Winter Storm in California, March 30 to 31, 2025

Area Forecast Discussion
National Weather Service Medford OR
1043 PM PDT Sun Mar 30 2025

Updated AVIATION discussion

.DISCUSSION.../Issued 220 PM PDT Sun Mar 30 2025/
A compact surface low is evident on satellite
imagery this afternoon, located directly west of Brookings as of
the time of this writing. This low is tracking just as the high-
resolution models depicted earlier today, and is on track to pass
just offshore of southern Oregon and move onshore around Cape
Blanco or perhaps a bit to the north. This low is responsible for
significant wind concerns today, and we have been watching
coastal and marine wind gusts spread north from Cape Mendocino
throughout the day so far. Winds at the marine buoys and points
along the coast have seen dramatic increases in very short
periods of time. Meanwhile, inland winds have responded to a
strong MSLP gradient, and enhanced with momentum transfer due to
showers and mountain wave effects, mid level winds have translated
to the surface as gusts. It has been a challenge to nail down the
details of where winds will occur, as changes in the low track by
just a few miles can and have been making significant effects on
various areas. For instance, the low tracking just slightly closer
to the coast has enhanced the inland winds, while simultaneously
reducing the expected winds along the coast north of Cape Blanco.
The strongest winds should weaken once the low passes, while
overall, winds will taper off through the evening. Numerous wind
headlines remain in effect for much of the area, and details on
these can be found at PDXNPWMFR. A High Wind Warning for coastal
areas and Wind Advisories for inland areas are in place into this
evening to highlight possible hazardous conditions. Additionally,
this front will bring slight thunderstorm chances (10-15%) along
the Oregon coast this evening and tonight with lesser chances for
inland areas west of the Cascades. And of course, any
thunderstorms are likely to produce additional periods of locally
gusty winds.

Impactful conditions turn from wind to winter on Monday and
Tuesday. With the front off to the north, a low pressure system
will draw closer to then move over the area. A cold air mass
moving with this system will bring cooler temperatures and lower
snow levels across the area. Southwesterly flow aloft will
continue to bring precipitation across the area. Snow levels are
forecast to drop to 2500-3500 feet through Monday and Tuesday,
with hazardous winter weather possible in certain areas. A Winter
Storm Watch has been upgraded to a Winter Storm Warning for areas
in Siskiyou County above 4500 feet, and will be in place from
early Monday morning through Tuesday evening. Peaks and ridgelines
in Siskiyou County could get 1 to 3 feet of snow through this
timeframe. Sawyers Bar Road west of Etna could see over 2 feet of
snow in places. A Winter Weather Advisory covers the Cascades and
Mount Ashland in the same timeframe, with 12 to 24 inches of
snowfall possible in these areas. A shorter Winter Weather
Advisory is in place for areas along I-5 south of Weed and Highway
89 from Tuesday morning through Tuesday evening. Snow levels are
forecast to reach their lowest in this period, possibly bringing
impactful snowfall to these highways and cities in this area.
Additionally, snow amounts to the east of the Cascades will just
reach advisory criteria, although spread out over Monday and
Tuesday. Another Winter Weather Advisory has been issued there,
with mention of more gusty winds that could result from the
expected showers.

For other areas, generally light to moderate precipitation
continues on Monday and Tuesday. Increased thunderstorm chances
(15-25%) are forecast for areas west of the west of the Cascades
on Monday afternoon. Curry and Josephine counties may see a period
of increased precipitation on Tuesday morning. Gusty southwest
winds are forecast to continue over elevated terrain, but that
change of direction will prevent further funneling into the Shasta
and Rogue valleys.

Active but less impactful weather continues on Wednesday, as an
upper trough moves over the area. Northwest flow along the back
edge of the trough could bring continuing showers and cool
temperatures on Wednesday and Thursday. As the upper pattern
continues to move eastward, a high pressure system could settle
over the area while low pressure remains over the southwest United
States. This rex block pattern (high pressure poleward/north of a
low pressure system) could bring a period of warmer temperatures
and drier conditions. Meteogram guidance supports this, with both
ECMWF and GFS outcomes showing an absence of precipitation for the
first weekend of April and only weak signals for the week beyond.
-BPN/TAD

&&

.AVIATION...31/06Z TAFs...Winds have calmed down in the valleys
through the evening and that is anticipated to continue tonight.
There will be plenty of rain showers through tonight as cold moist
air surges into the forecast area. Showers, and perhaps a stray
thunderstorm, will remain a persistent feature into the overnight
hours west of the Cascades. VFR ceilings remain most likely through
the TAF period with pockets of MVFR ceilings developing under
pockets of heavier showers or perhaps weak thunderstorms on Monday.

Snow is anticipated east of the Cascades Monday evening as
temperatures cool off into the evening hours. Accumulation should be
no more than 2 inches within KLMT.

-Smith

&&

.MARINE...Updated 1000 PM Sunday, March 30, 2025... Seas still
remain high and steep as of this Sunday evening and they will likely
push higher into Monday. Seas will be hazardous to smaller crafts
and perhaps some larger crafts as wave heights begin to push higher
towards 16 feet at 11 or 10 seconds around Monday evening.

Expect showers to continue, along with a slight chance of
thunderstorms. A tapering to steep seas follows late Tuesday morning
through Tuesday evening. Gradual improvement is expected to continue
Tuesday night into the end of the week with light to moderate
northerly winds. -Spilde/Smith

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 11 PM Monday to 5 PM PDT Tuesday
     for ORZ027>031.

CA...Winter Storm Warning until 5 PM PDT Tuesday for CAZ080-082-083.

     Winter Weather Advisory from 11 PM Monday to 5 PM PDT Tuesday
     for CAZ082-085.

PACIFIC COASTAL WATERS...Hazardous Seas Warning until 8 AM PDT
     Tuesday for PZZ350-356-370-376.

&&