[willamette-fcst] Forecast - Thursday, May 1st, 2008

Thu May 1 07:59:45 PDT 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.

...No noon update today and possibly no update until 9 am Monday, May 5th.

Issued: 
     Thursday, May 1st, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     The upper-level trough that brought showers and cool weather
     to the state Tuesday and Wednesday shifted eastward to over
     the Northern Rockies by early this morning.  Weak high
     pressure had nosed into the west coast with a dry
     northwesterly flow aloft over Oregon.  Some middle and high
     clouds, from an approaching warm front, helped to keep
     temperatures from falling below the freezing mark across
     most of Western Washington and Western Oregon overnight. 
     Willamette Valley minimums this morning dropped to 33
     degrees in Eugene, Corvallis, and Hillsboro.  Salem fell to
     35 and McMinnville 36.  Even the southwestern valleys were
     cold with Medford dropping to at least 33 this morning. 
     Meanwhile, the Portland Airport held up at 41 degrees.

     Skies were more clear east of the Cascades, which allowed
     temperatures to cool into the teens 20s across much of that
     region.  The final minimums will not be available until
     after 11 am, but it dropped to at least 14 degrees in Burns
     early this morning, 18 at Rome, and 19 at both Klamath Falls
     and Lakeview.  Redmond dipped to at least 20 degrees, and
     Baker City hit 23.  It was warmer in the Columbia Basin,
     with Pendleton holding at 39 degrees.  The Dalles held up at 40.

     The ODA surface analysis this morning showed weak high
     pressure centered over the Southern Willamette Valley and
     the Columbia Basin, in NE Oregon.  Gradients were flat to
     slightly offshore across Western Oregon with just a touch of
     westerly gradient remaining near the Idaho Border.  Light
     winds will make for poor ventilation condtions over Western
     Oregon today.

     The air aloft was still quite cool this morning with the
     freezing levels over Salem and Medford measured at just 3000
     and 3800 feet respectively.  Warming aloft today should lift
     the freezing level to near 7000 feet by late this afternoon
     with mid and high clouds filtering the sunshine over Western
     Oregon.  High temperatures should warm close to 60 degrees.

     The transitory upper-level ridge is forecast to shift east
     of the Cascades tonight with a warm front spreading light
     rain onto the coastline by Friday morning.  Mostly cloudy
     skies tonight will combine with a warming air mass to hold
     minimum temperatures near 40 across Western Oregon, so frost
     should not be an issue.  Temperatures should still fall
     below the freezing mark overnight across much of Central and
     Eastern Oregon, but it will not be a cold Friday morning as
     it was this morning.

     A weak frontal system is forecast to bring light rain to
     Western Oregon Friday with a few showers possibly lingering
     into early Saturday...especially over the Cascades.  Only a
     few showers are likely to make it east of the Cascades late
     Friday and saturday.  Temperatures will be near normal
     Friday with western valley highs likely climbing into the
     low 60s.  Ventilation conditions will improve slightly but
     may still not be good enough to allow for stack burning.

Surface Winds:
     Var 0-5 this morning, SE 0-5 this afternoon.
Transport Winds:
     S 5 this morning, SW 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 25.
High Temperature:
     Salem\'s high temperature today will be near 60.
Humidities:
     Minimum relative humidity will be near 41%.
Sunrise/Sunset:
     Salem sunset tonight: 8:18pm; sunrise tomorrow: 5:59am.

Extended Outlook:
     A weak upper-level trough is forecast to maintain a chance
     of showers, mainly from the Cascades eastward, Saturday with
     a ridge of high pressure bringing warmer and dry conditions
     Sunday and Monday.  Another fairly cool weather system will
     likely bring an end to the spring-like weather Tuesday or Wednesday.

Tomorrow (02 May):  Light Rain at Times.  Snow Level 5000 Feet.  41/61

Sat (03 May):  Mostly Cloudy.  Slight Chance of Showers.  Snow Level 5000 Feet.  43/62

Sun (04 May):  Partly Sunny and Warmer.  39/66

Mon (05 May):  Partly Sunny and Warm.  42/70

Tue (06 May):  Mostly Cloudy.  Increasing Chance of Showers.  Snow Level 5-6000 Feet.  43/65

Wed (07 May):  Showers and Cooler.  Snow Level 3-4000 Feet.  42/59

Thu (08 May):  Decreasing Showers.  Snow Level 3-4000 Feet.  39/59

ODA Meteorologist
weather at oda.state.or.us