Grants Pass, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

989
FXUS66 KMFR 230523
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
923 PM PST Mon Dec 22 2025

.DISCUSSION...Update marine discussion.


&&

.AVIATION...23/06Z TAFs...A cold front will reach the coast this
evening then dissipate overnight. Meanwhile, a stronger warm front
lifts northwestward across northern California tonight and
continue onward to the coast on Tuesday.

Conditions are VFR at the start of this evening, but the pattern
will make for a wide range of changing conditions overnight through
Tuesday. This includes areas of west side valley LIFR/IFR late
tonight into Tuesday morning, with generally lowering ceilings and
developing areas of mountain obscuration across the area. MVFR looks
to become the most widespread condition during Tuesday morning
through the evening. Expect increasing wind speeds across NorCal
and over the East Side Tuesday night. Low-level wind shear is
possible before winds surface in some areas then.


&&

.MARINE...Updated 850 PM PST Monday, December 22, 2025...Winds
gradually ease tonight into Tuesday, but seas will remain steep.

Two potentially significant storm systems will impact the area this
week...the first, quick-moving system, arrives late Tuesday through
Wednesday morning and the second, slower-moving system, arrives late
Wednesday night and persists into Friday morning.

There is STILL quite a range in solutions (and therefore, low
confidence) for the first system as it moves south to north along
the coast. This brings a wide range of possible scenarios in terms
of wind strength over the marine waters since the position of the
low is uncertain. Most of the guidance maintains that gale force
winds and very steep seas are the most likely scenario and this is
what the forecast reflects. Two other scenarios, which lie closer to
the extremes (on both ends) are possible, however. Stronger model
solutions (about a 20-30% chance) show a period of southerly storm
force winds occurring during the early morning hours Wednesday.
Weaker solutions (similar %) move the low into Cape Mendocino and
keep the strongest winds to our south. We will maintain the gale
watch and allow future shifts to upgrade as new information becomes
available.

The second system remains farther offshore on Thursday and lingers
over a longer period of time into Friday morning. Confidence is
higher regarding some details with this system as guidance is in
better agreement, but another round of gales is likely with this
storm. Both systems will also bring a round of very steep and
hazardous seas and difficult bar crossings. Winds will gradually
ease late Friday, but seas are likely to remain steep into early
Saturday. Once the Christmas system moves out of the region, the
overall weather pattern looks to settle down over the weekend,
possibly into next week, and conditions will improve overall.


&&

.PREV DISCUSSION... /Issued 528 PM PST Mon Dec 22 2025/

..Updated the Aviation Section...

AVIATION...23/00Z TAFs...A cold front will reach the coast this
evening then dissipate overnight. Meanwhile, a stronger warm front
lifts northwestward across northern California tonight and continue
onward to the coast on Tuesday.

Conditions are VFR at the start of this evening, but the pattern
will make for a wide range of changing conditions overnight through
Tuesday. This includes areas of west side valley LIFR/IFR late
tonight into Tuesday morning, with generally lowering ceilings and
developing areas of mountain obscuration across the area. MVFR looks
to become the most widespread condition during Tuesday morning
through the afternoon.

MARINE...Updated 200 PM PST Monday, December 22, 2025...Gusty south
to southwest winds will persist today along with steep to very steep
seas for all areas. Isolated gale force gusts are possible north of
Cape Blanco through this afternoon. Conditions gradually improve
tonight into Tuesday, but seas will remain steep through the day
Tuesday.

Two systems will impact the area this week...the first, quick moving
system, arrives late Tuesday through Wednesday morning and the
second, slower moving system, arrives late Christmas (Thursday)
morning and persists into Thursday morning. There is quite a range
in solutions for the first system as it moves south to north along
the coast, and this brings a range of possible scenarios in terms of
wind strength over the marine waters. Most of the guidance maintains
that gales, potentially strong, are the most likely scenario and
this is what the forecast reflects. It is possible, however, if the
stronger model solutions come to fruition (about a 30% chance), that
a period of southerly storm force winds occur during the early
morning hours Wednesday. Latest guidance is boosting confidence some
in the weaker solutions, so have leaned toward a gale watch for that
period at this time.

