[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 12:00pm.

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 low-pressure centers
     affecting the west coast late this morning.  One was about 150 miles
     west of Astoria, Oregon, and another was just off the central California
     coastline.  Both systems have very low barometric pressure,
     but the combination of systems was not allowing for very strong
     pressure-gradients to develop over Oregon.  Southerly winds did
     pick up, from south to north, along the Oregon coast and
     in the Willamette Valley this morning, but most areas have only seen
     gusts to about 30 mph or less.  The southerly winds had advanced as far
     north as McMinnville, in the Willamette Valley, by midday.

     As the system off the coast of Astoria continues to weaken and migrate
     slowly northward, southerly winds will advance onto the northern Oregon
     coast and into the extreme northern Willamette Valley this afternoon. 
     Winds in the Portland area were still light easterly at midday.  Winds
     are not expected to be very strong, with gusts only to about 30 mph on the
     coast and 15-25 in the Willamette Valley.  Winds will decrease later this
     afternoon.

     The air aloft is still mild, for mid-January.  The freezing level is near 5000
     feet, and ODOT road cameras showed wet pavement over the Cascade passes at midday.
     Pass temperatures were well above freezing.  Only slight cooling aloft is forecast
     for this afternoon.  Satellite imagery was showing ample sunbreaks south of the
     low-pressure center, over most of western Oregon, with very little shower activity.

     A little sunshine was combining with the mild south breeze to lift valley temperatures
     well into the 50s.  Valley highs should climb into the mid to upper 50s this afternoon,
     which is near some daily records and 10-15 degrees above normal.  We can thank El Nino
     for this mild mid-winter weather.  Surface heating could create enough instability to
     trigger a few light showers this afternoon.
     
Surface Winds:
     S 7-17 G25...slowly decreasing this afternoon.
Transport Winds:
     S 20 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 57.
Humidities:
     Minimum relative humidity will be near 40%.
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 mostly cloudy
     and 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\'s near-record highs.  A transitory upper-level ridge will likely bring some drying
     over the weekend.

     A warm front is forecast to bring rain back onshore by Sunday afternoon, along with
     rising snow levels.  The trailing 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.  That is very typical of an \"El Nino influenced\" weather pattern.

     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.  38/50

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