High Wind Watch 4, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
850 PM PST Sat Feb 9 2019

.UPDATE...The main front has passed through the region with the
low pressure center moving down the coast and quite visible with
the rotation showing on the satellite images and radar. showers
are continuing around the cold core low and expiring the more
inland warnings and advisories still look on track for 06Z, with
the coast and inland in Curry County still looking on track
through 12Z. Sven

&&

.PREV DISCUSSION... /Issued 321 PM PST Sat Feb 9 2019/

SHORT TERM...A strong, cold, and wet low pressure system now
centered just off the coast from Newport, OR continues to move
south in our direction. The main cold front is unusually well
defined on radar and can be seen in observations by an abrupt wind
shift (such as the one seen at Klamath Falls around noon today).
The front now stretches from just east of Mt. Shasta City (where
they reported heavy snow last hour) to just west of Lakeview and
northeast from there into eastern Lake County. This front will
continue to move across the east side and produce a period of
moderate to heavy snow as it does so.

There is more wind than expected with the front, and blowing snow
with near blizzard conditions has been an issue today in several
locations - most notably up the highway 97 corridor as the front
passed earlier today. This wording was added to the winter storm
warnings and advisories for the appropriate locations. Folks
who've yet to see the front, such as in Lakeview and Alturas,
will want to be careful of these conditions through this evening.

On the west side, we had quite a lot of snow in the higher
elevations with the front this morning. So far, the biggest snow
total we've heard of from the west side was 11 inches on highway
227 between Tiller and Trail. We also saw a report of 10 inches on
the Mt. Ashland road. Certainly, there were higher amounts. As
usual, snow varied wildly across the area, but just about
everywhere above the immediate valley floors got at least a few
inches. In Medford we have had several periods of snow, but it's
been just a few degrees too warm to stick, SO FAR.

As the upper low nears this evening, the air mass will continue
to cool, and there are several spokes of energy and precipitation
expected to wrap around the low and across our area. It has
already snowed in a few locations along the coast, and this shows
just how cold the incoming airmass is. Once we get past sunset,
all areas will be subject to snow accumulations when any bands
move through. Given the convective nature of these bands, it's
hard to say exactly where they will go, but there is one
pronounced wave moving onshore now, and high resolution models
show this one moving across Josephine and Jackson counties over
the next several hours. This will likely produce more snow at the
lower passes, and valley locations could pick up an inch or two as
it passes. Waves of precipitation later this evening and tonight
look less organized, but they will be around through the night,
and we've kept pops high through the night. Snow tapers off later
tonight, and then we've just got nuisance snow showers Sunday.

HOWEVER, Snow redevelops from the north later Sunday and really
picks up Sunday night and Monday. The mountains will get another
hefty dose of snow (at least a foot in the Cascades) with this
system for sure. The valleys are, again, questionable, but the
potential impact from snow in the valleys for a Monday morning
commute would be high. It seems likely that cold air will remain
trapped in many west side valleys, so this may come in as snow
over much of our area Sunday night and then change to rain as snow
levels rise Monday. There is also the issue of downsloping winds
limiting or even preventing precipitation in the valleys.
Residents and travelers in southwest Oregon and northern
California will need to stay alert for the potential for more low
elevation snow Sunday night into Monday morning. -Wright

LONG TERM...Monday night through Saturday...The cold and wintry
weather pattern will continue. A strong and wet frontal system will
move into the area Monday night, then slowly move through Tuesday
and Tuesday night. Recent trends in the guidance have slowed this
front down a bit allowing for stronger mid level winds (55-65 knots)
to develop in advance of it. RDD-MFR pressure gradients peak around
8 to 9 mb, so expect some strong, gusty south winds in northern
California, especially in the Shasta Valley, and also from the
Cascades eastward before the front arrives. Of note, the ACV-OTH
gradient is also nearing 10 mb Monday evening, which is often
associated with strong winds along the coast. 925-850mb winds are
around 50 knots, which usually translates to peak gusts around 55
mph. Local guidance is not supporting high wind criteria at this
time, but we'll keep an eye on this potential.

