High Wind in California, December 26 to 27, 2022

Area Forecast Discussion...Updated
National Weather Service Medford OR
518 PM PST Mon Dec 26 2022

Updated aviation section

.SHORT TERM...This afternoon into Thursday morning...The remnants
of the first front linger across the area this afternoon with light
to moderate showers indicated on radar. Observations show generally
between a quarter to half inch of rain has fallen in the last 6
hours or so, with closer to an inch being reported along the coast
at the typical places. Gusty winds are being observed across the
terrain where gusts of 25 to 35 mph are common. There are some areas
that are already flirting with advisory/warning level
criteria...Weed airport is reporting gusts 35 to 40 mph, Squaw Peak
gusting to around 50 mph and Flynn Prairie is gusting to 45 to 50
mph. This is just one in a series of fronts anticipated this week
and into the weekend.

The strongest front in the series is knocking on the door, and winds
will only get stronger this evening and overnight. Low pressure is
deepening out near 140W and a ~970 mb surface low is expected to
move inland into northern Washington Tuesday afternoon. This will
bring a strong front inland with strong winds expected area wide.
All but the most sheltered valleys are expected to see at least
advisory if not warning level winds starting this evening and
continuing through much of Tuesday and High wind warnings and wind
advisories are in place for much of the forecast area. There were
some adjustments made to timing and the inclusion of more locations
in the advisory area and details can be found at NPWMFR. Model
surface pressure gradients peak at -13 mb for Medford to Redding and
-12 mb for North Bend to Arcata. Gradients of this magnitude
correspond with strong winds across the region, especially for the
typically sheltered valleys like the Rogue and Illinois Valleys
where winds in the 30 to 40 mph range are anticipated. Along the
coast, in the Shasta Valley and across the higher terrain, where
High Wind Warnings are in effect, gusts of 60 to 80 mph are likely.
It's going to be quite windy tonight into tomorrow, so take
precautions now to secure your property and prepare for possible
power outages.

Periods of moderate to heavy precipitation will be the other main
impact with this front. Snow levels will be high with the bulk of
the precipitation, up around 7000-9000 ft, so we aren't anticipating
winter impacts at this time. The main consideration with this setup,
however, is given the high snow levels, rain on lower-mid elevation
snowpack will lead to increased runoff and we'll be seeing some
rather significant rises on area rivers. Nothing is forecast to go
into flood stage at this time, but the Coquille does approach action
stage Tuesday afternoon and evening. Another area we'll be
monitoring is the Chetco River where the amount of precipitation in
the forecast will lead to a significant flow rate with the potential
for any debris to washed down the river. Overall, the amount of rain
we're expecting will be largely beneficial, but we'll be monitoring
the flood potential during this event. Snow levels will lower down
to 4000 ft by late Tuesday morning, and this could present some
wintry impacts around this time. Overall precipitation should be
dwindling down by then, but there could be a period where
precipitation lines up with the lowering snow levels and brings some
travel impacts to the Cascades. We'll continue to monitor the trends
and issue any necessary winter headlines if the need arises.

Tuesday night into Wednesday, swift westerly flow will maintain
precipitation activity along west facing slopes, but overall, the
weather will be quieting down. Precipitation will wind down
Wednesday afternoon and evening as a shortwave ridge passes through
the region. This break in the weather will be shortlived, however,
as the next front in the series approaches the coast early Thursday
morning. This front won't be nearly as strong as the one anticipated
tonight into Tuesday, but will bring another round of beneficial.
/BR-y

.LONG TERM...Extended discussion...Thu 29 Dec 2022 through Mon 02
Jan 2023.

A fast progressive pattern will persist through the extended period
with low amplitude troughs and ridges parading through the Pacific
Northwest. This will support a series of warm and cold fronts moving
through the area. Given the low amplitude of the upper level
systems, none of the fronts will be particularly strong.

A warm front will move north through the area Thursday, followed by
a cold front Friday. Another weak warm front/cold front combo will
move onshore to the south Saturday morning.

There will be a relative break in the action Saturday night into
Sunday night as a flat ridge moves through the area. Precipitation
will diminish, but not end, and there will still be plenty of cloud
cover as moisture streams over the ridge.

The next cold front will move onshore Monday. This looks to be the
strongest of the bunch, but it still won't amount to much. Although
there will be significant snow at higher elevations throughout the
extended period, it appears that Warnings or Advisories will not be
necessary for any given shorter period, except that there may be
enough snow for an Advisory next Monday in the Mount Shasta area.

&&

.AVIATION...27/00Z TAFs...Significant storm moving onshore this
evening with moderate to heavy rain and strong winds. Winds will
cause low level wind shear this evening through Tuesday morning at
all sites. Cloud cover will remain thick and widespread with
generally MVFR conditions expected along and west of the Cascades,
with cloudy VFR weather east of the Cascades. Overnight
precipitation will increase and become heavy at times in some areas
with periods of IFR conditions possible. After midnight into
daybreak Tuesday, frontal passage occurs and winds will shift
southwesterly with wind shear continuing in some areas, especially
east of the Cascades, through Late morning. Should see also a
lowering of cloud bases and more MVFR with areas of IFR clouds from
late morning Tuesday through afternoon. Stavish

&&

.MARINE...Updated 230 PM PST Monday 26 December 2022...Tonight
though Tuesday, a very strong low pressure center will move from the
Oregon offshore waters toward Vancouver Island. Dangerous marine
conditions will develop. South winds will increase to storm force
later this afternoon and remain at that level through tonight. Very
steep seas will accompany the winds for severe marine conditions
with wind gusts to 50 to 60 kts tonight and seas peaking at 25 to 30
feet Tuesday as a very heavy west swell arrives. These wave heights
will also result in dangerous surf conditions along the Oregon
beaches continuing into Wednesday morning. The maximum high surf is
likely to occur Tuesday afternoon. After a break on Wednesday,
another system arrives with unsettled weather Wednesday night
through Thursday. Winds were lowered in this forecast for Friday and
Friday night which is looking less windy. Stavish

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 PM this evening to 4 PM PST Tuesday for
     ORZ023>025.

     Wind Advisory from 10 PM this evening to 10 PM PST Tuesday for
     ORZ029>031.

     High Wind Warning from 10 PM this evening to 10 PM PST Tuesday
     for ORZ030-031.

     High Surf Warning until 7 PM PST Tuesday for ORZ021-022.

     High Wind Warning until 10 AM PST Tuesday for ORZ021-022.

     Flood Watch from 10 PM PST this evening through Tuesday evening
     for ORZ022.

     Wind Advisory from 7 PM this evening to 4 PM PST Tuesday for
     ORZ026.

     High Wind Warning from 7 PM this evening to 10 PM PST Tuesday
     for ORZ027-028.

CA...Wind Advisory from 7 PM this evening to 4 PM PST Tuesday for
     CAZ080-082.

     High Wind Warning until 4 PM PST Tuesday for CAZ081-083.

     Wind Advisory from 10 PM this evening to 10 PM PST Tuesday for
     CAZ084-085.

     High Wind Warning from 10 PM this evening to 10 PM PST Tuesday
     for CAZ085.

PACIFIC COASTAL WATERS...High Surf Warning until 7 PM PST Tuesday for
     PZZ350-356.

     High Wind Warning until 10 AM PST Tuesday for PZZ356.

     Storm Warning until 1 AM PST Tuesday for PZZ350-356-370-376.

     Gale Warning from 1 AM to 10 AM PST Tuesday for PZZ356-376.

     Gale Warning from 1 AM to 4 PM PST Tuesday for PZZ350-370.

&&

MNF/JRS/MTS