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

[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.

             ...No Updates Before Monday, March 29th, 2010...

Issued: 
     Thursday, March 25th, 2010 at 12:00pm.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 5:30pm.
     Straw stack burning is allowed from now until 5:00pm.

Weather Discussion:
     By late this morning, the strong cold front that brought rain to all of western Oregon
     overnight had already advanced northeastward...arcing from northern and eastern Washington,
     through central and southeastern Idaho, into Utah.  In it\'s wake, a cold upper-level trough
     was moving onshore and circulating showers into western Oregon.  

     The early morning Salem sounding showed significant cooling aloft, with the freezing level
     down to just 4500 feet.  Late-morning ODOT road cameras still showed mostly wet pavement
     over the Cascade passes, with pass temperatures in the mid to upper 30s.

     Infrared satellite imagery showed a circulation center less than 100 miles off the northern
     Oregon coast.  A counter-clockwise circulation around it was rotating a surge of showers
     onshore into western Oregon. The Willamette Valley was in a relatively calm zone, for much
     of the morning, but that is about to change.  Doppler radar showed a large batch of showers,
     stretching from Astoria to Florence, rotating northeastward towards the Willamette Valley.

     The late-morning ODA surface analysis southerly pressure-gradients tightening along the
     central Oregon coast, in association with the upper-level disturbance bringing to showers
     onshore.  South-southwesterly winds were gusting to 35 mph along the coast, with southerly
     winds gusting to 30 mph in the Willamette Valley.  Under mostly cloudy skies, temperatures
     had only climbed into the upper 40s and low 50s.

     A couple a upper-level disturbances will increase the shower activity across western
     Oregon this afternoon through Friday morning.  With snow levels dropping to as low as
     3000 feet, and showers expected to increase, the National Weather Service has issued a
     Winter Weather Advisory for Cascades valid from 2 p.m. today until 9 a.m. Friday. Up to a
     foot of new snow is possible.  Another one-quarter to one-half inch of rain is possible
     along sections of the coast and across the western valleys, by Friay, along with blustery
     south-southwesterly winds.  High temperatures will top out today in the low to mid 50s.

Surface Winds:
     SW 12-25 G35 this afternoon.
Transport Winds:
     SW 30 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 90.
High Temperature:
     Salem\'s high temperature today will be near 54.
Humidities:
     Minimum relative humidity will be near 66%.
Sunrise/Sunset:
     Salem sunset tonight: 7:31pm; sunrise tomorrow: 7:04am.

Extended Outlook:
     A cold northwesterly flow aloft is forecast to drive another
     upper-level disturbance through the region Friday morning,
     maintaining shower activity across most of the state.  An
     upper-level ridge is forecast to begin clearing skies, from
     west to east, across Oregon late Friday.  That should lead
     to some pretty chilly temperatures Saturday morning, with
     valley minimums dropping into the mid 30s.  Patchy frost is
     possible.  After the chilly start, mostly sunny skies will
     make for a very pleasant Saturday afternoon, with
     temperatures rebounding to well above normal.

     The next weather system should spread rain back across
     western Oregon by midday Sunday.  This will be a warmer
     storm, with snow levels likely above the Cascade passes.  A
     quite strong system is forecast to come onshore Monday, with
     significant rain and possibly windy conditions...especially
     on the coast.  Snow levels will initially be fairly high but
     should drop substantially Monday night, in the wake of the
     cold front.

     Tuesday looks showery and cool, with some much-needed
     mountain snowfall.  The next system is forecast to take aim
     mainly at California, on Wednesday.  However, it should
     spread some rain and mountain snow northward over
     Oregon...with the greatest amounts in the south. 
     Temperatures will stay below normal.

Fri (26 Mar):  Showers Decreasing Late with Partial Clearing. Snow Level 3-4000 Feet.  40/56

Sat (27 Mar):  Chilly Start...Becoming Mostly Sunny and Warmer.  35/63

Sun (28 Mar):  Rain Developing.  Snow Level 5-6000 Feet.  44/58

Mon (29 Mar):  Increasing Rain and Wind.  Snow Level 5-6000 Feet.  46/59

Tue (30 Mar):  Rain Turning to Showers.  Snow Level Dropping to 3-4000 Feet.  43/56

Wed (31 Mar):  Rain and Mountain Snow...Mainly South.  Snow Level 3-4000 Feet.  38/55

Thu (01 Apr):  Showers Likely.  Snow Level 3-4000 Feet.  37/55

ODA Meteorologist
weather at oda.state.or.us