[willamette-fcst] Forecast - Monday, July 21st, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Mon Jul 21 08:00:33 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, July 21st, 2008 at 9:00am.
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is allowed from 2:00pm until 5:00pm.
Stack burning is not allowed.
Increasing onshore flow brought cooler conditions to the
Willamette Valley Friday and Saturday with below normal
temperatures for the first time this month. The onshore
flow weakened Sunday with valley highs rebounding into the
mid to upper 80s.
An upper-level low pressure area, centered just off the
Northern California Coastline, was responsible for
south-southwesterly flow aloft over Oregon this morning.
That was transporting smoke north-northeastward, from
California wildfires, making for hazy conditions over most
of Oregon, Idaho, and SE Washington.
Morning satellite imagery showed low clouds along the
Washington and Oregon Coastlines with a few low clouds
making it into the extreme northern and southern Willamette
Valley. The remainder of Western Oregon had mostly clear but
hazy skies. Moisture from the California system was circulating
into Central and Eastern Oregon, where skies were partly to mostly
cloudy this morning. Afternoon heating should result in scattered
thunderstorm development over Southern Oregon and areas east
of the Cascades, as the California system moves onshore.
Some storm may form in Lane County, near an over the Cascades.
The Salem sounding this morning showed minor cooling below
8000 feet, so high temperatures today should be a few
degrees cooler than on Monday. Most of the valley will
climb into the low 80s this afternoon. A stable layer from
the surface to about 3000 feet will not allow mixing heights
to climb above 3000 feet until surface temperatures reach
the upper 70s...about 2 pm. Transport winds were
north-northeasterly and are forecast to turn northerly at
midday and north-northwesterly later this afternoon.
The ODA surface analysis showed high pressure over Western
Washington and along the Oregon Coast with a weak thermal
trough extending from Eastern Washington to SW Oregon.
Pressure-gradient-stacking and Medford-Draw conditions were
in effect but are weak enought that daytime heating may act
to alleviate them. That may allow for limited open burning
opportunities this afternoon. However, thnunderstorm
development may raise surface pressures over Central Oregon
this afternoon and reinforce the gradient-stacking problem.
That will need to be monitored closely.
N 5-10 this morning, NNW 8-15 this afternoon.
NNE 8 this morning, NNW 11 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 4000 feet. Ventilation index 44.
Salem\'s high temperature today will be near 82.
Relative humidity drops to 50% by 12pm.
Minimum relative humidity will be near 35%.
Salem sunset tonight: 8:50pm; sunrise tomorrow: 5:47am.
The California system is forecast to move into Northern
Nevada Tuesday morning and to over Idaho Tuesday afternoon.
That will increase the onshore flow into Western Oregon with
marine low clouds likely penetrating into the Willamette
Valley Tuesday morning. Thundershower activity will be
shifted mostly into Idaho Tuesday with a more stable
westerly flow aloft moving over Oregon. The westerly flow
aloft should also help to clear the air of haze from the
California wildfire smoke.
A weak upper-level system, dropping down from the Gulf of
Alaska, will maintain the westerly flow aloft over Oregon
Tuesday and Wednesday. Tranport winds are forecast to
become more westerly Tuesday, over the Willamette Valley,
which may create open buring opportunities, in the
afternoon, depending on gradient-stacking issues. The
trough is forecast to move east of the region Wednesday
afternoon with the flow aloft turning northwesterly and the
transport winds becoming more northerly.
The upper-level winds are forcast to become southwesterly
Thursday through Monday with weak onshore flow at the
surface across Western Oregon. That should produce
near-normal weather conditions with coastal low clouds and
mostly sunny conditions over the interior of Western Oregon.
The southwesterly flow aloft is forecast to strengthen
Friday, as a weak trough approaches the coast. That may
increase the onshore flow enough to create another limited
Tomorrow (22 Jul): Morning Clouds...Mostly Sunny in the Afternoon. 54/76
Wed (23 Jul): Brief Morning Clouds. Sunny in the Afternoon. 50/81
Thu (24 Jul): Sunny. 50/85
Fri (25 Jul): Sunny. 51/85
Sat (26 Jul): Mostly Sunny. 52/83
Sun (27 Jul): Mostly Sunny. 53/82
Mon (28 Jul): Mostly Sunny. 53/82
weather at oda.state.or.us
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