Grants Pass, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

103
FXUS66 KMFR 220429
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
829 PM PST Sat Dec 21 2024

.DISCUSSION...The impacts of note look to be relatively few for
such a prolonged period of active weather. Frontal passages
will produce numerous episodes of wet, windy weather during the
next 10 days. The most significant impacts will be to marine
weather, and dangerous high surf at beaches. Please see the
marine and beach hazards sections below for details. Rainfall
will be moderate at the coast Sunday afternoon into Sunday night.
This will also produce another episode of gusty southerly winds
for the Coast, Shasta Valley, southern Rogue Valley, and much of
the east side during Sunday. A stronger front follows Monday night
into Tuesday.

A break between systems is expected Tuesday night into Christmas
morning. The most impactful weather inland looks to occur during
Wednesday evening into Thursday evening, with snow levels around
4500 to 5000 feet. This will affect travel with advisory or
warning level snowfall possible in the Diamond Lake, Crater Lake,
and Willamette Pass areas, and lesser/minor impacts also possible
for Highway 140/Lake of the Woods, mountains and passes east of
the Cascades, and also Snowmans Summit near Mount Shasta.

Additional strong frontal passages likely follow Friday through
the weekend, but snow levels are likely to nudge higher, above the
mountain passes. The progressive nature and relatively seasonably typical
strength of these systems is likely to prevent river flooding.
But, the sheer number of disturbances will produce gradual rises
on rivers, creeks, and streams through the week.

&&

.AVIATION...22/00Z TAFS...Post-frontal showers continue to move
across areas west of and over the Cascades, with very little
activity getting farther east. Coastal areas are seeing ceilings
from MVFR to LIFR this afternoon, while inland areas are staying at
VFR levels.

Another cold front will approach northern California and southern
Oregon late Sunday, bringing another round of widespread showers.
Snow levels of 7000 feet or higher will minimize snow showers. Rain
showers could locally bring lower ceilings and visibilities as well
as possibly obscuring elevated terrain. Guidance shows low level
wind shear developing over the Oregon coast and mountainous terrain,
with southerly winds of 40 to 50 kts at 200 feet. -TAD

&&

.MARINE...Updated 800 PM PST Saturday December 21, 2024...Winds will
remain relatively light tonight, but very high and steep west swells
will keep seas hazardous to all craft. South winds increase rapidly
Sunday morning as the next strong front arrives. This front will
bring sustained south gales with occasional storm force gusts by
late morning and afternoon along with very high, steep, and chaotic
mixed seas.

The pattern repeats again Sunday night and Monday as winds ease by
very high background west swell remains. This is immediately
followed by another strong front later Monday. As deepening low
pressure moves along 130W Monday afternoon, pressure gradients will
be stronger with this front, and as a result winds will be higher -
gales at least and storm force winds are possible.

Yet another deep low pressure system and strong front is expected
Christmas day into Thursday. Guidance shows the highest swell of the
series behind the Christmas front with west swells possibly
exceeding 25 feet. -Wright

&&

.BEACH HAZARDS...Updated 200 PM PST Saturday, December 21, 2024...
Numerous fronts will bring periods of increasing swells and
dangerous surf conditions this weekend and through next week. A High
Surf Advisory remains in effect this weekend, with large breaking
waves of 21 to 26 feet expected. It will be followed immediately by
a High Surf Warning from late Sunday evening through Monday evening
as the next, stronger front will bring dangerously large breaking
waves of 25 to 33 feet. Hazardous conditions this weekend will reach
a peak this afternoon and evening, but conditions worsen Monday
morning into Monday afternoon as large breaking waves increase.
Conditions are expected to slowly improve on Tuesday.

Extremely large breaking waves will create very hazardous conditions
along beaches and area shorelines. Waves will inundate beaches and
surge into normally dry areas. Infrastructure damage and significant
beach erosion can be expected. Stay away from area beaches during
this period of active weather. -Wright/BR-y

&&

.PREV DISCUSSION... /Issued 401 PM PST Sat Dec 21 2024/

DISCUSSION...Tonight through Tuesday night...A series of cold
fronts will continue to move over northern California and southern
Oregon through the end of the weekend and into the week. Post-
frontal showers continue tonight, especially west of the Cascades.
Snow levels of 4500 to 5000 feet will make light snow showers
possible over higher terrain. Gusty winds continue to funnel into
Shasta Valley and over higher elevations, but remain below
advisory levels.

The first cold front in the short term will affect the area from
late Sunday morning into late Sunday night. Showers from this front
are looking non-impactful, especially with snow levels forecast to
be at 7000 feet or higher. Precipitation amounts will be highest
over Curry County, western Siskiyou County, and over elevated
terrain. Gusty winds will return to Shasta and southern Rogue
valleys, with a Wind Advisory in place from Sunday at 10 AM through
7 PM for these areas. Widespread Advisory-level winds do not look
likely over broad areas east of the Cascades, although gusts over
mountain peaks may reach those speeds.

Scattered post-frontal showers will move over the area to start
Monday and before the next cold front moves over the area from late
Monday morning through the day Tuesday. Precipitation will be
heavier with this front. Curry and western Siskiyou counties as well
as the Mount Shasta region could see 2 inches or more of
precipitation. Other areas are forecast to see half an inch to an
inch of precipitation. Snow levels will fall to 4000 to 4500 feet on
Tuesday morning and afternoon, which could bring snowfall to
highways passing around Diamond Lake and Crater Lake. Right now, 2
to 6 inches is forecast over these highways. While a Winter Weather
Advisory does not look necessary right now, these conditions could
still be hazardous for holiday travelers who are not used to
traveling through snowfall. Another round of gusty southerly winds
is expected with this front as well, but high-resolution guidance
will help to determine if and when additional wind products are
needed for Shasta and Rogue valleys and east side terrain. -TAD

Christmas Eve through Saturday...The weather stays active. The
airmass cools down Christmas Eve with a trough passage to the
east however precipitation looks to end before snow levels fall
below the passes. So Christmas morning looks a bit chilly but
void of significant new snow or ice. Another front incoming later
Christmas Day could allow for some light accumulations in the
Cascades and higher Siskiyous by late day. Christmas night
through Thursday still looks good to bring the area a fair slug
of mountain snow with the NBM showing an 80% chance for the
Cascades above 5000 ft to receive 6+ inches of snow by Late
Thursday afternoon. Should be a similar impact for Mt Ashland and
Mt. Shasta. When we raise those amounts to 10" in 24 hours, the
higher probabilities shift toward Shasta and maintain 60-70%.

An active onshore flow regime continues through Friday and the
weekend with ample rainfall for the coast region looking likely.
NBM probabilities are showing some likelihood greater than 50% of
5+ inches of QPF from Curry through Josephine and western
Siskiyou county. Combined with the rainfall between now and
Thursday, the weekend amounts may lead to some problematic river
rises so we`re keeping an eye on this. Stavish

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 10 AM to 7 PM PST Sunday for ORZ026.

     High Surf Advisory until 10 PM PST Sunday for ORZ021-022.

     High Surf Warning from 10 PM Sunday to 10 PM PST Monday for
     ORZ021-022.

CA...Wind Advisory from 10 AM to 7 PM PST Sunday for CAZ081.

PACIFIC COASTAL WATERS...Hazardous Seas Warning until 4 AM PST Sunday
     for PZZ350-356-370-376.

     Gale Warning from 4 AM to 7 PM PST Sunday for PZZ350-356-370-
     376.

&&

$$