[willamette-fcst] Forecast - Friday, January 16th, 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: 
     Friday, January 16th, 2009 at 9:00am.

...The Portland National Weather Service has extended the air stagnation advisory through Sunday
   for the Willamette Valley.  Unseasonably warm air aloft is trapping cool air near the surface
   and creating poor ventilation conditions...

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

Weather Discussion:
     Little change in the weather is expected today, as a strong
     upper-level ridge remains anchored over the Pacific
     Northwest.  Infrared satellite imagery showed only some high
     clouds circulating mainly across Washington.  However, low
     clouds and fog blanketed many of the valley locations, on
     both sides of the Cascades, this morning.

     The morning ODA surface analysis showed a thermal trough off
     the Oregon coast and high pressure over eastern Washington
     and Oregon.  That was continuing to produce strong offshore
     flow across western Oregon.  Easterly winds were gusting to
     60 mph at Corbett, in the western Columbia Gorge, this
     morning and to 40 mph in Troutdale.  The drier low-level
     Gorge winds were helping to keep skies clear in the extreme
     north valley, near Portland.  The fog even cleared from
     Hillsboro this morning, which allowed the temperatures there
     to drop into the low 20s.  Foggy conditions continued from
     about McMinnville and Aurora south to Eugene with visibilities
     locally one-quarter of a mile or less.  Much of the valley had
     temperatures near of slightly below freezing at mid-morning.

     The Salem sounding this morning showed an almost identical
     temperature profile to Thursday morning.  The air aloft
     rapidly warmed to 50 degrees at an elevation of just 2000
     feet and to nearly 70 degrees from 3-5000 feet.  The air
     slowly cooled above 5000 feet but stayed above freezing all
     the way to 12,700 feet.  The warm temperatures aloft were
     reflected in surface temperatures on Mt. Hood this morning. 
     Government Camp (5000 feet) was 60 degrees at 8 am and
     Timberline Lodge (6000 feet) was 55 degrees.

     Weather stations in the central coast range (near 2000 feet)
     were also reoorting temperatures in the low 60s this
     morning.  Easterly winds were dropping off the coastal range
     and spreading across the beaches this morning.  Newport was
     getting gusts to over 20 mph and had a temperature of 45
     degrees.  Coastal highs climbed into the upper 50s and low
     60s on Thursday and should do so again today with sunny
     skies.  Fog and low clouds will persist in the central and
     southern Willamette Valley again today, with the dry
     easterly flow unable to break the valley inversion.  High
     temperatures will struggle to reach 40 degrees in the south
     valley and mid 40s in the central valley.  Meanwhile, much
     of the extreme north valley will have another sunny
     afternoon with highs in the mid to upper 40s.

     East of the Cascades, fog and low clouds have become more
     extensive each day in the Columbia Basin of northeastern
     Oregon and extend well into the Hood River Valley and south
     to Jefferson County this morning.  Widespread fog was also
     visible, on satellite imagery, from Baker City to Ontario,
     in eastern Oregon.  Temperatures were in the teens and 20s
     across the central and eastern sections of the state. 
     Temperatures cooled a few degrees yesterday in most areas
     east of the Cascades, and that trend will continue today. 
     South-central Oregon will continue to see mostly sunny
     skies, with highs in the low 50s, but fog and low clouds
     will encompass more lower elevation locations today with
     many valley areas staying below freezing.  Fog and low
     clouds will likely penetrate south into Redmond and Bend by
     Saturday with much cooler temperatures there.

Surface Winds:
     NE 0-6 this morning, NE 0-6 this afternoon.
Transport Winds:
     NE 3 this morning, NE 3 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 500 feet.  Ventilation index 2.
High Temperature:
     Salem\'s high temperature today will be near 43.
Humidities:
     Minimum relative humidity will be near 73%.
Sunrise/Sunset:
     Salem sunset tonight: 4:59pm; sunrise tomorrow: 7:45am.

Extended Outlook:
     The protective ridge of high pressure is expected to last at
     least through this weekend. Stagnant ventilation conditions
     will continue with Willamette Valley fog and low clouds
     locally giving way to partly sunny skies in the
     afternoons...mainly north.  Temperatures will be well above
     normal along the coast, in the coastal range, and in the
     Cascades, with mostly sunny skies.  Valley temperatures will
     range from slightly below normal, in cloudy/fogy areas, to
     slightly above normal, where dry offshore flow helps the sun
     cut through the fog.

     Long-range computer models show the upper-level ridge
     shifting east, to over the Rockies, early next week, with
     the flow aloft becoming southerly over Oregon.  Surface
     winds will remain strongly offshore, which will continue to
     bring some afternoon clearing...mainly to the north valley. 
     Mostly sunny and unseasnably mild weather will continue
     along the coast and in the mountains.

     A splitting and weakening weather system will approach the
     coastline late Tuesday.  It appears as if it will be a dry
     system and only spread some high clouds acorss the region. 
     It will weaken the offshore flow, with temperatures
     beginning to cool in the mountains and along the coast. 
     Valley temperatures may warm a few degrees.

     Long-range computer model forecasts vary considerably, after
     Tuesday, with the latest guidance suggesting the a weak
     upper-level trough may drop into the region by late
     Wednesday and begin to improve ventilation conditions. 
     There is even a slight chance of showers.  Valley
     temperatures will likely warm, as the low-level temperature
     inversion weakens.  The flow aloft may turn more northerly
     by Thursday, with cooler air, at all levels, beginning to
     spill into the region from British Columbia.

Tomorrow (17 Jan):  Valley Low Clouds/Fog.  Afternoon Clearing...Mainly North.  30/47

Sun (18 Jan):  Valley Low Clouds/Fog.  Afternoon Clearing...Mainly North.  30/47

Mon (19 Jan):  Valley Low Clouds/Fog.  Afternoon Clearing...Mainly North.  30/47

Tue (20 Jan):  Valley Low Clouds/Fog.  Afternoon Clearing. Increasing High Clouds.  31/48

Wed (21 Jan):  Mostly Cloudy.  Slight Chance of Showers.  34/49

Thu (22 Jan):  Partly Cloudy.  Slight Chance of Showers.  Snow Level 2-3000 Feet.  33/46

Fri (23 Jan):  Partly Cloudy.  32/46

ODA Meteorologist
weather at oda.state.or.us