The second system remains farther offshore on Thursday and lingers
over a longer period of time into Friday morning. Confidence is
higher regarding some details with this system as guidance is in
better agreement, but another round of gales is likely with this
storm. Both systems will also bring a round of very steep and
hazardous seas and difficult bar crossings. Winds will gradually
ease late Friday, but seas are likely to remain steep into early
Saturday. Once the Christmas system moves out of the region, the
overall weather pattern looks to settle down over the weekend,
possibly into next week, and conditions will improve overall.
/BR-y

PREV DISCUSSION... /Issued 311 PM PST Mon Dec 22 2025/

SYNOPSIS...

A high impact winter storm will hit the region starting on Tuesday
and persist through most of the week. It will come in two waves
with the first Tuesday night into Wednesday and another Thursday
into Friday morning. The highest impacts will be felt in Siskiyou
County at elevation. Pockets of power outages are likely through
this event.

DISCUSSION...

Rather quiet weather before the storm on this Monday afternoon
with a few clouds here and there and some showers on radar. That
should all change going into tonight as the stationary front and
atmospheric river(AR) begin to target Siskiyou County. Warmer air
remains to the south east with snow levels up to 7000 feet in the
far south eastern section of Siskiyou County. However, snow
levels are notably lower for areas west of the Cascades down to
3500 feet in some places. This will lead to a mix of where snow
accumulates in northern California, but the main impact area is
likely Snowmans Summit and Shasta Ski Park.

A couple of inches of snow will start to accumulate in Siskiyou
County before snow levels shoot up ahead of stronger southerly
flow. We`ll likely see an area of strong low pressure spin up
along our coast as ensembles show mean sea level pressure minimums
around 980 to 990mb. Winds will become the main concern during
this time, especially in Siskiyou County as 700 mb flow aligns
with that valley at 70 knots according to the GFS, which is a
reasonable solution in the ensemble set. Those winds will impact
Modoc County and spread northwards through the night.

A more easterly track from the low, which differs from a lot of
the deterministic guidance, would lower the wind threat west of
the Cascades. However, there was enough a threat to warrant a wind
advisory. Another thing that stood out was the extreme forecast
index(EFI) with regards to wind gusts, although that lowered west
of the Cascades with the latest set of ensembles. However, the EFI
is still highlighting spots within northern California.

Lastly, we opted for a winter weather advisory in the Cascades for
the first round of this event. The snow is not even advisory level
in the higher terrain with snow accumulation up to 6 inches mainly
above 5500 feet. However, winds will be quite strong, especially
over exposed terrain Tuesday night into Wednesday morning as the
low shoots north out of our forecast area.

Colder air will settle back in behind this low on Christmas Eve and
we will start to see the snow accumulation really start to pick
up during the evening of Christmas Eve and Christmas within
Siskiyou County. During this second wind of this winter event,
elevations above 4500 feet will likely see 2 to 3 feet of snow in
Siskiyou County near Mt. Shasta City.

Ensembles again are hinting at another low developing and
undergoing cyclogenesis off the northern California coast
Thursday night. Wind hazards will likely develop again as a low
around 985 mb develops just off our coastline. One would think
snow levels would jump up again as this happens, but they remain
stubbornly low around 3500 to 4000 feet.

Conditions improve significantly into the weekend as high pressure
begins to build.

-Smith

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 7 PM Tuesday to 7 AM PST Wednesday for
     ORZ029>031.

     Wind Advisory from 10 PM Tuesday to 10 AM PST Wednesday for
     ORZ023>026.

     Winter Weather Advisory from 10 AM Tuesday to 10 AM PST
     Wednesday for ORZ027-028.

CA...Winter Storm Warning from 4 AM Tuesday to 10 AM PST Friday for
     CAZ080-082>085.

     High Wind Warning from 7 PM Tuesday to 7 AM PST Wednesday for
     CAZ081-084-085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 10 PM PST Tuesday
     for PZZ356-376.

     Gale Watch from Tuesday evening through Wednesday afternoon for
     PZZ350-356-370-376.

     Hazardous Seas Warning until 10 PM PST this evening for PZZ350-
     356-370-376.

     Small Craft Advisory until 10 PM PST Tuesday for PZZ350-370.

&&

$$