[willamette-fcst] Forecast - Monday, July 6th, 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.

Issued: 
     Monday, July 6th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 8:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     A dry cold front shifted the windflow pattern to onshore
     Sunday and began a cooling trend across western Oregon. 
     Willamette Valley highs Sunday topped out in the upper 70s
     and low 80s...about 10-15 degrees cooler than they were
     Thursday through Saturday. A significant push of cooler
     marine air surged inland overnight. Low clouds blanketed the
     western valleys this morning and should be quite persistent
     today. High temperatures will be another 10 degrees cooler
     today, with highs struggling to reach 70.

     The initial cold front was strong enough to bring some
     shower and thundershower activity to Washington state, which
     extending southward into northeastern Oregon Sunday evening.
     Pendleton and Meacham both picked up about one-tenth of an
     inch of rain and thunderstorms extended as far south and
     east as Baker City, with CoCoRaHs reports showing close to a
     tenth of an inch of rain falling is sections of northern
     Baker County.  West of the Cascades, the northern and
     central coast loally picked up a couple hundredths of an
     inch of rain overnight with some sprinkles making it into
     the northwestern interior.

     The mid-morning ODA surface analysis showed the initial cold
     front moving into central Idaho, with cooler air spreading
     across of all of Oregon.  Onshore pressure gradients were
     strongest east of the Cascades, with westerly winds were
     gusting to around 30 mph from Hermiston and Pendleton
     southweard to Rome.  Winds had turning mostly southerly
     across the Willamette Valley and along the coast in the 5-15
     mph range.

     Infrared satellite imagery showed a band of middle and high
     clouds, associated with the cold front, extending from
     eastern Washington to northeastern Oregon and a secondary
     line of middle and high clouds moving onto the Washington
     coast. Visible satellite imagery showed extensive low clouds
     covering all of western Washington and all but the extreme
     southern interior of western Oregon.  Skies were sunny just
     east of the Cascades, across all of central and southeastern
     Oregon. Temperatures were generally in the mid to upper 50s
     across western Oregon and ranged from the mid 50s to the low
     70s east of the Cascades.  The warmest readings were along
     the Idaho border.

     Doppler radar showed scattered showers and a few
     thunderstorms over eastern Washington with a few light
     showers extending into extreme northeastern Oregon.  Some
     light showers were also showing up over western Washington
     with possible sprinkles over northwestern Oregon, about as
     far south as Salem.  The Salem sounding this morning showed
     massive cooling aloft, compared with Sunday morning, along
     with a saturated air mass between 3000 and 6500 feet (the
     thickness of the marine clouds).

     The upper-level trough responsible for the drastic change in
     the weather was centered over Vancouver Island, British
     Columbia this morning.  Little movemove of this system is
     expected today wtih continued strong onshore flow both aloft
     and at the surface.  The marine clouds should be quite
     persistent over the Willamette Valley today, with a chance
     of sprinkles this morning.  High temperatures may not climb
     out the 60s across much of the valley this afternoon.  If we
     get a few sunbreaks, then the low 70s are possible.

Surface Winds:
     S 5-15 this morning, W 5-15 this afternoon.
Transport Winds:
     SW 12 this morning, W 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 54.
High Temperature:
     Salem\'s high temperature today will be near 68.
Humidities:
     Minimum relative humidity will be near 51%.
Sunrise/Sunset:
     Salem sunset tonight: 9:01pm; sunrise tomorrow: 5:34am.

Extended Outlook:
     The parent upper-level low pressure center will slowly drift
     inland, across the interior of southern British Columbia,
     Tuesday and Wednesday.  Weak disturbances, rotation around
     it, will swing onshore across western Washington and western
     Oregon.  That will turn the flow aloft southwesterly and
     maintain strong onshore flow at the surface.  Thick marine
     low clouds will be persistent again with a chance of
     sprinkles or light showers.  Temperatures will remain well
     below normal.

     The upper-level trough is forecast to stall and weaken over
     the region Thursday and Friday, with continued southwesterly
     flow aloft.  Onshore flow at the surface will maintain night
     and morning marine low clouds across the Willamette Valley
     with increasing amounts of afternoon clearing leading to
     slowly warming temperatures.  The trough is then forecast to
     get kicked inland over the weekend, which will maintain the
     threat of a shower through Sunday.

Tomorrow (07 Jul):  Mostly Cloudy.  Chance of Sprinkles or Light Showers.  52/68

Wed (08 Jul):  Mostly Cloudy.  Chance of Sprinkles or Light Showers.  52/68

Thu (09 Jul):  Mostly Cloudy.  Chance of Sprinkles.  Partial Afternoon Clearing.  52/72

Fri (10 Jul):  AM Clouds.  Partly Sunny in the Afternoon.  Slight Chance of a Shower.  53/78

Sat (11 Jul):  AM Clouds.  Partly Sunny in the Afternoon.  Slight Chance of a Shower.  54/79

Sun (12 Jul):  Mostly Cloudy.  Slight Chance of a Shower.  55/78

Mon (13 Jul):  Becoming Mostly Sunny and Warmer.  53/83

ODA Meteorologist
weather at oda.state.or.us