[willamette-fcst] Forecast - Thursday, September 3rd, 2009
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Sep 3 09:10:39 PDT 2009
Daily Smoke Management Forecast
Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.
...Corrected winds and ventilation index...
Issued:
Thursday, September 3rd, 2009 at 9:00am.
Burn Advisory:
Agricultural burning is not recommended.
Preparatory burning is allowed from 11:00am until 2:00pm with a 100 acre limit.
Propane flaming is allowed from 11:00am until 2:00pm.
Stack burning is not allowed.
Weather Discussion:
A vigorous upper-level trough of low pressure brought some
showers and thundershowers to the extreme northern
Willamette Valley overnight. The Portland area picked up
about one-tenth of an inch of rain, with thunderstorms, but
no rain was reported south of a line from about McMinnville
to Aurora. Clouds were breaking up over western Oregon by
mid-morning, in the wake of the trough, which was rapidly
pushing northeastward across western Washington. Partly
cloudy skies are expected today across western Oregon, as
the region gets a break between weather systems and
continued southwestery flow aloft.
The Salem sounding this morning showed brisk southwesterly
flow aloft and sigificant cooling since Wednesday afternoon.
After reaching the mid 80s Wednesday, Willamette Valleys
highs should only climb into the mid to upper 70s today.
With the air aloft so cool, that may enable mixing heights
to climb to around 6000 feet by mid to late afternoon.
Transport winds are forecast to be southwesterly, which
would allow for open burning this afternoon, if there is not
a gradient-stacking issue.
Surface Winds:
S 5-10 this morning, W 5-12 this afternoon.
Transport Winds:
SSW 15 this morning, SW 12 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 6000 feet. Ventilation index 90.
High Temperature:
Salem\'s high temperature today will be near 77.
Humidities:
Relative humidity drops to 50% around 10am.
Minimum relative humidity will be near 32%.
Sunrise/Sunset:
Salem sunset tonight: 7:45pm; sunrise tomorrow: 6:38am.
Extended Outlook:
The next weather system is forecast to stall near the
coastline Friday, before moving onshore Saturday. It is
unlikely that there will be a burning opportunity, ahead of
that system, as the flow aloft becomes more southerly. When
the cold front finally swings onshore saturday, it should be
strong enough to bring rain to all of western Oregon
Saturday. Computer models have not been consistent with
forecast rainfall amounts, with the latest guidance
suggesting that the Willamette Valley will pick up around
one-quarter of an inch. The heaviest amounts sould be in
the north valley.
A cool upper-level trough is forecast to follow the cold
front onshore late Saturday through early
Monday...maintaining some showers across the region with
well below normal temperatures. A return more summer-like
weather is expected next week, with a strong ridge of high
pressure forecast to build back over the region.
Tomorrow (04 Sep): Increasing Clouds. 51/80
Sat (05 Sep): Rain Turning to Showers. Much Cooler. 54/67
Sun (06 Sep): Mostly Cloudy and Cool. Showers Likely. 52/65
Mon (07 Sep): Showers Ending...Becoming Mostly Sunny and Warmer in the Afternoon. 49/74
Tue (08 Sep): Mostly Sunny and Warm. 51/82
Wed (09 Sep): Mostly Sunny and Warm. 52/85
Thu (10 Sep): Mostly Sunny and Warm. 51/79
ODA Meteorologist
weather at oda.state.or.us
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