High Wind in Oregon, October 10, 2020

Area Forecast Discussion
National Weather Service Medford OR
851 AM PDT Sat Oct 10 2020

.DISCUSSION...A cold front continues to make it's way across
southern Oregon and northern California, currently pushing
through Jackson, Josephine and eastern Douglas Counties. Rainfall
amounts with this front have been between .75"-1" along the
coast, between 0.30"-0.60" for areas in the Umpqua Basin, and
around 0.20"-0.40" for areas into Josephine County and western
Jackson County. Even areas east of the Cascades have measured a
few hundreths. Rainfall totals will increase as the day goes on,
both with the frontal passage and with showers expected behind the
front late this afternoon and evening. In addition to the
beneficial rainfall, gusty winds are occurring east of the
Cascades where a Wind Advisory remains in effect until 8 pm.
Winds will diminish this evening as the upper trough begins
pushing east of the area. Snow levels will lower to around 6000 ft
tonight and some light snow is possible along the highest peaks
overnight. For more details on the upcoming weather, see the
previous discussion below. /BR-y

&&

.AVIATION...For the 10/12Z TAFS...IFR/MVFR will prevail this morning
from the coast to the Cascades along with higher terrain obscured in
areas of rain. Rain will taper off to showers from west to east
later this morning/early this afternoon as a cold front pushes east
of the Cascades with VFR returning in most areas. Ceilings/vis may
lower to MVFR with some higher terrain obscurations east of the
Cascades as the front moves through early this afternoon, but
conditions should be mostly VFR. -Spilde

&&

.MARINE...Updated 850 AM PDT Saturday, 10 Oct 2020...Moderate and
gusty southerly winds are turning westerly beyond 10NM of the
coast this morning. Choppy, wind affected steep seas will persist
due to a mix of wind waves and fresh swell this morning, then
moderate west to northwest swell will move in this afternoon
through tonight and continue through Sunday. Therefore, seas will
remain hazardous to small craft due to a mix of wind waves and
fresh swell. Seas transition to moderate west to northwest swell
tonight into Sunday, peaking at 10-12 feet.

After that, more fronts will move through the waters, one Sunday
night and another on Tuesday. Each will bring moderate south winds,
mainly from Cape Blanco north, but also steep seas.

Offshore high pressure will build Wednesday along with a thermal
trough near the coast. This will bring a return of gusty north winds
and steep seas Wednesday into Friday. ~BTL/Spilde

&&

.PREV DISCUSSION... /Issued 514 AM PDT Sat Oct 10 2020/

DISCUSSION...A cold front has pushed in across western Oregon
early this morning associated with a strong short wave at 500
millibars digging through the northeast Pacific. Radar and
surface reports confirm rain is falling along the entire coast and
inland to the Cascades near Crater Lake but only as far inland as
Cave Junction near the CA border as of 3am.

The weather change today will bring welcome rains area-wide, but
not as much as was expected perhaps as we looked out to this date
last weekend. Also, strong southwest winds will aid in gusty
surface winds east of the Cascades where a wind advisory is in
effect until late-day. Temperatures today and tomorrow will be
10-15 degrees cooler versus what was experienced around the region
on Friday. Snow levels are expected to fall to about 6000 ft
behind the front this evening and 1 to 3 inches of accumulation
should impact the higher elevations above 6500 in the Cascades.

As the main frontal rains taper to showers overnight into early
Sunday, rain totals should be between .75 and 1.25 inches across
the coast range, Umpqua and Cascades north of highway 140, with
lighter amounts of around a quarter to half inch in the valleys of
SW Oregon and wester Siskiyou county. East side valleys should
get enough to knock the dust down a bit, while the higher terrain
there should a quarter to half inch.

Sunday the rain and wind show will be mostly over except for some
light showers affecting the Coos coast, Umpqua foothills and
adjacent Cascades. Shower chances should increase across southwest
OR a bit Sunday night through early Monday as warm frontal
overrunning trails the quickly retreating cool airmass.

Another weak short wave is showing some promise to graze the
northern CWA with some light rain Tuesday night into early
Wednesday but pops are pretty low right now. This may change a bit
as recent model runs are a little more encouraging. The main
story for next week will be rebounding temperatures. Stavish

&&

.FIRE WEATHER...Updated 800 PM PDT Friday 9 October 2020...Expect
west to southwest winds to increase beginning this afternoon and
evening for areas east of the Cascades, but also along some of the
higher ridges in the Coast range and Siskiyous. These winds will
become breezy to gusty. Relative Humidity has trended higher than
yesterday, so there are no critical fire weather concerns despite
the breezy winds.

The front will push through tonight into Saturday morning. The
moisture associated with this front looks more robust than
previously mentioned in the fire weather briefing, 80 percent or
higher chances for wetting rains for areas along and west of the
Cascades. Most of our westside fires (Slater/Devil, Obenchain,
Archie Creek and Thielsen) could see a quarter to a half an inch of
rain over a 6 hour period. This will largely limit the debris flow
potential for most areas that have these concerns, but we will
continue to monitor the situation. Meanwhile, east of the Cascades,
we are looking at a grater than 50 percent chance for wetting rains
of at least a tenth of an inch for most areas (except for Modoc
County where those chances drop to 20 to 30 percent). This system
will work to douse the ongoing fires with some much needed rain, but
it will likely not end our fire season completely.

Conditions will remain showery on Saturday with showers providing
brief periods of light to moderate rainfall--again not really
reaching our known debris-flow burn scar thresholds. Additionally,
we are not expecting thunderstorms this weekend.

Otherwise, humidities and their recoveries will jump much higher
this weekend than today. Beginning Sunday, a few lingering and light
showers may be possible along the coast, across the Coast range, in
the Umpqua Basin, and the Cascades with everywhere else starting the
drying process. Overall, this system looks to be the best chance for
rainfall in the next 14 days despite another system possibly moving
through by Tuesday and Wednesday of next week.

Should the mid-week front stay to the north as we are forecasting,
expect another thermal trough to form with more east winds that
could really dry out the mid to upper slopes and ridges,
particularly across the Cascades and for the Coast Range, including
the Slater/Devil fires. Stay tuned for updates.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 8 PM PDT this evening for ORZ030-031.

CA...Wind Advisory until 8 PM PDT this evening for CAZ085.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Monday for
     PZZ350-356-370-376.

MNF/MTS/MAS