Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
401 PM PST Monday Nov 30 2015
Short term...through Wednesday night.
A few lingering showers of rain...sleet...and snow exist across
the area this afternoon. West side roads have become just wet
where ice was observed this morning. Through this evening, a
isolated to scattered showers will occur, with just a dusting of
snow across the mountains and colder portions of the east side and
up to a few hundredths of an inch of rain elsewhere.
Tonight through early Tuesday it will be quiet. Tuesday into
Wednesday a stronger front will push into the coastal waters and
onto the coast, and then weaken as it moves inland. Rain is
expected Tuesday into Wednesday over much of the west side,
focused along the coast. Beginning Wednesday we expect winds to
pick up across some of the valleys such as the Shasta and the
rogue in and near parts of Ashland.
Thursday into Friday there is the potential of a significant and,
possibly, major storm system affecting the area. The GFS and
nam12 indicate a low in the 980 to 990mb range moving inside of
130 west longitude. This kind of scenario would yield moderate to
strong winds across much of the forecast area. In short, warning
level high winds will be possible for the Cascades and Siskiyous,
mountains of the east side and Summer Lake area, and the Shasta
Valley Thursday. Valleys like the rogue and those of the east side
would experience advisory level wind during that same time frame.
Elsewhere, some models show a strong frontal passage Thursday into
Thursday night that could yield wind impacts elsewhere on the west
side as well as snow levels falling to near 3500 feet. At this
point, we'll begin to highlight the potential of strong winds and
refine details over the coming days. Those planning to travel
Thursday or Friday should pay close attention to the forecast and
other weather product updates. Btl
Long term...Thursday through Sunday.
The next system in line, due into our region Thursday, has the
potential to have a very impact on our forecast area. While models
across the board are producing a very vigorous and sharp upper level
trough with a negative tilt, it is possible that the low could
deepen rapidly off the coast and hold the surface front offshore
longer. This scenario would lead to a potential wind storm in our
area. We have increased winds across our forecast area for Thursday,
especially the mountains and the Shasta Valley. However this
scenario will also lead to downsloping and much of the Rogue Valley
could end up being dry. Confidence is higher that we will see
precipitation Thursday night as the upper level trough moves inland.
After a brief one to two day break, both the GFS and the European model (ecmwf) bring
another front inland around Sunday. /Fb
Aviation...for the 01/00z taf cycle...the front has moved
ashore...and most of the precipitation has concluded. For the coast
Rogue Valley and east of the Cascades...VFR/MVFR ceilings and visibilities are
expected until the next system moves in bringing rain across
southern Oregon and northern California tomorrow afternoon. Winds
will be quite strong near the coast as well. Meanwhile for the
Umpqua basin...VFR ceilings and visibility will deteriorate into IFR/LIFR as
fog and areas of low stratus develop after 06z. Areas of higher
terrain will become obscured over the basin. -Schaaf
Marine...updated 845 am PST Monday 30 Nov 2015...
Small Craft Advisory winds and seas will continue for the rest of
today as a front moves through the waters. Moderate westerly swell
will peak this evening. A stronger front will move through the
waters Tuesday night and this will bring gale force winds and
hazardous seas to the area. More fronts will follow Wednesday into
Thursday. South winds may approach storm force Thursday afternoon
and evening. Heavy westerly swell will build Thursday night and
subside Friday into Friday night.
Previous discussion... /issued 853 am PST Monday Nov 30 2015/
a few reports of freezing rain and sleet this morning prompted a
341 am PST upgrade and expansion of the Special Weather Statement
for the possibility of wintry precipitation (issued yesterday
morning and expanded in the afternoon) to a Freezing Rain
Advisory. Multiple traffic accidents have been attributed to icy
roads across Douglas County already this morning. Odot Road
cameras indicate sleet and/or freezing rain on some of the area
roadways in the advisory area. For the latest Road conditions
please check out the websites or call odot for roads in Oregon or
caltrans for roads in California.
Both radar, gages, and Road cameras indicate precipitation this
morning to be spotty and light. East of the advisory area most of
the precipitation has not reached the ground. The further east one
GOES, the greater the chances that any precipitation that fall
will be snow rather than sleet or freezing rain. We'll be
monitoring temperatures, precipitation, and cameras through the
morning to determine if the advisory needs to be expanded or
extended beyond 18z/10am local time.
At this point, the forecast is on track, so no update is needed.
Pacific coastal waters...
- Small Craft Advisory until 4 am PST Thursday for pzz350-356.
- Gale Warning from 1 PM Tuesday to 4 am PST Thursday for
- Small Craft Advisory until 1 PM PST Tuesday for
- Gale Warning from 7 am Tuesday to 4 am PST Thursday for