[willamette-fcst] Forecast - Wednesday, February 18th, 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: 
     Wednesday, February 18th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:30pm.
     Stack burning is not allowed.

Weather Discussion:
     Satellite imagery showed an impressive low-pressure system,
     an associated cloud-shield, centered several hundred miles
     off the northern California coastline this morning. 
     Precipitation from that system should stay offshore today
     with an upper-level ridge continuing to build over Oregon
     and Washington.  The freezing level over Salem rose from
     4300 feet Tuesday afternoon to 5200 feet early this morning
     and should continue to slowly climb today.

     With the expection of valley low clouds and fog thsi
     morning, skies were generally fair over Washington and
     Oregon this morning.  Clearing skies overnight allowed
     temperatures to drop below freezing across most of the
     Willamette Valley overnight.McMinnville was one of the
     colder spots, dipping to just 28 degrees.  Calm winds even
     helped the, normally warmer, Portland Airport drop briefly
     below the freezing mark this morning (31 degrees).

     The ODA surface analysis showed very weak offshore pressure
     gradients across western Oregon, and morning winds were
     mostly calm at mid-morning.  Temperatures were generally in
     the low to mid 30s with some sunbreaks beginning to make it
     through the widespread valley fog.  The fog should give way
     to at least partly sunny skies today with valley
     temperatures climbing mostly into the mid 50s (a little
     above normal).  Surface winds will remain lightly offshore. 
     Stack burning is not allowed today due to light northerly
     transport winds combined with mixing heights at or below
     2000 feet.  Offshore gradients are forecast to slowly
     increase tonight and Thursday, as the offshore low-pressure
     system drifts closer to the California coastline.

Surface Winds:
     Var 0-5 this morning, N 2-7 this afternoon.
Transport Winds:
     N 3 this morning, N 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 10.
High Temperature:
     Salem\'s high temperature today will be near 56.
Humidities:
     Minimum relative humidity will be near 38%.
Sunrise/Sunset:
     Salem sunset tonight: 5:45pm; sunrise tomorrow: 7:06am.

Extended Outlook:
     Middle and high clouds will likely increase Thursday and
     Friday, as the storm off the California coastline slowly
     moves eastward.  However, it should remain mostly dry in the
     Willamette Valley, with some light rain possibly making it
     into southwestern Oregon by Friday.  Surface winds will
     remain light offshore with mild afternoon temperatures.
     Ventilation conditions may deteriorate slightly, as the air
     aloft continues to warm.

     The sry conditions may hold through Saturday with a good
     chance of light rain moving into western Oregon by Sunday. 
     Ventilation conditions are expected to improve early next
     week, with an increasing chance of rain and lowering snow
     levels.

Tomorrow (19 Feb):  Areas of AM Fog.  Becoming Partly Sunny.  31/56

Fri (20 Feb):  Areas of AM Fog.  Partly Sunny.  33/57

Sat (21 Feb):  Areas of AM Fog.  Partly Sunny.  34/57

Sun (22 Feb):  Chance of Rain.  38/53

Mon (23 Feb):  Rain Likely at Times.  Snow Level Dropping to 3500 Feet.  40/52

Tue (24 Feb):  Showers.  Mountain Snow.  Snow Level 2500 Feet.  38/50

Wed (25 Feb):  Showers.  Mountain Snow.  Snow Level 1500 Feet.  36/49

ODA Meteorologist
weather at oda.state.or.us