[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 12:00pm.

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 24-hour rainfall totals along the southern
     Oregon Coast on the order of 1-2 inches.  Between one-quarter and three-quarters
     of an inch of rain fell from the northern and central coast across 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 this morning.
     Precipitation turned from rain to wet snow on the Cascade passes overnight, with 
     a few inches accumulating by daybreak.  The higher ski araes picked up 5-10 inches
     of much-needed new snow. 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.

     Surface winds turned southerly just after midnight, with coastal and valley
     temperatures quickly warming about 5-10 degrees.  late-morning readings were
     mostly in the low to mid 50s...some 10 degrees warmer than Tuesday\'s highs.
     The freezing level is still around 5000 feet and the snow level will hover
     near Cascade pass level this afternoon.  ODOT road cameras showed slushy pavement
     over the Cascade passes, at midday, with temperatures just above freezing.
 
     A moist southwesterly flow aloft will keep lots of clouds over the state today, with
     southerly surface winds making for a mild afternoon.  Weak convection, induced by the
     combination of mild surface temperatures and cool air aloft, should cap highs in the
     mid 50s but make for good ventilation.  Doppler radar was showing an increase in light
     shower activity over mainly the coast range at midday.  Some showers will likely develop
     over the Willamette Valley this afternoon.  A weak upper-level impulse may continue the
     threat of showers through early Thursday. 

Surface Winds:
     SSW 5-15 G20 this afternoon.
Transport Winds:
     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 56.
Humidities:
     Minimum relative humidity will be near 64%.
Sunrise/Sunset:
     Salem sunset tonight: 5:53pm; sunrise tomorrow: 6:57am.

Extended Outlook:
     A transitory ridge of high pressure will bring some drying late Thursday morning, but an
     active warm front is forecast spread more rain onshore as early as midday Thursday and into
     the Willamette Valley no later than Thursday evening (possibly as early as midday). A cold
     front will follow the warm front onshore Friday and continue the steady rain across
     western Oregon.  However, it will encounter the split-flow jet stream pattern, with the
     bulk of its strength forecast to hit California.  A cool (not cold) upper-level trough
     will drop snow levels only to near the Cascade passes 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 possibly 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):  Showers Ending Early.  Rain Developing PM.  Snow Level 4000 Feet.  40/54

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