Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 191000
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
300 AM PDT Tue Oct 19 2021

.DISCUSSION...The High Wind Watch was upgraded to a High Wind
Warning for the portion of southern oregon coast south of Cape
Blanco to Pistol River. All other headlines are on track.

Individual forecast elements have otherwise remained in-line with
the inherited forecast. Any changes to the forecast were made to
the period from 5 days out and beyond, highlighted by a broad
increase to the chance of precipitation by roughly 10%-15%.

Please see the previous discussion below for details on near term
forecast. -Miles

PREV DISCUSSION... /Issued 250 PM PDT Mon Oct 18 2021/

DISCUSSION...Quiet conditions will continue through the night. On
Tuesday an uncommonly strong October front will approach the
forecast area, and south winds will become gusty, in the Shasta
Valley first, then the coast, Rogue Valley, and areas east of the
Cascades. We`ve issued Wind Advisories for the Shasta Valley and
portions of the Rogue Valley, and portion of the East Side. We`re
confident these areas will see wind gusts to 45mph. At the coast,
there`s potential for a band of strong winds to impinge upon the
coast, especially if the GFS model solution comes to fruition with
low pressure deepening and moving towards the coast. Therefore,
we have a High Wind Watch out for portions of the coast, generally
from Cape Blanco south to Pistol River, including Gold Beach and
Port Orford. Rain reaches the coast Tuesday evening and spreads
inland. Due to the strong southerly flow, we expect the coast and
Siskiyou County to see the brunt of the precipitation. We lowered
snow levels down to around 4300 feet in the Mount Shasta area
because of expected heavy precipitation there, but we think any
snow impacts will be limited to areas above 5000 feet, based on
the early season nature of this system and expected road
temperatures. We`ll keep an eye on this for any potential winter
weather impacts to the Snowmans Summit area on Highway 89. Many
valley areas, including the Rogue Valley, will see a lot of
downsloping and drying under this wind regime, and rain totals
here will be much less than high terrain areas.

Conditions will dry out late Wednesday into Thursday morning,
though continued moderate southerly wind flow will keep
precipitation chances going in the Mount Shasta area. South winds
will continue in many areas Thursday, and it`s likely we`ll have
additional wind hazards in places like the Shasta and Rogue
Valleys. A deep low well off the coast will be weakening some
Thursday, and the trajectory of this low will likely prevent high
winds from affecting the coast Thursday, but this another area
we`ll be monitoring. The moisture with the front that arrives late
Thursday into Friday morning has IVT values around 750 near the
coast, placing it in the moderate- strong category in terms of how
much moisture is being pushed into the forecast area along the
front. We`ve increased forecast rain totals in the Brookings area
Thursday evening and overnight to account for this strong onshore
wind and high moisture content. Snow levels with this second
system will be very high, peaking around 10000 feet before
dropping Friday behind the front.

The regime will likely shift to westerly-flow type systems over
the weekend, and snow levels will begin to lower. Those areas that
see little rainfall during the first southerly flow systems will
begin to see more precipitation over the weekend and into early
next week. There`s additional potential for wind impacts too, as
some models hint at some deep low pressure development off the
coast. In short, the active, wet weather will continue into early
next week. Keene

&&

.AVIATION...Ceilings have improved to mainly VFR this
evening as weak high pressure builds in. Stratus is expected to
develop late tonight into early Tuesday morning at North Bend, and
portions of the Coquille, Umpqua, and Klamath Basins with residual
low-level moisture from recent rainfall. This includes Roseburg and
Klamath Falls, but confidence is not sufficiently high to add the
lower conditions at Medford.

Winds aloft will increase at the coast Tuesday morning, and surface
winds will increase Tuesday afternoon into the early evening, with
moderate to strong winds possible in the Shasta Valley and Rogue
Valley. Gusts in the Shasta Valley could approach 40 kts and 30 kts
in the Rogue Valley. The arrival of the front will bring
deteriorating conditions to the coast Tuesday evening, moving inland
with precipitation and mountain obscuration late Tuesday night.
-Petrucelli/DW

&&

.MARINE...Updated 245 AM PDT Tuesday, 19 October 2021...Southerly
winds increase today ahead of a very strong cold front. Gales are
expected this afternoon and tonight with seas becoming very high and
very steep and hazardous. Some storm force wind gusts are possible
beyond 5 nm from shore at peak intensity tonight. Seas are forecast
to peak at 18 to 23 ft tonight over the outer waters and 12 to 17
feet over the inner waters. After this system moves through, seas
remain chaotic Wednesday with southerly fresh swell moving
through the waters mixed with a relatively high 10 foot westerly
swell.

Another very strong cold front is expected early Thursday into
Thursday afternoon with another episode of gales likely. The stormy
pattern looks to continue this weekend into next week. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 9 PM this evening to 2 PM PDT Wednesday for
     ORZ030-031.
     High Wind Warning from 9 PM this evening to 5 AM PDT Wednesday
     for ORZ021-022.
     Wind Advisory from 5 PM this afternoon to 5 AM PDT Wednesday for
     ORZ026.

CA...Wind Advisory from 9 PM this evening to 2 PM PDT Wednesday for
     CAZ085.
     Wind Advisory from 11 AM this morning to 8 AM PDT Wednesday for
     CAZ081.

Pacific Coastal Waters...
     Small Craft Advisory from 11 AM this morning to 5 PM PDT this
     afternoon for PZZ350-356.
     Small Craft Advisory from 5 AM Wednesday to 5 AM PDT Thursday
     for PZZ350-356-370-376.
     Gale Warning from 5 PM this afternoon to 5 AM PDT Wednesday for
     PZZ350-356.
     Small Craft Advisory until 11 AM PDT this morning for
     PZZ370-376.
     Gale Warning from 11 AM this morning to 5 AM PDT Wednesday for
     PZZ370-376.

$$


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