[willamette-fcst] Forecast - Wednesday, March 10th, 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: 
     Wednesday, March 10th, 2010 at 12:00pm.

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 weakening cold front pushed east of the Willamette Valley early this
     morning, with showers tapering off during the morning.  With some sunbreaks,
     valley temperatures had climbed into the mid to upper 40s by late this morning.
     
     Satellite imagery showed some convective cloud development continuing over
     western Oregon late this morning, but there were lots of breaks in the clouds
     ...especially along the coast.  Doppler radar was still showing some scattered
     shower activity across the Willamette Valley, with some enhancement of the showers
     over the Cascades.  Snow levels remain low, but the lack of shower activity was
     allowing the overnight snow to clear from the Cascade passes.

     A weak and transitory upper-level ridge of high pressure is slowly stabilizing
     the air mass over the region.  The late-morning ODA surface analysis showed the
     weak pressure gradients were turning more southerly across western Oregon, with
     valley winds only in the 5-15 mph range.  

     The threat of showers will continue to decrease during the day, as the weak
     upper-level ridge axis moves overhead.  Some showers could produce small hail.
     Sunbreaks will help temperatures recover into the lower 50s this afternoon. The
     break in the weather will be brief, however, with clouds expected to increase this
     evening, ahead of the next weather system slated to come onshore early Thursday.
     The increased cloud-cover should keep temperatures above freezing overnight across
     the Willamette Valley.

Surface Winds:
     S 5-15 this afternoon.
Transport Winds:
     SSW 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 75.
High Temperature:
     Salem\'s high temperature today will be near 51.
Humidities:
     Minimum relative humidity will be near 47%.
Sunrise/Sunset:
     Salem sunset tonight: 6:12pm; sunrise tomorrow: 6:32am.

Extended Outlook:
     A warm front may bring rain back to northwestern Oregon as
     early as the pre-dawn hours on Thursday, along with an
     increase in south-southeastery winds.  A cold front is
     forecast to slowly sag southeastward, into northwestern
     Oregon, during the day Thursday, with increasing rain and
     rising snow levels. A stronger low-pressure area is forecast
     to form along the frontal zone, eventually bringing it
     inland, with more rain and possibly windy conditions on Friday.

     A cold upper-level trough, with very low snow levels, is
     forecast to swing over the region Friday afternoon through
     early Saturday.  A weak upper-level ridge may be just strong
     enough to deflect a warm front north of the region on
     Sunday.  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.

Tomorrow (11 Mar):  Increasing Rain...Mainly North.  Snow Level Rising To 5000 Feet.  40/54

Fri (12 Mar):  Rain and Windy...Turning Showery. Snow Level Dropping Below 2500 Feet.  45/52

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

Sun (14 Mar):  Cool Start...Becoming Partly Sunny.  33/58

Mon (15 Mar):  Increasing High Clouds and Mild.  37/63

Tue (16 Mar):  Rain Likely Developing.  Snow Level Above 5000 Feet..Dropping Late.  42/57

Wed (17 Mar):  Decreasing Chance of Showers.  Snow Level 3-4000 Feet.  38/55

ODA Meteorologist
weather at oda.state.or.us