[willamette-fcst] Forecast - Thursday, August 14th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Aug 14 08:03:50 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.
Thursday, August 14th, 2008 at 9:00am.
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Stack burning is not allowed.
A strong ridge will continue building over the Pacific
Northwest today with offshore surface flow. The Salem
sounding this morning showed considerable warming aloft
since Wednesday with north-northeasterly winds below 3000
feet. Temperatures are forecast to continue to warm aloft
enough to support 100 degree heat in the Willamette Valley
NNE transport winds are expected to continue today and are
conducive to good ventilation of smoke from western valley
fields. The morning ODA surface analysis showed a broad
thermal trough of low pressure over Western Oregon with weak
northerly gradients across the Willamette Valley. Surface
winds were generally from the north at less than 10 mph
across Western Oregon.
Satellite imgery showed a narrow band of low clouds along
the coast with clear skies over the remainder of Oregon.
Temperatures were already quite warm with most of the
western valleys near 70 degrees. It was cooler on the coast
with readings near 60. The air mass aloft will continue to
warm today in response to the building ridge over the
region. Valley temperatures will approach daily record
highs with increasing north to northeasterly winds.
The combination of hot temperatures and low humidities
should push the Willamette Valley into State Fire Marshal
conditions around 2-3pm. The winds may also pick up enough
to meet Fire Marshal criteria.
N 5-12 this morning, NNE 10-20 this afternoon.
NNE 15 this morning, NE 15 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 3500 feet. Ventilation index 53.
Salem\'s high temperature today will be near 100.
Minimum relative humidity will be near 23%.
Salem sunset tonight: 8:19pm; sunrise tomorrow: 6:15am.
The upper-level ridge axis is forecast to shift far enough
east Friday for southerly flow aloft to develop over Western
Oregon. That will likely begin transporting smoke, from
California wildfires, back over Western Oregon and begin to
turn skies hazy. The air aloft will continue to warm. A
broad thermal surface trough will remain over Western Oregon
with offshore flow sending valley temperatures over the
century mark...likely setting some new daily record highs.
An upper-level disturbance is forecast to move close enough
to the coastline Saturday to bring a threat of
thundershowers to the state...mainly from the Cascades
westward starting Saturday afternoon. The best chance of
thunderstorms in the Willamette Valley appears to be
Saturday night. The increasing southerly flow aloft may
shift the thermal trough east of the Cascades late Saturday,
which would cool temperatures a few degrees in the
The upper-level ridge is forecast to shift over Western
Montana Sunday with increasing southerly flow aloft
spreading the chance of thunderstorms eastward across
Oregon. The thermal trough is expected to shift to Eastern
Oregon Sunday with onshore flow bringing some cooling to
There is considerable uncertainty in the long-range models
regarding the transition out of the hot weather early next
week. There could be burning opportunities early next week,
depending on the strenghth and timing of the systems
forecast to move onshore. The flow aloft is forecast to
become southwesterly Monday, which would stabilize the air
mass over Western Oregon and bring additional cooling with
onshore flow. A stronger trough forecast to move onshore
Tuesday. Either system may end up being strong enough to
produce light showers across Western Oregon.
Most of the computer models (not all) bring a significant
trough onshore by Wednesday of next week. That would bring
much cooler temperatures to the region and at least a chance
of showers statewide.
Tomorrow (15 Aug): Record Heat and Turning Hazy. 65/103
Sat (16 Aug): Mostly Sunny, Hot, and Hazy. Slight Chance of T-Storms Late. 65/99
Sun (17 Aug): Partly Cloudy. Slight Chance of T-storms. 60/90
Mon (18 Aug): Mostly Cloudy and Cooler. Chance of Showers. 55/75
Tue (19 Aug): Mostly Cloudy. Chance of Showers Late. 55/77
Wed (20 Aug): Mostly Cloudy and Cooler. Chance of Showers or Light Rain. 55/72
Thu (21 Aug): Mostly Cloudy. Chance of Showers. 55/70
weather at oda.state.or.us
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