[willamette-fcst] Forecast - Tuesday, February 9th, 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 9th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 11:00am to 3:30pm.
     Stack burning is not allowed.

     ...The rules for stack burning have changed.  Stack burning
     permits must be obtained from ODA smoke management personnel...

Weather Discussion:
     Fog and low clouds only partially cleared from the
     Willamette Valley on Monday, with high temperatures varying
     from the mid 40s, in foggy areas, to the low 50s where the
     fog gave way to afternoon sunshine.  As an offshore weather
     system split apart, with the main energy heading south, into
     California, fog thickened overnight across the valleys of
     western Oregon.  Temperatures locally dropped below the
     freezing mark in the Willamette Valley.  Hillsboro dipped
     down to 29 degrees this morning.  Meanwhile, Salem held up
     at 38 degrees and Eugene only dipped to 41 degrees.  Fog was
     widespread across the valley again this morning, with
     visibilities locally less than one-quarter of a mile.

     Much like yesterday, visible satellite imagery showed low
     clouds and fog covering the western valleys of both
     Washington and Oregon this morning.  Fog and low clouds were
     also extensive east of the Cascades.  Skies were mostly
     clear over the Cascades and along much of both coastlines. 
     The ODA surface analysis showed weak high pressure centered
     over south-central Washington and extending into the
     Willamette Valley.  A low-pressure system was moving onshore
     into northern California.  That was producing light
     north-northeasterly winds across western Oregon.

     A persistent split-flow jet stream pattern will direct yet
     another weather system inland across California today, while
     Oregon stays high and dry.  The air aloft remains mild, with
     the freezing level near 5000 feet.  However, fog and low
     clouds will be slow to clear across the inland valleys of
     western Oregon this afternoon.  That will keep temperatures
     from reaching 50 degrees across much of the Willamette
     Valley.  However, the north valley and the coast will likely
     see some sunshine today, with highs climging into the low to
     mid 50s.  Once again, ventilation conditions will only
     improve to fair, at best, this afternoon, so stack burning
     is not allowed.

Surface Winds:
     NNE 3-7 this morning, N 3-7 this afternoon.
Transport Winds:
     NE 5 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 49.
Humidities:
     Minimum relative humidity will be near 68%.
Sunrise/Sunset:
     Salem sunset tonight: 5:32pm; sunrise tomorrow: 7:20am.

Extended Outlook:
     A transitory ridge of high pressure will move onshore this
     evening and turn the flow aloft northwesterly.  That should
     dry the air mass slightly, allowing temperatures to drop
     well down into the 30s across western Oregon overnight. 
     Some of the traditionally colder pockets in the Willamette
     Valley will likely dip below freezing with widespread fog
     again by Wednesday morning.

     A warm front will increase cloud-cover across western Oregon
     Wednesday morning, with light rain movning onshore in the
     afternoon.  Increasing southeasterly winds will improve
     ventilation conditions Wednesday afternoon.  Rain and snow
     will push into the Cascades by Wednesday evening, with the
     snow level rising from 3500 feet Wednesday afternoon to more
     than 5000 feet Wednesday night.  The trailing cold front
     should drop snow levels back to the Cascade passes by late
     Thursday, as the steady rain turns showery and begins to
     taper off.

     The next weather system is forecast to spread more rain
     onshore Friday, with the snow level dropping to around the
     Cascade passes.  Southerly winds should make for good
     ventilation conditions.  A transitory ridge of high pressure
     may dry things out Saturday, especially south, as a warm
     front brushes by to our north.  If there is enough mixing of
     the air mass, temperatures could become quite mild Saturday
     afternoon.  A weak cold front may bring some light rain
     Sunday, with snow levels likely remaining near or above the
     Cascade passes.  Another warm front will bring a chance of
     rain Monday, with snow levels lifting above the Cascade
     passes.  The trailing cold front is forecast to come onshore Tuesday.

Wed (10 Feb):  Increasing Clouds.  Rain Developing PM.  Snow Level 3500-5000 Feet.  34/48

Thu (11 Feb):  Rain Likely.  Blustery Along the Coast.  Snow Level 5000 Feet.  42/53

Fri (12 Feb):  Rain Likely.  Snow Level Dropping to 4000 Feet.  40/53

Sat (13 Feb):  Chance of Light Rain...Mainly North.  Mild.  Snow Level 4-5000 Feet.  42/55

Sun (14 Feb):  Mostly Cloudy and Mild.  Chance of Light Rain.  Snow Level 4000 Feet.  41/53

Mon (15 Feb):  Chance of Light Rain...Mainly North.  Snow Level 5000 Feet.  37/53

Tue (16 Feb):  Chance of Rain.  Snow Level 5000 Feet.  37/54

ODA Meteorologist
weather at oda.state.or.us