Frost and Freeze in Oregon, September 5, 2016

Area Forecast Discussion
National Weather Service Medford OR
852 PM PDT SUN SEP 4 2016

.SHORT TERM...Behind an exiting trough, clear skies and a cold
night are expected for areas east of the Cascades tonight and
Monday morning. Model guidance continues to show temperatures
lowering into the lower 30s and locally into the upper 20s for
eastern valleys. A frost advisory and freeze warning remain in
effect for valleys east of the Cascades. See the NPWMFR for
details. For western portions of the area, expect low clouds to
develop tonight and Monday morning along the coast from Cape
Blanco northward and into portions of the Umpqua Valley. Other
areas in Southwest Oregon and Siskiyou County are expected to stay
mostly clear with light winds and cool temperatures tonight.

On Monday, expect continued dry conditions and mild temperatures.
High temperatures Monday afternoon will warm a few degrees
compared to today.

Monday night into Tuesday, models continue to show a front moving
into the Northern and Central Oregon coast. As this front pushes
inland expect it to bring some areas of light showers into
Southern Oregon, with the best chance for light rain in Coos,
Douglas and into the South Central Cascades from near Crater Lake
north. With this pattern, breezy to gusty winds northwest winds
are likely late Tuesday afternoon and Tuesday evening east of the
Cascades.

&&

.AVIATION...05/00Z TAF CYCLE...Areas of VFR/MVFR cigs will likely
return to the coast and the Umpqua basin tonight. Smoke from the Gap
Fire will bring IFR to MVFR visibilities to western Siskiyou county,
especially within the lower Klamath and Scott valleys. All other
areas should remain VFR through the TAF period. -BPN

&&

.MARINE...Updated 1000 AM PDT Sunday 4 September 2016...A thermal
trough will continue to produce gusty north winds and choppy seas.
Small Craft Advisory conditions south of Cape Blanco will persist
through Monday night. A front will move onshore Tuesday. Offshore
high pressure and the coastal thermal trough will both rebuild
Wednesday into Thursday. Sven

&&

.PREV DISCUSSION... /Issued 227 PM PDT SUN SEP 4 2016/

DISCUSSION...Cool conditions continue today with high
temperatures about 10 degrees below normal. For perspective, this
air mass is in the coldest 10 percent for this time of year since
1979. Tonight, as skies clear, winds calm, and the air mass dries
some, frost and freeze conditions are likely. Guidance generally
suggests temperatures tonight will be 2 to 5 degrees colder than
last night. A freeze warning and frost advisory have been issued
to account for temperatures in the 20s and 30s in portions of
Northern California and areas east of the Cascades. This product
can be found at NPWMFR.

Tomorrow will bring warmer temperatures behind the departing upper
trough, but another impulse will move in from the northwest early
Tuesday. This will bring temperatures back down on Tuesday and
will bring a chance of rain to mostly northern Douglas, Klamath,
and Lake Counties. With continued moderate onshore flow, breezy
afternoon northwest winds are expected the next several days, and
morning clouds are expected at least in coastal valleys and the
Umpqua Basin. Since the marine inversion is still mixed out, it's
more difficult to pin down how much cloud cover there will be at
the coast overnight and into the morning, but we have confidence
that Monday afternoon should be partly to mostly sunny.

After the next trough moves through on Tuesday, significant
warming and drying is expected through the weekend at least.
Recent model runs have trended warmer for this week. By the
weekend temperatures should be 5 to 10 degrees above normal.
Looking further out, the CFSv2 and Climate Prediction Center 3-
and 4-week outlooks suggest warm conditions will continue for much
of September.

FIRE WEATHER...Updated 200 PM PDT Sunday 4 September 2016...
Another cold night, especially in portions of the east side where
areas of frost are expected and even some areas that will see below
freezing temperatures. Good humidity recoveries will accompany these
cooler temperatures. Monday will be a bit drier than today.

A weak front comes ashore late monday night and moves through the
north half of the forecast area. This front will bring little in the
way of rain, but it will be followed by a strong marine push that
looks to spill over the Siskiyous into Northern California by
Wednesday morning.

An upper level ridge then begins to build after this and the region
will see warming and drying into the weekend with temperatures
rising above 100 in the valleys of western Siskiyou county by
Saturday. Sven

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory from 3 AM to 8 AM PDT Monday for ORZ029>031.
     Freeze Warning from 3 AM to 8 AM PDT Monday for ORZ029>031.

CA...Frost Advisory from 3 AM to 8 AM PDT Monday for
     CAZ080-082-084-085.
     Freeze Warning from 3 AM to 8 AM PDT Monday for CAZ082-084-085.

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Tuesday for PZZ356-376.
     Small Craft Advisory for hazardous seas until 5 AM PDT Tuesday
     for PZZ356-376.

CC