[willamette-fcst] Forecast - Wednesday, May 7th, 2008

[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: 
     Wednesday, May 7th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 6:30pm.
     Straw stack burning is allowed from 11:00am until 6:30pm.

Weather Discussion:
     A dry but farily cool upper-level trough slid across Oregon
     overnight...dropping the freezing levels over the state,
     from 10,000 feet, to around 5000 feet this morning.  The
     system produced a fair amount of clouds but only a few
     sprinkles.  East of the Cascades, clouds were giving way to
     sunshine this morning with strong onshore flow resulting in
     westerly winds of 10-25 mph...even during the usually calm
     morning period.  Across Western Oregon, strong onshore flow
     is spreading a solid deck of marine clouds from well
     offshore all the way to the crest of the Cascades.  Only the
     extreme southern coast and sections of Southwestern Oregon
     were seeing any sun-breaks.

     Temperatures held up in the mid 40s overnight across Western
     Oregon with westerly winds making for a mild morning over
     Central and Eastern Oregon.  Most of Eastern Oregon stayed
     above 40 degrees overnight.  One big exception was Redmond,
     where the wind settled down enough for the temperature to
     briefly drop to 26 degrees (the cold spot in the state).

     As the upper-level trough moves into Idaho this afternoon,
     weak disturbances will continue to move across Oregon today
     in a northwesterly flow aloft.  That will maintain the
     strong onshore flow across the state.  Morning aircraft
     reports indicate that the marine clouds over the Willamette
     Valley are about 4000 feet thick this morning with areas of
     drizzle.  At most, only partial late-afternoon clearing is
     likely.  Valley temperatures will be cooler today with highs
     likely staying in the upper 50s.  In contrast, skies will be
     mostly sunny east of the cascades, but cool west winds will
     keep temperatures in the 50s and 60s.

     The marine low clouds will likely thicken back up overnight,
     west of the Cascades, with areas of drizzle again by
     Thursday morning.  Temperatures overnight will locally fall
     into the mid to upper 30s, but I do not expect frost to be
     an issue.  East of the Cascades, fair skies will combine
     with a cool air mass to allow temperatures to locally drop
     below the freezing mark in wind-sheltered valleys.

Surface Winds:
     WNW 5-8 this morning, NW 8-15 this afternoon.
Transport Winds:
     WNW 8 this morning, NW 12-15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 32.
High Temperature:
     Salem\'s high temperature today will be near 59.
Humidities:
     Minimum relative humidity will be near 44%.
Sunrise/Sunset:
     Salem sunset tonight: 8:26pm; sunrise tomorrow: 5:51am.

Extended Outlook:
     Another dry but cool upper-level trough, in the
     northwesterly flow aloft, is foreast to move onshore
     Thursday and across Oregon Thursday night.  That will likely
     keep skies mostly cloudy over Western Oregon with strong
     onshore flow at the surface holding temperatures mostly in
     the 50s.  The trough may be strong enough to produce areas
     of morning drizzle west of the Cascades and a few sprinkles
     or light showers around the state...mainly over the mountains.

     After a cool start to the day Friday, a weak ridge of high
     pressure should bring partly sunny and warmer weather Friday
     afternoon with temperatures recovering to near normal across
     the Willamette Valley.  A weak cold front is forecast to
     approach the coastline Saturday with a chance of light rain
     moving onshore by late afternoon.  Temperatures will be near
     normal, ahead of the front, Saturday and drop back below
     normal with a chance of showers Sunday.  Showers could
     produce sticking snow over the Cascade Passes Sunday, but
     significant accumulations are not expected.

     Showers are forecast to taper off Monday, as the upper-level
     trough pushes east of the region.  A warm front is forecast
     to bring clouds and perhaps light rain as far south as
     Northwestern Oregon Tuesday, but that may be the last threat
     of rain for awhile...

     The long-range computer models are still indicating the
     possibility of much warmer and dry weather for the latter
     half of next week...extending into the following weekend,
     but that is still a long way out.  If we get a large ridge
     of high pressure to build over the region, as forecast by
     some of the long-range models, then temperatures in the
     Willamette Valley would easily climb into the 80s.  However,
     the Canadian model backed away from this warm solution
     today, so I am not going to make that call yet.

Thu (08 May):  Chance of AM Drizzle.  Slight Chance Showers. Snow Level 4000 Feet.  39/58

Fri (09 May):  Becoming Partly Cloudy.  36/63

Sat (10 May):  Increasing Clouds.  Chance of Showers Late...Mainly North.  40/65

Sun (11 May):  Chance of Showers and Cooler.  Snow Level Dropping to 3-4000 Feet.  43/58

Mon (12 May):  Mostly Cloudy.  Afternoon Clearing.  40/63

Tue (13 May):  Slight Chance of Rain North.  Partly Cloudy South.  45/65

Wed (14 May):  Becoming Partly Sunny and Warmer.  46/70

ODA Meteorologist
weather at oda.state.or.us