[willamette-fcst] Forecast - Tuesday, April 7th, 2009

[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: 
     Tuesday, April 7th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 6:00pm.
     Straw stack burning is allowed from 12:00pm until 6:00pm.

Weather Discussion:
     An upper-level low pressure area was centered about 350
     miles off the central California coastline this morning. 
     The associated cold front was nearing the california Coast
     with only some high cluods circulating northward over
     Oreegon.  Fair skies and light winds overnight allowed
     western Oregon minimums to drop as low as the mid 30s, after
     peaking in the mid to upper 70s Monday afternoon.  Hillsboro
     and Eugene were a couple of the cooler spots in the valley
     this morning, both dropping to 37 degrees.  Tillamook, on
     the north coast, dipped down to 36 degrees this morning.

     The warm weather pattern is beginning to break down this
     morning.  The ODA surface analysis showed the thermal trough
     had shifted inland to over the Willamette Valley.  Onshore
     flow had pushed areas of fog onto the coast.  In contrast,
     the air mass over the valley remainded very warm and dry
     this morning, with the early morning sounding over Salem
     showing even warmer temperatures aloft compared with Monday
     morning.  Mid-morning temperatures had, once again, warmed
     into the 50s in the Willamette Valley, so well above normal
     temperatures are in store for one more day east of the coast
     range.

     As the cold front moves onshore, into California, this
     afternoon, the surface thermal trough over western Oregon
     will shift east of the Cascades.  That will induce cooler
     onshore flow, from south to north, across western Oregon. 
     High temperatures will likely cap out in the upper 60s in
     the southern Willamette Valley but may reach the mid 70s in
     the north valley.  It will be 10-15 degrees cooler along the
     coast today with highs ranging from about 55 to 65 degrees.

     Some showers could develop across southern Oregon later this
     afternoon and evening...especially over the mountains. 
     Clouds will continue to increase, from south to north,
     overnight with the chance of showers migrating northward
     into central Oregon.  It will likely stay dry in the
     Willamette Valley with the best chance of sprinkles in Lane
     County.

Surface Winds:
     N 0-5 this morning, NNW 5-10 this afternoon.
Transport Winds:
     NE 5 this morning, NNW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2300 feet.  Ventilation index 18.
High Temperature:
     Salem\'s high temperature today will be near 74.
Humidities:
     Minimum relative humidity will be near 33%.
Sunrise/Sunset:
     Salem sunset tonight: 7:48pm; sunrise tomorrow: 6:39am.

Extended Outlook:
     Onshore flow will increase across western Oregon Wednesday,
     as the upper-level trough moves inland across Nevada and
     Utah.  More clouds and some showers will likely rotate
     northward over mainly the southern and eastern portions of
     Oregon.  Willamette Valley high temperatures will quickly
     drop to near mormal with the snow level dropping to around
     5500 feet in the Cascades.

     The next weather system is forecast to weaken as it moves
     onshore Thursday, but it should be strong enough to bring
     some showers to most of western Oregon, with lowering snow
     levels.  A weak westerly flow aloft is forecast for the
     remainder of the week.  The latest computer guidance is
     uncertain on the timing of a stronger system slated to move
     onshore sometime between Sunday afternoon and Monday
     morning.

Tomorrow (08 Apr):  Mostly Cloudy and Cooler.  Chance of Light Showers South.  43/57

Thu (09 Apr):  Showers Likely.  Snow Level Dropping to 4000 Feet.  42/54

Fri (10 Apr):  Mostly Cloudy.  Chance of Light Showers.  40/55

Sat (11 Apr):  Becoming Mostly Cloudy.  Chance of Showers.  40/57

Sun (12 Apr):  Increasing Clouds.  Chance of Rain.  Snow Level Dropping to 3000 Feet.  40/57

Mon (13 Apr):  Showers Likely.  Snow Level 2500 Feet.  42/54

Tue (14 Apr):  Decreasing Showers.  Snow Level 2500 Feet.  37/55

ODA Meteorologist
weather at oda.state.or.us