[willamette-fcst] Forecast - Friday, May 22nd, 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

...Next Update Not Scheduled Until Monday, June 1st, 2009...

Issued: 
     Friday, May 22nd, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 6:30pm.
     Straw stack burning is allowed from now until 6:30pm.

Weather Discussion:
     Skies stayed clear over most of the Willamette Valley overnight.
     Increasing onshore flow brought marine low clouds onto the coast
     and into the interior valleys of southwestern Oregon...including
     the southern Willamette Valley.  Late-morning visible satellite
     imagery showed the blanket of low clouds along the coast beginning
     to back offshore, with considerable low clouds remaining from Linn
     County south to Douglas County.  Skies were generally sunny elsewhere
     across Oregon and over virtually all of Washington and Idaho.

     Temperatures stayed mostly above 40 degrees overnight across
     western Oregon.  Eugene was one the coldest spots, with a
     minimum of 38 degrees.  Low clouds formed in the Eugene area
     around daybreak and were breaking up late this morning.  By
     11am most of the interior valleys of western Oregon had
     warmed into the low 60s.  The exception was Roseburg, where
     persistent marine low clouds were holding temperatures in
     the mid 50s.  Coastal temperatures were in the 50s with
     sunshine coming out along most of the coastal strip. East of
     the Cascades, temperatures ranged from the mid 60s to the mid 70s.

     The late-morning ODA surface analysis showed onshore flow
     across all of Oregon with generally northwesterly pressure
     gradients.  Northerly winds were already gusting between 25
     and 30 mph along the central and southern coast but were
     still generally less than 10 mph across the interior of the
     state.  The morning sounding over Salem showed that the flow
     aloft had become light southwesterly, in response to a weak
     upper-level trough approaching the coast.  The air aloft was
     still warm, with the freezing level measured at 10,300 feet.
     That will prohibit the development of convective clouds
     again this afternoon, so sunny skies should prevail
     statewide this afternoon.

     Some tightening of the northwesterly pressure gradients is
     expected today, so north-northwesterly winds should increase
     this afternoon across the state.  Afternoon temperatures
     will be similar to Thursday with highs near 60 along the
     coast and in the low 70s in the Willamette Valley.  Cascade
     pass temperatures should climb into the 60s this afternoon,
     with 70s and low 80s across central and eastern Oregon.

Surface Winds:
     NNW  8-15 G20 this afternoon.
Transport Winds:
     NNW 16 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 80.
High Temperature:
     Salem\'s high temperature today will be near 72.
Humidities:
     Minimum relative humidity will be near 39%.
Sunrise/Sunset:
     Salem sunset tonight: 8:42pm; sunrise tomorrow: 5:35am.

Extended Outlook:
     A very weak upper-level trough is forecast to remain over
     Oregon Saturday, with continued onshore flow keeping
     temperatures near normal with plenty of afternoon sunshine
     across western Oregon. Skies should be mostly sunny across
     central and eastern Oregon. Transport winds should maintain
     enough of a northwesterly component to make for good
     ventilation for possible stack burning.

     The flow aloft is forecast to turn northwesterly and dry out
     again by late Sunday.  Slight warming aloft and decreased
     onshore flow will help temperatures climb a few degrees. A
     flat upper-level ridge is forecast to build over the region
     early next week, which should warm temperatures a few more
     degrees.  However, very weak onshore flow will keep
     temperatures from getting too much above average west of the
     Cascades. The upper-level flow is forecast to turn more
     southerly by the end of next week, which may introduce some
     moisture into the region for a chance of showers or thundershowers.

Tomorrow (23 May):  Morning Clouds.  Mostly Sunny in the Afternoon.  41/70

Sun (24 May):  Morning Clouds.  Mostly Sunny in the Afternoon.  43/73

Mon (25 May):  Brief Morning Clouds...Sunny and a Little Warmer in the Afternoon.  43/76

Tue (26 May):  Mostly Sunny and Warm.  46/79

Wed (27 May):  Mostly Sunny and Warm.  48/78

Thu (28 May):  Partly Cloudy.  Slight Chance of Showers or Thuundershowers.  49/75

Fri (29 May):  Partly Cloudy.  Chance of Showers or Thundershowers.  50/75

ODA Meteorologist
weather at oda.state.or.us