[willamette-fcst] Forecast - Tuesday, June 2nd, 2009

Tue Jun 2 09:10:12 PDT 2009

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: 
     Tuesday, June 2nd, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level trough, centered about 700 miles off the
     central California Coastline, is continuing to produce a
     warm and humid southeasterly flow aloft over Oregon. 
     Showers and a few thundershowers developed over mainly the
     southern two-thirds of Oregon Monday, with temperatures
     continuing well above normal for early June.  Most of the
     rainfall was light Monday, but Redmond, in central Oregon,
     picked up one-third of an inch.  Even under considerable
     cloud-cover, temperatures climbed into the upper 70s and
     lower 80s across the interior valleys of western Oregon. 
     Some onshore flow held temperatures along the immediate
     coastline in the upper 50s and 60s.  East of the Cascades,
     high temperatures Monday ranged from the upper 70s to the
     middle 90s.  The Dalles was the warm spot in the state with
     a high of 94 degrees.

     Cloudy skies made for quite mild night across the state. 
     Overnight temperatures, on both sides of the Cascades,
     stayed mostly in the 50s, with some spots not dropping below
     60 degrees.  Mid-morning satellite imagery showed a wide
     band a clouds, circuating around the parent upper-level
     trough off the California Coast, covering most of Oregon. 
     In addition, for and low clouds covered the coastal strip. 
     Doppler radar showed light embedded shower activity
     stretching from south-central Oregon, northwestward to just
     off the northern coast.  Light rain was falling in both
     Klamath Falls and Redmond, with showers reported over
     extreme northwestern Oregon near Scappoose.  Mid-morning
     temperatures ranged from the mid 50s to mid 60s across most
     of the state.  The Dalles was still the warm spot with a
     temperature in the low 70s.

     The late-morning ODA surface analysis showed a weak thermal
     trough centered over the interior of western Oregon with
     onshore flow only along the immediate coastal strip.  Winds
     in the Willamette Valley were light and variable.  The Salem
     sounding this morning showed northeasterly winds up to about
     4000 feet...turning to southeasterly above 9000 feet.  There
     was a small warm layer from 4-5000 feet, which will likely
     mark the top of the afternoon mixing layer.  Light surface
     winds and north-northeastery transport winds will make for
     poor ventilation conditions over the Willamette Valley today.

     Mostly cloudy skies will help to hold afternoon temperatures
     in the mid 70s to lower 80s across the Willamette Valley
     today, even though the air aloft would support much warm
     temperatures, if skies were sunny.  Even with the
     cloud-cover, daytime heating will act on the moist and
     unstable air mass to enhance convective activity this
     afternoon...likely leading to scattered showers...mainly
     over the southern two-thirds of the state. The temperature
     profile of the atmosphere is unstable from about 5000 feet
     all the way up to 40,000 feet, so any convection that
     manages to rise above the weak cap at 5000 feet will likely
     develop into impressive thunderstorms this
     afternoon...possibly as far north and west as the Willamette
     Valley.  Scattered thundershowers are likely this afternoon
     and evening over the Cascades and central Oregon.

Surface Winds:
     Var 3-7 this morning, NNE 5-10 this afternoon.
Transport Winds:
     NE 4 this morning, NNE 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4100 feet.  Ventilation index 49.
High Temperature:
     Salem\'s high temperature today will be near 79.
Humidities:
     Minimum relative humidity will be near 41%.
Sunrise/Sunset:
     Salem sunset tonight: 8:53pm; sunrise tomorrow: 5:28am.

Extended Outlook:
     The moist and unstable southeasterly flow aloft will
     continue Wednesday and then weaken and turn more easterly
     Thursday, as the upper-level low-pressure area drifts
     further south to off the southern California Coast.  A drier
     and more stable northeasterly flow will develop, from north
     to south, across Oregon on Friday, as the upper-level trough
     moves inland over California.  As the trough moves eastward
     Saturday, to over Nevada, the flow aloft over Oregon will
     will turn more northerly with the main area of upper-level
     moisture heading east, into Idaho.

     Increasing low-level onshore flow will begin to cool
     temperatures across western Oregon this weekend.  A weak
     upper-level trough is forecast to drop southward, from
     southern British Columbia, and should induce enough onshore
     flow to drive marine clouds into much of western Oregon by
     Sunday morning.  The trough may be strong enough to bring
     some rain to western Oregon Sunday and/or Monday, but that
     is getting beyond the accuracy range of the long-range
     computer models.  It does appear as if temperatures may drop
     below normal, for a change, early next week.

Tomorrow (03 Jun):  Mostly Cloudy.  Chance Showers and PM T-Storms...Mainly South.  58/79

Thu (04 Jun):  Mostly Cloudy.  Chance Showers and PM T-Storms...Mainly South.  56/76

Fri (05 Jun):  Mostly Cloudy and Cooler.  54/74

Sat (06 Jun):  Partly to Mostly Cloudy.  52/74

Sun (07 Jun):  Mostly Cloudy.  Increasing Chance of a Showers.  52/70

Mon (08 Jun):  Cloudy.  Chance of Rain.  51/67

Tue (09 Jun):  Mostly Cloudy.  Chance of Showers.  50/70

ODA Meteorologist
weather at oda.state.or.us