Small Craft Advisory 9, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
946 PM PST Wed Jan 22 2025

...Updated AVIATION discussion for 06Z discussion...

.AVIATION...23/06Z TAFS...VFR levels continue across northern
California and southern Oregon tonight. Chances of fog remain in
guidance for the Umpqua Valley and chances of patchy fog remain for
the Rogue Valley. Satellite imagery indicates no development to
start the TAF period, so develpment for both areas remains in the
forecast but at slight to moderate confidence. Any development
should clear out by early Thursday morning.

Other areas will remain at VFR levels through the TAF period. -TAD

&&

.MARINE...Updated 945 PM Wednesday, January 22, 2025...
Gusty northery winds continue to build steep seas, generally beyond
5 nm from shore but also near shore of Cape Blanco and Gold Beach.
North of Coos Bay, steep seas are expected beyond 25 NM.

There's good agreement for a further increase with moderate to
strong north winds later in the week through the weekend due to a
strong thermal trough developing along the coast. The probability of
gale force winds being met at some point in time is high and around
55 percent south of Port Orford. Winds should peak in strength
Friday afternoon/night.

-Smith/Hermansen

&&

.PREV DISCUSSION... /Issued 229 PM PST Wed Jan 22 2025/

DISCUSSION...High pressure aloft is positioned just off the
Oregon and northern California coast late this afternoon.
Meanwhile, a strong surface high is building in east of the
Cascades. This is resulting in strong subsidence over our forecast
area and skies are largely clear, aside from a few high cirrus. The
last couple of days have really dried things out around here and fog
has not been as prevalent as it was last week. With the high
building in tonight, there could be a little more west side valley
fog than the previous couple of nights, but don't foresee the
widespread fog that plagued us last week. Expect the usual areas
like the Umpqua Basin near Roseburg and the Rogue Valley near Grants
Pass to have several hours of fog/freezing fog late tonight/Thursday
morning. Patchy fog/freezing fog could also develop here in Medford
and portions of the Illinois Valley. It'll be another cold one with
low temperatures tonight ranging from 20-30F for the interior west
side valleys and 10-20F over the East Side. Some single digit
readings are expected in the Klamath Marsh area between Chiloquin
and Chemult. Coastal areas around Coos Bay will once again drop to
near freezing, but should be a few degrees higher than last night,
so will forgo a freeze warning since the duration of temps that low
won't be as long.

The high will settle southward along the California coast on
Thursday maintaining dry weather over the area. Models are showing a
bit more cirrus, especially over northern and western areas as the
ridge flattens, but there should still be at least some filtered
sunshine for most. High temperatures will be very similar to today.

The next upper trough will press southward from western Canada
Thursday night, then move through the PacNW Friday. Since this
system will be moving from north to south with an over land
trajectory, we aren't expecting much, if any, precipitation. There
could be a few snow flurries over the mountains, but that's about
it. What it will do, however, is end the pattern of air stagnation
(at least briefly). Our air stagnation advisory has an ending time
of noon PST Friday, which is fine. A strong pressure gradient will
develop across the area and this will bring strong N-NE winds late
Fri/Fri night that will become NE-E Sat. Mid-level (700 mb) winds
are projected to be in the 35-45kt range with even up to ~55kt over
the mountains Fri night/Sat morning. Expect widespread breezy to
windy conditions over the upper slopes/ridges and also some of the
valleys that happen to align with the wind (Illinois valley). Local
fire weather guidance is showing NE winds in the 25-35 mph range at
many of the RAWS sites with gusts of 45-55 mph over the higher
terrain. It isn't often that we need wind advisories for NE offshore
flow, but this may be one where it's necessary in some places.
Models are showing a strong MFR- RDD pressure gradient (in reverse
compared to what we usually see with southerly storms). In this
case, we'll see stronger northerly winds through the Shasta Valley
that may also bring very breezy conditions to Mount Shasta City on
Saturday. We'll continue to evaluate wind advisory potential. In
addition to the winds, there will also be a much colder air mass
moving in from the north, so this will result in very cold
conditions over the East Side. We'll be considering a cold weather
advisory for the combination of the cold/wind expected Friday night
through Saturday night. Right now, apparent temperatures near or
even below zero are possible during this period. One other thing we
should note is that while there is a substantial snow pack near and
above 5000 feet in the mountains/Cascades, those that have
prescription burn interests should be aware of the wind potential
coupled with potentially lower RHs as another dry air mass moves in
over the weekend. This could lead to some potential for pile burns
to escape. Please use caution if planning to burn this weekend.

After the upper trough pushes southward into the Great Basin, it
will close off and settle into southern California Sunday into
Monday. This will allow the offshore upper high to flop over into
the PacNW again resulting in a transition back to (you guessed it)
more stagnant conditions. This means more dry weather with cold
nights, mainly sunny days with slightly milder afternoons. Winds
should relax to more typical levels. Fog may not be as much of an
issue this go around because of the drying air mass and the strong
offshore event This pattern looks to last through at least mid next
week. Guidance is trying to show the ridge breaking down toward the
end of next week and some fronts at least trying to reach the coast
at the end of the month/beginning of February.
-Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Air Stagnation Advisory until noon PST Friday for ORZ021-023>026-
     029>031.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 10 AM PST Friday
     for PZZ350-356-370-376.

     Gale Watch from Friday morning through Saturday morning for
     PZZ356-376.

     Hazardous Seas Warning from 4 PM Thursday to 10 AM PST Friday
     for PZZ370-376.

&&