Area Forecast Discussion
Issued by NWS Medford, OR
FXUS66 KMFR 091724
Area Forecast Discussion
National Weather Service Medford OR
924 AM PST Fri Dec 9 2016
Warmed up temperatures just a tad for the west side valleys today
as we`re already sitting in the mid 40`s and we were on the cold
side of guidance. The focus for today will be on snow levels and
trying to hone in on storm total snow for Friday night and
Saturday morning along the Cascades and east side.
The current pattern suggests a good Cascade snow event with strong
westerly flow aloft onto the Cascade range. For more information
on this, read the previous discussion below. There is still some
uncertainty with snow levels near Mount Shasta and will review
that once new data becomes in. Not expecting any major
accumulation there, but periods of snow are possible this evening.
.AVIATION...09/12Z TAF CYCLE...Precipitation and mountain
obscurations will continue through the TAF period. Conditions are
mainly VFR and MVFR across the region, but visibilities and ceilings
should deteriorate through the morning. Conditions will improve this
afternoon as clouds and cigs lift, but lowered flight conditions are
expected again late afternoon through tonight. -BPN
.MARINE...Updated 230 aM PST Friday 9 December 2016...Winds will
ramp up again today as another low pressure system moves by to our
north, but winds are still expected to remain below gales. The
combination of continued wind wave and increasing fresh swell will
keep seas elevated through Friday, especially over the waters north
of Cape Blanco where wind waves will be higher.
After reviewing the latest model runs and checking the buoy
observations offshore, it appears that the swell train expected to
arrive Saturday will not quite reach hazardous seas conditions.
However, as the first p[art of this wave train arrives late today,
it is expected to combine with residual wind waves to produce
steep to very steep seas this afternoon and this evening. Once the
wind waves subside, swell will keep small craft advisory
conditions in place through Saturday night.
Relatively calmer weather is expected for Sunday through early next
week. The storm track may become active again later next week.
.PREV DISCUSSION... /Issued 446 AM PST Fri Dec 9 2016/
DISCUSSION...The main focus of tonight`s forecast will be the
system that moves in this afternoon through Saturday morning. The
warm front that moved through most of the area is currently just
south of Bend OR. The front stalls over the region as the next
round of heavy precipitation moves in ton the nose of a 130 kt
jet. Current IVT models still are indicating a strong atmospheric
river event with this. With westerly 700 mb winds increasing to 50
kt overnight much of the moisture is expected to be squeezed out
over the Cascades with the east side being somewhat shadowed.
These winds decrease towards morning allowing more precip to spill
over to the east side as snow levels continue to drop to below
4000 feet by sunrise. A dry slot moves into the region at 700 mb
around 18Z, cutting off moist of the moisture, and the system
splits with the IVT shifting south turning the firehose over the
Sierras. Another, weaker system moves in from the northwest
Saturday evening. This system will not be nearly as wet as this
tonight`s system, but with the northwest flow snow levels will be
lower, bringing snow down to the west side ridges, and another
dose of healthy snow pack to the mountains. Sven
OR...Winter Weather Advisory from 10 PM this evening to 10 AM PST
Saturday for ORZ029>031.
Winter Weather Advisory from 10 PM this evening to 10 AM PST
Saturday ABOVE 4000 FEET for for ORZ027-028.
Winter Storm Warning from 10 PM this evening to 10 AM PST
Saturday ABOVE 5000 FEET for for ORZ027-028.
CA...Winter Weather Advisory from 10 PM this evening to 10 AM PST
Saturday for CAZ085.
Pacific Coastal Waters...Small Craft Advisory from 10 PM this evening to 4 AM PST Sunday
Hazardous Seas Warning until 10 PM PST this evening for