[willamette-fcst] Forecast - Thursday, June 11th, 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: 
     Thursday, June 11th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 7:00pm.
     Straw stack burning is allowed, for dry stacks, from now until 7:00pm.

Weather Discussion:
     Western North America remains under a split-flow jet stream
     pattern this morning, with one branch of stronger winds aloft
     diving southeastward, from northern Alaska, into eastern
     Montana.  Another, southern, branch is cutting across the
     Pacific Ocean and sending weak upper-level troughs into the
     the west coast of the United States.  Daytime heating on
     Wednesday helped destabilize the atmosphere, with shower
     activity developing, once again, across much of
     Oregon...mainly over southern Oregon and from the Cascades
     eastward.  The showers continued overnight,and southeasterly
     flow aloft carried the showers northwestward, into the Willamette
     Valley, this morning.

     An upper-level trough was centered over extreme southwestern
     Oregon this morning and bringing cloudy skies to most of the
     state.  The main exception was a pronounced area of mostly
     clear skies extending from extreme north-central Oregon to
     the northeastern tip of Oregon.  That region, along with
     eastern Washington, was getting a drier northeasterly flow
     aloft, in response to the northern branch of the jet stream
     cutting into Montana.

     Doppler radar showed a line of showers extending northwestward,
     from central Oregon near Bend, across the Cascades and into the
     central Willamette Valley, to just north of Newport along the coast.
     Salem received just under one-tenth of an inch of rain this morning,
     but points not far to the north and south of Salem stayed dry.  The
     heaviest rainfall totals have been over southern Oregon during the
     past 24 hours.  Over one-quarter of an inch fell from Medford to
     Lakeview, with Burns getting over a tenth of an inch.

     The mid-morning ODA surface analysis showed onshore flow
     across western Oregon, which will keep temperatures near to
     slightly below normal again today.  It will also keep the
     atmosphere stable enough so that showers will not likely
     develop into thunderstorms west of the Cascades this
     afternoon.  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 central
     Willamette Valley, but radar was showing a general decrease
     in the shower activity.  Temperatures east of the Cascades
     ranged from near 50 in Klamath Falls, under cloudy skies, to
     the mid 60s, with sunshine, in Hermiston.

     With a weak upper-level trough maintaining southeasterly flow
     aloft over Oregon today, daytime heating will, once again,
     destabilize the air mass enough for some showers to develop...mainly
     over southern and eastern Oregon.  There may also be a few thunderstorms
     from the Cascades eastward. Southeasterly flow aloft could swing some
     showers northwestward, into the Willamette Valley, again tonight, much
     like the past two nights.

Surface Winds:
     Var 3-6 this morning, W 5-10 this afternoon.
Transport Winds:
     Var 4 this morning, NW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4200 feet.  Ventilation index 34.
High Temperature:
     Salem\'s high temperature today will be near 70.
Humidities:
     Minimum relative humidity will be near 59%.
Sunrise/Sunset:
     Salem sunset tonight: 8:59pm; sunrise tomorrow: 5:25am.

Extended Outlook:
     Little change in the weather pattern is expected through this weekend
     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, but another trough is forecast to renew the
     shower threat by mid-week.  Onshore flow will hold temperatures to near
     or slightly below normal across western Oregon through at least Sunday,
     with temperatures warming to near normal Monday and Tuesday.

Tomorrow (12 Jun):  Mostly Cloudy.  Chance of Showers.  Slight Chance of T-Storms.  55/72

Sat (13 Jun):  Mostly Cloudy.  Chance of Showers.  Slight Chance T-Storms.  55/72

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 Cloudy.  Chance of Showers.  50/70

Thu (18 Jun):  Mostly Cloudy.  Slight Chance of Showers.  53/70

ODA Meteorologist
weather at oda.state.or.us