[willamette-fcst] Forecast - Wednesday, January 20th, 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: 
     Wednesday, January 20th, 2010 at 9:00am.

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

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

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

Weather Discussion:
     A classic mid-winter \"El Nino\" weather pattern has set up
     across the Pacific Ocean.  A strong jet stream is continuing
     to direct strong storm systems into California, with an
     unseasonably mild south-southwesterly flow aloft over
     Washington and Oregon.  The bulk of the rainfall from the
     incoming weather systems will stay south of the Willamette
     Valley, this week, but some rain and blustery winds can be
     expected at times...mainly south and along the coast.

     Infrared satellite imagery showed a broad cloud-shield,
     associated with a strong cold front, extending across all of
     northern and central California.  Cloudy skies stretched
     northward over southwestern Oregon, with high clouds
     extending as far north as the Washington/Oregon border. 
     This system was bringing heavy rain and strong southerly
     winds to the northern and central California coastal areas,
     with moderate rain pushing northward into extreme
     southwestern Oregon.  Doppler radar showed light rain
     spreading as far northward as the southern Willamette Valley.

     The low-pressure center associated with this cold front was
     just off the northern California coastline at mid-morning
     and is forecast to slowly move north, to off the northern
     Oregon coast, by Thursday morning.  It will increase the
     offshore gradients across the Willamette Valley today, and
     then turn the surface flow strongly southerly by Thursday
     morning.  Some rain will likely make it northward, across
     western Oregon, this afternoon, but the bulk of the rain from
     this system will stay over extreme southern Oregon and California.

     The air aloft remains unseasonably mild.  The freezing
     levels over Salem and Medford were measured near 5000 this
     morning.  ODOT road cameras showed light snow showers over
     the central Cascade passes this morning, with generally dry
     conditions in the north.  Pass temperatures were near the
     freezing mark.  The air mass aloft will likely warm slightly
     today, ahead of the approaching cold front, so ventilation
     conditions are not expected to be as good today as they were
     on Tuesday.

     Temperatures were mild again this morning across western
     Oregon, with mid-morning readings mostly in the low to mid
     40s.  Winds were mostly light, with a slowly increasing
     offshore flow.  Clouds should thicken, from south to north,
     today, with an increasing chance of light rain.  Increasing
     northeasterly winds will help to mix warmer air aloft down
     to the surface, which should help afternoon temperatures
     climb, once again, into the mid 50s(about 10 degrees above normal).

Surface Winds:
     NE 3-10 this morning, NE 5-15 this afternoon.
Transport Winds:
     ESE 10 this morning, ENE 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 38.
High Temperature:
     Salem\'s high temperature today will be near 55.
Humidities:
     Minimum relative humidity will be near 50%.
Sunrise/Sunset:
     Salem sunset tonight: 5:04pm; sunrise tomorrow: 7:42am.

Extended Outlook:
     The low-pressure system is forecast to track northward, just off
     of the Oregon Coast, Wednesday night and early Thursday, it
     will likely bring a burst of strong southerly winds to the
     Oregon Coast, where high wind watches are in effect for
     later tonight through Thursday.  Depending on the track of
     the low-pressure center, strong southerly winds may also
     briefly make it into the Willamette Valley Thursday morning.
     Rainfall from this system is forecast to be light.

     A broad upper-level trough is forecast to move onshore
     Friday, with showers and slightly lower snow levels.  A
     transitory upper-level ridge will likely bring some drying
     over the weekend.  The next weather system is forecast to
     come onshore Sunday night.  It also has the potential to
     bring strong winds to mainly the northern coastal strip. A weak
     upper-level ridge may briefly dry things out Tuesday night,
     but another mild storm is forecast to come onshore Wednesday afternoon.

Tomorrow (21 Jan):  Rain and Windy Early...Turning to Showers.  Snow Level 3500 Feet.  40/50

Fri (22 Jan):  Showers.  Snow Level 3000 Feet.  36/48

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

Sun (24 Jan):  Increasing Clouds.  Rain Late.  Snow Rising to 4000 Feet.  34/48

Mon (25 Jan):  Rain Likely.  Snow Level 4500 Feet.  39/50

Tue (26 Jan):  Mostly Cloudy.  Chance of Showers.  Snow Level 4000 Feet.  37/50

Wed (27 Jan):  Increasing Chance of Rain.  Snow Level Rising to 5-6000 Feet.  37/49

ODA Meteorologist
weather at oda.state.or.us