[willamette-fcst] Forecast - Thursday, February 25th, 2010

Willamette Valley Ag/Burning Forecast willamette-fcst at listsmart.osl.state.or.us
Thu Feb 25 12:08:24 PST 2010




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: 
     Thursday, February 25th, 2010 at 12:00pm.

Burn Advisory:
     Recommended burn times for agricultural burning are from now to 4:00pm.
     Straw stack burning is allowed from now until 4:00pm.

Weather Discussion:
     Late-morning visible satellite imgery showed considerable low clouds lingering over the
     Willamette Valley, but clouds had cleared from much of the coastline and across southwestern
     Oregon.  Clouds were also clearing out of central Oregon but were continuing to hand on
     across the eastern third of the state.  Doppler radar showed the last of the showers pushing
     east of the northern Willamette Valley and into the extreme northern Cascades.

     The freezing levels were measured over Salem and Medford early this morning at 4400 feet
     and 5200 feet respectively but are on the rise, due to the approaching warm front.  ODOT
     road cameras showed the packed snow from early this morning had given way to just wet
     pavement over the mountain passes, with pass temperatures in the upper 30s and low 40s.
     Freezing levels should rise to more than 6000 feet later this afternoon.

     The ODA surface analysis showed southeasterly pressure gradients across western Oregon in
     response to an approaching warm front, about 250 miles off the northern California/southern
     Oregon coast.  Winds had increased to around 5-15 mph.  Late-morning temperatures ranged
     from the upper 40s to the mid 50s across western Oregon and from the upper 30s to mid 50s
     across central and eastern Oregon.  It will be another very mild afternoon, with highs
     topping out in the mid to upper 50s across western Oregon.

     Infrared satellite imagery showed high clouds, from a strong warm front,
     already advancing onshore late this morning. Clouds will thicken and lower this
     afternoon, with rain moving onto the coast around mid-afternoon and into the
     southern Willamette Valley around sunset.  Rain and increasing southeasterly
     winds will continue to spread north and east across the remainder of western
     Oregon tonight.  Southerly winds could briefly become quite blustery along the
     coastline, with the passage of the warm front overnight.  Rainfall totals of
     one-quarter of an inch, or more, are likely across western Oregon by sunrise Friday.

Surface Winds:
     SE 5-15 this afternoon.
Transport Winds:
     S 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 36.
High Temperature:
     Salem\'s high temperature today will be near 58.
Humidities:
     Minimum relative humidity will be near 54%.
Sunrise/Sunset:
     Salem sunset tonight: 5:54pm; sunrise tomorrow: 6:55am.

Extended Outlook:
     A warm front is forecast to push north of Oregon Friday morning, but a trailing cold
     front should maintain fairly steady precipitation over western Oregon through Friday
     afternoon.  The cold front will be slow to move onshore Friday afternoon, as it
     encounters a split-flow jet stream pattern.  The bulk of its energy will get directed
     south of Oregon, into California, but its slow speed will help additional rainfall
     totals climb another one-quarter to one-half of an inch across western Oregon.

     Clouds and rain will hold morning minimums in the low to mid 40s, but afternoon highs
     will struggle into the lower 50s.  Snow levels will hold at 5-6000 feet, with mostly
     rain over the passes.  The higher elevations, including the ski areas, should pick up
     about a foot of much-needed snowfall.

     A cool (not cold) upper-level trough will drop snow levels only to near the Cascade
     passes Saturday, as showers taper off across western Oregon.  Valley highs will climb
     above normal with some afternoon sunbreaks.  A ridge of high pressure is forecast to
     rebuild over the west coast late in the weekend, with mostly sunny and very mild
     conditions likely returning to western Oregon Sunday and Monday. Increasing
     south-southwesterly flow aloft will likely bring a weakening weather system onshore
     by late Monday, with rain and much cooler temperatures Tuesday. Showers will taper off
     Wednesday with a break in the weather possible on Thursday.

Tomorrow (26 Feb):  Rain Likely.  Snow Level Near 5000 Feet.  45/52

Sat (27 Feb):  Mostly Cloudy.  Showers Ending.  Snow Level 4000 Feet.  38/57

Sun (28 Feb):  Partly to Mostly Sunny and Very Mild.  37/60

Mon (01 Mar):  Increasing Clouds. Continued Mild.  Freezing Level Near 7000 feet.  38/62

Tue (02 Mar):  Rain Likely.  Snow Level 5-6000 Feet.  44/53

Wed (03 Mar):  Mostly Cloudy.  Decreasing Showers.  Snow Level 4-5000 Feet.  38/54

Thu (04 Mar):  Partly Sunny.  39/57

ODA Meteorologist
weather at oda.state.or.us



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