[willamette-fcst] Forecast - Tuesday, April 1st, 2008

Tue Apr 1 06:59:46 PST 2008

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, April 1, 2008 at 9:00 am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 5:30 pm.
     Stack burning is not allowed.

Weather Discussion:
     Another upper-level disburbance, from British Columbia,
     brought scattered showers to Washington and the northern
     third of Oregon Monday afternoon and evening.  Snow levels
     were quite low (2000 feet) over Northern Oregon, but
     not much additional snow fell in the mountains due to the
     lack of moisture.  Rainfall amounts were generally only a
     couple hundredths of an inch across extreme Northern Oregon
     with a trace of rain falling as far south as Salem.

     The upper-level disturbance moved into Northeastern Oregon
     overnight with clearing skies and a cold air mass bringing
     near-record cold temperatures to Western Oregon this
     morning.  Valley minimums ranged from 25-30 degrees. 
     Official low temperatures will not be available until 11 am,
     but preliminary readings show that Aurora, Salem, Corvallis,
     and Eugene all dropped down to at least 30 degrees. 
     McMinnville dipped to at least 27 and Hillsboro to at least 25.

     As you would expect, it was much colder east of the Cascades
     this morning.  Meacham, in Northeastern Oregon, was one of
     the coldest spots...dropping to at least 5 degrees.  Redmond
     dropped to at least 10 degrees and Lakeview to at least 19. 
     Clouds and snow flurries kept temperatures from falling
     quite as low over extreme Eastern Oregon, but it was still
     plenty cold.  Baker City fell to at least 23 degrees with
     some very light snow overnight. 

     Northerly flow aloft will continue over the Pacific
     Northwest today.  The air mass will slowly dry and warm, as an
     upper-level ridge builds closer to the coastline.  Temperatures
     will warm, both at the surface and aloft, with sunny skies helping
     afternoon temperatures climb into the mid and upper 50s across
     Western Oregon.  Northerly surface and transport winds are not
     favorable for good valley ventilation, so stack burning is not
     allowed again today.

     The next upper-level disturbance will drop down from British
     Columbia across Eastern Washington, Northern Idaho, and
     Northeast Oregon tonight.  That is too far east to bring
     much in the way of cloud-cover to Western Oregon, but it
     will help to maintain the unseasonably cold air mass over
     the region.  Light northerly winds and mostly clear skies
     will allow for another very cold night, across Oregon, with
     near record low temperatures likely again in the Willamette
     Valley.  Frost sensitive crops may need protection.

     This is a very typical early spring La Nina weather pattern.
     In fact, my top analog year to this year (1971) had a
     similar cold spell at this same time of year.  April of 1971
     went on to be colder than normal across the state, with
     near-normal precipitation (slightly wet west of the Cascades
     and slightly dry east).  I am expecting this April to be
     similar.  My seasonal climate outlook for April-June is
     available in either PowerPoint or PDF format on the web at
     http://oregon.gov/ODA/NRD/weather.shtml#Weather_forecasts.

Surface Winds:
     N 5-10 this morning, N 10-15 this afternoon.
Transport Winds:
     NNE 10 this morning, NNE 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 68.
High Temperature:
     Salem\'s high temperature today will be near 56.
Humidities:
     Minimum relative humidity will be near 33%.
Sunrise/Sunset:
     Salem sunset tonight: 7:41pm; sunrise tomorrow: 6:50am.

Extended Outlook:
     Further warming is expected Wednesday and Thursday, as the
     upper-level ridge continues to build into the west coast. 
     Northerly flow will prevail, both at the surface and aloft. 
     The dry air mass and fair skies will allow morning minimums
     to dip near or below the freezing mark across the valley. 
     Afternoon highs should reach near 60 Wednesday and into the
     60s Thursday.

     The weather system slated to move into the region Friday
     shows up stronger on the latest computer model projections. 
     It now appears strong enough to bring a significant threat
     of showers to Western Oregon, as it pushes through the
     upper-level ridge and turns the surface flow onshore.  That
     should help to keep minimums above the freezing mark Friday
     morning and cool afternoon temperaures back into the 50s.

     A transitory ridge is still forecast to rebuild over the
     region for some drying and warming Saturday.  The long-range
     models are all over the board after Saturday, so my
     confidence in the forecast for early next week is low.  The
     models want to maintain some form of onshore flow, which
     would give mostly cloudy skies and at least a chance of
     showers to Western Oregon.  Temperatures are most likely
     going to stay near or slightly below normal.

Tomorrow (02 Apr):  Sunny and Warmer.  Winds N 5-15.  29/59

Thu (03 Apr):  Mostly Sunny.  31/63

Fri (04 Apr):  Mostly Cloudy.  Good Chance of Showers.  35/58

Sat (05 Apr):  Becoming Partly Cloudy.  35/61

Sun (06 Apr):  Mostly Cloudy.  Chance of Rain.  Snow Dropping to 4000 Feet.  38/57

Mon (07 Apr):  Mostly Cloudy.  Chance of Showers.  Snow Level 4000 Feet.  38/56

Tue (08 Apr):  Mostly Cloudy.  Chance of Showers.  Snow Level 4000 Feet.  39/57

ODA Meteorologist
weather at oda.state.or.us