River Flood Warning 7, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
235 PM PST Thu Dec 26 2024

.SHORT TERM...Overview:

Our active weather continues today with hazards from the coast
through the Cascades over into the eastside. Our current Winter
Weather Advisory will expire late tomorrow morning. A new Wind
Advisory is in place across the forecast area as wind speeds are
expecting to ramp up again tonight through Friday morning. We are
also looking at higher elevation snowfall and heavy rainfall
potential along/near the coast. Snow levels start to quickly rise
Friday afternoon into Saturday and the flood potential may start to
ramp up with snow melt and moderate to heavy rainfall on top of
already saturated soils.

Further Details:

Lingering precipitation will continue through the short term.
Frontogenesis is progged to weaken through the day with snow levels
rising, but we are still expecting snowfall to occur at elevations
mainly above 5000 feet, but it would not be out of the question to
see very light amounts elsewhere on the eastside at even lower
elevations. Another period of increased frontogenesis will occur
tonight around 10pm and continue through late morning on Friday, so
we could see another peak in snowfall rates between 10pm and 2am for
those locations within the advisory. Thereafter we will likely see
snowfall rates quickly diminishing. In fact, we may be able to
cancel the advisory early by a few hours or so depending on how the
500mb wave progresses through the region. Rainfall will then become
our main issue which could lead to flooding, especially areas near
the coast on/near the Coquille. We are currently highlighting this
threat in the Hydrologic Outlook, in addition to river forecast from
the River Forecast Center. The peak in the flooding will be in the
long term forecast, but we are currently looking at impacts starting
around the 29th and continuing through the 30th. Please see long
term discussion for more details.

.LONG TERM...The long term will begin with light to moderate rain
mainly in northern California and in southern Oregon west of the
Cascades at the coast. A cold front will be moving in and by the
late afternoon Saturday, there will be heavy rain in the forecast.

The heaviest rain will fall late Saturday afternoon and continue
through Sunday morning. There is a 50-60% probability for eastern
Curry County and far western Josephine County to see 1 inch of
rainfall in 6 hours Saturday night. Climatologically, PWATs are
around 0.45" near the end of the year at Medford. Forecast PWATs
with this system are forecast to be double that. 6 hour rainfall
forecast for the Rogue Valley could reach 0.25"-0.50" Saturday
night. More westerly upper level flow will help support the moisture
intake for the area with RHs forecast to stay above 80% until Sunday
night.

The probability for 4 inches of snow to fall in 6 hours in the
Cascades, including the Crater Lake area, is near 60-70% Sunday
morning. Between Sunday morning and Monday morning, 8 to 15 inches
could fall.

The heavy rain along with snow melt will bring a concern for
flooding for small streams and rivers. As of this afternoon the
forecast calls for the Coquille River at Coquille to reach action
stage tonight and will reach minor flood stage by Sunday morning
before peaking in to Moderate Flood Stage Sunday night into Monday.
The Rogue River at Agness is forecast to reach Minor Flood Stage
Sunday morning and crest at ~21 feet Sunday afternoon. Please see
ESFMFR for more information on the Flood Potential Outlook.

The introduction of ridging to the PNW Monday will bring calmer
conditions through the day Monday into Tuesday. This will also means
the chance for lighter winds. The threat of fog will need to be
evaluated those mornings as forecast soundings are favoring
inversions to set up at least in the Umpqua Basin. Temperatures will
return to near normal for this time of year by early next week.
After the quieter start to the week the next system will come just
in time for the New Year, but they will be lighter and focus on
areas west of the Cascades. -Hermansen

&&

.AVIATION...26/18Z TAFS...Active weather continues across the area,
with passing showers bringing VFR or MVFR ceilings. Showers will
decrease into this afternoon before another disturbance brings
another round of activity tonight into Friday morning. Snow levels
of 4500 to 5500 feet will limit most snowfall to elevated areas, but
showers can locally lower snow levels and bring snow showers to
lower elevations.

Low level wind shear could return tonight into Friday morning. After
the rain becomes less widespread early tomorrow morning, MVFR/IFR
conditions are likely with mountain obscurations. There is only a 30-
40% prob for IFR ceilings in Medford for tomorrow morning, so kept
tomorrow morning at low MVFR for now. -TAD/Hermansen

&&

.MARINE...Updated 200 PM PST Thursday December 26, 2024...Stormy
weather will continue over the waters through the weekend with
gale-producing fronts one right after another each day through
Sunday. All of this wind will occur in the presence of high and
very steep background west swell, so even though there will be
lulls in the wind between fronts, conditions will remain dangerous
to all craft in between fronts due to high seas.

The first lull in wind between fronts is occurring right now, but
seas remain upwards of 20 feet. Winds will increase rapidly this
evening and tonight and remain at gales until the next front passes
Friday morning. This will be followed by another lull in
wind Friday afternoon and evening.

Confidence is high that this pattern will repeat twice more with
frontal passages Saturday morning and Sunday morning or early
afternoon. Confidence is lower regarding the details of weekend
fronts - in particular: the strength and landfall location of low
pressure waves along these fronts. Should any of the lows be
stronger than currently indicated or make landfall close to us,
winds may be higher than expected.

The weather finally gives us a bigger break between systems early
next week along with a decrease in seas. However, more fronts are in
the offing New Year's Day and beyond. -Wright

&&

.BEACH HAZARDS...Updated 200 PM PST Thursday December 26, 2024...
Swell dominated seas will continue to produce dangerous surf through
the weekend. Surf conditions will be occasionally worsened by high
winds and seas as fronts pass each day through Sunday. Breaking
waves in excess of 30 feet remain possible through the weekend.

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. -Wright

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 10 AM PST Friday for ORZ027-028-
     030.

     Wind Advisory from 10 PM this evening to 10 AM PST Friday for
     ORZ022>024-026-030-031.

     High Surf Warning until 7 AM PST Sunday for ORZ021-022.

CA...Winter Weather Advisory until 10 AM PST Friday for CAZ080-082-
     083.

     Wind Advisory from 10 PM this evening to 10 AM PST Friday for
     CAZ081-084-085.

PACIFIC COASTAL WATERS...Gale Warning until 7 AM PST Sunday for
     PZZ350-356-370-376.

&&

Preliminary Local Storm Report
National Weather Service Medford OR
422 PM PST Thu Dec 26 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0400 PM     Rain             2 WSW Obrien            42.06N 123.73W
12/26/2024  M3.00 Inch       Josephine          OR   Trained Spotter

            24 hour amount.

&&