[willamette-fcst] Forecast - Wednesday, August 5th, 2009
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Wed Aug 5 08:23:22 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.
Wednesday, August 5th, 2009 at 8:20am.
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Stack burning is not allowed.
An upper-level low pressure center was about 200 miles off
the northern California coastline and drifting slowly
eastward this morning. It will continue the weak southerly
flow aloft over Oregon today, along with a chance of
afternoon and evening thunderstorms...mainly from the
Marine low clouds penetrated across most of the Willamette
Valley this morning but should give way to mostly sunny
skies this afternoon. Mid-morning temperatures were in the
comfortable 55-60 degree range across most of western
Oregon. Willamette Valley highs only climbed to near-normal
Tuesday and will be similar today (the normal high for Salem
today is 83 degrees).
The Salem sounding this morning showed a few degrees more
cooling aloft, compared to Tuesday morning, so mixing
heights should climb to just over 4000 feet by late this
afternoon (compared to a maximum of about 3700 feet Tuesday
afternoon). Forecast northwesterly transport winds should
allow for limited open burning this afternoon, assuming the
weak gradient-stacking from last night\'s marine influx is
reversed by daytime heating. Once again, thunderstorm
development over the Cascades, and across central Oregon,
will need to be closely monitored.
By this evening, enough moisture may feed far enough north
and west to include a slight chance for a shower or
thunderstorm over the Willamette Valley, but it appears that
the bulk of the shower activity will stay east of the region.
W 0-6 this morning, NW 5-15 this afternoon.
SW 4 this morning, NW 10 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 4200 feet. Ventilation index 42.
Salem\'s high temperature today will be near 82.
Relative humidity drops to 50% by 12pm.
Minimum relative humidity will be near 33%.
Salem sunset tonight: 8:33pm; sunrise tomorrow: 6:04am.
A weak weather system, cutting across southern British
Columbia on Thursday, will finally force the upper-level
trough off the California coast onshore. That will initiate
a significant increase in onshore flow across western Oregon
with much cooler temperatures. A burning opportunity is
possible with this transition to a cooler air mass, because
most of the moisture is forecast to stay south and east of
the Willamette Valley. There will be considerable clouds and
at least a slight chance of showers...especially over the
southern Willamette Valley.
The threat of showers and thunderstorms will increase, from
the Cascades eastward, Thursday and Friday, with some storms
possibly becoming quite strong. Due to the recent hot and
dry weather, these storms have the potential to start many
wildfires. The trough is forecast to continue eastward,
into Idaho, Friday with a drier northwesterly flow aloft
spreading from west to east across Oregon. A weak system is
forecast to move across southern British Columbia over the
weekend...maintining onshore flow, and below normal
temperatures, across the interior of western Oregon.
The long-range models differ on their timing and strength of
a system coming onshore early next week. It should maintain
below normal temperatures across western Oregon and could
introduce a chance of rain...especially in the northern
Tomorrow (06 Aug): Mostly Cloudy and Cooler. Slight Chance of Showers. 52/75
Fri (07 Aug): AM Clouds. Slight Chance of a Shower. Partial PM Clearing. 52/72
Sat (08 Aug): AM Clouds. Partly Sunny. 51/77
Sun (09 Aug): Partly Sunny and Continued Seasonably Cool. 52/77
Mon (10 Aug): Mostly Cloudy. Chance of Rain...Mainly North. 54/74
Tue (11 Aug): Mostly Cloudy. Chance of Showers...Mainly North. 54/78
Wed (12 Aug): Mostly Cloudy. Chance of Showers...Mainly North. 54/78
weather at oda.state.or.us
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