[willamette-fcst] Forecast - Tuesday, November 10th, 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: 
     Tuesday, November 10th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:00pm.
     Straw stack burning is allowed from now until 3:00pm.

Weather Discussion:
     The cold front that swept across western Oregon Monday
     stretched from central Montana to southern Idaho this
     morning.  In it\'s wake, a few showers were falling this
     morning, mainly over northeastern Oregon.  Satellite and
     radar imagery revealed a fairly dry zone, in the wake of the
     cold front, covering eastern Washington and most of Oregon
     at mid-morning.  However, there was a large area of showers,
     associated with a cold upper-level trough, just off of the
     Washington and northern Oregon coast.

     Southwesterly flow aloft was rotaing those showers onshore
     across western Washington and extreme northwestern Oregon. 
     A few showers will also coming onshore into southwestern
     Oregon.  The ODA surface analysis showed weaker southeastery
     pressure-gradients, across western Oregon, than on Monday. 
     Winds were light enough across the Willamette Valley this
     morning for areas of fog to form, with visibilities locally
     less than one-quarter of a mile.  Mid-morning temperatures
     were mostly in the mid to upper 40s, except for foggy areas,
     which were mostly still in the 30s.

     The freezing levels over Salem and Medford were measured
     this morning at 4200 and 6000 feet respectively...putting
     the snow level at or below the Cascade passes.  ODOT road
     cameras showed an inch or two of new snow on the passes this
     morning.  Southwesterly flow aloft is forecast to continue
     rotating showers onshore today...mainly into western
     Washington and northwestern Oregon. The showers will fall as
     snow over the Cascade passes.  The air aloft is cold enough
     to support the development of isolated thundershower
     activity, especially near the coast.

     The showers rotating onshore will help to mix the air mass
     today, lifting the fog from the Willamette Valley and making
     for good ventilation conditions.  Cold air aloft will cap
     high temperatures in the mid 50s this afternoon, even with
     some sunbreaks.  Temperatures will quickly fall back into
     the 40s near showers.  Some showers could produce small
     hail, especially near the coast and over the coast range.

Surface Winds:
     SSE 5-15 this morning, S 5-15 this afternoon.
Transport Winds:
     S 15 this morning, SSW 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2700 feet.  Ventilation index 54.
High Temperature:
     Salem\'s high temperature today will be near 55.
Humidities:
     Minimum relative humidity will be near 64%.
Sunrise/Sunset:
     Salem sunset tonight: 4:48pm; sunrise tomorrow: 7:05am.

Extended Outlook:
     Showers will increase on Wednesday, as the offshore
     upper-level trough swings over the region.  The snow level
     will continue to drop...possibly as low as 2500 feet in
     heavier showers.  Locally heavy snow is possile over the
     Cascade passes.  A somwwhat drier northwesterly flow aloft
     is forecast by Thursday afternoon.

     Another cold weather system is forecast to drop into the
     region, from the Gulf of Alaska, on Friday.  That system
     could also produce locally heavy snow, over the Cascade
     passes.  A warm front is forecast to quickly lift snow
     levels back above the passes by late Saturday.  A cold front
     is forecast to come onshore Sunday...mainly in Washington
     and northern Oregon.  A warmer westerly flow aloft will keep
     snow levels above the Cascade passes.  Another system is
     forecast to come onshore next Tuesday.

Tomorrow (11 Nov):  Increasing Showers.  Snow Level 3000 Feet.  40/50

Thu (12 Nov):  Mostly Cloudy.  Decreasing Showers.  Snow level 3000 feet.  38/49

Fri (13 Nov):  Rain and Mountain Snow.  Snow Level 3000 Feet.  40/48

Sat (14 Nov):  Mostly Cloudy.  Chance of Light Rain.  Snow Level Rising to 5000 Feet.  36/50

Sun (15 Nov):  Rain...Mainly North.  Snow Level 5000 Feet.  42/54

Mon (16 Nov):  Mostly Cloudy and Mild.  41/55

Tue (17 Nov):  Rain Developing.  41/52

ODA Meteorologist
weather at oda.state.or.us