[willamette-fcst] Forecast - Tuesday, March 9th, 2010

[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, March 9th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 4:00pm.
     Straw stack burning is allowed from now until 4:00pm.

Weather Discussion:
     A transitory upper-level ridge of high pressure brought
     partial clearing overnight to western Oregon.  However a
     very weak upper-level disturbance kept a few rain and snow
     showers going over northwestern Oregon, with snow mixing
     down to near sea level at times.  Much of the Willamette
     Valley saw minimum temperatures drop to near or below the
     freezing mark.  Eugene dropped to 28 degrees and Corvallis
     hit 30.  McMinnville and Salem also dipped to freezing. 
     Much of the extreme north valley stayed just above freezing,
     due to stirring of the air from the shower activity.

     Another cold weather system will quickly move onshore Today,
     with rain and mountain snow increasing in the afternoon. 
     Significant accumulations of snow are likely over the
     Cascade passes and possibly the coastal range passes. 
     Satellite imagery showed the main cloud-shield from the
     approaching weather system already moving over western
     Oregon.  Doppler showed the early morning showers exiting
     the northern Willamette Valley, to the east, and incoming
     rain just offshore.

     The ODA surface analyis showed southerly gradients beginning
     to increase across western Oregon, with winds in the 5-15
     mph range.  Mid-morning temperatures were quite cool, with
     most of western Oregon still in the mid to upper 30s.  Snow
     levels will start out near 1000 feet, when the precipitation
     moves onshore later this morning.  Some snowflakes could mix
     with rain all the way to sea level across northwestern
     Oregon.  Snow levels should climb to about 1500 feet this
     afternoon, when the bulk of the precipitation moves onshore.
     Increasing rain and cool offshore flow will hold valley
     highs in the mid to upper 40s this afternoon.

Surface Winds:
     S 5-15 this morning, SE 10-20 this afternoon.
Transport Winds:
     S 15 this morning, S 25 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 125.
High Temperature:
     Salem\'s high temperature today will be near 47.
Humidities:
     Minimum relative humidity will be near 53%.
Sunrise/Sunset:
     Salem sunset tonight: 6:10pm; sunrise tomorrow: 6:34am.

Extended Outlook:
     Showers will continue into Wednesday morning, with western
     valley temperatures dropping into the mid 30s and snow
     levels lowering back down to around 1000 feet.  Some afternoon
     clearing will help temperatures recover into the lower 50s. 
     A warm front may bring rain back to northwestern Oregon as
     early as Thursday morning, with a cold front coming onshore
     Thursday afternoon.  Snow levels should briefly rise to near
     or slightly above the Cascade passes, Thursday afternoon,
     before dropping again Thursday night and Friday.

     Another cold upper-level trough, with very low snow levels,
     is forecast to swing over the region Friday through early
     Saturday.  A weak upper-level ridge may be just strong
     enough to deflect a warm front north of the region on
     Sunday, but a slight chance of rain can\'t be ruled out for
     northwestern Oregon.  Oregon should be under the influence
     of a mild southwesterly flow aloft on Monday, with the next
     weather system forecast to bring more rain onshore late Tuesday.

Wed (10 Mar):  Decreasing Showers.  Clearing Late.  Snow Level Rising to 2500 Feet.  34/51

Thu (11 Mar):  Increasing Rain and Wind.  Snow Level Rising To 5000 Feet.  36/55

Fri (12 Mar):  Rain Turning to Showers. Snow Level Dropping Below 2500 Feet.  40/51

Sat (13 Mar):  Decreasing Showers.  Snow Level 1000 Feet Early...Rising to 2500 Feet.  35/52

Sun (14 Mar):  Cool Start...Possibly Becoming Partly Sunny.  Slight Chance of Rain.  32/55

Mon (15 Mar):  Increasing Clouds and Mild.  37/62

Tue (16 Mar):  Rain Likely Developing.  Snow Level Above 5000 Feet..Dropping Late.  42/56

ODA Meteorologist
weather at oda.state.or.us