[willamette-fcst] Forecast - Wednesday, June 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.

...Next Update Not Scheduled Until Thursday, June 11th, at 9:00am...

Issued: 
     Wednesday, June 10th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 7:00pm.
     Straw stack burning is allowed from 11:00am until 7:00pm.

Weather Discussion:
     Western North America is under a split-flow jet stream
     pattern, with one branch of strong winds aloft being
     directed over the top of a ridge of high pressure, in the
     northern Gulf of Alaska, and then diving southeastward into
     Montana.  A weaker southern branch is undercutting the Gulf
     of Alaska Ridge and sending weak upper-level troughs into
     the the west coast of the United States.

     An upper-level trough approached the central and southern
     Oregon coastline Tuesday, triggering the development of
     mumerous afternoon and evening showers and thunderstorms
     across Oregon.  The storms were slow-moving, due to farily
     light winds aloft, and produced locally heavy rainfall. 
     Burns received over one-half inch of rain Tuesday evening
     with up to three-quarters of an inch reported near Bend, in
     central Oregon.

     Low-level onshore flow, into western Oregon, helped to keep
     shower and thunderstorm development confined mainly from the
     Cascades eastward Tuesday.  However, some of the showers
     continued through the night, with southeasterly flow aloft
     bringing them northwestward over the northern Willamette
     Valley this morning.  Some sprinkles fell this morning as
     far south as Salem with light rain reported in McMinnville,
     Aurora, and Hillsboro.

     Satellite imagery showed generally cloudy skies over all of
     Oregon at mid-morning.  Doppler radar showed a band of light
     rain stretching from near Redmond, in central Oregon,
     northwestward to over the northern Willamette Valley.  The
     areas of rain were decreasing in intensity, with the cool
     morning air helping to stabilize the atmosphere.  The ODA
     surface analysis showed the thermal trough had shifted
     eastward, into Idaho, with low-level onshore flow now
     extending across most of Oregon.  That will slightly
     stabilize the air mass over Oregon today, with the strongest
     afternoon shower and thundershower development shifting east
     of the state.

     Mid-morning temperatures were mostly in the mid to upper 50s
     across western Oregon, under cloudy skies.  Light rain was
     still falling over parts of the extreme northern Willamette
     Valley.  Skies were partly to mostly cloudy over central and
     eastern Oregon with temperatures ranging from the low 50s,
     with light rain in Redmond, to the mid 60s in Hermiston and
     Ontario.

     With a weak upper-level trough maintaining southerly to
     southeasterly flow aloft over Oregon today, daytime heating
     will, once again, destabilize the air mass enough for some
     showers to develop...mainly from the Cascades eastward. 
     There may also be a few thunderstorms.  Southeasterly flow
     aloft could swing some showers northwestward into the
     Willamette Valley tonight, much like last night.  Continued
     onshore flow will keep skies mostly cloudy today west of the
     Cascades with Willamette Valley high temperatures only
     climbing to near or slightly below normal.

Surface Winds:
     S 3-6 this morning, SW 5-10 this afternoon.
Transport Winds:
     SW 5 this morning, W 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 40.
High Temperature:
     Salem\'s high temperature today will be near 70.
Humidities:
     Minimum relative humidity will be near 55%.
Sunrise/Sunset:
     Salem sunset tonight: 8:58pm; sunrise tomorrow: 5:25am.

Extended Outlook:
     Little change in the weather pattern is expected through
     this week with a series of weak upper-level troughs
     continuing to bring mostly cloudy skies to western Oregon
     with a chance of showers and even a slight chance of
     thundershowers.  A weak ridge should bring some drying early
     next week.  Onshore flow will hold temperatures near or
     slightly below normal across western Oregon through at least
     Sunday with some warming early next week.

Tomorrow (11 Jun):  Mostly Cloudy.  Chance of Light Showers.  52/70

Fri (12 Jun):  Mostly Cloudy.  Chance of Showers.  Slight Chance of T-Storms.  53/71

Sat (13 Jun):  Mostly Cloudy.  Chance of Showers.  Slight Chance T-Storms.  52/70

Sun (14 Jun):  Mostly Cloudy.  Slight Chance of Showers.  52/71

Mon (15 Jun):  Morning Clouds.  Becoming Partly Sunny.  50/74

Tue (16 Jun):  Morning Clouds.  Becoming Mostly Sunny.  50/75

Wed (17 Jun):  Mostly Sunny.  50/77

ODA Meteorologist
weather at oda.state.or.us