Winter Storm Warning 12, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
1004 AM PST Sat Mar 9 2024

.Updated AVIATION Discussion...

&&

.AVIATION...09/18Z TAFs....The first in a series of fronts is
pushing east of the Cascades this morning, with showers following
behind west of the Cascades. Overall conditions are generally VFR
with widespread terrain obscurations. Conditions are temporarily
lowering to MVFR/IFR with the front and heavier precipitation
associated with post-frontal showers, but the prevailing conditions
are expected to be VFR through the evening. Additionally, expect
gusty southwest winds to persist across the region through this
afternoon.

The next front approaches the coast tonight and passes through the
region through Sunday morning. This will bring the return of low
level wind shear concerns (LLWS) by this evening for coastal
locations, then spreading inland in the Umpqua Basin around 06z and
the remainder of the area towards the end of the current TAF period.
Expect conditions to lower to MVFR/IFR with the frontal passage
starting around 12z at the coast, and pushing inland west of the
Cascades by 18z. Gusty winds are expected area wide tonight into
Sunday afternoon, strongest east of the Cascades, across the higher
terrain and in the Shasta/Scott Valleys. /BR-y

&&

.PREV DISCUSSION... /Issued 840 AM PST Sat Mar 9 2024/

DISCUSSION...The forecast does not need any updates this morning.
A band of precipitation ahead of a warm front is moving over the
Cascades and post frontal showers are building along the Oregon
coast. Elevated, gusty winds are expected through this evening for
areas east of the Cascades. Quiet conditions tonight will precede
a stronger front arriving Sunday morning, with similar effects:
Abundant rain along the Oregon coast and strong winds past the
Cascades. -TAD

MARINE...Updated 830 AM Saturday, March 09, 2024...Seas have
increased this morning ahead of the incoming cold front. We're
anticipating gale force winds in the waters later this evening with
the gusts up to 50 knots in the outer waters. Another cold front
will push through the waters later tonight. A west swell will move
into the waters later on Sunday afternoon with a swell group around
17 feet at 14 to 15 seconds. The last front will push through the
waters around Monday evening with another chance of gales and high
and steep seas. Overall, a very active weather pattern is expected
over the next 36 hours, with seas gradually subsiding later Tuesday
into the later half of the week as high pressure builds. -Smith

PREV DISCUSSION... /Issued 354 AM PST Sat Mar 9 2024/

DISCUSSION...Satellite image shows a slightly negatively tilted
upper trough approaching the coast. At the same time a strong front
is also closing in at the coast and south winds are already
increasing there and the Shasta Valley. Radar returns are showing
precipitation filling in along the coast. The front will reach the
coast in the next few hours, then moving onshore during the day.

Moderate to occasionally strong winds are likely east of the
Cascades late this morning through this afternoon. Advisory level
winds are also likely in the Shasta Valley near Weed.

Precipitation amounts are not expected to be excessive, with the
highest amounts at the south coast and coastal mountains in Curry
and Josephine County, and Western Siskiyou County. Precipitation
amounts along the Cascades have trended lower which makes sense
given most of the energy will be south of there. Therefore the
Winter Weather Advisory for Crater Lake and Diamond Lake areas has
been canceled.

Post frontal showers will follow this afternoon, then we'll catch a
brief break before the next front arrives late Saturday night.

This front will bring stronger winds to the coast, Shasta Valley,
east of the Cascades, and possibly the south end of the Rogue
Valley. Although confidence on moderate to strong winds in the south
end of the Rogue Valley is low. An additional Wind Advisory has been
issued for these areas (except the Rogue Valley) for this stronger
front.

The ingredients are still there (tight pressure gradient and
moderate to strong 925 mb winds close to 65 kts) for high winds to
night for exposed areas along the coast, including exposed areas on
highway 101, and the High Wind Watch has been upgraded to a High
Wind Warning. Please see NPWMFR for all the details on the
Advisories and Warning.

The bulk of the precipitation Sunday will be in similar locations as
the previous front, with the bullseye along the south coast, and
south coastal mountains, western Siskiyou County and the mount
Shasta area. Precipitation amounts will be higher overall on Sunday,
with lesser amounts Sunday evening and night as we get into a post
frontal shower environment.

We'll catch a "relative break" in the action Sunday night into
Monday afternoon, meaning, we'll still have showers, but most will
be light. The third front will move towards the coast late Monday
afternoon, bringing increasing winds at the coast and moderate to
occasionally heavy precipitation. The front will move inland Monday
night with post frontal showers once again as an upper trough moves
over the area Monday night through  Tuesday.

The upper trough will move east Tuesday night with showers
diminishing in coverage. Other than a few leftover showers along the
northern Cascades Wednesday morning. Wednesday will be a
transition day were we go from an cool wet active pattern towards a
quiet, dry and warmer pattern and will set up next Thursday and is
likely to last through next weekend, and possibly into the
early part of the following week (March 18th- 21st) -Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 5 AM to 5 PM PST Sunday for ORZ029>031.

     High Wind Warning from 10 PM this evening to 8 AM PST Sunday for
     ORZ021-022.

CA...Winter Weather Advisory until 4 PM PST this afternoon for CAZ080-
     082-083.

     Wind Advisory from 5 AM to 5 PM PST Sunday for CAZ081-084-085.

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

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

&&

TAD/MAP/MNF