[willamette-fcst] Forecast - Tuesday, March 31st, 2009

Tue Mar 31 11:59:33 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.

NOON UPDATE

Issued: 
     Tuesday, March 31st, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 5:30pm.
     Straw stack burning is allowed from now until 5:30pm.

Weather Discussion:
     In the wake of the warm front that brought very light
     precipitation to northern Oregon overnight, a cold front was
     moving across northern Washington late this morning.  Dopler
     radar and surface reports showed areas of light rain and
     mountain snow across much of Washington and, to a lessor
     extent, the northern half of Oregon.  The strong
     northesterly jet stream associated with this system does not
     have much of an over-water trajectory, so moisture has been
     limited west of the Cascades.  However, strong
     south-southwesterly winds, ahead of the cold front, will
     turn more westerly this afternoon.  That will increase the
     upslope flow into the northern Oregon and Washington
     Cascades, with significant snow accumulations likely above
     3000 feet this afternoon and evening.

     Some light snow fell over the northern Cascades this
     morning, with the snow level lifting from arond 2500 feet
     Monday afternoon to around 4000 feet early this morning. 
     Government Camp and Santiam Pass both picked up about 1 inch
     of snow this morning.  A late-morning check of ODOT road
     cameras showed only flurries over the passes with pass
     temperatures near 30 degrees.  With increasing snow expected
     this afternoon, the National Weather Service has issued a
     Winter Weather Advisory for the Oregon Cascades, from
     Santiam Pass northward, through 9pm, for 5-10 inches of new
     snow.  About 3-7 inches of new snow are likely over
     Willamette Pass.

     Astoria picked up another tenth of an inch of rain in the 6
     hours ending at 11am, while most of the Willamette Valley
     saw only some sprinkles.   The late-morning ODA surface
     analysis showed tightenting pressure gradients across
     southern Washgton and northern Oregon, in response to the
     cold front.  Just ahead of the cold front, southwesterly
     winds were gusting over 30 mph across most of central and
     eastern Washington and northeastern Oregon.  In the wake of
     the front, winds had turned westerly, and were gusting to
     about 30 mph, across western Washington and along the the
     northern Oregon coast.  Winds in the Willamette Valley were
     still southwesterly and gusting to about 25 mph.

     Midday satellite imagery showed a broad band of clouds
     extending, from northwest to southeast, across most of
     Washington and virtually all of Oregon.  Temperatures ranged
     from the mid 40s to the low 50s across western Oregon. 
     Colder air moving over the region, in the wake of the fairly
     dry cold front, will keep temperatures from climbing out of
     the low 50s this afternoon. Skies should remain mostly
     cloudy, but a peek at the sun is possible.  Winds will
     continue to be blustery and turn more westerly across the
     Willamette Valley.  The chance of showers will decrease later
     this afternoon, as evening cooling stabilizes the air mass.

Surface Winds:
     Becoming W 10-20 G25 this afternoon.
Transport Winds:
     W 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3700 feet.  Ventilation index 74.
High Temperature:
     Salem\'s high temperature today will be near 52.
Humidities:
     Minimum relative humidity will be near 54%.
Sunrise/Sunset:
     Salem sunset tonight: 7:39pm; sunrise tomorrow: 6:52am.

Extended Outlook:
     Another warm front will keep skies cloudy overnight with
     some light rain likely spreading back across western Oregon
     by Wednesday morning.  A cold front will increase the
     rainfall Wednesday night and Thursday with more significant
     snow expected in the Cascades.  A cool upper-level trough
     will bring showers Friday with low snow levels.  The trough
     will push east of the region, with showers decreasing Friday
     evening.

     Saturday appears as if it will be dry and warmer, more
     spring-like, as a ridge of high pressure builds into the
     coast.  There is still disagreement in the computer model
     forecasts beyond Saturday, mainly on the timing of the next
     weather system.  The latest computer guidance is forecasting
     the next weather system to bring more rain onshore starting
     between midday Sunday and very early Monday. This system
     also apprears cold enough to be a snow-maker for the
     Cascades Sunday night and Monday. Showers are forecast to
     linger into Tuesday with continued low snow levels.

Tomorrow (01 Apr):  Cloudy.  Light Rain at Times.  Sow Level Rising to 5000 Feet.  38/50

Thu (02 Apr):  Rain Turning to Showers.  Snow Level Dropping to 3000 Feet.  42/52

Fri (03 Apr):  Decreasing Showers.  Snow Level 2-3000 feet.  37/53

Sat (04 Apr):  Partly Cloudy and Warmer.  34/62

Sun (05 Apr):  Chance of Rain by Afternoon.  Snow Level near 4000 Feet.  37/59

Mon (06 Apr):  Rain Turning to Showers.  Snow Level Dropping to 3000 Feet.  40/54

Tue (07 Apr):  Mostly Cloudy. Chance of Showers. Snow Level 3000 feet.  38/57

ODA Meteorologist
weather at oda.state.or.us