312
FXUS66 KMFR 230554
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
954 PM PST Fri Nov 22 2024

...Updated Aviation Section...


.AVIATION (06Z TAFs)...

Shower activity will continue through most of this cycle before
relief tomorrow afternoon, but the coast may not see as much
relief. Also, there could be isolated thunderstorms along and
near the coast tomorrow afternoon that could impact North Bend.
There will be isolated shower activity inland tomorrow afternoon,
and Klamath could see snow. At this time, not expecting much
accumulation so no Airport Weather Warning at this time, but may
need to reconsider this in subsequent TAFs. Lastly, inland sites
may see a majority of this cycle in MVFR/IFR.

-Guerrero

&&

.PREV DISCUSSION... /Issued 858 PM PST Fri Nov 22 2024/

DISCUSSION...Areal Flood Warnings have been downgraded to Flood
Advisories for the area including Curry, Josephine, Coos and
Siskiyou Counties. Have had no reports of flooding throughout this
event despite enormous amounts of rainfall including appreciable
rain-on-snow. The Coquille at Coquille is forecast to get pretty
close to the Flood Stage of 21 ft and after collaboration with the
River Forecast Center in Portland this evening we opted for a
Flood Watch for 10pm tonight through 4pm Saturday. The official
forecast leaves the stage just shy of reaching flood, but this
scenario warrants a watch as the stage rises to near flood. Folks
in Coos on the lower Coquille should be prepared for the elevated
river level.

Deeper moisture associated with the recent atmospheric river has
moved east and satellite shows the colder air within the offshore
upper low starting to push inland and some convective activity
showing up with lightning detected. Thunderstorms will be
possible (generally 10-20 percent chance) today and tonight over
the coastal waters and coastal inland areas.

We`re not quite done with snowfall for the higher terrain and this
batch of 3 to 8 inches or so with incoming snow showers tonight
through Saturday will turn appreciably colder and fluffier, at
least above 4000 feet, as temperatures cool down considerably
aloft. Have opted to keep the area free of winter headlines with
this as the daytime totals Saturday aren`t expected to produce a
significant impact over the higher mountains. Stavish

AVIATION...23/00Z TAFS...Overall, expect a mix of VFR/MVFR
conditions with widespread terrain obscurations tonight through
Saturday. Low pressure offshore will continue to send waves of
precipitation inland. Convective elements could cause isolated
lightning over the coastal waters and near the beaches, but
confidence wasn`t high enough to include at North Bend TAF at this
time. Behind a cold front, snow levels will drop tonight into
Saturday morning and some light snow will occur over the mountains
(mostly above 4000 feet) and over the east side. This could bring
local visibility and ceiling reductions to IFR. Right now, it
doesn`t appear that snowfall will be consistent enough to cause much
accumulation at Klamath Falls Saturday morning, and temperatures are
also expected to be near or just above freezing. As such, the snow
will mostly melt as it falls. Expect mostly VFR/MVFR and terrain
obscurations to continue in Saturday afternoon. -Spilde

PREV DISCUSSION... /Issued 410 PM PST Fri Nov 22 2024/
DISCUSSION...A cold front has passed through the forecast area
earlier this morning with an upper level low still situated within
130W. There are still plenty of showers on the radar scope this
afternoon and we will continue to see those into the late evening
hours with a cool unstable airmass overhead. There is also a low
risk of thunderstorms Saturday evening into Sunday along the
coast. In addition, flood risk still exists around the region as
rain continues to accumulate, although the bulk of the rain has
already fallen from this atmospheric river event over our forecast
area. We`ll still keep the areal flood warning our for urban and
small streams within Curry, Josephine and Siskiyou Counties as
another 1 to 2 inches is expected to fall within Curry County over
the next 24 hours.

A broad upper level low with a few embedded shortwaves will
continue to impact our weather into Saturday and Sunday with
precipitation continuing to accumulate. The flow from this low
will also lower snow levels a bit Saturday into Sunday and drop
them down 4000 feet on both days. Snow will continue to accumulate
during this time, although the amounts should be non impactful
with 3 to 6 inches of additional snow fall in the mountains over
48 hours. Sunday is interesting as it appears an occluded front or
another cold front will set up along our coastline, although the
winds and precipitation rates shouldn`t be as intense as what
happened earlier this week.

Even with all this new precipitation falling, we consider the
potential flooding on the rivers as rather low on mainstem rivers.
Some rivers have already crested like The Coquille River at
Powers, and this point is anticipated to continue to lower into
the week. The Coquille River at Coquille is tricky and is expected
to crest just below minor flood stage, although should reach
action stage later tonight into the morning hours.

Eventually, this upper level low that has been bringing us active
weather through the week will swing through the forecast area
late Monday and Tuesday. With the airmass remaining cool and
unstable, we`re in store for more showers early Monday into
Tuesday. The NBM is also showing some lower probabilities for
thunderstorms along the coast as the center of this low moves
overhead.

Once the low departs early next week, conditions trend notably
drier around Wednesday and Thursday as a broad area of high
pressure likely sets up across southern Oregon and northern
California. There wasn`t anything notable or extreme popping up
in the ensembles. We`ll have to start to watch out for fog or
freezing fog next week as all this rain and clearing skies should
lead to fog. -Smith

AVIATION...23/00Z TAFS...Overall, expect a mix of VFR/MVFR
conditions with widespread terrain obscurations tonight through
Saturday. Low pressure offshore will continue to send waves of
precipitation inland. Convective elements could cause isolated
lightning over the coastal waters and near the beaches, but
confidence wasn`t high enough to include at North Bend TAF at this
time. Behind a cold front, snow levels will drop tonight into
Saturday morning and some light snow will occur over the mountains
(mostly above 4000 feet) and over the east side. This could bring
local visibility and ceiling reductions to IFR. Right now, it
doesn`t appear that snowfall will be consistent enough to cause much
accumulation at Klamath Falls Saturday morning, and temperatures are
also expected to be near or just above freezing. As such, the snow
will mostly melt as it falls. Expect mostly VFR/MVFR and terrain
obscurations to continue in Saturday afternoon. -Spilde

MARINE...200 PM PST Friday, November 22, 2024...Buoy data has
suggested winds will continue to ease into the afternoon and evening
hours. However,  seas will remain high and very steep into Saturday
and a hazardous seas warning still remains in effect. Another low is
anticipated to spin up along coast with strong south winds
developing around Sunday afternoon. The probability of gales is
about 50% in the southern waters.
-Smith

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.

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

Gale Watch from Saturday evening through Sunday evening for
     PZZ350-356-370-376.

&&

$$