[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.

NOON UPDATE...Updated Burn Advisory to Include Stack Burning...

Issued: 
     Monday, July 6th, 2009 at 12:00pm.

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.
     Straw stack burning is allowed from 11:00am until 8:00pm.

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 Sunday night. Low clouds blanketed
     the western valleys this morning and should be persistent
     today, especially in the northern Willamette Valley. 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, spots along the
     northern and central coast picked up a couple hundredths of
     an inch of rain overnight with some sprinkles making it into
     the northwestern interior.

     The late-morning ODA surface analysis showed the cold front
     advancing across central Idaho, with cooler onshore flow
     spreading over of all of Oregon.  Onshore pressure gradients
     were strongest east of the Cascades, with 25-35 mph westerly
     wind gusts extending from Hermiston and Pendleton southweard
     to Rome.  Southelry winds in the Willamette Valley were
     beginning to turn southwesterly, in the 5-15 mph range, with
     gusts to around 20 mph in the north.

     Infrared satellite imagery showed the main cloud-band,
     associated with the surface cold front, had pushed mostly
     east of Washington and northeastern Oregon.  More middle and
     clouds were circulating around the parent low-pressure
     center, over Vancouver Island, into northwestern Washington.
     Visible satellite imagery showed extensive low clouds
     covering all of western Washington...extending southward
     across western Oregon through Linn County.  The low clouds
     were beginning to break up over Lane County, where the
     onshore flow was not as strong.  Skies were sunny over
     southwestern Oregon and east of the Cascades, except for a
     few clouds near the Idaho border.

     Midday temperatures were generally in the mid 50s across the
     coast and low to mid 60s in the western valleys.  Readings
     east of the Cascades ranged from the mid 60s, in central
     Oregon, to the low 80s in Ontario, near the Idaho border.

     Doppler radar showed a few showers developing in
     north-central Washington and possible sprinkles , out ot the
     marine deck, over western Washington and northwestern
     Oregon.  The showers and thunderstorms from the initial cold
     front had pushed eastward to over Idaho and Montana.  The
     Salem sounding this morning showed almost 20-25 degrees of
     cooling aloft, up to about 7000 feet.  The air mass was also
     saturated between 3000 and 6500 feet (the thickness of the
     morning marine clouds).

     The upper-level trough responsible for the drastic change in
     the weather will slowly drift eastward today, into southern
     British Columbia, with continued westerly flow aloft over
     Washington and Oregon.  Strong onshore flow will help marine
     clouds to be quite persistent over the northern Willamette
     Valley today.  The south valley will see a fair amount of
     clearing this afternoon.  High temperatures may not climb
     out the 60s across much of the north valley this afternoon. 
     However, more clearing in the south valley should help
     temperatures there climb into the low 70s.

Surface Winds:
     S 5-15 G20...becoming W 5-15 later this afternoon.
Transport Winds:
     SW 12...becoming W 10 later 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 50%.
Sunrise/Sunset:
     Salem sunset tonight: 9:01pm; sunrise tomorrow: 5:34am.

Extended Outlook:
     The upper-level low pressure center will slowly drift across
     the interior of southern British Columbia Tuesday and
     Wednesday.  Weak disturbances, rotating 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 forecast to move
     inland this weekend, with the flow aloft turning
     northwesterly, and drying out, early next week.

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 or Light Showers.  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