Wind Advisory 15, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
828 PM PST Fri Mar 8 2024

.DISCUSSION...Satellite imagery is showing some coastal in Curry
County. Some higher clouds are starting to form along the terrain
along and west of the Cascades, but the main feature is a front
offshore that will move inland tonight. This front will be the
first of several that may bring impactful snow to the mountains.
Each system looks a bit stronger than the last. For example, the
one arriving early Saturday being the weakest, the front arriving
Sunday morning bringing some decent snows to Siskiyou County, and
then the Monday evening through Tuesday evening storm to be more
impactful to the Cascades.

In general, the forecast looks reasonable; with several winter,
wind, and marine headlines. The nature of the longer duration
storm early next week may bring some prolonged rainfall to the
coast and coastal basins--thus providing a chance for additional
flooding along the Coquille River at Coquille, and a river flood
watch continues there as well. Please see the previous discussion
below for more details. -Schaaf

&&

.AVIATION...09/00Z TAFs....VFR conditions prevail across the region
and will do so through this evening. Offshore flow will be in place
through this afternoon, and with gusty southeast winds at the
southern end of the Rogue Valley, there could be some pockets of low
level wind shear around 20-30 kt for any southern approaches today.

An incoming front tonight should limit fog development, though
isolated pockets of LIFR are possible in the more sheltered valleys;
which includes the Rogue Valley. This incoming front will bring some
aviation impacts toward the 12z TAF period, with the main impact
being low level wind shear (LLWS) concerns and increasing terrain
obscurations. LLWS will be most prevalent along the coast and west
of the Cascades ahead of this front between 06z-14z Saturday. Expect
gusty south winds in the Shasta Valley and east of the Cascades
ahead of this front, with the main frontal passage expected between
12z-18z (west of Cascades) and 15z-21z (east of Cascades).
Otherwise, MVFR conditions from rain/snow showers are expected with
the snow level hovering around 4500 feet.
/BR-y/Miles

&&

.MARINE...Updated 800 PM Friday, March 08, 2024...South
winds and seas will increase this evening before conditions
deteriorate rapidly later tonight with the arrival of the first in a
series of three strong fronts.

The first front later this evening into early Saturday morning will
result in increasing south winds across the waters bringing a
combination of high, steep to very steep wind waves and increasing
west swell behind it. A Hazardous Seas Warning remains in effect for
this evening into Saturday evening. There's a 30-50% chance for gale
force gusts with this front (on the higher end of that range in the
northern outer waters). Right now it's looking more likely that gale
force winds will be occasional and isolated.

Gales are certain (70-100%) with the next, stronger front Saturday
night into early Sunday. There is also a moderate 20-50% chance that
storm force winds surface at the waters north of Cape Blanco, but
given that this is only for a six hour period Saturday night, we
felt confident enough to upgrade the gale watch to a warning, with
an emphasis that the wind-driven seas will be very hazardous
Saturday night. Seas are forecast to become very high (17-23 feet)
with highest seas in the northern waters from late Saturday night
into Monday morning, with a peak early Sunday morning. Winds also
peak early Sunday morning.

Behind this second front, a long period swell of 14 to 17 feet at 14
or 15 seconds is expected Sunday evening into Monday morning. This
could lead to offshore equipment being damaged and increasingly
hazardous bar crossings.

The third front, Monday night, also has a high chance to bring gales
across all the waters. Winds, and to a lesser extent, seas, are
likely to diminish Tuesday into Wednesday, but a weaker disturbance
is likely to cause high and steep seas to persist.

-Miles/CSP

&&

.PREV DISCUSSION... /Issued 256 PM PST Fri Mar 8 2024/

SHORT TERM...Through Monday morning (3/11)...Calm conditions under
an upper ridge will continue across northern California and southern
Oregon this evening. Overnight lows will be 5 to 10 degrees warmer in
most places as moisture moves into the area ahead of an approaching
warm front. This will help keep the Oregon coast and west side
valleys comfortably above 32 degrees tonight. Elevated west side
terrain, the Cascades, and areas east of the Cascades will remain
near or below freezing temperatures.

Saturday morning's warm front will be the first of three systems
arriving over the weekend and into next week. Widespread
precipitation is expected, with snow levels of 3500 to 4500 feet
during the main precipitation band keeping snowfall to higher
elevations. Rainfall amounts will be highest along the Oregon coast
with southern coastal ranges getting about an inch, while the Oregon
coast will get between a quarter and a half of an inch. Other lower
elevation areas will see lower totals. While widespread impactful
snowfall is not expected, parts of the Siskiyou Mountains and over
the Cascades have a 50-80% chances of seeing 4 or more inches of
snow on Saturday. A Winter Weather Advisory is in place for
elevations above 4500 feet in western Siskiyou County and the Mount
Shasta area. An additional Winter Weather Advisory is in place for
areas around Crater Lake. These products will cover Saturday from 4
AM to 4 PM.

