Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Medford or
429 am PST Tue Dec 6 2016

Discussion...a potent short wave trough is moving into southern
Oregon tonight. The hrrr short term model is bringing another
burst of snow showers into Jackson County around sunrise. Snow had
been falling down to the valley floor overnight but has not
accumulated at the Medford Airport. However, with temperature
hovering near freezing, the next round of snow showers could lead
to temporary accumulation on the roadway around this morning
travel. By mid morning expect snow showers to decrease in
coverage for areas west of the Cascades. Snow level on the west
side are expected to rise to around 1900 feet in Roseburg to 2300
feet in Medford...and 2600 feet in the Yreka area. Snow is
expected at the valley floor for the east side all day today.

By this evening the short wave trough is expected to push east
into the Warners with only the Goose Lake area of Lakeview and
Alturas seeing wrapped around and upslope snow showers into the
Warner mtns. With the cold air in place, clearing tonight will
lead to a very cold night. Coos County could even see freezing
temperature tonight, especially slightly inland from the
immediate coast such as Coquille and Myrtle Point, with frost
potential at the immediate coast. Temperatures are not expected to
be as cold in Curry County and only frost is expected. Below
freezing temperatures are expected in the Umpqua basin as well as
further south into the Rogue Valley.

We have issued a freeze warning for Coos County and the Umpqua
basin as this is the first major freeze of the fall season. To the
east, single digit temperatures will be widespread from the
Klamath basin into the Goose Lake basin and subzero in Northern
Lake County.

Models are not deviating from this trend and today's forecast
flows along the previous trend and our emphasis was more toward
making sure snow levels are representative of the temperature
forecasts at various time of day.

On Wednesday another low pressure will bring an occluded front
toward northern California coast. For the first half of the day,
the weather will be quiet but the warm front part of this storm
will spread warm air and precipitation into our forecast area. The
forecast going into Wednesday night will be tricky as warm air
overrunning cold air will lead to snow and areas of freezing rain.
The sequence of event is such that we can see freezing rain at the
high elevation of SW Oregon and western Siskiyou County Wednesday
evening, the potential for freezing rain spreading east into the
Klamath basin overnight. Thursday could present a big challenge
for the east side with freezing rain potential most of the day and
spreading into the Lakeview/Alturas area by Thursday afternoon and
evening. Confidence is only moderate at this time as a lot will
depend on how deep the cold pool is. The day shift will need to
assess on this potential and we may need to issue another
statement on this development.

After Thursday, temperatures are expected to climb into the
seasonal norms but we will not be completely dry as a series of
fronts will move across the area..


Aviation...06/12z taf cycle...widespread MVFR ceilings are expected
this morning into early this afternoon with terrain obscured. Snow
could lower ceilings and visibilities down to IFR at times this
morning at kmfr and klmt. Local IFR may also occur at krbg. Ceilings
will improve to VFR all sites this afternoon and evening, but areas
of IFR low clouds and fog/freezing fog are likely to develop in many
of the valleys overnight into Wednesday morning, including at krbg
and kmfr. Klmt may also have some freezing fog patches around
sunrise Wednesday. -Spilde


Marine...updated 300 am PST Tuesday 6 December 2016...steep
seas will persist through late this afternoon. Showers this morning
will gradually diminish this afternoon. High pressure will briefly
build into the area tonight into Wednesday morning, then east to
southeast winds will begin to increase Wednesday afternoon. A strong
front will move through the area Wednesday evening through Thursday.
Model boundary layer winds during this time are in excess of 40kt,
so confidence is high enough to issue a gale watch. Steep to very
steep seas will also accompany this front. Weaker systems will
then move through Thursday into the weekend. Spilde


Mfr watches/warnings/advisories...
or...Winter Weather Advisory until 10 am PST this morning for
Frost advisory from midnight tonight to 8 am PST Wednesday for
Winter Weather Advisory until 10 am PST this morning above 1500
feet for for orz021-023-024.
Winter Storm Warning until 10 am PST this morning above 2000
feet for for orz021-023-024.
Winter Weather Advisory until 10 am PST this morning above 2000
feet for for orz025.
Winter Storm Warning until 10 am PST this morning above 2000
feet for for orz025.
Winter Weather Advisory until 10 am PST this morning for
Freeze warning from 7 PM this evening to 9 am PST Wednesday for
Freeze warning from 1 am to 7 am PST Wednesday for orz021.
Winter Storm Warning until 10 am PST this morning above 2000
feet for for orz026.
Winter Weather Advisory until 10 am PST this morning above 1500
feet for for orz026.

California...Winter Weather Advisory until 10 am PST this morning above 1500
feet for for caz080-081-083.

Pacific coastal waters...gale watch from late Wednesday night through Thursday morning
for pzz350-356.
Small Craft Advisory for hazardous seas until 4 PM PST this
afternoon for pzz350-356-370-376.
Gale watch from Wednesday afternoon through Thursday morning for



National Weather Service Glossary of Abbreviations