[willamette-fcst] Forecast - Thursday, July 5th, 2007

[Willamette Valley Ag/Burning Forecast]

Daily Smoke Management Forecast




Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

Issued: 
     Thursday, July 5th, 2007 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 7:00pm.
     Stack burning is not allowed.

Weather Discussion:
     A strong upper-level ridge of high pressure is giving the
     Pacific Northwest sunny skies and well above normal
     temperatures.  The one exception is along the Pacific Coast,
     where an increasing onshore flow is producing areas of low
     clouds and .  The ridge axis is slowly shifting eastward and
     was centered from Eastern Idaho into Central Montana this
     morning.  Near record high tempertures are forecast today
     for Central and Eastern Oregon, with many areas climbing
     over 100 degrees.  A weak onshore surface flow will cap
     temperatures in the lower 90s for the Willamette Valley
     today.

     A general cool-down is expected to begin Friday, as the
     upper-level ridge continues to slide eastward.  A weak
     weather disturbance will push into Southern British Columbia
     Friday, with onshore surface gradients increasing across
     Western Oregon.  Coastal low clouds may briefly penetrate
     into some interior valley locations Friday morning with
     Willamette Valley afternoon temperatures cooling to the mid
     80s.  Marine air will also begin spilling into Central and
     Eastern Oregon Friday, resuling in brisk westerly winds
     along with somewhat cooler conditions.

Surface Winds:
     N 5 this morning, N 8-12 this afternoon.
Transport Winds:
     N 10 this morning, N 10-15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4200 feet.  Ventilation index 42.
High Temperature:
     Salem\'s high temperature today will be near 92.
Humidities:
     Relative humidity drops to 50% by 1pm.
     Minimum relative humidity will be near 30%.
Sunrise/Sunset:
     Salem sunset tonight: 9:01pm; sunrise tomorrow: 5:33am.

Extended Outlook:
     The upper-level ridge that was responsible for the very warm
     weather this week will shift east of the region over the
     weekend.  That will give way to a weak westerly flow aloft
     and continued dry conditions for the Pacific Northwest. 
     Typical summertime onshore surface gradients will bring a
     return of near-normal temperarures across Oregon.

     Long-range computer models forecast the building of another
     upper-level ridge over the region, but this time it is
     expected to extend from Nevada northward to the Southern
     British Columbia Coastline.  That will cause surface
     gradients to become more northerly across Oregon on Monday
     with temperatures climbing above normal in the Willamette
     Valley.

     We may have some thermal trough development in the
     Willamette Valley by Tuesday, but the long-range models do
     not agree on this feature, so my confidence is low at this
     time.  We are likely to see another warm-up, but the hottest
     temperatures may, once again, stay east of the Cascades. 
     All of the models show the thermal trough shifting east of
     the Cascades Thursday or Friday, with a significant
     cool-down and a threat of showers or thunderstorms.

Tomorrow (06 Jul):  Sunny.  56/84

Sat (07 Jul):  Sunny.  52/82

Sun (08 Jul):  Sunny.  51/83

Mon (09 Jul):  Sunny.  53/86

Tue (10 Jul):  Sunny.  54/92

Wed (11 Jul):  Sunny.  58/93

Thu (12 Jul):  Chance of thundershowers.  56/82



ODA Meteorologist
weather at oda.state.or.us