[willamette-fcst] Forecast - Wednesday, January 14th, 2009

[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 14th, 2009 at 9:00am.

...The National Weather Service has issued an Air Stagnation Advisory
   for the Willamette Valley through Saturday...

Burn Advisory:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     A upper-level ridge of high pressure built over the Pacific
     Northwest this past weekend is continuing to strengthen. 
     The ridge axis was just off the coastline this morning, with
     a dry northwesterly flow aloft spreading only some high
     clouds over Washington and Oregon.  The Salem sounding
     showed further warming aloft, since Tuesday, with
     temperatures over 50 degrees between 2000 and 7000 feet. 
     Temperatures peak in the low 60s at around 3000 feet, so
     much the Cascade and coastal ranges will have unseasonable
     warm temperatures today.

     Strong low-level temperature inversions remained over Oregon
     this morning, with a blanket of clouds covering the
     Willamette Valley.  The freezing level was near 13,000 feet
     over Oregon this morning.  Timberline Lodge, at the
     6000-foot elevation on Mt. Hood, was in the low 50s this
     morning.  Meanwhile, Willamette Valley temperatures were
     mostly in the upper 30s with low clouds.  Warm air aloft and
     colder air trapped in the interior valleys is resulting in
     very poor ventilation conditions, and the National Weather
     Service has issued an Air Stagnation Advisory for the
     Willamette Valley through Saturday.

     The ODA surface analysis showed offshore pressure gradients
     beginning to increase, which may help to clear the low
     clouds from the north valley this afternoon.  Low clouds
     will be persistent in the central and south valley.  High
     temperatures will range from the mid 40s in the central and
     south valley to the low 50s, and possibly mid 50s, in the
     north valley.  Meanwhile, afternoon temperatures along the
     coast, in the coastal range, and in the Cascade foothills
     should climb well into the 50s, and perhaps the low 60s,
     with a little sunshine.  

Surface Winds:
     NE 3-8 this morning, NE 5-10 this afternoon.
Transport Winds:
     NE 5 this morning, NE 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 500 feet.  Ventilation index 4.
High Temperature:
     Salem\'s high temperature today will be near 45.
Humidities:
     Minimum relative humidity will be near 70%.
Sunrise/Sunset:
     Salem sunset tonight: 4:56pm; sunrise tomorrow: 7:46am.

Extended Outlook:
     Very little change in the weather pattern is expected
     through Sunday, as the strong upper-level ridge of high
     pressure moves directly over Oregon and Washington. 
     Stagnant air conditions will continue with valley low clouds
     locally gining way to party sunny skies in the afternoons. 
     Temperatures will be well above normal along the coast, in
     the coastal range, and in the Cascades, with some sunshine. 
     Valley temperatures will vary considerably and range
     generally from near to slightly above normal, due to trapped
     low-level cool air and areas of persistent low clouds.

     Long-range computer models show the upper-level ridge
     shifting east, to over the Rockies, early next week, with
     the flow aloft becoming southwesterly over Oregon.  A
     weather system may drop into the region, from the Gulf of
     Alaska, by Tuesday, which would bring an end to the dry and
     stagnant weather pattern.  A significant change in the
     weather pattern my take place around the middle of next
     week, with much colder air moving back into the region, but
     that is too far out to be sure of at this time.

Tomorrow (15 Jan):  AM Clouds/Fog.  Afternoon Clearing...Mainly North.  34/48

Fri (16 Jan):  AM Clouds/Fog.  Afternoon Clearing...Mainly North.  33/50

Sat (17 Jan):  AM Clouds/Fog.  Afternoon Clearing...Mainly North.  33/50

Sun (18 Jan):  AM Clouds/Fog.  Afternoon Clearing...Mainly North.  33/50

Mon (19 Jan):  AM Clouds/Fog.  Afternoon Clearing...Mainly North.  35/51

Tue (20 Jan):  Increasing Clouds.  Chance of Rain Late.  35/50

Wed (21 Jan):  Showers.  Snow Level Dropping to 2000 Feet.  37/45

ODA Meteorologist
weather at oda.state.or.us