[willamette-fcst] Forecast - Tuesday, March 2nd, 2010

Tue Mar 2 12:08:30 PST 2010

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, March 2nd, 2010 at 12:00pm.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 4:00pm.
     Straw stack burning is allowed from now until 4:00pm.

Weather Discussion:
     Increasing south-southwesterly flow aloft spread considerable high and mid-level clouds
     across the entire Pacific Northwest overnight, in advance of a rapidly weakening frontal
     system.  The El Nino driven jet stream remains focused at California, where the real
     punch of this system was directed.  Not much in the way of rainfall advanced northward
     over Oregon.  Mostly just sprinkles have fallen across western Oregon today, with a few
     spots receiving minor amounts of measurable rain.  Brookings, on the extreme southern
     Oregon coast, has picked up about two-thirds of an inch of rain today.  Elsewhere
     across western Oregon, amounts have varied from nothing to just under a tenth of an
     inch.  Only some areas of sprinkles have been reported east of the Cascades.

     The air mass aloft has cooled slightly since Monday, with the freezing level measured
     at 6700 feet early this morning over both Salem and Medford.  Continued slow cooling
     aloft should drop the snow level to around 5000 feet by this afternoon, but not much
     snow accumulation is expected due to the lack of precipitation over the Cascades.

     Doppler radar showed only a few areas of very light rain streaming northward across
     Oregon at midday.  Much of the precipitation showing up on radar was probably not
     even making it to the ground.  Computer models show a spoke of upper-level
     energy rotating northward, over the region, this afternoon, in association with
     what\'s left of the surface cold that was moving onshore at midday.  That will
     maintain a few areas of sprinkles or very light rain across the state.

     The ODA surface analysis showed fairly weak souteasterly pressure gradients across
     Oregon. Winds had increased to 5-15 mph across western Oregon, with local gusts just
     over 20 mph.  Considerable middle and high clouds will continue to stream northward
     over Oregon today.  Even with the cloud-cover and slight cooling aloft, southerly
     surface winds and better mixing of the air mass today will lift valleys highs into
     the upper 50s. Rainfall will be very light and spotty today, with valley totals
     ranging from nothing to possibly a few hundredths of an inch.

Surface Winds:
     SSW 5-15 G20 this afternoon.
Transport Winds:
     SSW 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 70.
High Temperature:
     Salem\'s high temperature today will be near 58.
Humidities:
     Minimum relative humidity will be near 53%.
Sunrise/Sunset:
     Salem sunset tonight: 6:01pm; sunrise tomorrow: 6:46am.

Extended Outlook:
     The next weather system will also head mainly into northern
     California, tonight and Wednesday, with only a chance of
     rain as far north as the Willamette Valley.  This system
     does have a little colder air aloft associated with it, so
     snow levels may drop as low as the Cascade passes on Wednesday.

     A transitory ridge of high pressure will dry things out on
     Thursday.  The next weather system, on Friday, will also
     encounter the split-flow pattern in the jet stream offshore
     and move mainly into California.  A ridge of high pressure
     will likely bring dry and mild conditions over most of the
     weekend, with the next system forecast to come onshore late
     Sunday.  Another weather system is forecast for late next Tuesday.

Wed (03 Mar):  Mostly Cloudy.  Chance of Rain...Mainly South.  Snow Level 4000 Feet.  40/54

Thu (04 Mar):  Partly Sunny.  35/55

Fri (05 Mar):  Chance of Rain...Mainly South.  Snow Level 5000 Feet.  38/57

Sat (06 Mar):  Partly Sunny.  35/58

Sun (07 Mar):  Increasing Clouds.  Chance of Rain Late.  Snow Level 4000 Feet.  37/56

Mon (08 Mar):  Decreasing Chance of Showers.  Snow Level 3-4000 Feet.  40/53

Tue (09 Mar):  Mostly Cloudy.  Chance of Rain Late.  36/56

ODA Meteorologist
weather at oda.state.or.us