323
FXUS66 KMFR 101657
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
857 AM PST Sun Nov 10 2024

.DISCUSSION...Sent an update this morning. Front strung out across
the area is bringing some light rain from the Curry coast to the
Rogue-Umpqua Divide over to the Cascades. Raised PoPs and allowed
for a few hundredths of QPF (which wasn`t depicted well by the
models this morning). This will gradually lift northward and
fizzle this afternoon while another front organizes offshore.
Precip chances will remain highest along the coast and into the
coast ranges this afternoon due to moist, onshore flow, while most
other areas have brief drying before the next front moves in
tonight into Monday. No other changes are expected this morning.
The next front is on track to bring a period of moderate
precip/wind (rain and mountain snow) later tonight into Monday
area wide. Impactful snow will be mostly above 5000 feet in the
Cascades where a winter weather advisory remains in effect. Winds
will be gusty (45-50 mph) from this evening to the early Monday
morning in the Shasta Valley and over the east side higher
terrain, but also including Highway 31 at Summer Lake. Post-
frontal showers continue behind this first front, especially from
the Cascades west tonight into Tuesday morning. With snow levels
dropping to around 4500 feet, there could be some snow
accumulation along Highway 97 north of Chiloquin and also near
Lake of the Woods, but not expecting advisory amounts. Be aware
though of potential wintry conditions going over the pass on
Highway 140 and on Dead Indian Memorial Road. After a brief break
as a warm front lifts northward Tuesday, another stronger front
will arrive at the coast TUesday night and move onshore Wednesday.
We`ll be looking at this system more in depth today to see what
weather hazards it may bring. -Spilde

&&

.AVIATION...10/12Z TAFS...VFR ceilings continue this morning with
some spotty rain moving through southern Oregon and northern
California. The main aviation hazard will be some speed shear along
the coast later this morning and into the evening hours. Winds
around 2000 feet at North Bend will be about 35 to 40 knots with
surface winds only around 10 knots. By the evening hours, winds
around 1000 feet will be up to 50 knots with 10 to 20 knot surface
winds.

Other than the shear, we`ll see some MVFR ceilings along the coast
later this evening and into tonight as a cold front approaches.
Ceilings may lower even further during the frontal passage,
although they should rise overnight behind the front.


&&

.MARINE...Updated 830 AM PST Sunday, November 10, 2024...

Southerly winds will be on the increase through the day ahead
of the next cold front. Conditions may become hazardous to smaller
crafts ahead of the gales. Otherwise, one has a good chance at
seeing wind gusts up to 40 knots closer to the coast early tonight.
The front should move through the waters by Monday morning and
a high long period swell will fill in the front`s wake. This
swell will linger in the waters on Tuesday before lowering a few
feet on Wednesday and Thursday. Even when the swell lowers, it will
be hazardous to smaller crafts with wave heights around 17 feet and
a wave period around 13 seconds.

-Smith/Hermansen

&&

.BEACH HAZARDS...Updated 830 AM PST Sunday, November 10, 2024...

Another large, long period swell is expected to arrive later today.
Model guidance has been consistently showing NW swells arriving
following the front later tonight into Monday. Seas briefly subside
immediately behind the front Monday (6 hours or so during the
morning), but then build significantly Monday afternoon and Monday
night, reaching a peak of 17-21 feet, 16 seconds by early Tuesday
morning. This will bring large breaking waves (23-27 feet) to the
beaches and coastline through Tuesday afternoon. Seas will gradually
subside Tuesday night. A high surf advisory has been issued for 10
PM Monday through 10 PM Tuesday because of these dangerous surf
conditions.

Large breaking waves create hazardous conditions along and within
the surf zone, and could inundate beaches and low lying shorelines.
If you have plans to venture out to the beaches early-mid next week,
pay close attention to the ocean, stay away from the surf zone and
off of jetties. Also, keep checking back for forecast updates.
-BPN/Hermansen


&&

.PREV DISCUSSION... /Issued 620 AM PST Sun Nov 10 2024/

SHORT TERM...A weak front and shortwave trough have moved inland
overnight and light precipitation has spread into the area. Radar
imagery shows rain and higher mountain snow (snow levels around
6000 to 7000 ft) over central and western portions of the area.
Chances for light precipitation will continue today. However,
precipitation may become spotty in the late morning and early
afternoon. This system will shift eastward during the afternoon
while another frontal system approaches from the west. A warm
front will move onshore and bring light precipitation this
afternoon and evening, with precipitation mainly concentrated
along the coast. Little impacts are expected today as this first
system gradually shifts east and the warm front moves onshore.

