High Wind Watch 13, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
356 PM PST Fri Dec 27 2024

.Updated AVIATION Discussion...

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.AVIATION...28/00Z TAFS...The next front in the parade of storms
is pushing into the region this evening. Mainly VFR conditions
currently prevail, but will gradually lower this evening and
overnight to a mix of low end VFR/MVFR conditions along with the
development of widespread terrain obscurations. Gusty winds will
return to the area, with low level wind shear expected for most
areas through around 06z/27th. A break in the precipitation is
expected late tonight through around sunrise Saturday, but lower
level cloud cover will persist and should limit the extent of fog
development with MVFR conditions persisting through the morning
hours. /BR-y

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.PREV DISCUSSION... /Issued 241 PM PST Fri Dec 27 2024/

Overview:

While snowfall is expected through the short term, we are not
expecting many impacts to where people actually live given the snow
levels. That said, its worth noting snow ratios are low, but liquid
equivalent amounts are forecast to be high, so we could see snow
load become an issue (heavy wet snow on trees/infrastructure) over
the next 48 to 72 hours. This would be mainly for areas in and
around Crater Lake and some of the higher elevations across the
Cascades (above 5500ft). Perhaps the more widespread impact through
the short term is going to be moderate to heavy rainfall that could
lead to potential flooding over the next 48 to 72 hours. The peak
for rainfall amounts through this stretch would be Saturday
afternoon into Sunday morning. Overall, we are expecting this to
cause rises along rivers into next week. Please see the latest flood
warnings and watches for more details.

Further Details:

Our next system is making its way into the PacNW today with rain
showers pushing onshore as of writing this (~2pm). Expecting shower
activity to increase west to east through the day with moderate to
heavy rainfall expected along and near the coast late this afternoon
through the overnight period into Sunday morning. While a break in
activity will be possible late Saturday morning/early afternoon, we
will see activity increase once again as a broader cyclone develops
in the Gulf of Alaska. This will be fueled with stronger dynamics,
higher PWATs, and better overall forcing. For example, isentropic
analysis shows strong uplift Saturday afternoon through Sunday
morning with warm air advection, especially on the 295K and 300K
surfaces where this additional forcing will lead to heavy rainfall
across Curry and Coos counties. Jet dynamics are also very strong
which will lead to further efficiency of rainfall. We essentially
have a lot of variables that are lining up to make efficient rain
producers. Dry air does move in late Sunday morning so we should see
coverage decrease in the afternoon; however, instability does
increase so we could have isolated thunderstorm activity over the
waters and near coastal areas through the afternoon hours and early
evening.

Rainfall amounts will be highest across Curry County through this
period of moderate to heavy rain. Areas in the county could see
rainfall totals (48-72 hours) around 5.0 to 7.0 inches, so there
will likely be nuisance flooding issues on roadways, but
rivers/creeks/tributaries will be especially susceptible to
potential flooding given our prolonged period of rainfall and
saturated soils. Coos County will see amounts closer to 3 to 5
inches when its all said and done. Given the high snow levels/warm
air, we could see snow melt contributing to river rises as well.
This is of course very hard to forecast, so we will likely be making
adjustments once we see exactly how this plays out with river gauges
and coordination through the River Forecast Center.

Snow load issues could arise and create impacts due to downed trees
from the weight of the snow. The snow to liquid ratio is relatively
low through this event given the warm air, but the atmosphere will
be very saturated with high PWATs, so the snow is going to be rather
high in moisture which means it will be heavy. That said, these
areas are mostly uninhabited at these elevations, but something to
be aware of due to potential infrastructure issues.

LONG TERM...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
rise from its current Minor Flood Stage 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 ~20 feet
Sunday afternoon. Please see FFAMFR 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 return of lighter winds. 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.
Temperatures will return to near normal for this time of year by
early next week.

It will be the coldest start of the work week Tuesday morning
with lows in the upper 20s and low 30s across west side valleys
and teens east of the Cascades. On average, these temperatures
will only be a few degrees below normal. Afternoon temperatures
will also be a few degrees below normal Tuesday with mostly 30s
and 40s.

After the quieter start to the week the next system will come just
in time for the New Year as it begins on New Year's Eve. However,
lighter rainfall amounts are favored with light winds as well.
Lighter rainfall and snow is expected through the rest of the
work week with continued mild temperatures.

AVIATION...27/18Z TAFS...VFR conditions have returned with the end
of the widespread rainfall for inland locations. The coast remains
at MVFR/IFR conditions that will lift through the day. Gusty winds
continues east of the Cascades but have mostly eased west of the
Cascades. Another disturbance will bring more showers this afternoon
and into Saturday morning. Snow levels of 5000 feet or above will
limit snow showers to over area peaks.

Wind shear will also be a factor through the TAF period. Currently,
guidance expected low level wind shear over and east of the
Cascades. These westerly winds are at 40 to 50 kts at 2000 feet.
Wind shear will ease through the morning before returning to the
Oregon coast this evening and building to the east. -TAD/Hermansen

MARINE...Updated 130 PM PST Friday December 27, 2024...Very high,
very steep, and at times, chaotic mixed seas will persist in the
marine waters through the weekend. Additional strong fronts will
pass through the area, bringing rounds of strong gale force south
winds. The next in the series is expected late tonight into Saturday
morning, then another late Saturday night into Sunday morning.
During this time, very steep and hazardous seas of 15 to 20 ft are
expected due to heavy long period swells. Seas will be augmented by
short period wind waves of 10 to 15 feet before and during frontal
passages.

Conditions look to gradually improve later Sunday as the onslaught
of storm systems slows down. Seas will remain high and steep into
early next week with a break in the weather expected through late
Tuesday. Active weather returns for the latter half of the week, and
while strong winds and building seas are expected, conditions don't
look to be as hazardous as we have been experiencing. /BR-y

BEACH HAZARDS...Updated 130 PM PST Friday December 27, 2024...
Heavy, long period swell dominated seas will continue to produce
dangerous surf conditions through the weekend. Surf conditions will
be occasionally worsened by high winds and seas as fronts pass each
day through Sunday. Large breaking waves 25 to 30 feet are expected
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. /BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Flood Watch from Saturday morning through Sunday afternoon for
     ORZ021>026.

     Wind Advisory from 7 PM this evening to 1 PM PST Saturday for
     ORZ024-030-031.

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

CA...Flood Watch from Saturday morning through Sunday afternoon for
     CAZ080>083.

     Wind Advisory from 7 PM this evening to 1 PM PST Saturday for
     CAZ081-085.

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

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MNF/JWG/ANH

Preliminary Local Storm Report
National Weather Service Medford OR
350 PM PST Fri Dec 27 2024

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

0350 PM     Rain             2 WSW Obrien            42.06N 123.73W
12/27/2024  M1.30 Inch       Josephine          OR   Trained Spotter

            24 hours ending 3 pm PST.

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