[willamette-fcst] Forecast - Friday, April 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.

...Corrected Afternoon Transport Windspeed and Ventilation Index...

...Next Update Scheduled Monday, April 13th, 2009 at 9:00am...

Issued: 
     Friday, April 10th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 6:00pm.
     Straw stack burning is allowed from now until 6:00pm.

Weather Discussion:
     A weak upper-level trough set up camp just off the Oregon
     coastline last night and pulled moisture northward into the
     state from another weather system moving into California. 
     That kept skies cloudy overnight with areas of rain and
     mountain snow.  Community Collaborative Rain, Hail & Snow
     Network (CoCoRaHS) observations showed that rainfall totals
     in the western Valleys, from Portland to Medford, ranged
     from about one-tenth to more than one-half of an inch.
     The greatest totals were in the Cascade foothills. The 
     coast only received from a few hundredths of an inch to
     around one-quarter of an inch.

     Significant snow fell in the Cascades overnight, with the
     snow level near 3000 feet.  Mt. Hood Skibowl reported 8
     inches of new snow and Mt. Hood Meadows ppicked up 5 inches.
     Further south, Mt. Bachelor received 4 inches of snow,
     Willamette Pass 2 inches, and Mt. Ashland picked up 6
     inches. Areas of rain and snow also circulated northward
     across central and eastern Oregon overnight.  Locally more
     than one-tenth of an inch fell from Klamath Falls north to
     Redmond and The Dalles.  Rain also extended east to Burns
     and Rome.  The lightest rain was in northeast Oregon, where
     most locations only picked up from a trace to a couple
     hundredths of an inch.

     The jet stream is pushing a vigorous upper-level trough into
     southern California this morning, with the trough along the
     Oregon coast weakening under a split-flow pattern aloft. 
     Satellite imagery showed the main cloud-bands associated
     with the northern trough beginning to shift north and east
     of western Oregon.  Some breaks in the clouds were appearing
     over the Willamette Valley, and Doppler radar showed most of
     the rain had moved north, into Washington.  The ODA surface
     analysis showed very weak southerly gradients across western
     Oregon and valley winds were light south-southeasterly at
     mid-morning.  Temperatures were mostly in the mid 40s.

     ODOT road reports indicated that snow shower activity had
     also tapered off over the Cascades this morning with pass
     temperature near freezing.  The offshore trough is forecast
     to continue weakening today, as it slowly drifts inland. 
     Weak southerly flow aloft will keep skies mostly cloudy with
     a chance for a few light showers...mainly over the mountains.
     Cool air aloft will help to cap valley high temperatures in
     the mid 50s, even with some sunbreaks.  Winds will stay
     fairly light and should turn more southwesterly this afternoon.

Surface Winds:
     SE 5-10 this morning, SW 5-10 this afternoon.
Transport Winds:
     SSW 10 this morning, SW 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 50.
High Temperature:
     Salem\'s high temperature today will be near 56.
Humidities:
     Minimum relative humidity will be near 62%.
Sunrise/Sunset:
     Salem sunset tonight: 7:52pm; sunrise tomorrow: 6:34am.

Extended Outlook:
     The next weather system will weaken considerably, under a
     split-flow jet stream, as it moves onshore Saturday.  It
     will be strong enough to bring mostly cloudy skies to
     western Oregon, but rainfall should be less than one-tenth
     of an inch.  The greatest valley rain totals will likely be
     in the northern Cascade foothills.  Snow levels will be in
     the 3-4000 foot range.

     The jet stream is forecast to become more consolidated over
     Washington and Oregon Sunday, with a stronger system slated
     to come onshore.  The lastest computer models show rain
     spreading across western Oregon by Sunday afternoon with the
     cold front moving through Sunday evening.

     A cold and vigorous upper-level trough is forecast to drop over
     the region Monday.  Showers on Monday could include small hail,
     in the afternoon, with quite low snow levels.  The trough will
     slowly push east Tuesday with showers tapering off. A transitory
     ridge is forecast to bring some drying and warming around the
     middle of next week.  Another system is forecast to move onshore
     late Thursday and Friday with more rain likely.

Tomorrow (11 Apr):  Mostly Cloudy.  Chance of Light Rain...Mainly North.  42/57

Sun (12 Apr):  Rain Developing by Afternoon.  Snow Level 5000 Feet.  44/57

Mon (13 Apr):  Showers with Mountain Snow.  Snow Level Dropping to 2500 feet.  41/52

Tue (14 Apr):  Decreasing Showers...Partial Clearing.  Snow Level 2500 Feet.  36/54

Wed (15 Apr):  Becoming Partly Sunny and Warmer.  35/61

Thu (16 Apr):  Partly Sunny Early...Increasing Clouds Late.  38/65

Fri (17 Apr):  Mostly Cloudy.  Chance of Rain.  42/63

ODA Meteorologist
weather at oda.state.or.us