[willamette-fcst] Forecast - Thursday, July 3rd, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Thu Jul 3 08:19:15 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, July 3rd, 2008 at 9:00am.
Due to the Olympic Trials in Eugene, ODA will not be issuing
any burning permits through July 8th.
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Stack burning is not allowed.
A very slow-moving upper-level low pressure area was
centered about 400 miles west of the Northern Oregon Coast
this morning. The counter-clockwise circulation around it
has been responsible for the southerly flow aloft, the past
few days, bringing smoke from California wildfires into
Oregon. Spokes of energy rotating around this system have
also touched off thundershowers the past several days with
an active line of thunderstorms developing over the Northern
Willamette Valley last night.
The overnight storms brought frequent lightning and up to
one-quarter of an inch of rain to the Northern Willamette
Valley. A few thunderstorms also developed over North-Central
Oregon near The Dalles. The entire complex of storms moved
rapidly north of Oregon, by daybreak, across Western and
Central Washington. Shower and thundershower activity was
still going on from near Seattle northward into Southern
British Columbia at mid-morning.
It was a mild and muggy night around the state with morning
minimums generally in the 50s and 60s. For the second day
in-a-row, Lakeview was the cool spot with 45 degrees. The
Dalles never cooled below 70 degrees with overnight
thunderstorms dropping .03 inches of rain. The morning
sounding over Salem showed southeasterly flow in the mid-levels
of the atmosphere, which continues to be favorable for
thundershower development over Western Oregon today. There
was some cooling below 10,000 feet, so afternoon temperatures
should be a couple of degrees cooler than on Wednesday.
Morning satellite imagery showed mostly cloudy skies across
Washington with a band of middle and high clouds over the
western half of Oregon. Low clouds were along the immediate
coastline with sunny skies over Central and Eastern Oregon.
Doppler radar showed considerable shower and thundershower
activity from about Centralia northward across Western
Washington with a few light showers over Central and Eastern
Washington. Dry conditions prevailed over Oregon.
Mid-morning temperatures were near 60 across Western Oregon
and ranged from the low 60s to the mid 70s east of the
Cascades. The ODA surface analysis showed the thermal
trough, which moved back into the Willamette Valley
Wednesday, had shifted back eastward and extended from
Central Washington through SW Oregon. Very weak onshore
flow had returned NW Oregon. Surface winds were light
across Oregon with a west winds at 10 mph in The Dalles.
As the offshore upper-level low pressure system slowly moves
northeastward, southerly flow aloft will continue to send
smoke from the California wildfires over Oregon today, so
skies will likely stay on the hazy side. Any upper-level
disturbances, riding along in the southerly flow aloft,
could trigger showers or thundershowers over Oregon, but the
computer models are forecasting a break between impulses
today. However, conditions remain unstable, so I will keep
a slight chance of a shower of thundershower in the forecast.
Var 0-5 this morning, W 5-10 this afternoon.
S 6 this morning, SSW 12 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 4500 feet. Ventilation index 54.
Salem\'s high temperature today will be near 82.
Relative humidity drops to 50% by 1pm.
Minimum relative humidity will be near 43%.
Salem sunset tonight: 9:02pm; sunrise tomorrow: 5:32am.
The upper-level trough is finally forecast to move onshore
early Friday with flow aloft becoming more westerly by
Friday afternoon. That should help to clear the smoke from
the region, but it will also increase the chance of showers
west of the Cascades and continue the cooling trend across
the region. The thundershower threat will shift east of the
Cascades, as the westerly flow aloft stabilizes the air mass
over Western Oregon.
Another weak frontal system is forecast to brush across
Washington and Oregon, in the westerly flow aloft, Saturday
afternoon...continuing a slight chance of showers in the
Willamette Valley. The jet stream begins to lift north
Sunday with a more typical summer-time pattern developing
for early next week. That means onshore flow across Western
Oregon with morning clouds and afternoon sunshine. The
storm track is forecast to remain close to the region with
slightly above normal temperatures through the first half of
next week and a possible cool-down late next week.
Tomorrow (04 Jul): Mostly Cloudy and Cooler. Chance of a Showers. 59/75
Sat (05 Jul): Mostly Cloudy. Slight chance of Showers. 56/78
Sun (06 Jul): Morning Clouds...Mostly Sunny. 53/80
Mon (07 Jul): Morning Clouds...Mostly Sunny. 54/82
Tue (08 Jul): Mostly Sunny. 54/85
Wed (09 Jul): Mostly Sunny. 54/85
Thu (10 Jul): Mostly Sunny. 54/79
weather at oda.state.or.us
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