[willamette-fcst] Forecast - Monday, September 8th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Mon Sep 8 08:02:57 PDT 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.
Monday, September 8th, 2008 at 9:00am.
...State Fire Marshal Conditions may be met this afternoon due to low humidities
and increasing northerly winds...
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Stack burning is not allowed.
A strong upper-level ridge of high pressure brought sunny
and very warm weather to Oregon over the weekend. Saturday
had similar tempertures to Friday with Willamette Valley
highs near 80 degrees. By Sunday, a building surface
thermal trough, along the Oregon Coast, produced dry
offshore winds across Western Oregon with valley
temperatures approaching 90 degrees. The combination of
brisk noth winds and very low relative humidities put the
valley into State Firre Marshal conditions Sunday afternoon.
The air mass remains very dry over Western Oregon this
morning. Dew-point temperatures are only in the mid 40s, so
realtive humidities will drop to 30%, when surface
temperatures climb into the low 80s shortly after noon.
North winds are expected to increase this afternoon, so much
of the valley may meet Fire Marshal Conditions by early this
The ODA surface analysis showed a strong thermal trough
extending northward along the length of the Oregon Coast and
into extreme SW Washington. Pressure gradients remained
offshore across Western Oregon, at mid-morning, with mostly
calm winds in the valley and light easterly winds along the
coast. Visible satellite imagery showed clear skies across
Western Oregon. Eugene was reporting a few low clouds.
The salem sounding this morning showed very warm air aloft.
Mixing heights will stay below 3000 feet until
mid-afternoon, when low humidity levels and increasing
northerly winds may put much of the valley back into State
Fire Marshal conditions. Transport winds were from the NE
this morning, which may allow for the burning of remaining
fields on the west side of the valley late this morning.
Infrared satellite imagery showed a couple of cloud-bands
moving across Vancouver Island at mid-morning. They are
associated with a weak upper-level disturbance which is
forecast to drop southeastward this afternoon across
Northern Washington. That system will likely turn tranport
winds from northeasterly to northerly this afternoon, across
the Willamette Valley, with minor cooling aloft and strong
surface heating combining to raise mixing heights over 5000 feet.
However, open burning is unlikely today, because northerly
surface and transport winds will likely combine with low
humidities to send much of the valley into Fire Marshal
conditions this afternoon. Valley temperatures will likely
start out a few degrees warmer today but top out at about
the same level as on Sunday due to the offshore flow
A little strong upper-level disturbance is forecast to
approach the coastline overnight with the surface thermal
trough shifting east of the Cascades. That should turn
surface winds onshore overnight and significantly raise
humidity levels in the Willamette Valley. Some marine
clouds may form in the valley by Tuesday morning.
N 5-13 this morning, N 10-20 this afternoon.
NE 13 this morning, N 15 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 5500 feet. Ventilation index 83.
Salem\'s high temperature today will be near 89.
Minimum relative humidity will be near 23%.
Salem sunset tonight: 7:35pm; sunrise tomorrow: 6:44am.
A weak upper-level trough is forecast to move across the
Pacific Northwest Tuesday with increasing onshore flow at
the surface. That will bring some patchy marine clouds into
the valley and cool temperatures significantly. Transport
wind are forecast to become northwesterly, especially in the
north valley, which may create a burning opportunity.
High pressure is forecast to begin building back over the
region Wednesday with the flow aloft, and transport winds,
becoming northerly. As the ridge move over the region
Thursday, the tranport winds may turn offshore, for further
warming and drying of the air mass. A weak upper-level
disturbance is forecast to flatten the ridge and turn the
flow weakly onshore Friday. That will bring another
cool-down to the regin and a potential burning
opportunity...especially for the north valley.
The ridge is forecast to rebuild over the Pacific Northwest
this weekend for continued sunny and warm weather. The
ridge may push east of thre region by early next week with
increasing southesterly flow aloft beginning a cooling
trend. The weather pattern for next week still appears dry
for Western Oregon but could create some burning
opportunities...especially for the north valley.
Tomorrow (09 Sep): Patchy AM Clouds...Sunny and Cooler. 50/78
Wed (10 Sep): Sunny. 46/80
Thu (11 Sep): Sunny and Warmer. 49/88
Fri (12 Sep): Mostly Sunny but Cooler. 52/81
Sat (13 Sep): Sunny. 50/83
Sun (14 Sep): Sunny and Warmer. 53/86
Mon (15 Sep): Mostly Sunny but Cooler. 51/80
weather at oda.state.or.us
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