[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.

NOON UPDATE

...An Air Stagnation Advisory is in effect for the Willamette Valley through Saturday. Warm air
   aloft is trapping colder air near the surface, resulting in very poor ventilation conditions...

Issued: 
     Wednesday, January 14th, 2009 at 12:00pm.

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

Weather Discussion:
     An upper-level ridge was just off the coastline this morning, with a dry north-northwesterly
     flow aloft spreading only some high clouds over Washington and Oregon.  However, visible
     satellite imagery showed extensive low clouds blanketing most of the western valleys at
     midday.  Low clouds also covered some of the valleys in eastern Oregon and much of the
     Columbia Basin of northeast Oregon.  Skies were mostly sunny over the remainder of the
     state...including along the coast.

     The Salem sounding showed further warming aloft, since Tuesday, with the freezing level at
     nearly 13,000 feet. Temperatures were warmer than 50 degrees between 2000 and 7000 feet and
     climbed as high as the low 60s near 3000 feet. The Cascades and coast range will have
     unseasonable warm temperatures again today.  Timberline Lodge, at the 6000-foot elevation on
     Mt. Hood, was 55 degrees at 11 a.m. Meanwhile, Willamette Valley temperatures were near 40
     degrees with low clouds.  Temperatures were in the mid 40s to low 50s, with mostly sunny
     skies and easterly winds, along the coast.  

     The ODA surface analysis showed a thermal trough building northward, alnog the Oregon Coast,
     with increasing offshore pressure gradients across western Oregon.  Drier outflow, from the
     Columbia gorge, 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
     mostly sunny skies.  

Surface Winds:
     NE 5-10 this afternoon.
Transport Winds:
     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:
     The protective ridge of high pressure is expected to last at least through this weekend.
     Stagnant ventilation conditions will continue with valley low clouds locally giving 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 mostly sunny skies.  Valley temperatures will
     range from slightly below normal, in cloudy/fogy areas, to well above normal, where the
     sunshine is able to break through.

     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.  The first threat
     of rain comes about Tuesday, but the track of that weather system is still in question.
     Better ventilation conditions are likely by late next week, as colder air aloft moves over
     the region and breaks up the low-level temperature inversions.  It is also possible that
     Arctic air will make another entrance into the Pacific Northwest late next week, but that
     is still too far out to forecast with certainty.

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):  Chance of Showers.  Snow Level Possibly Dropping to 2000 Feet.  37/45

ODA Meteorologist
weather at oda.state.or.us