[willamette-fcst] Forecast - Thursday, April 10th, 2008

Thu Apr 10 15:55:14 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.

Issued: 
     Thursday, April 10, 2008 at 4:45 pm.

Burn Advisory For Friday, April 11, 2008:
     Agricultural burning is allowed.  Suggested burn times are from 11:00 am until 6:00 pm.
     Stack burning is not allowed.

Weather Discussion:
     A dissipating warm front kept skies cloudy most of the day
     over Northwest Oregon with areas of light rain persisting
     until early this afternoon over the north valley and the
     Northern Cascade Foothills.  Meanwhile, skies were mostly
     sunny today from Central through Southwest Oregon.  Skies
     were also beginning to clear over the eastern portion of the
     state, as the light rain and snow showers across that region
     earlier today moved into Idaho.

     The air aloft is slowly warming and drying, with an
     upper-level ridge building into the west coast.  The
     freezing levels were still quite low this morning, at 3-4000
     feet over the state, with a couple of inches of new snow
     falling at pass levels in the Cascades earlier today.

     Doppler radar showed a few remaining showers over the
     Nothern Cascades, but even those shoud be dying off in the
     next few hours.  With some late-afternoon sunshine, valley
     temperatures ended up a couple of degrees warmer than on
     Wednesday with highs in the mid to upper 50s.

     Temperatures east of the Cascades were generally in the
     upper 40s and 50s this afternoon with low 60s across
     Southwest Oregon.  The late-afternoon ODA surface analysis
     showed that high pressure had built far enough into Western
     Oregon to switch pressure gradients from southerly to
     westerly across the Willamette Valley where west winds were
     blowing at 5-10 mph.  Pressure gradients were becoming
     northwesterly across Central and Eastern Oregon with wind
     speeds of 15-25 mph common.  

     High pressure will continue to build into the Pacific
     Northwest overnight with clearing skies leading to colder
     minimum temperatures.  Willamette Valley lows will dip into
     the mid 30s with local pockets of frost.  Frost-sensitive
     crops in normally cold regions may need protection.

     The weather forecast models all strongly build a ridge of
     high pressure over the Pacific Northwest Friday for sunny
     and warmer conditions.  Surface gradients will turn
     northerly Friday morning and weakly offshore Friday
     afternoon.  Northerly transport winds are not conducive to
     good valley ventilation, so stack burning is not allowed
     Friday.  With rapid warming of the air mass aloft, valley
     temperatures should top out into the upper 60s Friday
     afternoon with the freezing level rapidly climbing to near
     9000 feet.  

Surface Winds:
     N 5-10 Friday morning, NNE 10-15 G20 south valley Friday afternoon.
Transport Winds:
     NNE 5-10 Friday morning, NNE 15 Friday afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height Friday will be near 2800 feet.  Ventilation index 14.
High Temperature:
     Salem\'s high temperature Friday will be near 69.
Humidities:
     Minimum relative humidity will be near 39%.
Sunrise/Sunset:
     Salem sunset tonight: 7:52 pm; sunrise Friday: 6:34 am; sunset Friday night: 7:53 pm.

Extended Outlook:
     Saturday will be the warmest day during this dry stretch,
     with the upper-level ridge shifting east of the region, to
     over Idaho, by Saturday night.  By Sunday afternoon, the
     upper-level ridge is forecast to be over Montana with
     increasing southwesterly flow aloft over Oregon.  The
     surface thermal trough will shift into Central Oregon by
     Sunday morning and progrees to Eastern Oregon Sunday
     afternoon, for the warmest day there.  That will bring
     cooler onshore flow to Western Oregon Sunday.

     A cold front is forecast to bring a good chance of rain to
     Western Oregon Sunday night or early Monday with onshore
     flow penetrating east of the Cascades and into Idaho.  A
     cool upper-level trough is forecast to either move over the
     region or set up camp just offshore.  In either case, it
     will be close enough for at least a chance of showers
     through much of next week.

     ...The updated ODA Long-Range Climate Forecast, covering the
     period from April through July, is available on the web at
     http://oregon.gov/ODA/NRD/weather.shtml#Weather_forecasts in
     either PowerPoint or PDF formats...

Fri (11 Apr):  Mostly Sunny and Warmer.  34/69

Sat (12 Apr):  Sunny and Warm.  Increasing High Clouds Late.  40/74

Sun (13 Apr):  Increasing Clouds and a Touch Cooler. Chance of Rain Late. 44/70

Mon (14 Apr):  Rain Likely and Much Cooler.  Snow Level Dropping to 4-5000 Feet.  42/59

Tue (15 Apr):  Chance of Showers and Cool.  Snow Level 4-5000 Feet.  38/58

Wed (16 Apr):  Chance of Showers and Cool.  Snow Level 4000 Feet.  37/57

Thu (17 Apr):  Chance of Showers and Cool.  Snow Level 3-4000 Feet.  37/58

Fri (18 Apr):  Chance of Showers and Cool.  Snow Level 3000 Feet.  37/56

ODA Meteorologist
weather at oda.state.or.us