NWS Medford, OR wrote its last area forecast discussion before the first event at Dec 28, 7:30 PM PST, 35 minutes earlier.
Area forecast discussion, Dec 28, 7:30 PM PST, 35 minutes before
Area Forecast Discussion
National Weather Service Medford OR
730 PM PST Sat Dec 28 2024
...Updated the aviation and marine sections...
.AVIATION...29/00Z TAFS...A very strong front will affect the region
through Sunday morning. This includes torrential rain, heaviest from
the coast to the Cascades. Also, south to southwest low level wind
shear of 40 to 50 kt at 2000 feet AGL, mountain obscuration, gusty
southerly winds, and areas of LIFR and IFR.
Precipitation intensity and coverage will diminish, but not end
altogether, Sunday afternoon into Sunday night. This will allow
conditions to improve slightly with a mix of MVFR and VFR likely.
But, snow levels will also fall Sunday morning into Sunday night,
from around 6000 feet to around 2500 feet MSL. A light accumulation
of snow of around an inch is possible for Klamath Falls during
Sunday evening. -DW
&&
.MARINE...Updated 730 PM PST Saturday December 28, 2024....Very
high and steep to very steep hazardous seas reached a peak this
afternoon. But, high and steep seas will continue tonight through
Monday.
Another front will continue south gales tonight, strongest south of
Cape Arago this evening. Behind the front, west to northwest wind
gusts on Sunday morning may approach gale force.
Currently, a period of below advisory conditions is forecast from
Monday evening into Tuesday evening. The next approaching front
could produce another round of south gales and very steep seas late
Tuesday night through Wednesday. Some improvement is likely for the
second half of the week, but persistent steep seas and frequent
episodes of advisory strength winds are likely. -DW
&&
.PREV DISCUSSION... /Issued 248 PM PST Sat Dec 28 2024/
DISCUSSION...Moderate to heavy rain, strong winds, and high
elevation snow will continue to impact the region over the next
24-36 hours. A front remains draped over the area and will wobble
northward throughout the day. The focus of precipitation has
shifted north of the OR/CA border, but the heavier rainfall rates
will arrive later this afternoon. The front will then shift north
of the Rogue-Umpqua Divide late this evening and into the
overnight hours before finally getting kicked eastward through the
region Sunday morning with precipitation tapering off late Sunday
afternoon and evening.
Hefty rainfall amounts are expected over the next 24-36 hours along
with another round of strong winds this evening and overnight. The
additional rainfall on already saturated soils will lead to numerous
flooding impacts ranging from standing water in low lying
areas/roadways and area streams reaching or surpassing bankfull to
some mainstem rivers reaching minor or moderate flood stages. A
plethora of flood watches are in effect for this anticipated impact,
and details can be found at water.weather.gov. Additionally, strong
winds are expected this evening as a surface low develops along this
stalled front this evening. This includes most of the East Side
locations as well as the Shasta Valley and the Coast, and details
can be found at NPWMFR. Medford/Redding pressure gradients are
forecast to peak around -8 (GFS) to -10 (NAM), and this tends to
equate to strong winds in the Shasta and Rogue Valleys. This is
likely to be realized in the Shasta Valley, but here in the Rogue
Valley however, the wind direction doesn't quite align with the
terrain which should keep that area sheltered from the strongest
winds.
Snow levels will be fairly high with this event. Our region is
currently bisected by high vs low snow levels with values around
8000 ft south of the OR/CA border and values closer to around 4500
ft from Crater Lake northward. The higher snow levels will spread
northward as the front lifts northward later today, so winter
impacts will be limited to the highest peaks through late tonight.
By early Sunday, however, as the front pushes eastward as a cold
front, snow levels will lower down to around 4500 ft as the bulk
of the precipitation is coming through. This will bring a quick
shot of advisory level snow accumulations to the Cascades Sunday
morning and afternoon. There is about an 80-90% of one inch/hour
rates with the frontal passage through around 1 pm Sunday and
those chances drop off significantly afterward. We've hoisted a
Winter Weather Advisory to cover this, and details can be found at
WSWMFR. Snow levels lower farther to around 3000 ft late Sunday
afternoon and evening, but precipitation will have transitioned to
showers by then so winter impacts should be minor and limited.
