[willamette-fcst] Forecast - Tuesday, February 23rd, 2010

[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, February 23rd, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 1:00pm to 4:00pm.
     Straw stack burning is allowed from 1:00pm until 4:00pm.

Weather Discussion:
     The upper-level ridge that has brought unseasonably warm and
     dry weather to the region for the past few days has shifted
     eastward, to over Idaho, this morning.  An increasing
     southwesterly flow aloft will direct a series of weather
     systems onto the west coast for the remainder of this week. 
     The main punch from these systems will be directed south of
     Oregon, into California, but western Oregon will see some
     rain and higher elevation snow at times through Friday.

     Clouds increased over western Oregon during the
     night, keeping overnight minimums generally just above the
     freezing mark.  By mid-morning, temperatures had risen into
     the upper 30s to mid 40s across western Oregon. Satellite
     imagery showed a solid cloud shield, associated
     with a weakening weather system, covering western Oregon and
     pushing east of the Cascades.  Doppler radar and surface
     reports indicated that areas of mostly light rain had pushed
     onshore and into the Willamette Valley.  More significant
     rainfall was moving into northern California.

     The ODA surface analysis continued to show offshore pressure
     gradients across Oregon, in response to the approaching
     frontal system.  Winds around to the state were mostly less
     than 10 mph, with easterly gusts to around 20 mph at the
     western end of the Columbia Gorge. Light rain at times is
     likely across the Willamette Valley today.  Winds will remain
     light southeasterly.  Rainfall totals should range from
     about one-tenth to one-quarter of an inch.  After several
     days of above normal temperatures, Willamette Valley highs
     should be held in the 40s today (the normal high for Salem
     today is 53 degrees).

     The air aloft is still fairly mild, with the freezing level
     measured at more than 7000 feet early this morning.  The
     snow level should remain above 5000 feet today and then
     lower to around 4000 feet by Wednesday morning.  The
     Cascades passes will likely get a mix of rain and snow today
     with accumulating snow likely overnight.

Surface Winds:
     SE 5-10 this morning, SE 5-15 this afternoon.
Transport Winds:
     S 10 this morning, S 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 45.
High Temperature:
     Salem\'s high temperature today will be near 47 (high on Monday was 55 degrees).
Humidities:
     Minimum relative humidity will be near 58%.
Sunrise/Sunset:
     Salem sunset tonight: 5:52pm; sunrise tomorrow: 6:58am.

Extended Outlook:
     The main frontal band is forecast to come onshore early
     Wednesday and could bring another one-tenth to one-quarter of
     an inch of rain to the Willamette Valley, followed by
     showers Wednesday afternoon.  The snow level should drop to
     about 3500 feet by Wednesday afternoon, with a few inches of
     snow likely over the Cascade passes.  Light southerly
     surface winds will help coastal and western valley
     temperatures climb close to normal Wednesday afternoon.

     A transitory ridge of high pressure will bring some drying
     on Thursday, with another system coming onshore Friday. That
     system will also encounter the split-flow jet stream
     pattern, just off the west coast, with the main surge of
     moisture headed south into California.  Enough energy will
     swing over Oregon, however, to bring back some rain and
     mountain snow.

     A ridge of high pressure is forecast to rebuild back over
     the west coast this weekend, with unseasonably mild
     conditions returning to western Oregon by Sunday. 
     Increasing southwesterly flow aloft will likely bring a
     weakening weather system onshore by late Monday. 
     Progressively stronger systems are forecast to come onshore
     later next week, as the jet stream takes aim a little more
     at Oregon, instead of California.

Tomorrow (24 Feb):  AM Rain...PM Showers.  Snow Level near 3500 Feet.  41/53

Thu (25 Feb):  Mostly Cloudy.  Showers Ending.  Snow Level 4000 Feet.  40/56

Fri (26 Feb):  Rain Likely.  Snow Level near 5000 Feet.  42/54

Sat (27 Feb):  Mostly Cloudy.  Showers Ending.  38/55

Sun (28 Feb):  Partly Cloudy and Unseasonably Mild.  37/62

Mon (01 Mar):  Increasing Clouds.  Chance of Rain.  Snow Level 6000 feet.  38/59

Tue (02 Mar):  Rain Likely.  Snow Level 5-6000 Feet.  41/57

ODA Meteorologist
weather at oda.state.or.us