Meanwhile, the band of moderate to heavy precipitation associated
with the front will move onshore Monday evening, pressing
southeastward across Douglas County to near or just north and west
of Medford overnight. The southwest flow aloft should allow snow
levels to rise to 2500 to 3500 feet in advance of the front, so when
the precipitation arrives, the passes north of Medford (Sexton,
Smith, Stage, Canyon Mt) should be rain (at least initially). There
is still the possibility of some cold air remaining trapped in the
more sheltered valleys, and, with heavy precipitation expected,
snow levels may be locally lower. So, we'll be watching for that.
Snow will continue to pile up above 3500 feet in the mountains,
including the Coast Ranges, Cascades and Siskiyous Tuesday and
Tuesday night, where amounts will be measured in feet. This
justifies a winter storm watch for this time period, but in the
interest of keeping our winter products simplified, we will wait
until the current event ends prior to issuing new headlines. The
frontal precipitation band will move east of the Cascades and into
northern California Tuesday night into Wednesday, where snow may
be heavy at times, especially in the Shasta region. Snow levels
will gradually lower again to the passes north of Medford and
perhaps also down to some of the valley floors west of the
Cascades. Precipitation should become more showery behind the
front, so snow amounts at the lower elevations should not be
excessive.

Models are showing a relative break in precipitation behind the
trough axis Wednesday night into Thursday, though some showers could
persist, especially in the southern Warner Mountains/Modoc
County. Another system is forecast to move into the area Thursday
night or Friday. -Spilde

.MARINE...Updated 200 PM PST Saturday 9 February 2019... A low
pressure system will slide south through the coastal waters this
evening. Another low will move down the coast and over the area
Sunday into Monday. These lows will bring a cold showery pattern
with rain and snow showers as well as a slight chance for
thunderstorms.

MARINE...Updated 200 PM PST Saturday 9 February 2019... A low
pressure system will slide south through the coastal waters this
evening. Another low will move down the coast and over the area
Sunday into Monday. These lows will bring a cold showery pattern
with rain and snow showers as well as a slight chance for
thunderstorms.

High and very steep seas will prevail tonight. Seas will subside a
bit on Sunday but still remain rather dangerous on Sunday. There
will be a mix of long period 19 to 22 second swell and a larger 11
to 13 second swell. Very steep and hazardous seas will make for
rough bar conditions through Sunday morning. Also, along beaches,
dangerous sneaker waves are possible tonight. Seas will gradually
subside Sunday afternoon into Sunday night, but remain high and
steep.

Winds and seas will increase again with the next front late Sunday
night into Monday and seas may become very steep and hazardous
again.

Model uncertainty increases beyond Monday, but the pattern is
likely to remain active with periods of high and steep seas
through the week. /KS

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 10 PM PST this evening for
     ORZ029>031.
     Winter Storm Warning until 10 PM PST this evening for
     ORZ029-030.
     Winter Storm Warning until 10 PM PST this evening above 4500
     feet in the for ORZ031.
     Beach Hazards Statement until 4 AM PST Sunday for ORZ021-022.
     Winter Weather Advisory until 4 AM PST Sunday below 1500 feet in
     the for ORZ021-022.
     Winter Storm Warning until 4 AM PST Sunday above 1500 feet in
     the for ORZ024.
     Winter Weather Advisory until 10 PM PST this evening below 1500
     feet in the for ORZ023.
     Winter Storm Warning until 10 PM PST this evening for
     ORZ027-028.
     Winter Storm Warning until 4 AM PST Sunday above 1500 feet in
     the for ORZ021-022.
     Winter Weather Advisory until 10 PM PST this evening below 2000
     feet in the for ORZ026.
     Winter Storm Warning until 10 PM PST this evening above 1500
     feet in the for ORZ023.
     Winter Weather Advisory until 10 PM PST this evening below 2000
     feet in the for ORZ025.
     Winter Storm Warning until 10 PM PST this evening above 2000
     feet in the for ORZ025.
     Winter Weather Advisory until 4 AM PST Sunday below 1500 feet in
     the for ORZ024.
     Winter Storm Warning until 10 PM PST this evening above 2000
     feet in the for ORZ026.

CA...Winter Weather Advisory until 10 PM PST this evening for CAZ085.
     Winter Storm Warning until 10 PM PST this evening above 4500
     feet in the for CAZ085.
     Winter Storm Warning until 4 AM PST Sunday above 4000 feet in
     the for CAZ080>083.
     Winter Weather Advisory until 4 AM PST Sunday below 4000 feet in
     the for CAZ080-081-083-084.

Pacific Coastal Waters...Hazardous Seas Watch from late Sunday night through Tuesday
     morning for PZZ350-356-370-376.
     Hazardous Seas Warning until noon PST Sunday for
     PZZ350-356-370-376.

SBN/SBN/SBN