171
FXUS66 KMFR 151138
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
338 AM PST Wed Jan 15 2025

.DISCUSSION...The dry weather pattern continues through the
weekend and into early next week as an upper level ridge remains
in place over the region. The ridge will weaken slightly Thursday
night as a dry front moves through and a shortwave trough moves
inland to the north and northeast. Then the upper level ridge
strengths, centered offshore, Friday through the weekend, while a
trough develops to the east of the area. Valley fog/freezing fog
and air stagnation are the main concerns with this pattern.
Otherwise, expect mild weather with temperatures near or above
normal.

Strong inversions, stable conditions and light winds along with
boundary layer moisture will result in continued areas of
overnight/morning valley fog and freezing fog at least through
Thursday morning. These conditions will be most widespread in
southwest Oregon valleys west of the Cascades, with areas of fog
and freezing fog possible east of the Cascades and in valleys in
Siskiyou County. Observations indicated that freezing fog is
occuring in the valleys in Joesphine and Jackson counties
overnight and fog is occuring across valleys in eastern Curry,
Coos and Douglas counties. Visibilities have dropped down to less
than a quarter of mile at times. Additionally, with freezing fog,
spots of ice may develop on area roadways. A dense fog advisory
(Douglas County) and a freezing fog advisory (Jackson, Josephine
and eastern Curry county) are in effect through late Wednesday
morning for these conditions. Please see the NPWMFR for details. A
weak front that moves through Thursday night may weaken the
inversion and lift the fog into stratus decks, but fog may return
to western valleys Friday night into Saturday as strong inversions
return.

With strong high pressure over the region today and Thursday,
models support continued strong inversions, resulting in limited
vertical mixing and transport winds. This brings continued
concerns for air stagnation and the potential for increased
pollutants in inland valleys. An air stagnation advisory (NPWMFR)
remains in effect through Thursday morning. Based on the current
models, mixing may improve slightly on Friday after a weak front
moves through. However, any improvement will likely be limited and
brief. Models continue to show high pressure rebuilding as the
upper ridge, centered offshore, strengthens late Friday into the
weekend.

A dry pattern with high pressure in place is likely to continue
into early to mid next week. Looking further out, there are
indications in the long term models and climate outlooks of a
return to a wetter (although any rain at this point would be
wetter) pattern around day 10/next Friday, and continuing during
the last week of January.


&&

.AVIATION...15/12Z TAFS...Fog remains in Oregon valleys west of the
Cascades this morning, bringing LIFR levels to Medford and Roseburg.
LIFR visibilities will remain through the morning, and should clear
out by early afternoon. Fog is expected to remain to the same areas
this evening. Ceilings and visibilities could also lower at North
Bend tonight as marine stratus could travel up the Oregon coast.

VFR levels are expected to continue across the rest of northern
California and southern Oregon through the TAF period. -TAD

&&

.MARINE...Updated 230 AM Wednesday, January 15, 2025...Steep seas
continue this morning as gusty northerly winds persist. Conditions
will improve late this morning, with seas expected to remain below
advisory levels this afternoon through Thursday afternoon.

A thermal trough looks to return late Thursday afternoon, bringing
gusty northerly winds and building steep seas in most outer waters
and possibly as close as 5 nm from Cape Blanco and Cape Sebastian. A
Small Craft Advisory is in place from Thursday at 4 PM through
Friday at 7 AM. Beyond this period, very steep and hazardous seas
are possible south of Port Orford from late Friday morning through
the day Saturday. Future products will cover the development of very
steep and hazardous seas. Areas of advisory level seas remain in the
forecast through Monday. -TAD

&&

.BEACH HAZARDS...Updated 830 PM PST Tuesday, January 14,
2025...Another episode of sneaker waves is possible Saturday
afternoon through Sunday afternoon, with a peak of hazardous
conditions early Sunday morning. This would be due to a combination
of northerly wind waves, northwest swell at 11 seconds, and a long
period west-northwest swell at 21 seconds. The period of the long
period swell will gradually decrease during the weekend, to 16
seconds by Sunday night.

Sneaker waves are a type of wave that can run higher up the beach
than a normal wave. Sneaker waves can possibly wash over pathways or
rock outcroppings. They can lift and carry logs, which can then
strike or pin beachgoers. Sneaker waves can knock a person off their
feet and carry them out to deeper waters, where hypothermia becomes
possible. Sneaker waves can pose a lethal threat. As these
conditions may occur while the sun is down, visibility will be
limited. Always keep your eyes on the sea and use extra caution.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Air Stagnation Advisory until 10 AM PST Thursday for ORZ021-
     023>026-029>031.

     Dense Fog Advisory until 10 AM PST this morning for ORZ023.

     Freezing Fog Advisory until 10 AM PST this morning for ORZ024-
     026.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 4 PM Thursday to 7
     AM PST Friday for PZZ350-356-370-376.

     Small Craft Advisory until 10 AM PST this morning for PZZ370-
     376.

&&

$$

CC