[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.

NOON UPDATE

Issued: 
     Tuesday, March 16th, 2010 at 12:00pm.

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:
     Clouds were continuing to lower and thicken across western
     Oregon late this morning, in advance of a weakening cold
     front just moving onto the coastline.  Satellite imagery
     showed a narrow band of clouds stretching from Vancouver
     Island, British Columbia to the northern California coast
     and then trailing offshore. The upper-level winds are
     blowing fairly parallel to the front (from the south-southwest),
     so the surface cold front is advancing eastward only very slowly.

     The ODA surface analysis showed the southeasterly pressure
     gradients turning more southerly across western Oregon.
     Winds had become south-southwesterly along the northern
     Oregon Coast and were gusting to around 30 mph.  Light rain
     had moved onto the coastline and was advancing into the
     western Willamette Valley.  Rainfall totals so far along the
     coast have been less than one-tenth of an inch, with the
     exception of Brookings, on the southern Oregon coast, where
     close to one-half of an inch has fallen.

     The air aloft is still quite warm, with the freezing level
     above 7000 feet.  Southerly winds will increase in the
     Willamette Valley this afternoon. Mixing of the air mass
     should help temperatures jump into the mid, and possibly
     upper 50s, in the early afternoon. Light Rain will spread
     across the Willamette Valley by mid-afternoon, likely
     putting a cap on high temperatures.

     Rainfall totals from this cold front should only be about one-tenth
     of an inch across the Willamette Valley, with most of the rain falling
     by 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 below 4000 feet by Wednesday morning, with a
     couple of inches of fresh snow possible in the Cascades overnight.

Surface Winds:
     SW 10-20 G30 this afternoon.
Transport Winds:
     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 returning over the weekend...only to be followed
     by a sharp cool-down early next week.  In the short-term, a
     cool upper-level trough will maintain a chance of showers
     over mainly the northern half of Oregon through about midday
     Wednesday, with some sunshine and increasing north-northwesterly
     surface winds in the afternoon.  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 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
     normally colder sections of 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 cool
     closer to normal, with a cold front spreading rain onshore
     by Sunday night.  High 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 with snow showers over the Cascade passes.

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. Offshore Flow.  31/62

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

Sun (21 Mar):  Mostly Sunny Early...Increasing Clouds Late.  35/60

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

Tue (23 Mar):  Showers...Decreasing Late.  Snow Level 2500 Feet.  37/54

ODA Meteorologist
weather at oda.state.or.us