[willamette-fcst] Forecast - Tuesday, January 27th, 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.

...Next update not scheduled until Monday, February 2nd, 2009 at 9am...

Issued: 
     Tuesday, January 27th, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:00pm.
     Straw stack burning is allowed from now until 3:00pm.

Weather Discussion:
     A cold and dry Arctic air mass moved into Washington and
     Oregon over the weekend and remained over the region this
     morning.  A Pacific weather system, in northwesterly flow
     aloft, brought increasing clouds overnight.  Willamette
     Valley temperatures dropped well into the 20s last night,
     before the clouds, and increasing southerly winds helped
     raise temperaures to near or slighty above freezing by
     mid-morning.  Precipitation moved into western Washington
     early this morning spread south, across northwestern Oregon,
     during the morning.

     The Salem sounding this morning showed considerable warming,
     compared with Monday morning, below 25,000 feet. However,
     the air mass was still cold enough for precipitation to begin
     mainly in the form of snow, north of about Salem in the
     Willamette Valley  As the air mass continued to moderate, the
     snow changed to rain south of the immediate Portland area by
     late this morning.  Midday valley temperatures ranged from near
     freezing, in Portland, to the upper 30s in Eugene.

     The low-level cold air mass could persist for a couple of more
     hours in the Portland area and most of the afternoon in the
     Columbia Gorge and areas east of the Cascades.  The National
     Weather Service has a Winter Weather Advisory in effect for the
     extreme northern Willamette Valley until 2 pm, but the advisory
     for the central Willamette Valley was allowed to expire at noon.

     Some areas, from about Salem north, managed to get a light snow cover, 
     before precipitation changed to rain.  The greatest valley snowfall
     was in the Portland area, where locally around an inch fell. Several inches
     of snow are possible in the Columbia Gorge today, along with sleet and
     freezing rain, due to cold easterly outflow keeping the low-level cold
     air in place there until later this afternoon.

     A little rain and snow is likely across central and eastern Oregon this
     afternoon, but increasing southerly winds will moderate temperatures there
     enough for the lowest elevations to changeover to rain by late this afternoon. 
     Since the low-pressure center is tracking across southern British Columbia,
     increasing southerly winds, gusting to near 30 mph across western Oregon,
     are in the process of lifting the snow level to around 2-3000 feet.  That
     has greatly improved ventilation conditions over the Willamette Valley.

     Valley temperatures will slowly continue to rise this afternoon, with most
     areas making it into the low to mid 40s.  The rain will taper off to a few
     showers tonight across western Oregon. The snow level will be about 2500 feet
     in northern Oregon and 4000 feet south.  Temperatures should stay above
     freezing west of the Cascades overnight.

Surface Winds:
     SSW 10-20 Gusts to near 30 mph this afternoon.
Transport Winds:
     SSW 25 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 63.
High Temperature:
     Salem\'s high temperature today will be near 44.
Humidities:
     Minimum relative humidity will be near 55%.
Sunrise/Sunset:
     Salem sunset tonight: 5:14pm; sunrise tomorrow: 7:36am.

Extended Outlook:
     A few showers may linger into Wednesday, as high pressure
     builds back over the region.  Warmer air near the surface
     and cool air aloft should maintain good ventilation
     conditions across the valley.  Light winds and clearing
     skies should allow valley temperatures to drop close to
     freezing Wednesday night with areas of fog forming.  As a
     strong upper-level ridge builds over the region Thursday,
     warmer air aloft will deteriorate ventilation conditions. 
     Valley high temperatures will vary, depending on the local
     extent of fog.

     A weak weather system is forecast to flatten the upper-level
     ridge, as it brushes the region Friday.  It may be strong
     enough to bring some light rain to the northern portions of
     the state, including the Willamette Valley.  Snow levels
     will drop to near 4000 feet with improved ventilation
     conditions.  A few showers may linger into Saturday with the
     snow level dropping below the Cascade passes.  The
     long-range models show the persistently strong upper-level
     ridge rebuilding over the region early next week.  However,
     it may not be strong enough to prevent some sprinkles or
     very light rain over the northern third of the state.

Tomorrow (28 Jan):  Mostly Cloudy.  Decreasing Chance of Showers.  35/46

Thu (29 Jan):  Areas of AM Fog.  Partly Sunny.  32/45

Fri (30 Jan):  Areas of AM Fog.  Increasing Clouds.  Chance of Light Rain.  33/48

Sat (31 Jan):  Mostly Cloudy.  Chance of Showers.  Snow Level 2500 Feet.  34/46

Sun (01 Feb):  Mostly Cloudy.  Chance of Sprinkles or Light Rain...Mainly North.  33/48

Mon (02 Feb):  Mostly Cloudy.  Chance of Light Rain...Mainly North.  36/50

Tue (03 Feb):  Mostly Cloudy.  36/50

ODA Meteorologist
weather at oda.state.or.us