844
FXUS66 KMFR 191811
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1010 AM PST Tue Feb 19 2019

.Updated aviation discussion.

.SHORT TERM...Low clouds and areas of fog are present this morning
in western valleys, especially in Douglas County, Josephine County
area northwest Jackson County. Then, another shortwave trough and
front will move towards the area today and across the area
tonight and Wednesday, bringing another round of lower elevation
snow. Snow impacts are expected for elevations of 2000 feet and
higher. However, light snow may fall down to 1500 feet elevation
at times Wednesday morning and down to lower valley floors in
light showers Wednesday evening and night. Winter weather
advisories and warnings are in effect for many areas across
southwest Oregon and northwest California. Please see the WSWMFR
for details.

By early this afternoon, expect light showers to moves down
from the north into portions of Coos and Douglas counties as the
next shortwave and front moves towards the area. This evening and
tonight, rain and snow will develop across the area as this
system moves into place with snow levels lowering to 2000 feet.
Rain and snow will continue across the area Wednesday morning
 afternoon. Expect widespread heavy snow in the western Cascade
foothills across eastern Douglas county, northwest Jackson County
from Prospect northeast and across the southern Oregon Cascades.
Moderate snow is expected to affect lower elevations by tonight
and into Wednesday for areas west of the Cascades down to 2000
feet. This includes the lower passes of Sexton Summit to Canyon
Mountain. Heaviest snow is expected tonight through Wednesday
morning. Also snow may fall down to 1500 feet at times Wednesday
morning. Daytime impacts across lower elevations near 2000 feet may
be less in the afternoon on Wednesday due to warming temperatures
during the day. However, expect continued moderate to heavy snow
in the higher elevations, especially over the Cascades.

Late Wednesday afternoon through Wednesday night, expect a
widespread showery pattern areas of moderate showers. Snow levels
will lower to 1000 to 1500 feet during the evening as light to
locally moderate showers move across the area. This may bring
light snow accumulations to lower valley floors west of the
Cascades, especially in Jackson and Josephine counties. Generally
amounts are expected to be between a trace to less than an inch
for these lower valley floors. However, due to upslope effects in
moist northwest flow, may see 1 to 2 inches of snow in the
Ashland area Wednesday evening and night.


&&

.AVIATION...For the 19/18Z TAFs..Areas of MVFR cigs/vsbys with local
IFR cigs/vsbys in low clouds and rain will develop over the coastal
waters today, spreading onshore this afternoon and inland to the
Cascades this evening with higher terrain becoming obscured. Snow
levels will be 1500 to 2500 feet. The lower conditions will spread
east of the Cascades tonight, where IFR will be more widespread
since precipitation will be all snow. Some improvement  Keene

&&

.MARINE...Updated 830 AM PST Tuesday 19 February 2019...Winds and
seas will be relatively low through the morning, but another front
will move into the area late tonight into Wednesday. This will bring
an area of small craft advisory winds followed by very steep seas
for most areas. The seas will be a combination of wind driven short
period waves, fresh northwest swell, and longer period northwest
swell. Winds and seas will subside Thursday into Friday as high
pressure moves through. Then another front will move in this
weekend, bringing another round of steep to very steep seas that
will last through Sunday. Details on timing and strength of this
system are still somewhat uncertain. Keene



&&

.PREV DISCUSSION... /Issued 404 AM PST Tue Feb 19 2019/

DISCUSSION...Significant changes have been made to the upcoming
storm this evening as models have trended wetter and a little bit
stronger.

However, current satellite data are showing areas of clouds north
of the Umpqua divide, at the coast, and some higher clouds east
of the Cascades. The clouds at the coast are moving southward
toward Brookings, and should keep temperatures above freezing, and
mitigate any frost. That being said, it wouldn`t surprise me to
see some frost in some coastal areas.

Overall today will be a rather benign day, at least through
Sundown. Mostly sunny skies are expected across most of southern
Oregon and northern California, however clouds will move in from
the northwest this afternoon, and precipitation chances will
increase from the coast and Umpqua valley south and eastward. As
previously mentioned this system has trended a little bit wetter--
and have increased the precipitation amounts. As a result, the
snowfall amounts have also increased, especially across the
southern Oregon Cascades, and portions of the Coastal Mountain
Ranges. Although snow can begin as early as 6-7 PM PST, the
heaviest snow will fall between 10 PM PST tonight and 4 PM PST
Wednesday.

Snow levels have remained quite constant, with small fluctuations
between 2000 to 2500 feet MSL during the daytime hours and falling
to 1500 and 2000 feet during the night. As a result, have gone
ahead and replaced the Winter Weather Advisory across the
southern Oregon Cascades with a Winter Storm Warning, and have
expanded the advisory to include portions of the Klamath Basin
(Highway 97, and portions of Highway 140 east of Bly and
Lakeview) as well as for portions of western Siskiyou County. The
highest impacts will be for the highest terrain of the Cascades,
namely Crater and Diamond Lakes. Please see the WSWMFR for more
details, including snowfall amounts. It is worth noting, although
Siskiyou Summit is not in an advisory, they could still see 6 to 8
inches of snow.

Conditions will turn showery yet again after the front passes
through around 4 PM Wednesday, but the front will also lower snow
levels. Since snow levels are already indicating low pass snow
ahead of the front, we could see yet another round of valley snow
Wednesday night into Thursday depending on whether the
precipitation ends before the snow levels actually drop. Overall,
the valley snow is not expected to be impactful with only a
dusting possible. It would be similar to what occurred last
weekend.

A quick break is expected on Thursday, with clearing skies. This
will allow temperatures to get cold, yet again. And another set of
Freeze Warnings may be needed for the coast. For now, am
forecasting temperatures in the low to mid 30s at the coast. These
temperatures will be mighty cold elsewhere, especially for areas
that received snowfall.

Then, another system is poised to arrive on Friday evening. Snow
levels will not have had a chance to rebound toward normal, so
another shot of low pass snow is looking more and more likely.
Behind that front, temperatures and snow levels will fall yet
again, but it is still unclear whether or not we could see another
skiff of valley snow this weekend. Thus, it`s important to stay
tuned to the forecast. -Schaaf

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 7 PM this evening to 10 PM PST
     Wednesday for ORZ029>031.
     Hazardous Seas Warning from 4 AM Wednesday to 10 AM PST Thursday
     for ORZ021.
     Winter Weather Advisory from 7 PM this evening to 10 PM PST
     Wednesday above 2000 feet in the for ORZ023-024-026.
     Winter Storm Warning from 7 PM this evening to 10 PM PST
     Wednesday for ORZ025-027-028.
     Winter Storm Warning from 7 PM this evening to 10 PM PST
     Wednesday above 3000 feet in the for ORZ026.
     Winter Weather Advisory from 7 PM this evening to 10 PM PST
     Wednesday for ORZ028.

CA...Winter Weather Advisory from 7 PM this evening to 10 PM PST
     Wednesday above 2000 feet in the for CAZ080-081.

Pacific Coastal Waters...Hazardous Seas Warning from 4 AM Wednesday
to 10 AM PST Thursday      for PZZ350-356-370-376.      Small Craft
Advisory from 10 PM this evening to 4 AM PST      Wednesday for
PZZ350-370-376.

$$

CC

NWS MFR Office Area Forecast Discussion