[willamette-fcst] Forecast - Thursday, March 18th, 2010

[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.

...ODA offices will be closed on Friday, March 19th, due to a mandatory statewide furlough day.
   The next update of this product will not be until Monday, March 22nd, 2010...

Issued: 
     Thursday, March 18th, 2010 at 12:00pm.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 4:30pm.
     Stack burning is not allowed.

Weather Discussion:
     Drier air filtering into the region cleared skies overnight and allowed for temperatures
     across the Willamette Valley to drop well down into the 30s, with patchy frost.  Hillsboro
     dipped to 30 degrees and Eugene fell to 31 degrees.  Salem dropped to the freezing mark.
     Freezing temperatures extended to the coast this morning, with Newpport dropping to 32
     degrees.  Dry northerly flow sent temperatures plummeting into the teens and 20s across
     most of central and eastern Oregon this morning.  Redmond was the cold spot with a minimum
     of 15 degrees.  Meacham dropped to 16 degrees.  

     Satellite imagery showed mostly clear skies across all of Oregon at midday.  As an
     upper-level ridge of high pressure builds just off the west coast today, a dry north-
     northwesterly flow aloft will prevail over Washington and Oregon.  The late-morning
     ODA surface analysis showed northerly gradients across all of Oregon, as pressures
     continued to build over Washington and north-central Oregon.  A thermal trough was
     starting to push northward, just off the southern Oregon coast...turning the flow offshore
     along the central and southern coast. 

     Late-morning temperatures were still in the chilly upper 40s and low 50s across western
     Oregon.  The exception was along the south coast, at Brookings, where temperatures were
     in the low 60s.  Even with a full day of sunshine, increasing cool northerly winds should
     keep highs in the 55-60 degree range this afternoon along the northern and central
     coast and across the Willamette Valley.  However, downsloping north-northeasterly winds
     should lift temperatures on the south coast, around Brookings, into the low 70s.  North-
     northeasterly transport winds are not favorable for stack burning.

Surface Winds:
     N 10-20 G25 this afternoon.
Transport Winds:
     NNE 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 50.
High Temperature:
     Salem\'s high temperature today will be near 60.
Humidities:
     Minimum relative humidity will be near 32%.
Sunrise/Sunset:
     Salem sunset tonight: 7:22pm; sunrise tomorrow: 7:17am.

Extended Outlook:
     There have been some significant timing changes to the
     extended forecast since yesterday.  Friday now appears as if
     it will be the warmest day of this dry spell, with the
     upper-level ridge forecast to move over western Oregon.  A
     building surface thermal trough, along the coast, will turn
     low-level winds offshore...further drying the air mass and
     leading to a large spread between morning minimums and
     afternoon maximums.  After another cold morning, with local
     areas of frost, afternoon highs should climb into the low to
     mid 60s in the Willamette Valley.  The northern and central
     coast could see high temperatures climb to near 70 degrees.

     The upper-level ridge is forecast to shift eastward on
     Saturday, to over eastern Oregon, with increasing
     southwesterly flow aloft initiating a marine push across
     western Oregon.  Temperatures will cool significantly along
     the coast, with afternoon onshore flow capping high
     temperatures a few degrees cooler across the Willammette
     Valley.  Clouds will also be on the increase Saturday
     afternoon, as a weak cold front comes onshore.  The latest
     computer guidance is suggesting that the cold front could be
     strong enough to bring some areas of light rain to western
     Oregon by Saturday evening...especially along the coast.

     A weak upper-level trough will turn the flow aloft westerly
     over Oregon on Sunday, with strong onshore flow producing
     mostly cloudy skies and some shower activity across western
     Oregon.  High temperatures will drop back below normal. 
     Snow levels may drop to the Cascade passes by late Sunday,
     with minor snow accumulations possible.  The upper-level
     trough will push east of the region late Monday with a weak
     ridge building over the west coast Tuesday.  Another weak
     weather system may bring back a chance of rain by later Wednesday.

Fri (19 Mar):  Possible Frosty Start...Sunny and Mild in the Afternoon. Offshore Flow.  31/63

Sat (20 Mar):  Increasing Clouds and Cooler.  Slight Chance of Rain late.   34/59

Sun (21 Mar):  Mostly Cloudy.  Scattered Showers.  Snow Level Dropping to 4000 Feet.  42/55

Mon (22 Mar):  Decreasing Showers.  Snow Level Dropping to 3000 Feet.  39/52

Tue (23 Mar):  Partly Sunny.  37/56

Wed (24 Mar):  Slight Chance of Light Rain Late.  Snow Level Rising to 4-5000 Feet. 36/56

Thu (25 Mar):  Becoming Partly Sunny.  38/60

ODA Meteorologist
weather at oda.state.or.us