[willamette-fcst] Forecast - Thursday, January 21st, 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: 
     Thursday, January 21st, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from now to 3:00pm.

              ...The rules for stack burning have changed...

     In 2010, a total of 1000 acres can be stack-burned in the Willamette
     Valley.  Pre-registration is now required, and stack burning permits must
     be obtained from an ODA staff member. 

Weather Discussion:
     A strong jet stream is continuing to drive potent storm
     systems into California, with an unseasonably mild southerly
     flow aloft over Washington and Oregon.  Considerable amounts
     of rain have been falling, and will continue to fall, across
     California, but mostly just bands of very light rain have
     been rotating as far north as Oregon.  The exception is
     along the extreme southern Oregon Coast, where Brookings has
     picked up close to an inch of rain in the past 24 hours.

     Infrared satellite imagery showed two distinct weather
     systems affecting the west coast this morning.  One
     low-pressure center was just off the central Oregon
     coastline, with another just off the central California
     coastline.  Both systems have very low barometric pressure,
     which was reducing the pressure-gradients across Oregon. 
     The strongest pressure-gradients were south of the second
     low-pressure center, over southern California, where winds
     were gusting to near 50 mph in the greater San Diego area.

     Meanwhile, in our neck of the woods, southerly winds began
     increasing, from south to north, along the Oregon coast and
     in the Willamette Valley early this morning, as the offshore
     low-pressure center slowly weakened and migrated northward. 
     Eugene briefly had southerly gusts to about 35 mph around
     6am, and Corvallis recorded gusts to near 30 mph around 7am.
     Southerly winds had progressed northward, into the Salem
     area, by 8am, but were only around 10 mph.  Winds in the
     northern valley were still light at mid-morning.  South
     winds were a little stronger along the central and southern
     coast but mostly gusting to around 30 mph.  North of the
     low-pressure system, the north coast was still getting a
     light easterly flow.

     The low-pressure center is forecast to continue drifting
     northward and should be well off the Washington coast, by
     this afternoon.  Southerly winds will advance northward,
     across the remainder of the Oregon coast, and the Willamette
     Valley, later this morning.  However, winds are not expected
     to be very strong, with gusts only to about 40 mph on the
     coast and 15-25 in the Willamette Valley.  Winds will
     decrease later this afternoon.  Skies should stay mostly
     cloudy today, with a little rain at times.  Once again,
     rainfall totals will be minimal.

     Mid-morning temperatures were mostly in the 40s across
     Western Oregon. The air aloft is still on the mild side of
     normal, for mid-January.  The freezing level is near 5000
     feet, but ODOT road cameras do show a fresh covering of
     light snow over the Cascades passes this morning.  Pass
     temperatures were near 30 degrees.  There will be only
     slight cooling aloft today, in the wake of this morning\'s
     weather system, so mild southerly winds should lift coastal
     and valley temperatures to near 50 by midday.  Highs should
     be in the 50-55 degree range this afternoon, with a
     continued chance of light showers.

Surface Winds:
     SSE 10-20 G30 this morning, S 5-15 G20 this afternoon.
Transport Winds:
     S 20 this morning, S 15 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 53.
Humidities:
     Minimum relative humidity will be near 50%.
Sunrise/Sunset:
     Salem sunset tonight: 5:05pm; sunrise tomorrow: 7:42am.

Extended Outlook:
     A broad upper-level trough is forecast to move onshore
     Friday, with skies staying mostly cloudy along with some
     showers.  Snow levels should remain just below the Cascade
     passes, where a couple of inches are possible.  Valley
     temperatures will likely cool a few degrees from today.  A
     transitory upper-level ridge will likely bring some drying
     over the weekend.

     A warm front, from the next weather system, is forecast to
     bring rain back onshore by Sunday afternoon, along with
     rising snow levels.  The following cold front has the
     potential to bring strong southerly winds to mainly the
     coastal strip Sunday night.  It appears as if energy from
     this storm may get split apart, as it comes onshore, with
     the bulk of the moisture heading both north and south of
     Oregon.

     Skies should stay mostly cloudy Monday, with a split-flow
     pattern, in the wake of Sunday night\'s storm, bringing only
     a few light showers to the state.  A weak ridge of high
     pressure will bring further drying on Tuesday.  Another mild
     storm is forecast to come onshore late Wednesday and Thursday.

Tomorrow (22 Jan):  Scattered Showers.  Snow Level 3000 Feet.  38/47

Sat (23 Jan):  Mostly Cloudy.  Decreasing Chance of Showers.  Snow Level 3000 Feet.  35/49

Sun (24 Jan):  Increasing Rain and Turning Breezy Late.  Snow Level 4000 Feet.  34/47

Mon (25 Jan):  Mostly Cloudy.  A few Showers.  Snow Level 4500 Feet.  41/50

Tue (26 Jan):  Mostly Cloudy.  Slight Chance of Showers.  Snow Level 4000 Feet.  38/50

Wed (27 Jan):  Increasing Clouds.  Snow Level Rising to 5-6000 Feet.  37/50

Thu (28 Jan):  Rain Likely and Mild.  Snow Level 6000 feet.  42/54

ODA Meteorologist
weather at oda.state.or.us