[willamette-fcst] Forecast - Friday, July 27th, 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: 
     Friday, July 27th, 2007 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 6:00pm.
     Preparatory burning is allowed from 12:00pm until 2:00pm with a 100 acre limit.
     Propane flaming is allowed from 1:00pm until 6:00pm.
     Straw stack burning is allowed from 12:00pm until 6:00pm.

Weather Discussion:
     Weak southwesterly flow aloft continues over the Pacific
     Northwest today.  The onshore flow is weaker this morning,
     across Western Oregon, with marine low clouds not as
     widespread or as thick as on Thursday.  Skies should clear
     across the Willamette Valley by noon, with high temperatures
     climbing into the middle 80s.

     The upper-air sounding, over Salem, this morning showed a
     nearly constant temperture from the surface to 3500 feet and
     a subsidence inversion from 3500 feet to 5000 feet. 
     Therefore, mixing heights will not go above 3000 feet until
     afternoon, when the marine low clouds are gone and the
     surface temperatures have warmed above 75 degrees.  Because
     of the subsidence inversion above 3500 feet, mixing heights
     are unlikely to climb much above 4500 feet, even with
     surface temperatures reaching the middle 80s this
     afternoon.

     Transport winds are still northerly this morning but are
     forecast to become light northwesterly this afternoon, which
     opens the door for limited preparatory burn opportunities. 
     Open field burning today is dependent on the transport winds
     taking on a significant westerly component this afternoon,
     which may not happen.  We will be monitoring the winds, with
     pibals, starting at 1pm.

Surface Winds:
     N 3 this morning, NNW 7 this afternoon.
Transport Winds:
     N 4 this morning, NNW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 36.
High Temperature:
     Salem\'s high temperature today will be near 85.
Humidities:
     Relative humidity drops to 50% by 1pm.
     Minimum relative humidity will be near 35%.
Sunrise/Sunset:
     Salem sunset tonight: 8:45pm; sunrise tomorrow: 5:53am.

Extended Outlook:
     After another warm day Saturday, a weak cold front is
     forecast to increase the onshore flow with more marine
     clouds and cooler temperatures in the Willamette Valley
     Sunday.  Precipitation will be limited to Western Washington,
     with a only slight chance for a shower in NW Oregon.

     High pressure will rebuild across the region Monday and
     Tuesday, with warming temperatures and northerly winds
     in the Willamette Valley.  Warm temperatures are in store
     for mid-week, before a stronger weather system brings in a
     surge of marine air, a chance of showers, and cooler
     temperatures Thursday evening and Friday.

     Burning potential will be low next Monday and Tuesday, with
     north winds forecast for the valley.  The transition, from
     very warm weather next Wednesday, to cooler weather either
     late Thursday or Friday has potential to create good
     ventilation conditions for burning.

Tomorrow (28 Jul):  Morning Clouds...Mostly Sunny with Increasing Clouds Late.  54/84

Sun (29 Jul):  Mostly Cloudy.  Slight Chance of Drizzle or Light Showers.  56/78

Mon (30 Jul):  Morning Clouds...Sunny. North Winds.  51/83

Tue (31 Jul):  Morning Clouds...Sunny. North Winds.  53/86

Wed (01 Aug):  Sunny and Very Warm.  55/90

Thu (02 Aug):  Mostly Sunny...Increasing Clouds Late.  57/85

Fri (03 Aug):  Mostly Cloudy and Cooler.  Chance of Showers.  56/75

ODA Meteorologist
weather at oda.state.or.us