[willamette-fcst] Forecast - Tuesday, March 16th, 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.

Issued: 
     Tuesday, March 16th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 4:30pm.
     Straw stack burning is allowed from now until 4:30pm.

Weather Discussion:
     It was a mild afternoon on Monday across western Oregon,
     with offshore flow bringing the warmest readings to the
     northern coast.  Astoria recorded a high Monday of 67
     degrees and Tillamook hit 68.  Highs in the Willamette
     Valley were mostly in the low to mid 60s.  Aurora was the
     warm spot with 66 degrees.  Eugene was the cool spot with a
     high of 59.  Southwesterly flow aloft spread middle and high
     clouds over the region last night...making for mild
     overnight temperatures.  Most of western Oregon stayed in
     the 40s this morning.  McMinnville was the cool spot with a
     minumum of 38 degrees.  Normally Willamette Valley minimums
     are in the mid to upper 30s for this time of year.

     Clouds were beginning to lower and thicken across western
     Oregon, by mid-morning, in advance of a weakening cold front
     just offshore.  Satellite imagery showed a narrow band of
     clouds stretching from the southern British Columbia
     coastline to the northern California coast and then trailing
     offshore to the southwest.

     The ODA surface analysis showed increasing southeastery
     pressure gradients across western Oregon, ahead of the
     approaching cold front. Southerly winds were already gusting
     to 30 mph along the coast, at Newport, with light rain just
     starting to fall.  Rain will spread across the entire
     coastline over the next couple of hours and into the
     Willamette Valley by early this afternoon.  Southerly winds
     will increase in the Willamette Valley later this morning.
     Mixing of the air mass should help temperatures jump into
     the mid, and possibly upper 50s around midday, because the
     air aloft is still very warm.  The freezing levels over
     western Oregon were measured at about 8-10 thousand feet
     early this morning.

     Cooling aloft and increasing light rain will likely chill
     valley temperatures into the lower 50s by late this
     afternoon.  Rainfall totals should only be about one-tenth
     of an inch across the Willamette Valley, with most of the
     rain falling between midday and early this evening. Partial
     clearing is likely in the wake of the cold front overnight
     with just a chance of a shower...mainly north and over the
     mountains.  The snow level will drop to between three and
     four thousand feet by Wednesday morning, with a couple of
     inches of fresh snow possible in the Cascades overnight.

Surface Winds:
     SSE 5-15 G20 this morning, SW 10-20 G30 this afternoon.
Transport Winds:
     S 15 this morning, SW 30 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 90.
High Temperature:
     Salem\'s high temperature today will be near 56.
Humidities:
     Minimum relative humidity will be near 60%.
Sunrise/Sunset:
     Salem sunset tonight: 7:20pm; sunrise tomorrow: 7:21am.

Extended Outlook:
     The roller-coaster ride in temperatures is likely to
     continue during the extended forecast period, with very mild
     conditions over the weekend followed by a sharp cool-down
     early next week.  A cool upper-level trough will maintain
     some showers over mainly the northern half of Oregon through
     about midday Wednesday.  A dry northwesterly flow aloft is
     forecast for Thursday, as an upper-level ridge of high
     pressure begins building just off the west coast.  That will
     lead to cool morning temperatures, but afternoon highs
     should recover to near or slightly above normal.

     The upper-level ridge is forecast to move over Oregon Friday
     and Saturday.  Offshore surface winds will keep the air mass
     dry...leading to a large spread between morning minimums and
     afternoon maximums.  Mornings may bring areas of frost to
     the Willamette Valley.  Afternoon highs will be well above
     normal, with the warmest temperatures along the coast, on
     Friday, and over the inland valleys on Saturday. The ridge
     is forecast to slide over Idaho by Sunday afternoon with
     increasing southwesterly flow aloft over western Oregon. 
     Highs on Sunday should be closer to normal, with a cold
     front is spreading rain onshore by Sunday night. 
     Temperatures will likely drop back below normal Monday and
     Tuesday with snow levels lowering below the Cascade passes. 
     Showers will taper off by Tuesday afternoon.

Tomorrow (17 Mar):  Chance of a Shower Early...Becoming Partly Sunny in the Afternoon.  37/57

Thu (18 Mar):  Cool Start, With Possible Areas of Frost...Becoming Mostly Sunny.  33/59

Fri (19 Mar):  Possible Frosty Start...Sunny and Mild in the Afternoon.  31/62

Sat (20 Mar):  Cool Morning...Sunny and Very Mild in the Afternoon.   33/65

Sun (21 Mar):  Increasing Clouds.  Chance of Rain Late.  35/60

Mon (22 Mar):  Rain Likely and Much Cooler.  Snow Level Dropping to 3000 Feet.  39/52

Tue (23 Mar):  Mostly Cloudy.  Chance of Showers...Mainly North.  37/54

ODA Meteorologist
weather at oda.state.or.us