 50 set in 1922). We are
forecasting 51F. The trough will be overhead on Monday and then
sink southward into California on Tuesday. This will keep the
pattern showery and unsettled. Given how cold this air mass will
be, we could have some frost/freezing conditions at some point
next week, but cloud cover and amount of precipitation will
continue to be the factors that might mitigate this risk a bit.
-Spilde

&&

.AVIATION...06/12Z TAFs...A wide mix of ceilings and visibilities
cover the forecast area this morning.  There are pockets of fog in
some of the valleys west of the Cascades and along the coast.
Visibilities have been down to 0.25 miles in some spots and down to
2.5 miles in the heavier showers.  In addition,  ceilings vary from
VFR down to IFR over Grants Pass and Medford this morning.  The warm
and relatively stable airmass will keep ceilings around MVFR to IFR
throughout the day.

Other than the ceilings and visibility issues, low level wind shear
will remain a feature in the forecast.  Upper level winds remain
rather strong as surface winds remain weak in the valley this
morning.  Once the winds begin to mix down,  wind shear won't be as
big of a factor.  Some of these strong winds will be observed along
the coast and make their way inland later today.

We also have an airport weather warning out for strong wind gusts in
Medford and Klamath Falls today.

Lastly,  there is a 15 to 20% chance of thunderstorms later this
afternoon and evening.  The best chances are east of the Cascades in
Lake and Klamath County.  We're not expecting severe storms, yet
some strong gusty winds could appear under storms or heavy showers.

-Smith

&&

.MARINE...Updated 300 AM PDT Friday 6 May 2022...Seas will remain
elevated through this morning as the next front approaches. Winds
will begin to increase out of the south and peak up to 40 knots.
There is a modest potential for gale force winds around the Coos
Bay Reedsport area as this cold front pushes on shore. However,
the period seemed rather brief and confidence was only about 50
percent, so we just stayed with the small craft advisory.

After the front passes,  seas will remain steep and elevated and
winds will shift out of the northwest and another weaker low moves
into the waters around Sunday. Overall, seas will remain hazardous
to smaller crafts as steep seas remain around 10 feet through
Monday. Between Monday and Thursday, we have moderate confidence
that seas will lower down to 6 feet as high pressure builds in.

-Smith

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 2 AM PDT Saturday for ORZ030-031.
     Wind Advisory from 11 AM this morning to 8 PM PDT this evening
     for ORZ023>026.
     Winter Weather Advisory from 9 PM this evening to 11 AM PDT
     Saturday above 5000 feet in the for ORZ027-028.
     Wind Advisory from 11 AM this morning to 11 PM PDT this evening
     for ORZ029.

CA...Wind Advisory until 2 AM PDT Saturday for CAZ085.
     Wind Advisory from 11 AM this morning to 8 PM PDT this evening
     for CAZ080-081.
     Wind Advisory from 11 AM this morning to 11 PM PDT this evening
     for CAZ084.

Pacific Coastal Waters...
     Small Craft Advisory until 5 PM PDT Monday for
     PZZ350-356-370-376.

MAS/CZS/MAP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
757 AM PDT FRI MAY 6 2022

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

0755 AM     HEAVY RAIN       BROOKINGS               42.06N 124.29W
05/06/2022  M1.31 INCH       CURRY              OR   TRAINED SPOTTER

            24 HR TOTAL AS OF 7 AM PDT. NO RAIN AT TIME
            OF REPORT. STATION ELEVATION: 293 FT.

&&

MCB