Then, as the main cold front arrives late tonight into Monday,
models continue to show widespread moderate to locally
precipitation spreading into the area. Heaviest precipitation with
the frontal passage Sunday night and Monday, is expected along
the coast and coastal mountains, with high chances (50-100%) for 1
one inch or more of rainfall. In the Curry coastal mountains, 2
inches or more or rain is likely (50-70% chance) during this
period. Inland, moderate to locally heavy precipitation
(generally 0.25 to 1.0 inches) is likely from the Cascades west
with the frontal passage. Then, light to moderate precipitation
(generally 0.10 to 0.50 inches) is expected east of the Cascades.
Additional light to moderate precipitation follows Monday night
into Tuesday as the upper trough moves across the area.
Thunderstorms are also possible (15-25% chance) behind the front,
along the coast and inland into the coastal mountains and
northwest Douglas County Monday afternoon through Monday night.

Snow impacts are expected in the Cascades with this front Sunday
night and Monday, as well as in showers behind the front Monday
evening through Tuesday morning. Snow levels will begin around
7500 feet but quickly lower to 4500 to 5000 feet with and behind
the frontal passage. This is likely to bring snow to the higher
passes in the Cascades on Monday, with moderate snow impacts
above 5000 feet elevation north of highway 140. Current forecasts
support 3 to 7 inches of snow falling above 5000 ft elevation
during the day Monday. Lighter snow impacts are expected elsewhere
on Monday for areas from Highway 140 south in the Cascades and
across higher mountains east of the Cascades and Siskiyous south.
Behind the front, a colder and wet pattern sets up Monday evening
through Tuesday as the upper trough moves into the region. Moist
onshore flow and upper level support allow for continued,
widespread showers, with greatest activity along and west of the
Southern Oregon Cascades. Snow levels are forecast to be down to
around 4500 feet and locally to 4000 feet. The National Blend of
Models supports additional moderate snow affecting areas above
5000 feet north of Highway 140 (with an additional 3 to 7 inches
falling). A winter weather advisory is in effect for portions of
the Southern Oregon Cascades above 5000 feet elevation (north of
Highway 140) Sunday night through Tuesday morning. Please see the
WSWMFR for details. Light snow impacts, with snowfall totals of 1
to 3 inches are expected in showers down to around 4500 feet in
the Cascades, including for areas near and south of Highway 140,
and for areas east of the Cascades along Highway 97 north of
Chiloquin. For other mountains and higher terrain above 4500 feet,
expect mainly light snow with showers.

Additionally, ahead of the front, gusty south to southwest winds
are expected as a 45 to 55 kt mid level, 700 mb, jet moves
overhead. This is expected to bring advisory level winds (gusting
to 45 to 50 mph) into the Shasta Valley and higher terrain east of
the Cascades tonight into Monday. A wind advisory remains in
effect for these areas. Please see the NPWMFR for details. Gusty
south winds are also likely over exposed higher mountains and
along the coast ahead of this frontal passage. Along the coast,
winds are expected to peak Sunday evening and night, with
moderate to high chances (40-70%) for winds gusting to 50 mph and
low chances (15% or less) for gusts to 60 mph. For inland areas,
winds are expected to peak Sunday night into Monday morning.

Tuesday afternoon, showers are expected to briefly decrease.
However a moist frontal system will approach the area and move
inland Tuesday night and Wednesday. This may bring rain, snow and
wind impacts to the area. For details, please see the long term
discussion below.

AVIATION...10/12Z TAFS...VFR ceilings continue this morning with
some spotty rain moving through southern Oregon and northern
California. The main aviation hazard will be some speed shear along
the coast later this morning and into the evening hours. Winds
around 2000 feet at North Bend will be about 35 to 40 knots with
surface winds only around 10 knots. By the evening hours, winds
around 1000 feet will be up to 50 knots with 10 to 20 knot surface
winds.

Other than the shear, we`ll see some MVFR ceilings along the coast
later this evening and into tonight as a cold front approaches.
Ceilings may lower even further during the frontal passage,
although they should rise overnight behind the front. -Smith

MARINE...Updated 200 AM PST Sunday, November 10, 2024...

Southerly winds will be on the increase through the day ahead
of the next cold front. Conditions may become hazardous to smaller
crafts ahead of the gales. Otherwise, one has a good chance at
seeing wind gusts up to 40 knots closer to the coast early tonight.
The front should move through the waters by Monday morning and
a high long period swell will fill in the front`s wake. This
swell will linger in the waters on Tuesday before lowering a few
feet on Wednesday and Thursday. Even when the swell lowers, it will
be hazardous to smaller crafts with wave heights around 17 feet and
a wave period around 13 seconds.

-Smith

BEACH HAZARDS...Updated 200 AM PST Sunday, November 10, 2024...

Another large, long period swell is expected to arrive later today.
Model guidance has been consistently showing NW swells arriving
following the front later tonight into Monday. Seas briefly subside
immediately behind the front Monday (6 hours or so during the
morning), but then build significantly Monday afternoon and Monday
night, reaching a peak of 17-21 feet, 16 seconds by early Tuesday
morning. This will bring large breaking waves (23-27 feet) to the
beaches and coastline through Tuesday afternoon. Seas will gradually
subside Tuesday night. A high surf advisory has been issued for 10
PM Monday through 10 PM Tuesday because of these dangerous surf
conditions.

