[willamette-fcst] Forecast - Wednesday, March 11th, 2009

Wed Mar 11 09:04:14 PDT 2009

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: 
     Wednesday, March 11th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 4:00pm.
     Stack burning is not allowed.

Weather Discussion:
     A cold northwesterly flow aloft helped a weakening Arctic
     cold front usher drier and cold air into the region
     overnight.  Clouds slowly cleared across Oregon with
     temperatures dropping well below freezing on both sides of
     the Cascades.  Willamette Valley minimums were generally in
     the mid to upper 20s this morning.  Eugene dropped down to
     at least 24 degrees.  Hillsboro was also one of the colder
     spots with a low of 25.  Salem and Portland dipped to at
     least 29.

     It was quite cold east of the Cascades this morning, with
     many areas in the teens or colder.  Meacham, in the blue
     Mountains of northeastern Oregon, dropped to 11 degrees
     below zero and was still at -10 degrees at mid-morning. 
     Sub-zero temperatures were also experienced across eastern
     Washington, where Deer Park, near Spokane, dropped to 12
     degrees below zero.  The cold air mass stretching from
     eastern Washington across Montana is one of the coldest ever
     on record for so late in the season.  Minimums dropped to
     more than 25 degrees below zero across sections of Montana
     this morning.

     Satellite imagery showed areas of fog in the central and
     southern Willamette Valley this morning.  Offshore flow kept
     the north valley clear overnight.  Increasing offshore flow
     will continue to dry the air mass today, resuting in sunny
     skies across all of the region by this afternoon.  even with
     a full day of March sunshine, temperatures will stay below
     normal, but to cold outflow from the Columbia Gorge and the
     near-record cold air mass in the Columbia Basin.  Valley
     highs will only climb into the upper 40s (normal would be in
     the mid 50s).  Stack burning was not allowed today due to
     north-northeasterly transport winds.

Surface Winds:
     N 5-12 this morning, NNE 8-17 this afternoon.
Transport Winds:
     NNE 12 this morning, NE 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 45.
High Temperature:
     Salem\'s high temperature today will be near 48.
Humidities:
     Minimum relative humidity will be near 46%.
Sunrise/Sunset:
     Salem sunset tonight: 7:13pm; sunrise tomorrow: 7:30am.

Extended Outlook:
     An upper-level ridge is forecast to build into the west
     coast Thursday and Friday.  That will bring adry conditions
     with moderating temperatures, although overnight minimums
     will remain chilly.  After another frosty morning, on
     Thursday, sunny skies and offshore winds will help afternoon
     temperatures climb into the low to mid 50s.  Afternoon
     temperatures will jump up about 5 degrees, on Friday, with
     another full day of sunshine and offshore flow at the surface.

     The next weather system will bring rain back to the region
     early Saturday with snow levels quickly dropping below the
     Cascade passes.  The rain will turn to showers by late
     Saturday, but a warm front is forecast to bring more rain
     Sunday, especially in the north.  Snow levels may lift above
     the Cascade passes by late Sunday, with increasing westerly
     flow aloft and southerly winds at the surface.

     The latest computer guidance is suggsting that a strong
     upper-level trough of low-pressure will develop over the
     eastern Pacific Ocean with southwesterly flow aloft over
     Oregon.  The jet stream may be far enough south to keep
     Washington and western Oregon under cloudy skies with a good
     chance of rain.  However, the latest computer guidance gives
     several possible jet stream positions, so the jury is still
     out as to how wet it will be next week.  A slight northward
     shift of the jet stream would bring spring-like conditions
     to the region, but a more southern track would bring
     increasing amounts of rain. In any case, it should be mild,
     with southwesterly flow aloft.  My forecast reflects a
     middle-of-the-road solution for now.

Tomorrow (12 Mar):  Another Cold Start.  Sunny and Warmer in the Afternoon.  25/53

Fri (13 Mar):  Frosty Morning.  Sunny and Warmer in the Afternoon. Clouds Late.  28/57

Sat (14 Mar):  Rain Turning to Showers. Snow Level 3-4000 Feet.  37/50

Sun (15 Mar):  Mostly Cloudy.  Light Rain Likely...Mainly North.  Snow Level 5000 Feet. 38/53

Mon (16 Mar):  Mostly Cloudy.  Chance of Rain...Mainly North.  40/57

Tue (17 Mar):  Mostly Cloudy.  Chance of Rain...Mainly North.  40/57

Wed (18 Mar):  Mostly Cloudy.  Chance of Rain.  40/55

ODA Meteorologist
weather at oda.state.or.us