[willamette-fcst] Forecast - Friday, December 26th, 2008

Fri Dec 26 12:02:30 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

...Next update scheduled for Monday, January 5th, 2009...

Issued: 
     Friday, December 26th, 2008 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 2:30pm.
     Straw stack burning is allowed from now until 2:30pm.

Weather Discussion:
     Christmas 2008 set snowfall records in the northern
     Willamette Valley.  It was the snowiest in Portland history,
     with 10 inches on the ground at the Portland National
     Weather Service office, in northeast Portland.  In addition,
     December 2008 will go into the record books as the snowiest
     December, in Portland, since records started at the Portland
     Airport (1940), with 18.9 inches, and one of the snowiest of
     all time.

     More on this record-setting snowy month can be found at:

     http://www.wrh.noaa.gov/total_forecast/getprod.php?wfo=pqr&pil=PNS&sid=PQR

     Historical information regarding Willamette Valley snow on
     Christmas is available at:

     http://www.wrh.noaa.gov/pqr/info/2008_December_Christmas.txt

     More snow showers fell in the northern Willamette Valley on
     Christmas, with eight-tenths of an inch falling at the
     Portland National Weather Service.  A cold upper-level
     trough was responsible for the rain and snow showers
     Christmas Day, with valley high temperatures only climbing
     into the mid to upper 30s.  There was not much melting of
     snow on the ground.  Partial clearing overnight allowed
     areas of icy fog to form in the valley with low temperatures
     generally falling below freezing.  That allowed slushy
     streets to refreeze in many areas, with visibilities locally
     less than one-half mile.  That made for difficult travel
     conditions again this morning.

     A major warming trend will begin, across Washington and
     Oregon, later today.  The first in a long seris of warmer
     weather systems will move onshore this afternoon.  A warm
     front was already spreading rain onto the northern and
     central Oregon Coast late this morning.  As precipitation
     moves inland this afternoon, the air mass over the wetern
     valleys may be cold enough for snow to fall at very low
     elevations.  No accumulation is expected below 1000 feet. 
     Increasing warm southerly winds should lift the snow level
     to around 2500 feet by this evening.

     Cold air remains trapped in the Columbia Gorge, so
     precipitation there will begin as snow or freezing rain. 
     The National Weather Service has issued a Winter Storm
     Warning, valid later this afternoon and tonight, for the
     Columbia Gorge and the upper Hood River Valley.  Snow in the
     Gorge, and in the upper Hood River Valley, should change to
     rain overnight, with possible areas of freezing rain.  Snow
     levels will quickly lift above the coastal range passes this
     afternoon, but increasing snow is expected in the Cascades
     through this evening, where Winter Storm Warnings have been issued.

     The incoming storm will also produce strong southerly winds
     along the coast, so the National Weather Service has issues
     a High Wind Warning for the northern and central Oregon
     Coast for later this afternoon and tnight.  Southerly winds
     may gust to 60 mph late this afternoon and tonight.  Rain
     and southerly winds will also increase in the Willamette
     Valley later today with temperatures climbing into the low
     40s by this evening.  South winds may gust to near 30 mph by
     tonight in the valley.

     Temperatures will remain steady or slowly rise overnight
     with the cold front not coming onshore until Saturday
     morning.  The combination of warm southerly winds,
     increasing rain, and melting snow will make for local
     ponding of water on north-valley and coastal range roadways,
     in addition to large quantities of slush.  That will make
     for locally hazardous travel...especially on less traveled roads.  

Surface Winds:
     S 10-20 G25 this afternoon.
Transport Winds:
     S 25 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 50.
High Temperature:
     Salem\'s high temperature today will be near 42.
Humidities:
     Minimum relative humidity will be near 89%.
Sunrise/Sunset:
     Salem sunset tonight: 4:37pm; sunrise tomorrow: 7:50am.

Extended Outlook:
     A strong westerly jet stream is forecast for this weekend
     and much of next week with rain in the valleys and snow for
     the mountains.  Snow levels will briefly rise to near 5000
     feet early Saturday, before dropping back to between 3-4000
     feet for most of next week.  Coastal and western valley
     temperatures will return to near seasonal normals.  Run-off
     from rain, combined with the significant melting of
     low-elevation snow, raises the concern for flooding.  At
     this time, major flooding is not expected, but rivers and
     streams will need to be closely monitored.

     The latest weather warnings, advisories, and forecasts, from
     the Portland National Weather Service, are available at:

     http://www.wrh.noaa.gov/pqr/

     River and stream information is avaiable from the Nortwest
     River Forecast Center:

     http://www.nwrfc.noaa.gov/

     Note:  Next update is not scheduled until Monday, January 5th, 2009.

     Have a Happy New year.

Tomorrow (27 Dec):  Rain at Times.  Snow Levels Rising to 5000 Feet. 40/46

Sun (28 Dec):  Rain at Times.  Snow Levels 3-4000 Feet. 40/46

Mon (29 Dec):  Rain at Times.  Snow levels 2-3000 Feet. 39/43

Tue (30 Dec):  Rain at Times.  Snow Level 2-4000 Feet.  36/44

Wed (31 Dec):  Rain at Times.  Snow Level 3-4000 Feet.  36/45

Thu (01 Jan):  Rain at Times.  Snow Level 2-3000 Feet.  37/44

Fri (02 Jan):  Rain at Times.  Snow Level 3-5000 Feet.  38/48

ODA Meteorologist
weather at oda.state.or.us