[willamette-fcst] Forecast - Wednesday, January 23rd, 2008

Wed Jan 23 09:00:48 PST 2008

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 23rd, 2008 at 9:00am.

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

Weather Discussion:
     Generally clear skies and a very dry air mass allowed
     temperatures to rapidly fall overnight...leading to another
     cold morning across the Pacific Northwest.  Much of Central
     and Eastern Oregon dropped to near or below zero again this
     morning.  Burns was the cold spot at 16 degrees below zero. 
     Baker City was almost as cold at 12 below zero.

     Temperatures west of the Cascades were very similar to what
     we saw Tuesday morning.  Eugene and Corvallis dropped to 21
     degrees, while Salem hit 24 and Portland a windy 27 degrees.
      On the coast, Astoria fell to 29 degrees and Newport dipped
     to 34.  Strong offshore winds were continuing with Newport
     getting easterly gusts to 30 mph again this morning. 
     Troutdale, at the western end of the Columbia Gorge, was
     seeing east winds gusting between 40 and 45 mph this morning
     with the temperature at 26 degrees.  That puts the windchill
     there in the single digits.

     Due to warming aloft, some of the mountain locations were
     not as cold this morning.  After dropping to a bone-chilling
     23 below zero Tuesday morning, Meacham, in the NE mountains,
     only fell to 1 degree below zero this morning...downright
     balmy!  However, due to the lack of solar insulation this
     time of year, cold air gets trapped and pools in the
     valleys, as the air aloft warms...leading to strong
     low-level temperature inversions.

     The freezing level over Salem this morning was 6700 feet,
     after being at the surface Tuesday morning.  Due to the
     increasing low-level inversion over the Willamette Valley,
     stack burning is not allowed today.  The morning ODA surface
     analysis showed strong high pressure extending from NE
     Washington through Eastern Oregon and a low perssure trough
     along the Oregon Coast.  That combination of pressure
     systems is responsible for the offshore flow across the
     state again today

     Willamette Valley temperatures will show little change from
     Tuesday with highs, once again, climbing into the low 40s
     under sunny skies.  Surface winds will remain offshore
     across Western Oregon with a northerly component in the
     Willamette Valley.  Under clear skies, temperatures will
     rapidly fall back into the 20s tonight.   With the lack of
     an insulating blanket of snow, frost sensitive crops will be
     in danger again tonight.

Surface Winds:
     N-NE 5-10 this morning, N-NE 5-15 this afternoon.
Transport Winds:
     NE 10-15 this morning, NE 10-15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1500 feet.  Ventilation index 15.
High Temperature:
     Salem\'s high temperature today will be near 42.
Humidities:
     Relative humidity drops to 50% by 10.
     Minimum relative humidity will be near 38%.
Sunrise/Sunset:
     Salem sunset tonight: 5:07pm; sunrise tomorrow: 7:40am.

Extended Outlook:
     A weather system is forecast to drop southeastward from the
     Gulf of Alaska to just off the Oregon Coast by Thursday
     afternoon.  That will maintain the surface offshore flow,
     keeping the cold and dry low-level cold air in place across
     Oregon, with increasing southerly flow aloft. This set-up
     has the potential to produce snow down to sea level. 
     However, most of the moisture from this system is forecast
     to stay offshore, as it drops southward off the Oregon
     Coast.  It appears that it will be mainly a cloud-maker for
     the Willamette Valley, which will act to cool daytime
     temperatures a few degrees from Wednesday.

     As the system moves southward along the Oregon Coast, it is
     forecast to connect with another low pressure system,
     currently near the San Francisco Bay area, and spread rain
     and snow into Northern California and Southern Oregon
     Thursday afternoon and night.  That will likely bring some
     snow to the Southern Cascades and the southern half of
     Central and Eastern Oregon.  Southwestern Oregon will likely
     get a little rain and snow with some light snow or flurries
     making it northward into the Willamette Valley. I do not
     anticipate significant accumulations in the valley at this
     time.

     Friday still appears to be a break-day from any storm
     activity with mostly sunny skies, offshore flow, and
     continued cool temperatures.  The forecast gets very tricky
     beginning Saturday, with a stronger system forecast by all
     the computer models to drop southeastward from the Gulf of
     Alaska into the Pacific Northwest.  With low-level cold air
     still in place across Western Oregon, the precipitation may
     begin as snow near midday Saturday...especially in and near
     the Columbia Gorge.

     It appears as if enough low-level warming will occur for the
     precipitation to turn to rain, outside of the Columbia
     Gorge, Saturday afternoon, with snow continuing above about
     2500 feet.  A strong cold front is forecast to sweep inland
     Saturday night with rapidly lowering snow levels in it\'s
     wake.

     A couple of very cold upper-level troughs are forecast to
     move over the region Sunday through Wednesday for showery
     conditions with continued very low snow levels.  Sticking
     snow above 500 feet, at times, is a real possibility, with a
     threat of wet sticking snow on the valley floor at times. 
     Heavy snow is likely in the Cascades and coastal range.

Thu (24 Jan):  Increasing Clouds.  Chance of Light Snow or flurries...Mainly South.  22/37

Fri (25 Jan):  Mostly Sunny and Cool.  25/42

Sat (26 Jan):  Rain or Snow...Likely Changing to Rain in the Afternoon.  28/42

Sun (27 Jan):  Showers of Rain or Snow.  Snow Level Near Valley Floors.  33/37

Mon (28 Jan):  Showers of Rain or Snow.  Snow Level Rising to 1500 Feet.  33/42

Tue (29 Jan):  Rain Turning to Showers.  Snow Level Dropping to 500 Feet.  35/42

Wed (30 Jan):  Rain or Snow Showers.  Snow Level Near 500 Feet.  33/41

ODA Meteorologist
weather at oda.state.or.us