[willamette-fcst] Forecast - Thursday, January 10th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Jan 10 09:00:44 PST 2008
Daily Smoke Management Forecast
Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.
Thursday, January 10th, 2008 at 9:00am.
Agricultural burning is allowed. Suggested burn times are from now until 3:00pm.
Straw stack burning is allowed from now until 3:00pm.
A strong warm front brought rainy and windy conditions to
Western Oregon overnight. Strong south winds hit the
northern and central Oregon Coast again around midnight last
night. Some peak gusts along the north coast were:
Cape Mears (1421 Feet near Tillamook): 71 mph
CLatsop Spit: 53 mph
Roacaway Beach: 46 mph
Winds were generally strongest along the central coast.
Here are a few of the peak gusts recorded from that
Sea Lion Caves: 65 mph
Newport (US 101 Bridge): 60 mph
Florence (Siuslaw Jetty): 58 mph
Lincoln City: 54 mph
South winds gusting to near 30 mph brought warmer air into
the Willamette Valley overnight, with temperatures climbing
from the low 40s around midnight into the upper 40s by
mid-morning. Surface observations and satellite imagery
indicated that the cold front was moving onshore at
mid-morning and should sweep eastward to near the Cascades
by midday. The air behind the cold front is not that cold,
so continued breezy south winds should lift valley
temperatures into the low 50s today with the steady rain
becoming showery in nature.
The freezing level over Northwestern Oregon took a huge jump
overnight from near 3000 feet to nearly 6000 feet. Snow
turned to rain over the Northern Cascade passes with pass
temperatures in the low to mid 30s this morning. The snow
level ranges from about 5000 over Northern Oregon to nearly
7000 feet over Southern Oregon this morning. It will
retreat back to about 3500 feet north and 4500 feet south,
in the wake of the cold front this afternoon. The cooler
air aloft and strong onshore flow will combine to bring
locally heavy snow back to the mountain passes this
afternoon through tonight.
The National Weather Service has issued a heavy snow warning
for the Northern Oregon Cascades from now until until 4 am
Friday. The passes could pick up 1-2 feet of of snow by
Friday morning. The valley will see very mild temperatures
along with breezy conditions and rain showers. Ventilation
conditions are excellent for burning.
S 15-25 G30 this morning, SSW 10-20 G25 this afternoon.
SW 30 this morning, SW 30 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 3000 feet. Ventilation index 90.
Salem\'s high temperature today will be near 52.
Minimum relative humidity will be near 74%.
Salem sunset tonight: 4:51pm; sunrise tomorrow: 7:49am.
Showers will taper off Friday as a transitory ridge of high
pressure moves over the region. The next weather system is
expected to be much weaker, as it moves across Oregon
Saturday with only a little rain and mountain snow likely.
Temperatures will remain above normal with snow levels
staying in the 4-5000 foot range. Ventilation conditions
are likely to stay good through Saturday and then
deteriorate Sunday, as a stronger ridge builds over the
The long-range computer models are coming in-line with their
forecast of the next system moving down the British Columbia
Coastline and into the region Monday afternoon. The real
punch of this system is forecast to stay just north of
Oregon, but it does appear to be strong enough to bring some
rain and mountain snow back to the region. More
significantly, it signals what now looks to be a significant
change in the jet stream pattern...
The long-range models have indication the likelihood of an
amplification of the jet stream pattern over North America,
but have been flip-flopping around on the forecast positions
of the large upper-level ridges and troughs expected to
develop. They are now moving towards a consensus solution
of an amplified ridge offshore, in the eastern Pacific
Ocean, which will open the door for arctic air to pour into
the Northern US.
Some modified cold and dry air is forecast to begin seeping
into the Pacific Northwest Tuesday and Wednesday, as the
upper-level flow switches from westerly to northerly. That
will bring an abrupt end to the wet and mild conditions west
of the Cascades. Temperatures should progressively cool to
below normal by Wednesday, as more cold and dry air pours
into the Columbia Basin, from Canada. Offshore flow is
likely to develop with the cold and dry air eventually
getting funneled through the Columbia Gorge and into the
This is a weather pattern not typically seen this late in
the winter season, except during a La Nina episode like we
are currently experiencing in the tropical Pacific Ocean.
That could be why the computer models have been havning a
tough time forecasting this major change in the weather. My
confidence in the forecast beyond Monday is still below
average, but a transition to colder and drier weather
appears likely. It is likely that much of the region will
experience their coldest temperatures so far this winter by
late next week...especially east of the Cascades. There is
also some indication that this may be a prolonged period of
cold weather, but my confidence in the computer models that
far out is very low.
Tomorrow (11 Jan): Decreasing Showers. Snow Level 4000 feet. 42/49
Sat (12 Jan): Light Rain Likely. Snow Level 4500 feet. 37/48
Sun (13 Jan): Partly Cloudy. Areas of Fog. 35/47
Mon (14 Jan): Increasing Clouds. Light Rain Likely...Mainly North. 33/47
Tue (15 Jan): Partly Cloudy. 32/42
Wed (16 Jan): Partly Cloudy. 28/37
Thu (17 Jan): Mostly Sunny. 25/35
weather at oda.state.or.us
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