[willamette-fcst] Forecast - Tuesday, July 3rd, 2007

[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: 
     Tuesday, July 3rd, 2007 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 6:00pm.
     Straw stack burning is allowed from 11:00am until 6:00pm.

Weather Discussion:
     A strong upper-level ridge of high pressure is expanding
     northward, into the Pacific Northwest, from the four-corners
     region of the United States.  That will bring an extended
     period of warm and dry weather to the region.  The ridge
     axis is forecast to position itself east of Oregon, over
     Idaho and extreme Western Montana, which will not allow for
     a surface thermal trough to develop west of the Oregon
     Cascades.  That will prevent excessive heat from making its
     way into Western Oregon this week, due to a continuation of
     onshore surface winds.

     The ODA morning surface analysis showed very little pressure
     gradient across the region with light winds being reported
     statewide.  Weak onshore flow was producing some areas of
     low clouds along sections of the coastal strip and coast
     range, with sunny skies elsewhere.  A dissapating surface
     cold front was stretching from the NW tip of Washington to
     well off of the Oregon Coastline.  This feature will
     continue to weaken, as surface high pressure builds north
     along the Oregon and Washington Coast today, helping to
     provide an afternoon seabreeze in the Willamette Valley.

     The Salem upper-air sounding was available this morning and
     and showed light south winds at the surface becoming
     southwesterly above 5000 feet.  Our friends at REMAX
     launched a hot-air balloon, just west of the Dept. of Ag.
     building this morning, which visually confirmed a light
     south low-level wind.  It would be nice, if they did that
     more often.

     I calculated a maximum mixing height of 6000 feet today,
     based on the Salem sounding. However, we should experience
     some warming aloft today, due to the building ridge of high
     pressure, so mixing heights are not likely to climb much
     above 4500 feet.  I have adjusted my forecast accordingly.

Surface Winds:
     S 3 this morning, NW 4-8 this afternoon.
Transport Winds:
     SSW 3 this morning, WNW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 36.
High Temperature:
     Salem\'s high temperature today will be near 86.
Humidities:
     Relative humidity drops to 50% by 2pm.
     Minimum relative humidity will be near 32%.
Sunrise/Sunset:
     Salem sunset tonight: 9:02pm; sunrise tomorrow: 5:31am.

Extended Outlook:
     An upper-level ridge will continue to build northward over
     the region Wednesday but will stay centered over Idaho and
     Western Montana.  That will result in surface thermal trough
     development near the Idaho border with 100 degree
     temperatures in the Eastern Oregon valleys Wednesday and
     Thursday.  Weak onshore gradients will help cap mid-week
     high temperatures near 90 degrees in the Willamette
     Valley.

     The upper-level ridge will begin to flatten and shift into
     Eastern Idaho Thursday evening, with the surface thermal
     trough moving into Idaho.  That will increase onshore
     gradients across Oregon and usher in cooler marine air.  The
     region will stay dry and warm through the extended forecast
     period, under the influence of a stable west-southwesterly
     flow aloft.

Tomorrow (04 Jul):  Sunny and Hot.  55/90

Thu (05 Jul):  Sunny and Hot.  57/91

Fri (06 Jul):  Sunny.  54/85

Sat (07 Jul):  Patchy Morning Clouds...Sunny.  51/83

Sun (08 Jul):  Patchy Morning Clouds...Sunny.  50/83

Mon (09 Jul):  Sunny.  51/86

Tue (10 Jul):  Mostly Sunny.  54/85



ODA Meteorologist
weather at oda.state.or.us