Large breaking waves create hazardous conditions along and within
the surf zone, and could inundate beaches and low lying shorelines.
If you have plans to venture out to the beaches early-mid next week,
pay close attention to the ocean, stay away from the surf zone and
off of jetties. Also, keep checking back for forecast updates.
-BPN/Hermansen

PREV DISCUSSION... /Issued 354 PM PST Sat Nov 9 2024/

LONG TERM...Tuesday through Saturday, Nov 12-16...

A warm front will pass through the area during Tuesday, producing
spotty precip, mainly along and west of the Cascades with snow
levels rising again. Generally speaking, winds will be a bit
breezy out of the south due to an increasing north/south pressure
gradient, and this will result in some increased winds in the
Shasta Valley and across the East Side, but nothing too out of the
ordinary. A brief period of dry weather and near normal
temperatures is expected late Tuesday afternoon into the evening
as the warm front lifts to the north, then conditions deteriorate
Tuesday night as the next storm system approaches the area.

The first concern with this system is rain. The leading edge of
precipitation should pass over the coast overnight Tuesday night,
with rain spreading west to the Cascades by midday, then to the East
Side through the afternoon. With IVT values of between 500 and 750,
moisture inflow will be strong, however, much of that is due to the
stronger winds associated with the system (more on that below). What
is important is the direction of the prevailing flow, which in this
case, will be out of the southwest. This will provide good upslope
mechanics along the coastal ranges, the Cascades, and the Siskiyous,
and especially in the Brookings area. These are where the heaviest
rainfall amounts will be, although totals will not be altogether
unusual for systems like these and during this time of year.
Forecast rain amounts were bumped up above NBM/WPC in these areas,
especially along the south coast near Brookings.  That wind
direction will, however, also produce downslope flow in the Rogue
Valley and east of the Cascades. Rainfall totals here were reduced
below NBM/WPC amounts, but we still expect a good precipitation
event for all of the forecast area. Overall, rainfall amounts will
be healthy, but given the low river levels, no major flooding is
expected. Nuisance flooding, such as small creeks and streams,
blocked ditches, or urban areas are possible.

Winds will also be a concern. Forecast surface pressure gradients
along the coast between Arcata and North Bend are approaching -10mb,
and gradients between Redding and Medford of around -7mb, and model
solutions are suggesting 60 to 70 kt winds at 700 mb. With this in
mind, it is likely that Wind Advisories and Warnings will be
necessary, especially along the coast and across the East Side. Wind
headlines may also be necessary in the Shasta Valley and the Rogue
Valley near Ashland, but the prevailing southwest flow will not
align well with the valleys, so these areas will be mainly gradient
driven and therefore a bit weaker than otherwise. Winds at the coast
will peak Wednesday afternoon, with inland areas peaking into the
evening and overnight.

The final concern is snow. With the southwest flow tapping into
warmer air to the south of us, snow levels will be a bit on the high
side, beginning the event at around 6000 feet, then only dropping to
around 4500 to 5000 feet after the front passes, when precipitation
has likely transitioned to a more showery regime. This will keep
snow from being a major impact, but heavier showers, or the very
last gasp of the front itself, could produce just enough snow at the
higher passes to cause some travel difficulties.

With all of these factors, there is still time for the forecast to
change, so we will be keeping a sharp eye on the latest model runs
over the next several days. That being said, it is never to early to
begin preparations for impactful wind and rain.

Once the front passes through the area (exiting by Thursday
morning), the system slows, keeping upper level troughing overhead
through Friday afternoon. Temperatures will cool to about 5 to 10
degrees below normal as the cold air settles into the region. Along
with ongoing onshore flow, precipitation chances will continue
through this time, with snow levels hovering between 3000 and 4000
feet. There will not be continuous precipitation, as the NBM
suggests with near continual high PoPs, but instead we expect hit-or-
miss and off-again-on-again showers will be the rule Thursday and
Friday. Precipitation amounts will vary greatly from place to place,
and some showers may be strong enough to produce graupel or very
small hail.

Friday night into Saturday, the trough shifts just far enough to the
southeast to allow ridging to nudge in from the west. The NBM keeps
showers across the whole region during this time, but it is much
more likely that the area dries out Saturday as high pressure
settles in. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 PM this evening to 7 AM PST Monday for
     ORZ030-031.

     High Surf Advisory from 10 PM Monday to 10 PM PST Tuesday for
     ORZ021-022.

     Winter Weather Advisory from 4 AM Monday to 10 AM PST Tuesday
     for ORZ027-028.

CA...Wind Advisory from 7 PM this evening to 7 AM PST Monday for
     CAZ081-085.

PACIFIC COASTAL WATERS...High Surf Advisory from 10 PM Monday to 10
     PM PST Tuesday for PZZ350-356.

     Gale Warning from 1 PM this afternoon to 10 AM PST Monday for
     PZZ350-356-370-376.

     Hazardous Seas Warning from 10 AM Monday to 4 PM PST Tuesday for
     PZZ350-356-370-376.

&&

$$

MAS/MAS/MAS