[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.

...Next Update Not Scheduled Until Tuesday, June 16th, at 9:00am...

Issued: 
     Thursday, June 11th, 2009 at 12:00pm.

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, with one branch of stronger winds aloft diving southeastward,
     from northern Alaska, into eastern Montana.  Another branch of the
     the stream is cutting across the Pacific Ocean and sending weak
     upper-level troughs into the the west coast of the United States.

     Daytime heating has been acting on the moist and somewhat unstable air mass
     to generate showers and a few thundershowers each of the past couple of
     afternoons.  Most of the shower activity has been over southern and eastern
     Oregon, with some of the slow-moving showers producing locally heavy rainfall
     and street flooding...especially in central Oregon.  The showers have
     continued overnight, the past two nights, with southeasterly flow aloft
     directing the showers northwestward, across the Cascades and into the Willamette
     Valley.  Salem picked up almost a tenth of an inch of rain this morning, while
     areas not far to the north and south of Salem remained dry.

     An upper-level trough was centered over extreme southwestern
     Oregon late 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.

     Late-morning Doppler radar showed showers building, once again, across
     much of the southern two-thirds of central and eastern Oregon, while the
     morning shower activity over the central Willamette Valley dissipated.
     The ODA surface analysis showed weak onshore flow across western Oregon,
     which will keep skies mostly cloudy and temperatures near to slightly below
     normal again today.

     Late-morning temperatures were mostly in the low to mid 60s across western
     Oregon, under cloudy skies.  Temperatures east of the Cascades
     ranged from the cloudy low 50s in south-central Oregon to the low 70s, under
     sunny skies, in Pendleton and 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:
     Becoming W 5-10 this afternoon.
Transport Winds:
     Becoming 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