[willamette-fcst] Forecast - Tuesday, November 10th, 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.

...No Updates Before Thursday, November 12th, 2009 at 9:00am...

NOON UPDATE

Issued: 
     Tuesday, November 10th, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:00pm.
     Straw stack burning is allowed, for dry stacks, from now until 3:00pm.

Weather Discussion:
     The cold front that swept across western Oregon Monday
     stretched from central Montana to southern Idaho late this
     morning.  In it\'s wake, southwesterly flow aloft was rotating
     a large area of showers, associated with a cold upper-level
     trough, into western Washington and extreme northwestern
     Oregon.  The remainder of Oregon was enjoying mostly sunny
     skies at midday.

     The ODA surface analysis showed weak high pressure, centered
     over eastern Oregon, with southeasterly pressure-gradients
     across western Oregon feeding into a low-pressure area off
     the British Columbia coastline.  Increasing
     south-southeasterly winds, gusting as high as 20 mph, cleared
     the areas of fog from the Willamette Valley by late this
     morning.  Mostly sunny skies helped temperatures climb into
     the low to mid 50s.

     The freezing levels over Salem and Medford were measured
     this morning at 4200 and 6000 feet respectively...putting
     the snow level at or below the Cascade passes.  ODOT road
     cameras showed mostly wet pavement over the Cascade passes,
     where midday temperatures had struggled to just above the
     freezing mark.  Southwesterly flow aloft is forecast to
     continue rotating showers onshore today...mainly into
     western Washington and northwestern Oregon.

     Doppler radar showed scattered showers along the north Oregon Coast
     and over the northern coast range at midday.  Any showers making it
     as far east as the northern Cascades will fall as snow over the passes. 
     The air aloft is cold enough to support the development of isolated
     thundershower activity over extreme northwestern Oregon this afternoon.

     South-southeasterly winds and fairly high mixing heights
     will make for good ventilation conditions today.  Cold air
     aloft will cap high temperatures in the mid 50s this afternoon, even
     with mostly sunny skies. Some of those showers rotating onshore into
     extreme northwestern Oregon could produce small hail this afternoon.
     Showers will spread south and east, across western Oregon, tonight,
     as the offshore upper-level trough moves closer to the coastline.

Surface Winds:
     S 5-15 G20 this afternoon.
Transport Winds:
     SSW 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2700 feet.  Ventilation index 54.
High Temperature:
     Salem\'s high temperature today will be near 57.
Humidities:
     Minimum relative humidity will be near 57%.
Sunrise/Sunset:
     Salem sunset tonight: 4:48pm; sunrise tomorrow: 7:05am.

Extended Outlook:
     Showers will increase on Wednesday, as the offshore
     upper-level trough swings over the region.  The snow level
     will continue to drop...possibly as low as 2500 feet in
     heavier showers.  Locally heavy snow is possile over the
     Cascade passes.  A somwwhat drier northwesterly flow aloft
     is forecast by Thursday afternoon.

     Another cold weather system is forecast to drop into the
     region, from the Gulf of Alaska, on Friday.  That system
     could also produce locally heavy snow, over the Cascade
     passes.  A warm front is forecast to quickly lift snow
     levels back above the passes by late Saturday.  A cold front
     is forecast to come onshore Sunday...mainly in Washington
     and northern Oregon.  A warmer westerly flow aloft will keep
     snow levels above the Cascade passes.  Another system is
     forecast to come onshore next Tuesday.

Tomorrow (11 Nov):  Increasing Showers.  Snow Level 3000 Feet.  40/50

Thu (12 Nov):  Mostly Cloudy.  Decreasing Showers.  Snow level 3000 feet.  38/49

Fri (13 Nov):  Rain and Mountain Snow.  Snow Level 3000 Feet.  40/48

Sat (14 Nov):  Mostly Cloudy.  Chance of Light Rain.  Snow Level Rising to 5000 Feet.  36/50

Sun (15 Nov):  Rain...Mainly North.  Snow Level 5000 Feet.  42/54

Mon (16 Nov):  Mostly Cloudy and Mild.  41/55

Tue (17 Nov):  Rain Developing.  41/52

ODA Meteorologist
weather at oda.state.or.us