[willamette-fcst] Forecast - Monday, December 15th, 2008

Mon Dec 15 11:59:11 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.

NOON UPDATE

Issued: 
     Monday, December 15th, 2008 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 2:30pm.
     Stack burning is not allowed.

Weather Discussion:
     A blast of wintry weather hit the Pacific Northwest over the
     weekend with valley rain and heavy snow in the Cascades
     Friday.  Snow levels lowered to near 1000 feet Friday night
     and Saturday with frequent showers bringing heavy snow to
     both the coastal range and the Cascades.  Some showers mixed
     snow down to the Willamette Valley floor at times.  Cold
     Arctic air sagged southward, into Washington, Saturday and
     through the Columbia Gorge, into Portland, by early Sunday
     morning. Ahead of the Arctic cold front, The surface winds
     were coming from off the relatively warmer ocean, so snow
     levels remained above the valley floor.

     The snow level dropped to the valley floor, in the Portland
     area, early Sunday, as the cold Arctic air began pouring
     directly into the valley, via the Columbia Gorge.  The
     Arctic cold front slowly marched south to near Salem by late
     Sunday afternoon and to Eugene Sunday night.  A surface low
     pressure area concurrently moved south, off the Oregon
     Coast, and circulated moisture over the Arctic cold front. 
     That helped keep the frontal system actively producing snow,
     as it moved south up the valley.  

     The following is a list of snow totals, as of 10:45 a.m,
     issued by the National Weather Service:

     NORTH OREGON CASCADES:

     TIMBERLINE LODGE........ 27 INCHES 6000 FT  

     MOUNT HOOD MEADOWS...... 24 INCHES 5250 FT

     TOMBSTONE PASS.......... 18 INCHES 4200 FT

     GOVERNMENT CAMP......... 19 INCHES 3995 FT

     SANTIAM JUNCTION........ 13 INCHES 3750 FT

     LANE COUNTY CASCADES:

     MCKENZIE SNOTEL......... 30 INCHES 4800 FT

     CASCADE SUMMIT ......... 24 INCHES

     LITTLE MEADOWS SNOTEL... 21 INCHES

     WILLAMETTE PASS......... 19 INCHES 5130 FT

     SALT CREEK FALLS........ 17 INCHES 4000 FT 

     COAST RANGE:

     SADDLE MOUNTAIN......... 16 INCHES 3250 FT

     WILSON RIVER SUMMIT..... 11 INCHES 1610 FT

     SUNSET SUMMIT........... 11 INCHES 1200 FT 

     VERNONIA................  3 INCHES

     NORTHERN WILLAMETTE VALLEY:

     PORTLAND (WEST HILLS).... 5.5 INCHES

     OREGON CITY.............. 5 INCHES

     WEST LINN................ 5 INCHES

     PORTLAND (SKYLINE)....... 4.5 INCHES

     LAKE OSWEGO.............. 4.5 INCHES

     BEAVERTON................ 4 INCHES

     TUALATIN................  4 INCHES

     SHERWOOD................  4 INCHES

     DAMASCUS................. 4 INCHES

     NEWBERG.................. 1 INCH

     TROUTDALE...............  1 INCH

     PORTLAND AIRPORT AREA...  1 INCH

     CENTRAL WILLAMETTE VALLEY:

     MONROE..................  4.5 INCHES

     DALLAS..................  4 INCHES

     MCMINNVILLE.............  3.5 INCHES

     SUMMIT..................  3.5 INCHES

     BLODGETT................. 3 INCHES

     ALBANY................... 3 INCHES

     CORVALLIS................ 3 INCHES

     KIEZER..................  3 INCHES

     SALEM...................  2 INCHES

     SOUTHERN WILLAMETTE VALLEY:

     EUGENE..................  3.5 - 5.0 INCHES

     SPRINGFIELD.............  2.0 - 3.5 INCHES

     COTTAGE GROVE...........  3 INCHES

     COLUMBIA RIVER GORGE:

     HOOD RIVER..............  4 INCHES

     COAST:

