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

Tue Mar 2 09:07:56 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 9:00am.

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 brought a
     weakening weather system onshore overnight, with clouds
     covering virtually all of the Pacific Northwest this
     morning.  The El Nino driven jet stream remains focused at
     California, with this weather system not potent enough to
     produce much rain as far north as Oregon.  Generally just
     sprinkles fell overnight across most of the coastline and in
     the Willamette Valley.  Astoria, Newport, and McMinnville
     all picked up measurable rain, but only a couple hundredths
     of an inch.  Brookings, on the extreme south Oregon coast,
     received 15 hundredths of an inch overnight, with spotty
     sprinkles reported across the interior of southwestern
     Oregon.  No rainfall was reported east of the Cascades.

     Cloudy skies held overnight temperatures in the mid to upper
     40s across western Oregon.  Some spots east of the Cascades
     dropped to near the freezing mark, but it was generally a
     mild night, statewide, for early March.  The air aloft has
     cooled a little 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, with only minor
     snow accumulations in the Cascades.

     Doppler radar showed a narrow band of mostly very light rain
     extending from near Tillamook to Salem at mid-morning.  It
     was moving north-northeastward and rapidly weakening.  Radar
     does not show any more bands of showers set to rotate
     northward across the Willamette Valley, but computer models
     indicate that a spoke of upper-level energy will rotate
     northward over the region this afternoon, increasing the
     threat of light showers.  The ODA surface analysis showed
     fairly weak souteasterly pressure gradients across Oregon. 
     Winds were mostly in the 5-15 mph range across the state,
     except for locations where topography was acting to
     accelerate the wind, with gusts to around 30 mph in places
     like Troutdate and La Grande.

     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 to
     about where they were on Monday (mid to upper 50s). Rainfall
     will be very light and spotty today, with valley totals
     ranging from nothing to possibly as much as one-tenth of an inch.

Surface Winds:
     SE 5-15 this morning, S 5-15 this afternoon.
Transport Winds:
     S 20 this morning, 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 57.
Humidities:
     Minimum relative humidity will be near 64%.
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