[willamette-fcst] Forecast - Thursday, July 3rd, 2008

Thu Jul 3 08:19:15 PDT 2008

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: 
     Thursday, July 3rd, 2008 at 9:00am.

Burn Advisory:
_____________________________________________________________________

     Due to the Olympic Trials in Eugene, ODA will not be issuing
     any burning permits through July 8th.
_____________________________________________________________________

     Agricultural burning is not recommended.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     A very slow-moving upper-level low pressure area was
     centered about 400 miles west of the Northern Oregon Coast
     this morning.  The counter-clockwise circulation around it
     has been responsible for the southerly flow aloft, the past
     few days, bringing smoke from California wildfires into
     Oregon.  Spokes of energy rotating around this system have
     also touched off thundershowers the past several days with
     an active line of thunderstorms developing over the Northern
     Willamette Valley last night.

     The overnight storms brought frequent lightning and up to
     one-quarter of an inch of rain to the Northern Willamette
     Valley.  A few thunderstorms also developed over North-Central
     Oregon near The Dalles.  The entire complex of storms moved 
     rapidly north of Oregon, by daybreak, across Western and
     Central Washington.  Shower and thundershower activity was
     still going on from near Seattle northward into Southern
     British Columbia at mid-morning.

     It was a mild and muggy night around the state with morning
     minimums generally in the 50s and 60s.  For the second day
     in-a-row, Lakeview was the cool spot with 45 degrees.  The
     Dalles never cooled below 70 degrees with overnight
     thunderstorms dropping .03 inches of rain.  The morning
     sounding over Salem showed southeasterly flow in the mid-levels
     of the atmosphere, which continues to be favorable for
     thundershower development over Western Oregon today.  There
     was some cooling below 10,000 feet, so afternoon temperatures
     should be a couple of degrees cooler than on Wednesday.

     Morning satellite imagery showed mostly cloudy skies across
     Washington with a band of middle and high clouds over the
     western half of Oregon.  Low clouds were along the immediate
     coastline with sunny skies over Central and Eastern Oregon. 
     Doppler radar showed considerable shower and thundershower
     activity from about Centralia northward across Western
     Washington with a few light showers over Central and Eastern
     Washington.  Dry conditions prevailed over Oregon.

     Mid-morning temperatures were near 60 across Western Oregon
     and ranged from the low 60s to the mid 70s east of the
     Cascades.  The ODA surface analysis showed the thermal
     trough, which moved back into the Willamette Valley
     Wednesday, had shifted back eastward and extended from
     Central Washington through SW Oregon.  Very weak onshore
     flow had returned NW Oregon.  Surface winds were light
     across Oregon with a west winds at 10 mph in The Dalles.

     As the offshore upper-level low pressure system slowly moves
     northeastward, southerly flow aloft will continue to send
     smoke from the California wildfires over Oregon today, so
     skies will likely stay on the hazy side.  Any upper-level
     disturbances, riding along in the southerly flow aloft,
     could trigger showers or thundershowers over Oregon, but the
     computer models are forecasting a break between impulses
     today.  However, conditions remain unstable, so I will keep
     a slight chance of a shower of thundershower in the forecast.

Surface Winds:
     Var 0-5 this morning, W 5-10 this afternoon.
Transport Winds:
     S 6 this morning, SSW 12 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 82.
Humidities:
     Relative humidity drops to 50% by 1pm.
     Minimum relative humidity will be near 43%.
Sunrise/Sunset:
     Salem sunset tonight: 9:02pm; sunrise tomorrow: 5:32am.

Extended Outlook:
     The upper-level trough is finally forecast to move onshore
     early Friday with flow aloft becoming more westerly by
     Friday afternoon.  That should help to clear the smoke from
     the region, but it will also increase the chance of showers
     west of the Cascades and continue the cooling trend across
     the region.  The thundershower threat will shift east of the
     Cascades, as the westerly flow aloft stabilizes the air mass
     over Western Oregon.

     Another weak frontal system is forecast to brush across
     Washington and Oregon, in the westerly flow aloft, Saturday
     afternoon...continuing a slight chance of showers in the
     Willamette Valley.  The jet stream begins to lift north
     Sunday with a more typical summer-time pattern developing
     for early next week.  That means onshore flow across Western
     Oregon with morning clouds and afternoon sunshine.  The
     storm track is forecast to remain close to the region with
     slightly above normal temperatures through the first half of
     next week and a possible cool-down late next week.

Tomorrow (04 Jul):  Mostly Cloudy and Cooler.  Chance of a Showers.  59/75

Sat (05 Jul):  Mostly Cloudy.   Slight chance of Showers.  56/78

Sun (06 Jul):  Morning Clouds...Mostly Sunny.  53/80

Mon (07 Jul):  Morning Clouds...Mostly Sunny.  54/82

Tue (08 Jul):  Mostly Sunny.  54/85

Wed (09 Jul):  Mostly Sunny.  54/85

Thu (10 Jul):  Mostly Sunny.  54/79

ODA Meteorologist
weather at oda.state.or.us