[willamette-fcst] Forecast - Monday, September 28th, 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: 
     Monday, September 28th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 10:00am until 6:00pm.
     Preparatory burning is not allowed.
     Propane flaming is allowed from 10:00am until 6:00pm.
     Straw stack burning is allowed from 10:00am until 6:00pm.

Weather Discussion:
     The upper-level ridge that brought sunny and warm weather to
     western Oregon over the weekend has shifted eastward to over
     Montana. Increasing southwesterly flow aloft was forcing the
     surface thermal trough east of the Cascades this morning,
     initiating a marnine push into the southern Willamette
     Valley. Low clouds blanketed much of the coastline and had
     penetrated east of the coast range, into the southern
     Willamette Valley, across Linn and Lane Counties. Skies were
     mostly sunny across most of the northern Willamette Valley,
     although some low clouds had formed near the Cascades in
     eastern Marion County.

     Onshore flow will push northward across the entire
     Willamette Valley today, with low clouds also filling into
     some of the the north valley later this morning. With the
     air mass rapidly cooling today, both at the surface and
     aloft, high temperatures will drop below normal, ranging
     from the upper 60s in the south valley to the low 70s in the
     north valley.

     Satellite imagery showed a cold front about 250 miles off of
     the Washington and Oregon coastline. As it advances
     eastward, light rain will likely push onto the coast in the
     mid to late afternoon, then across the Willamette Valley
     this evening. Rainfall amounts, with the initial cold front,
     are expected to be light, with most areas picking up around
     one-tenth of an inch. A fairly cold upper-level trough will
     follow the cold front onshore Tuesday with more showers and
     even cooler temperatures.

     We are not aware of any available fields for burning at this time. 

Surface Winds:
     S 5-12 this morning, SW 7-15 this afternoon.
Transport Winds:
     SSW 15 this morning, SSW 19 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 67.
High Temperature:
     Salem\'s high temperature today will be near 70.
Humidities:
     Relative humidity drops to 50% around 1pm.
     Minimum relative humidity will be near 42%.
Sunrise/Sunset:
     Salem sunset tonight: 6:58pm; sunrise tomorrow: 7:08am.

Extended Outlook:
     The coldest upper-level trough so far of the early autumn
     season will move onshore Tuesday with snow levels dropping
     as low as 4000 feet in stronger showers.  Willamette Valley
     temperatures will drop well below normal with showers
     dropping another one-tenth to one-quarter of an inch of
     rain.  There is even a slight chance of a thundershower.  A
     transitory weak upper-level ridge is forecast to move over
     the reigon Wednesday for some drying and minor warming.

     Another cold front is forecast to come onshore
     Thursday...mainly into western Washington.  The trailing
     edge of the front may bring some light rain to extreme
     northwestern Oregon.  That system will likely be followed by
     a cool trough Friday that may bring some showers to mainly
     the northern valley.  The upper-level trough is forecast to
     deepen over the Pacific Northwest Saturday, for a better
     chance of showers and lowering snow levels.

     The upper-level trough is forecast to drop south of the
     region Sunday and Monday.  Temperatures should slowly moderate,
     with a drier but continued cool northeasterly flow aloft.  

Tomorrow (29 Sep):  Showery and Cool.  Slight Chance T-Storm.  Snow Level 4-5000 Feet.  47/61

Wed (30 Sep):  Showers Ending Early...Becoming Partly Cloudy.  45/63

Thu (01 Oct):  Increasing Clouds.  Light Chance of Light Rain North.  44/67

Fri (02 Oct):  Mostly Cloudy.  Chance of Showers...Mainy North.  47/66

Sat (03 Oct):  Mostly Cloudy.  Chance of Showers.  Snow Level 4-5000 Feet.  45/63

Sun (04 Oct):  Becoming Partly Cloudy.  A little Warmer.  43/67

Mon (05 Oct):  Partly Sunny.  42/69

ODA Meteorologist
weather at oda.state.or.us