Showers will continue into the overnight hours Sunday, then
gradually taper off Monday morning. /BR-y
Long term:
There will be lingering showers early Monday that will mainly be at
the Coast and into Douglas County and into the Cascades. Ridging
will return to the area Monday and remain through Tuesday afternoon.
Even with the few showers Monday, calmer conditions are ahead for
Monday and Tuesday with drier conditions, calmer winds and mild
temperatures. The threat of fog will need to be evaluated those
mornings as forecast soundings are favoring inversions to set up in
the Umpqua Basin and Rogue Valley.
Clearer skies are expected Monday night. This, along with lighter
winds, will allow the air to cool well. Tuesday is forecast to have
the coldest morning of the week with lows in the upper 20s and low
30s across west side valleys and teens east of the Cascades. These
cold temperatures occuring when forecast soundings show inversions
in west side valleys bring a threat of freezing fog Tuesday morning.
This has been added to the forecast grids.
Afternoon temperatures will be a few degrees below normal Tuesday
with mostly 30s and 40s. Temperatures will be similar Tuesday and
Wednesday afternoons before warming slightly above normal Thursday
afternoon. This will bring highs in the 30s and 40s to the 40s and
50s Thursday and Friday.
After the quieter start to the week the next system will come on New
Year's Eve. A trough will reach the PNW Tuesday. Ensembles are in
agreement that the deepest part of this trough will be into
Washington, meaning the impacts will be focused north of the area.
Lighter precipitation amounts are forecast for most locations later
in the work week, although light to moderate rainfall will be
possible at the Curry County coast when the next trough arrives
Friday.
BEACH HAZARDS...Updated 200 PM PST Saturday December 28, 2024...
Heavy, long period swell dominated seas will continue to produce
dangerous surf conditions through tomorrow morning. Large breaking
waves of 22 to 25 feet are expected through early Sunday
morning, with the worst conditions expected this afternoon.
During these events, extremely large breaking waves will create very
hazardous conditions along beaches and area shorelines. Waves will
inundate beaches and surge into normally dry areas, especially at
times of high tide. Infrastructure damage and significant beach
erosion can be expected. Stay away from area beaches during this
period of active weather. -BPN/BR-y
HYDROLOGY...Significant rises on mainstem rivers are expected
tonight into Sunday with additional precipitation amounts of 1 to
3 inches over the West Side valleys and 2 to 4 inches in the
mountains and along the coast, with up to 6 inches of rain in the
Curry coastal ranges. There is currently a Flood Warning in
effect for the Coquille River at Coquille as it is currently
flooding and in a Moderate Flood Stage. Later this afternoon and
into the start of Sunday, the Coquille will fall to Minor Flood
Stage before rising again to the Moderate Flood Stage by Sunday
afternoon, peaking Sunday morning. The Rogue River at Agness is
forecast to reach Minor Flood Stage Sunday afternoon and crest
Sunday evening, and a Flood Watch is in effect for that location.
The second Flood Watch is in effect for Deer Creek at Roseburg is
forecast to reach Minor Flood Stage Sunday morning.
Additionally, heavy rain along with snow melt and already
saturated soils brings a concern for flooding for urban areas
and small streams/creeks during this time. Expect plenty of
standing water on roadways and low lying areas, along with storm
drains and ditches becoming clogged with debris. Please see
FFAMFR and FLWMFR for more information on the Flood hazards.
Conditions will improve early next week as dry period arrives.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Flood Watch through Sunday afternoon for ORZ021>026.
High Wind Warning until 7 AM PST Sunday for ORZ021-022-030-031.
Wind Advisory until 10 AM PST Sunday for ORZ029>031.
High Surf Advisory until 7 AM PST Sunday for ORZ021-022.
Winter Weather Advisory from 4 AM to 10 PM PST Sunday for ORZ027-
028.
CA...Flood Watch through Sunday afternoon for CAZ080>083.
High Wind Warning until 7 AM PST Sunday for CAZ081-085.
Wind Advisory until 10 AM PST Sunday for CAZ084-085.
PACIFIC COASTAL WATERS...Gale Warning until 7 AM PST Sunday for
PZZ350-356-370-376.
Small Craft Advisory from 7 AM Sunday to 4 PM PST Monday for
PZZ350-356-370-376.
&&