[willamette-fcst] Forecast - Friday, September 4th, 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: 
     Friday, September 4th, 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:
     A weakening cold front will stall along the coastline
     today...bringing lots of clouds to western Oregon, but
     little to no rainfall. Doppler radar showed possible
     sprinkles or very light showers over the central coast and
     coastal range at mid-morning...moving northeastward into the
     northern Willamette Valley.  Hillsboro reported some
     sprinkles earlier this morning, but they didn\'t amount to
     much.  The ODA surface analysis showed very weak pressure
     gradients across the state, with winds less than 10 mph
     statewide.  Much of the Willamette Valley was calm.

     Mid-morning temperatures were in the low to mid 50s along
     the coast and mid 50s to low 60s in the Willamette Valley. 
     Warming aloft and increased cloud-cover will combine to keep
     mixing heights below 3000 feet for most, if not all, of the
     day. In addition, transport winds will be very light, making
     for poor ventilation conditions. The high temperature
     forecast is tricky, because the warm air aloft supports
     80-degree heat at the surface. However, considerable clouds
     will block the sun, at times, so highs will likely only
     climb into the mid 70s.

Surface Winds:
     Var 0-5 this morning, NW 3-8 this afternoon.
Transport Winds:
     N 3 this morning, NW 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2700 feet.  Ventilation index 14.
High Temperature:
     Salem\'s high temperature today will be near 76.
Humidities:
     Relative humidity drops to 50% around 11am.
     Minimum relative humidity will be near 36%.
Sunrise/Sunset:
     Salem sunset tonight: 7:43pm; sunrise tomorrow: 6:39am.

Extended Outlook:
     A strong cold front is forecast to slowly sweep inland and
     across western Oregon Saturday.  The latest computer
     guidance indicates that this system will likely drop from
     one-tenth to one-quarter of an inch of rain across the
     Willamette Valley, with the greatest amounts in the north. 
     The coast and coast range may more than one-half inch of
     rain...especially north.

     An unseasonably cool upper-level trough is forecast to
     follow the cold front onshore late Saturday through
     Monday...maintaining some showers across the region with
     well below normal temperatures.  It appears that the
     heaviest shower acitivity will move inland across western
     Washington, but the Willamette Valley could pick up another
     one-tenth to one-quarter of an inch of rain...especially north.

     A building ridge of high pressure will bring a return of
     more summer-like weather after the holiday weekend. 
     Temperatures should recover to near-normal on Tuesday. 
     Highs may climb back into the 90s by the end of the week.
     Transport winds are forecast to turn offshore next week,
     which may allow for burning of fields on the extreme west
     side of the valley, after they have had a chance to dry.

Tomorrow (05 Sep):  Rain Turning to Showers Late.  Much Cooler.  54/67

Sun (06 Sep):  Mostly Cloudy and Cool.  Showers Likely.  52/65

Mon (07 Sep):  Showers Ending...Afternoon Clearing.  49/74

Tue (08 Sep):  Mostly Sunny...Warming Back to Normal.  48/79

Wed (09 Sep):  Sunny and Warm.  50/83

Thu (10 Sep):  Sunny and Very Warm.  53/88

Fri (11 Sep):  Sunny and Very Warm.  55/92

ODA Meteorologist
weather at oda.state.or.us