     ASTORIA.................  2 INCHES

     ROCKAWAY BEACH..........  2 INCHES

     FLORENCE................  1 INCH

     TILLAMOOK...............  1 INCH

     LINCOLN CITY............  1 INCH

     OCEAN PARK..............  0.5 INCH

     OYSTERVILLE............   0.5 INCH

     The Arctic cold front extended south to near the
     Oregon/California border late this morning.  Snow levels
     were at the surface north of the front, including along the
     coast all the way south to Brookings.  Strong offshore
     surface flow was continuing to pour cold Arctic air into the
     region.  A surface low-pressure center was just off the
     northern California coast and continuing to throw some
     moisture over southern and eastern Oregon.  Light snow
     showers were still falling as far north as Eugene, west of
     the Cascades, and all the way north to Pendleton in eastern
     Oregon.  The air mass was drying out over northwest Oregon
     with some sunshine in the north valley.

     Skies will continue to slowly clear, from north to south,
     across the Willamette Valley today, as the cold Arctic air
     pours into the region and the low-prresure center off the
     Californais coast continues to move south.  Temperatures
     will stay well below freezing across the valley with
     northeasterly winds sending windchill values into the teens.
     Strong easterly winds, gusting over 40 mph, will send
     windchill values into the single digits in the Porland area.     

Surface Winds:
     N 10-15...East 15-30 G40 near Portland this afternoon.
Transport Winds:
     NE 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2600 feet.  Ventilation index 39.
High Temperature:
     Salem\'s high temperature today will be near 28.
Humidities:
     Relative humidity drops to 50% by 12pm.
     Minimum relative humidity will be near 48%.
Sunrise/Sunset:
     Salem sunset tonight: 4:31pm; sunrise tomorrow: 7:44am.

Extended Outlook:
     Drier and cold Canadian air will continue to move into the
     Willamette Valley tonight, with clearing skies and a fresh
     snow cover allowing temperatures to drop well down into the
     teens or even near 10 degrees...especially in wind-sheltered
     locations.  Brisk easterly winds will continue in the
     Portland area with northerly winds in the remainder of the
     valley.  The north valley, near Portland, will continue to
     have dangerously cold wind-chill values of near or below
     zero overnight.

     Tuesday will be dry and cold with winds decreasing some but
     remaining briskly offshore with low wind-chill values.  The
     next weather system is forecast to drop down the British
     Columbia coastline, and into the Pacific Northwest,
     Wednesday.  The air mass will initially be cold enough for
     the precipitation to begin across western Oregon as snow. 
     However, the track of the storm may bring low-pressure
     inland across westner Washington.  If that occurs, then
     enough onshore flow may develop to change the lowest
     elevations in the Willamette Valley to rain.  Snow will
     likely change to rain along the coast.

     Another cold Arctic front is forecast to bringsnow to
     northern Oregon Thursday morning and sweep south across all
     of the state by Thursday night.  Accumuling snow is likely,
     once again, across most of the state...including the
     Willamette Valley.  Cold Arctic air will pur into the regin
     Friday, bringing dry and very cold conditions by Friday
     night.  The next weather system is forecast to move in over
     the weekend, with temperatures moderating enough to bring a
     wintry mix of precipitation to the region.  It appears that
     another reinforcing shot of Arctic air may invade the region
     early next week, for a return to snowy and cold conditions.

Tomorrow (16 Dec):  Mostly Sunny and Cold.  12/25

Wed (17 Dec):  Snow Likely...Possibly Changing to Rain South of the Portland Area.  15/34

Thu (18 Dec):  Rain or Snow Turning to Snow.  Accumulations Likely.  27/35

Fri (19 Dec):  Snow Ending...Becoming Partly Cloudy. Continued Cold.  18/27

Sat (20 Dec):  Chance of Snow.  24/32

Sun (21 Dec):  Wintry Mix Likely.  28/35

Mon (22 Dec):  Changing Back to Snow...Colder.  27/33

ODA Meteorologist
weather at oda.state.or.us