[willamette-fcst] Forecast - Friday, January 16th, 2009

Fri Jan 16 12:04:52 PST 2009

Daily Smoke Management Forecast

Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

...Next Update scheduled for Tuesday, January 20th at 9:00am...

NOON UPDATE

...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...

Issued: 
     Friday, January 16th, 2009 at 12:00pm.

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 across Washington and northern Oregon. 
     However, low clouds and fog continued to blanket many of the
     valley locations, on both sides of the Cascades, at midday.

     The late-morning ODA surface analysis continued to show 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 (western
     Columbia Gorge) early this morning and were still gusting to
     just over 50 mph at midday.  Easterly winds were gusting to
     40 mph in Troutdale early this morning with gusts near 25
     mph at midday.

     The drier low-level Gorge winds were helping to keep skies
     clear in the extreme north valley, near Portland, where it
     was sunny late this morning.  The fog even cleared from
     Hillsboro early this morning, which allowed the temperatures
     there to drop to a low of 22 degrees.  It had only warmed to
     the freezing mark there by 11am.  Low clouds and fog
     continued to blanket the Willamette Valley, from a
     Newberg-to-Aurora line south to Eugene.  Visibilities were
     still locally one-quarter of a mile or less.  Most of the
     valley had temperatures in the low to mid 30s.

     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 late this
     morning.  Government Camp (5000 feet) was 64 degrees at 11
     am and Timberline Lodge (6000 feet) was 60 degrees.

     Weather stations in the central coast range (near 2000 feet)
     were also reoporting temperatures as warm as the upper 60s
     late this morning.  Easterly winds were dropping off the
     coastal range and spreading westward to the beaches. 
     Newport was getting gusts to near 20 mph and had a
     temperature of 54 degrees at 11 am.  It was also in the mid
     50s at North Bend and 60 degrees in Brookings.  Coastal
     highs climbed into the upper 50s and low 60s on Thursday and
     should be at least that warm 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 but
     may climb into the upper 40s, with sunshine, in the extreme
     north valley, near Portland.

     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.  Early morning temperatures were in the
     teens and 20s across the central and eastern sections of the
     state and ranged from the mid 20s to the upper 40s at
     midday.  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
     over the weekend, with much cooler temperatures there.

Surface Winds:
     NE 0-6 this afternoon.
Transport Winds:
     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