NWS Medford, OR wrote its last area forecast discussion before the first event at Feb 7, 9:25 AM PST, 1 hour 36 minutes earlier.
Area forecast discussion, Feb 7, 9:25 AM PST, 1 hour 36 minutes before
Area Forecast Discussion...CORRECTED
National Weather Service Medford OR
925 AM PST Tue Feb 7 2017
.UPDATE...
The forecast has been updated for the issuance of flood watches
for the Scott River near Fort Jones, the Klamath River near Seiad
Valley, and the Sprague River near Beatty between Thursday
afternoon and Saturday afternoon. Also, the Pit River near Canby
is expected to rise from action stage this morning to flood stage
this afternoon, with a forecast peak of 9.3 feet early Wednesday
afternoon. This could cause significant flooding in portions of
southwestern Modoc and Lassen Counties. Additionally, for rivers
such as the Klamath, since flooding has not occured in quite some
time, the river is likely to contain significant debris as it
floods. BTL
&&
.DISCUSSION...
A strong frontal system pushed across the forecast area overnight
and is winding down this morning. Snow totals have been
significant, with 10 inches reported in the town of Summer Lake
and even a slushy dusting at Camas Mountain on Highway 42,
Jacksonville Hill, Sexton Summit, and Hayes Hill. Rainfall
amounts of 1-2 inches occured at the coast and in far Western and
Southern Siskiyou Counties. One report of 2.31" was received at
4kft 6 miles west of Black Butte in Siskiyou County in just 11
hours through 8am PST this morning.
Light to moderate showers will affect the area through early this
evening with snow levels in the 5kft to 7kft range. This will give
some waterways a chance to recede a bit before the next significant
storm system, but only in some areas. Snow melt across the East
Side and Northern California will cause rivers to stay high until
this next round of rain comes in, and then they'll rise higher.
Snow levels with this next storm system appear as if they'll be up
around 8000 feet over the Cascades for the bulk of it, so flood
concerns are very real Wednesday night through Friday. With the
already saturated ground and the combined effects of snow melt
and heavy rainfall, rock, wet snow, and mud slides will also be
possible in steep areas. We'll be updating wind headlines and
flood products through the day to prepare for this next warm storm
system. BTL
&&
.AVIATION...07/18Z TAF Cycle...Overall, TAF confidence is low due
to the differences in model solutions and the somewhat complex
pattern behind the departing warm front. A mix of MVFR/IFR
conditions with rain showers will continue west of the Cascades
this morning, with a gradual clearing to mostly VFR this
afternoon. VFR is expected east of the Cascades, except for areas
of MVFR in areas of snow and rain lifting to the north through
late this morning. Tonight, MVFR/IFR conditions are likely to
return to many of the area valleys. -BPN
&&
.MARINE...Updated 830 AM PST Tuesday 7 February 2017...Moderate
south swell and generally light winds are expected this morning,
but conditions will begin to deteriorate tonight as a strong
frontal system approaches the area. The front will reach the
coastal waters by Wednesday afternoon, then stall briefly before
moving onshore Thursday morning. Gale force winds and very steep
and hazardous seas are possible with this system, and a Gale Watch
is in effect. Conditions will gradually improve through Friday,
with generally unsettled conditions remaining through the
weekend. -BPN
&&
.PREV DISCUSSION... /Issued 413 AM PST Tue Feb 7 2017/
DISCUSSION...A warm front is bringing moderate to heavy snow to much
of Southern Oregon high terrain and areas east of the Cascades
this morning. The warm front is not making much northward progress
this morning, so snow levels will make it up to about 5000 to
6000 feet this morning and not much higher before precipitation
begins to diminish. Therefore, have adjusted snow levels some for
areas like Siskiyou Summit, and about 10 inches of snow are
expected there before a changeover to rain later this morning.
East of the Cascades, the rain/snow line is around Klamath Falls
with areas to the north like Spring Creek along Highway 97 still
seeing snowfall. Further south, over Northern California, current
snow levels are about 5000 feet and will continue to rise this
morning.
Later this morning as precipitation diminishes, winds will increase,
especially east of the Cascades near Summer Lake where we have issued
a High Wind Warning at NPWMFR. Blowing and drifting snow can be
expected in many areas, especially in the higher terrain and in
northern Lake and Klamath Counties.
Attention then turns to a tropically-originating atmospheric
river (AR) affecting the coastline late Wednesday into Thursday.
GEFS and GFS AR tools indicate good agreement on the general idea
of high Integrated Vapor Transport (IVT) values impinging upon the
coast and points inland Wednesday night and Thursday, with
moisture values near the top for this time of year. No doubt there
is still some uncertainty in exactly where the heaviest rain will
fall, and this AR does not linger for a very long time, but there
is enough confidence in a period of heavy rain that could cause
some flooding that an Areal Flood Watch has been issued for parts
of the coast, Illinois Valley, and Central and Western Siskiyou
County. Reports of unstable soils in some of the wildfire burn
scars in Western Siskiyou County may prompt Flash Flood Watches
for that area as we examine more data today.
Winds will increase as well with this front late Wednesday into
Thursday, and High Wind Watches have been issued for the coast,
Shasta Valley and portions of the East Side. All guidance points
toward some impressively windy conditions.
Additional precipitation is expected Friday with a weaker system
before upper ridging and drier conditions arrive for the weekend.
Please see the previous long-term discussion below.
Long Term...Friday through Monday...By Friday, the atmospheric
river from the short term will have sagged well south of us.
However, the main upper low and its attendant secondary cold front
will move through Friday and bring another round of moderate
precipitation. Snow levels will be much lower than preceding days,
dropping to 4500 feet Friday morning and then 3500 feet by day's
end. This may lead to some travel issues from snow in the mountain
passes and portions of the east side. An end to our latest spate
of stormy weather is in sight by next weekend, however, as an
upper ridge builds in over the PacNW. It looks like a dry and
potentially mild weekend coming up depending on the amount of fog
and low cloud we get in the valleys. -Wright
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 10 PM PST this evening for ORZ030-031.
Winter Weather Advisory until 10 AM PST this morning for
ORZ029>031.
Winter Storm Warning until 10 AM PST this morning for
ORZ029>031.
High Wind Watch from Wednesday afternoon through Thursday
afternoon for ORZ030-031.
Winter Weather Advisory until 10 AM PST this morning for
ORZ027-028.
Flood Watch from late tonight through Thursday afternoon for
ORZ021-022-024.
High Wind Watch from Wednesday afternoon through Thursday
afternoon for ORZ021-022.
Winter Weather Advisory until 10 AM PST this morning ABOVE 2000
FEET for for ORZ023>026.
Winter Storm Warning until 10 AM PST this morning for
ORZ027-028.
CA...Flood Watch from late tonight through Thursday afternoon for
CAZ080-082-083.
High Wind Watch from Wednesday afternoon through Thursday
afternoon for CAZ081.
Pacific Coastal Waters...
- Gale Watch from Wednesday afternoon through Thursday morning
for PZZ350-356-370-376.
BTL/NSK/JRS/BPN