Periods of gusty southerly winds are also expected with this first
front, especially over elevated terrain and areas east of the
Cascades. The Shasta Valley also tends to see strong winds when
southerly flow gets funneled into the valley. A Wind Advisory is in
place for the Shasta Valley for Friday at 11 PM through Saturday at
10 AM. An additional Wind Advisory is in place for areas of southern
Lake County as well as over the Warner Mountains from Saturday at 7
AM through 7 PM. Gusts of 40 to 50 mph look possible in both areas,
with even stronger winds over elevated terrain east of the Cascades.

A brief lull early Sunday morning will precede a second front
approaching the area during the day. This system will have very
similar but heavier effects to Saturday's front, with 1.5 to 2.5
inches of rainfall forecast along the Oregon coast and moderate to
heavy snowfall at higher elevations. While snow levels will drop
slightly to 3000 to 4000 feet, impactful snowfall will remain
limited to parts of Siskiyou County and possibly over the Cascades.
This front also looks to bring another round of elevated and gusty
southerly winds, especially to the Shasta Valley and high elevation
areas. A High Wind Watch is already in place for areas along the
Oregon Coast from Saturday at 10 PM through Sunday at 7 AM that
marks when the leading edge of the front is expected to arrive.
Additional wind and winter products will be issued tomorrow to cover
the specific impacts from Sunday morning's system. The main band of
precipitation should be past the area by Sunday evening, with post-
frontal showers continuing into Monday morning. -TAD

LONG TERM...Monday morning (3/11) through Friday night
(3/15)...The extended forecast begins with active weather as the
last in the series of fronts passes through the region late Monday
into Tuesday. A transition to high pressure with dry conditions
and unseasonably warm temperatures is anticipated around mid-week
and expected to continue through at least the following weekend.

The third and last front in the series of systems from the short
term will pass through the area late Monday into Tuesday. This front
looks weaker in terms of wind compared to the Sunday system, with
700 mb winds maxing out around 35 to 45 kts. So we don't currently
expect this front to bring any warning level winds to the region,
but borderline advisory criteria is possible, especially along the
higher terrain east of the Cascades. Additionally, we do expect
another round of moderate snowfall with this front with snow levels
hovering around 4000 ft. With the westerly orientation of mid-level
jet (vs southwesterly with the previous fronts), we do expect the
Cascades to receive the bulk of the snow with this system (around 10-
16 inches) and additional winter weather headlines will likely be
needed for Monday night into Tuesday. The main front looks to be
through the region by Tuesday morning, then as the upper trough
pushes through, expect showers to continue through the afternoon and
evening. Showers will linger the longest overnight into Wednesday
morning along the coast, north of the Umpqua Divide and along the
Cascades.

Wednesday will be a transition day as an upper level ridge builds
over the eastern Pacific, bringing an end to showers and closing the
storm door for a while. High pressure amplifies Thursday and into
the weekend, gradually moving over the Pacific Northwest over the
weekend. Temperatures will trend warmer on Thursday with afternoon
highs in the low 60s (low 50s) west (east) of the Cascades. A
thermal trough also develops on Thursday, and this will induce east
to northeasterly flow across the region, aiding in the unseasonably
warm temperatures west of the Cascades through the weekend. Upper
60s to low 70s (maybe even mid 70s?) are anticipated Friday into the
weekend for locations west of the Cascades. Current records for mid-
March are roughly in the upper 70s to low 80s, so this doesn't look
like record challenging temperatures at this time, though afternoon
temperatures will be more typical of May than mid-March. /BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 10 AM PST Saturday for ORZ030-031.

     High Wind Watch from Saturday evening through Sunday morning for
     ORZ021-022.

     Winter Weather Advisory from 4 AM to 4 PM PST Saturday for
     ORZ027.

CA...Winter Weather Advisory from 4 AM to 4 PM PST Saturday for
     CAZ080-082-083.

     Wind Advisory until 10 AM PST Saturday for CAZ081-085.

PACIFIC COASTAL WATERS...Hazardous Seas Warning until 7 PM PST
     Saturday for PZZ350-356-370-376.

     Gale Warning from 7 PM Saturday to 5 PM PST Sunday for PZZ350-
     356-370-376.

&&