[willamette-fcst] Forecast - Monday, April 6th, 2009

Mon Apr 6 09:03:42 PDT 2009

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: 
     Monday, April 6th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 6:00pm.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level ridge of high pressure moved onshore, as
     forecast, over the weekend.  After a frosty Saturday
     morning, with Willamette minimums in the upper 20s, rapid
     warming of the air mass and increasing offshore flow helped
     Saturday afternoon temperatures recover to near normal
     (about 60 degrees).  Valley minimums stayed just above
     freezing Sunday morning, with continued warming of the air
     mass pushing Sunday afternoon temperatures into the upper
     60s and low 70s.  Offshore flow extended to the beaches over
     the weekend, with highs Saturday 55-60 and Sunday in upper
     50s to mid 60s.

     The upper-level ridge axis had flattened slightly, and
     shifted eastard to over Idaho, this morning.  The next
     weather system had cut off from the main flow pattern and
     was spinning around about 550 miles off the central
     California Coastline.  Satellite imagery showed the main
     cloud-shield from that system well off the California Coast,
     with mostly clear skies extending from the Pacific Northwest
     to the Desert Southwest.  The morning sounding over Salem
     showed further warming aloft, since Sunday afternoon, with
     weak northerly winds below about 5000 feet and weak
     southerly flow aloft.  The air mass continued to be very dry
     at all levels.

     Fair skies and light winds allowed temperatures to locally
     drop into mid 30s across the Willamette Valley this morning.
     Hillsboro was the coldest spot I could find with a minimum
     at least down to 34 degrees.  Eugene dropped to at least 36
     degrees. the The ODA surface analysis continued to show
     offshore flow across western Washington and western Oregon
     with light north-northeasterly gradients across the
     Willamette Valley.  Valley temperatures had already climbed
     into the 50s by mid-morning, indicating that a quick warm-up
     is in store today.  Very warm air aloft and offshore surface
     winds should combine to raise afternoon temperatures to
     near-record levels across western Oregon this afternoon. 
     Willamette Valley highs will climb into the mid and upper
     70s.  78 degrees is the daily record high for both Salem and
     Eugene today, set back in 1906 and 1989 respectively.

Surface Winds:
     N 0-5 this morning, NNE 5-10 this afternoon.
Transport Winds:
     N 5 this morning, NNE 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2100 feet.  Ventilation index 17.
High Temperature:
     Salem\'s high temperature today will be near 74.
Humidities:
     Minimum relative humidity will be near 28%.
Sunrise/Sunset:
     Salem sunset tonight: 7:47pm; sunrise tomorrow: 6:41am.

Extended Outlook:
     The slow-moving upper-level low pressure system off the
     California Coast will slide far enough eastward to bring
     clouds and some showers into California by Tuesday
     afternoon.  Some middle and high clouds will spread north
     over Oregon Tuesday, but the main effect from this system
     will be to shift the thermal trough east of the Cascades
     Tuesday afternoon.  The will allow cooler marine air to
     begin spilling into the Willamette Valley, capping high
     temperatures near 70 degrees.  North-northeasterly transport
     winds should veer to northwesterly Tuesday afternoon, with
     mixing heights climbing above 3000 feet, in response to
     cooling aloft.

     Onshore flow will increase Wednesday, as the upper-level
     trough moves inland over northern and central California. 
     More clouds and some showers will likely rotate northward
     over mainly the southern half of Oregon.  Willamette Valley
     high temperatures will quickly drop to near mormal with the
     snow level dropping to around 5500 feet in the Cascades. 
     The next weather system is forecast to weaken as it moves
     onshore Thursday, but it should be strong enough to bring
     some showers to most of western Oregon, with lowering snow
     levels.  The next break appears to be Easter Sunday, with
     rain returning Monday.

Tomorrow (07 Apr):  Increasing Middle and High Clouds.  Onshore Flow Late.  42/70

Wed (08 Apr):  Moslty Cloudy and Cooler.  Chance of Showers...Mainly South.  43/57

Thu (09 Apr):  Showers Likely.  Snow Level Dropping to 4000 Feet.  42/54

Fri (10 Apr):  Mostly Cloudy.  Chance of Showers.  40/54

Sat (11 Apr):  Mostly Cloudy.  Chance of Showers.  40/57

Sun (12 Apr):  Partly Sunny.  40/62

Mon (13 Apr):  Rain Likely.  Snow Level Dropping to 3000 Feet.  42/55

ODA Meteorologist
weather at oda.state.or.us