[willamette-fcst] Forecast - Wednesday, February 24th, 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: 
     Wednesday, February 24th, 2010 at 9:00am.

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

Weather Discussion:
     A slow-moving frontal system brought steady light rain to
     western Oregon Tuesday. CoCoRaHS reports this morning showed
     that total rainfall amounts, over the past 24 hours, were
     heaviest along the southern Oregon Coast, where between 1.5
     and 2 inches were common.  Between one-quarter and
     three-quarters of an inch of rain fell along the northern and
     central coast and in the Willamette Valley, with over an
     inch falling in the northern coastal range.

     The occluded front finally moved through the Willamette
     Valley around midnight and continued to weaken as it pushed
     across central and eastern Oregon in the early morning
     hours.  Precipitation started as rain, at the Cascade pass
     level, on Tuesday but changed to wet snow overnight.  ODOT
     road reports indicated about one-half inch of water-equivalent
     precipitation fell at pass level, with over an inch falling
     in the higher ski areas.  The passes picked up as much as 5 inches
     of new snow overngiht with close to 10 inches at the ski resorts.
     
     Rainfall amounts were considerably lighter east of the Cascades,
     but most areas picked up at least a few hundredths of an inch.  Burns
     was one of the wettest location...receiving almost one-half of rain.

     We have a moist, but not very unstable, southwesterly flow
     aloft this morning, in the wake of the frontal system.  That
     will keep lots of clouds over the state today, along with some
     sunbreaks.  Daytime heating will act to increase the chance of
     showers somewhat this afternoon, with the chance of showers
     continuing into early Thursday.

     The freezing level was still over 5000 feet this morning, so the air
     mass behind this front was not very cool.  The snow level should only
     drop to about 3500 feet this afternoon, with a few more inches of wet
     snow likely over the Cascade passes.  At the surface, the winds turned
     southerly, in the wake of the warm occluded front, with coastal and valley
     temperatures warming about 5-10 degrees shortly after midnight.
     Mid-morning readings ranged from the mid 40s to the low 50s, in most cases
     warmer than at any time on Tuesday.  For instance, Salem\'s high on Tuesday
     was only 44 degrees, with their temperature warming into the upper 40s
     shortly after midnight.  Continued southerly winds will make for good
     ventilation conditions today and will help coastal and western valley
     temperatures climb close to normal.

Surface Winds:
     S 5-15 G20 this morning, SSW 5-15 G20 this afternoon.
Transport Winds:
     SSW 20 this morning, SW 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 60.
High Temperature:
     Salem\'s high temperature today will be near 53.
Humidities:
     Minimum relative humidity will be near 71%.
Sunrise/Sunset:
     Salem sunset tonight: 5:53pm; sunrise tomorrow: 6:57am.

Extended Outlook:
     A transitory ridge of high pressure will bring some drying
     on Thursday, with a warm front bringing more rain onshore
     Thursday night.  The cold front will will encounter a
     split-flow jet stream pattern, just off the west coast on
     Friday, with the main surge of moisture headed south into
     California.  Enough energy will swing over Oregon, however,
     to maintain rainy conditions with higher elevation snow.  A
     cool upper-level trough will drop snow levels slightly
     Saturday, as showers taper off.

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

Tomorrow (25 Feb):  Mostly Cloudy.  Showers Ending.  Snow Level 4000 Feet.  41/55

Fri (26 Feb):  Rain Likely.  Snow Level Near 5000 Feet.  45/55

Sat (27 Feb):  Mostly Cloudy.  Showers Ending.  Snow Level 4000 Feet.  38/53

Sun (28 Feb):  Partly Cloudy and Turning Mild.  37/60

Mon (01 Mar):  Increasing Clouds. Continued Mild.  Freezing Level Near 7000 feet.  38/62

Tue (02 Mar):  Rain Likely.  Snow Level 5-6000 Feet.  41/54

Wed (03 Mar):  Mostly Cloudy.  Decreasing Showers.  Snow Level 4-5000 Feet.  38/54

ODA Meteorologist
weather at oda.state.or.us