[willamette-fcst] Forecast - Tuesday, September 22nd, 2009

[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, September 22nd, 2009 at 8:50am.

Burn Advisory:
     Agricultural burning is not recommended.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     Autumn officially begins today at 2:18pm. However, the
     weather pattern is going to stay in summer mode, with an
     unseasonably strong upper-level ridge of high pressure
     remaining over the region. At the surface, a very dry
     offshore flow was keeping skies mostly cloud-free over
     Oregon this morning. However, satellite imagery showed
     smoke, from southern Oregon Cascade wildfires, being
     directed over the central and southern Willamette Valley and
     much of the coastline, by southeasterly winds aloft.

     After recording high temperatures in the mid to upper 80s
     Monday, Willamette Valley minimums this morning ranged from
     the mid 40s, in the Eugene area, to the mid 50s in the
     Portland area. At the western end of the Columbia Gorge,
     strong easterly winds, gusting over 30 mph at Troutdale,
     held overnight temperatures near 70 degrees. Temperatures
     east of the Cascades ranged from the low 30s, in Meacham, to
     the low 50s, in John Day.

     As the ridge of high pressure slowly shifts eastward,
     surface winds will likely decrease and turn more
     southeasterly along the coast and in the Willamette Valley
     today. The flow may turn onshore along the southern coast
     this afternoon, bringing significant cooling to that region,
     which recorded highs Monday in the low 90s. The flow should
     stay offshore along the north coast today, where highs, once
     again, should climb well into the 80s.

     Very warm air aloft will keep mixing heights below 1500 feet
     most of today, with a maximum mixing height just above the
     2000-foot mark late this afternoon. Warm air aloft will
     combine with mostly sunny skies and down-sloping
     southeasterly winds to warm Willamette Valley temperatures
     into the low to mid 90s...perhaps locally reaching record
     highs. Winds will not be as strong today, especially away
     from the Columbia Gorge, but sections of the valley could
     still meet State Fire Marshal Conditions this afternoon.

Surface Winds:
     ESE 5-10 this morning, ESE 5-10 this afternoon.
Transport Winds:
     SE 5 this morning, SE 6 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2200 feet.  Ventilation index 13.
High Temperature:
     Salem\'s high temperature today will be near 95.
Humidities:
     Minimum relative humidity will be near 13%.
Sunrise/Sunset:
     Salem sunset tonight: 7:09pm; sunrise tomorrow: 7:01am.

Extended Outlook:
     The strong upper-level ridge will continue to shift slightly
     eastward Wednesday, with surface winds turning northwesterly
     across the valley late in the day.  That should bring a few
     degrees of cooling to the valley, but temperatures will
     still climb at least into the mid to upper 80s.  The
     upper-level ridge is forecast to shift over Idaho Thursday,
     with a very weak trough moving into southern British
     Columbia.  That should increase the onshore flow and cool
     temperatures closer to normal across western Oregon.

     The upper-level ridge is forecast to rebuild over the
     region, beginning Friday, with well above normal
     temperatures lasting at least through Sunday.  An
     upper-level trough is forecast to approach the coastline
     late Monday with a chance of precipitation returning to the
     region about next Tuesday.

Tomorrow (23 Sep):  Sunny and Very Warm.  Wind Becoming NW in the Afternoon.  52/89

Thu (24 Sep):  Mostly Sunny and Warm.  Increasing NW Winds.  50/83

Fri (25 Sep):  Patchy AM Clouds...Sunny.  Wind Becoming Northerly.  47/84

Sat (26 Sep):  Sunny and Very Warm.  NNE Winds.  48/86

Sun (27 Sep):  Sunny and Very Warm.  NNE Winds.  48/88

Mon (28 Sep):  Mostly Sunny but Cooler.  Increasing Onshore Flow Late.  49/82

Tue (29 Sep):  Mostly Cloudy and Cooler.  Increasing Chance of Showers.  48/73

ODA Meteorologist
weather at oda.state.or.us