[willamette-fcst] Forecast - Thursday, August 6th, 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: 
     Thursday, August 6th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     The upper-level low pressure center, that has been off the
     California coastline for the past several days, is being
     forced onshore this morning by another system sliding across
     southern British Columbia. Increasing southerly flow aloft
     has spread cloudy skies and smoke, from California and
     southern Oregon wildfires, over most of Oregon this morning.
     Some sprinkles have fallen over the Willamette Valley, but,
     so far, the bulk of the moisture from this system has stayed
     south and east of the region.

     Partial clearing is expected this afternoon, especially in
     the north valley, as the upper-level trough  continues
     eastward to over northwest Nevada.  Some sprinkles or light
     showers are possible, but the main shower activity appears
     as if it will stay south and east of the Willamette Valley.

     The combination of cooling aloft, onshore flow, and mostly
     cloudy skies will drop Willamette Valley high temperatures
     about 10 degrees today (only climbing into the low 70s).
     Ventilation conditions will improve over western Oregon this
     afternoon. Mixing heights should climb to around 4000 feet
     with forecast westerly transport winds.  Those are favorable
     conditons for open burning this afternoon.  However, light
     showers are possible, which is not favorable for burning. 
     In addition, the gradient-stacking is significant this
     morning and would need to be reversed, by daytime heating,
     for open burning to be possible this afternoon.

Surface Winds:
     S 5-10 this morning, SW 5-10 this afternoon.
Transport Winds:
     SW 5 this morning, W 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 40.
High Temperature:
     Salem\'s high temperature today will be near 72.
Humidities:
     Relative humidity drops to 50% by 1pm.
     Minimum relative humidity will be near 47%.
Sunrise/Sunset:
     Salem sunset tonight: 8:31pm; sunrise tomorrow: 6:05am.

Extended Outlook:
     The upper-level trough is forecast to continue northeastward,
     into Idaho, Friday with a drier northwesterly flow aloft spreading
     from west to east across Oregon.  Westerly transport winds are
     forecast Friday afternoon, but gradient-stacking, once again,
     may inhibit the chances for open burning.

     A weak system is forecast to move across southern British
     Columbia over the weekend...maintining onshore flow, and
     slightly below normal temperatures, across the interior of
     western Oregon. A stronger system is forecast to come
     onshore Monday with the potential to bring measurable rain
     to the Willamette Valley.  Depending on the timing of this
     system, it may also create a burning opportunity.  An even
     more potent system may come onshore as early as next
     Wednesday, but that is uncertain at this time.

Tomorrow (07 Aug):  AM Clouds.  Slight Chance of a Shower.  Partial PM Clearing.  52/72

Sat (08 Aug):  AM Clouds.  Partly Sunny.  51/77

Sun (09 Aug):  AM Clouds.  Mostly Sunny in the Afternoon.  52/80

Mon (10 Aug):  Mostly Cloudy.  Increasing Chance of Rain...Mainly North.  54/77

Tue (11 Aug):  Mostly Cloudy.  Chance of Showers...Mainly North.  53/75

Wed (12 Aug):  Mostly Cloudy.  Chance of Rain.  54/75

Thu (13 Aug):  Mostly Cloudy.  Chance of Showers. 54/75

ODA Meteorologist
weather at oda.state.or.us