[willamette-fcst] Forecast - Thursday, April 1st, 2010

Thu Apr 1 09:24:40 PDT 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, April 1st, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 10:00am until 5:30pm.
     Straw stack burning is allowed from 10:00am until 5:00pm.

Weather Discussion:
     Showers rapidly tapered off Wednesday evening, with clearing
     skies and a cold air mass allowing overnight temperatures to
     drop into the low to mid 30s across most of western Oregon. 
     The exception was along the northern coast, where mostly
     cloudy skies, and continued light showers, held temperatures
     in the low 40s.  The shower activity was not able to
     penetrate eastward, beyond the coast range, due to the
     stabilizing effects of nighttime cooling across the interior
     valleys.  In the Willamette Valley, Hillsboro dropped to at
     least 30 degrees early this morning, and Hillsboro fell to
     31 degrees.  Salem and Eugene both dipped to at least 33
     degrees and Corvallis fell to at least 34.  The final
     morning minimums will be available by the noon update.

     Temperatures were still in the 30s across most of western
     Oregon at mid-morning, with many locations east of the
     Cascades still below freezing.  Satellite imagery showed
     considerable residual low clouds on both sides of the
     Cascades, with the most clearing on the east side of
     mountain ranges (especially over central Oregon).  Doppler
     radar showed a few light showers continuing to circulate
     onto the north coast, in a weak westerly flow aloft.  The
     ODA surface analysis showed high pressure building into
     western Oregon and weak southerly gradients across the
     Willamette Valley. Winds in the valley were less than 10 mph.

     A transitory ridge of high pressure will turn the flow aloft
     more northwesterly today, with further drying and slight
     warming of the air mass.  There will be just enough warming
     aloft to counteract the destabilizing effects of daytime
     heating, so afternoon and evening shower activity will be
     far less expansive than on Wednesday. More sunshine will
     help afternoon temperatures to recover into the low to mid
     50s.  That will lead to high mixing heights again this
     afternoon, with southwesterly transport winds making for
     good ventilation conditions.

Surface Winds:
     S 5-10 this morning, SW 5-12 this afternoon.
Transport Winds:
     SSW 10 this morning, SW 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 60.
High Temperature:
     Salem\'s high temperature today will be near 52.
Humidities:
     Minimum relative humidity will be near 46%.
Sunrise/Sunset:
     Salem sunset tonight: 7:40pm; sunrise tomorrow: 6:51am.

Extended Outlook:
     Another strong Pacific weather system is forecast to bring
     more stormy weather to Oregon Friday.  A rather impressive
     low-pressure center is forecast to track close enough to the
     coastline to bring strong winds to the coastal strip late
     tonight and Friday morning.  A High Wind Watch has been
     issued for the Oregon coast, from late tonight through
     Friday, for possible gusts to around 65 mph.  Blustery south
     winds may also make it into the Willamette Valley Friday
     morning, with gusts to around 40 mph possible.  Rain and
     mountain snow will increase overight, with snow levels
     staying below the Cascade passes.  A Winter Storm Watch has
     been issued for the Cascades and upper Hood River Valley for
     Friday.  Snow totals in the Cascades will likely range from
     1-2 feet, with up to a foot in the upper Hood River Valley. 
     a few inches of snow are also likely in the higher
     elevations of the coast range. 

     An  upper-level trough will maintain shower activity across
     western Oregon Saturday, with a few more inches of snow
     possible in the mountains.  The next system now appears as
     if it will be directed at extreme southern Oregon and mainly
     northern California, on Easter Sunday, with some rain and
     mountain snow pushing northward across most of Oregon by
     late in the day.  A cool northwesterly flow aloft will keep
     showers going across western Oregon on Monday, with very low
     snow levels.

     Things may dry out briefly next Tuesday, before another
     fairly strong spring storm moves onshore Wednesday. Showers
     will linger into Thursday, with yet another system slated to
     come onshore Friday.  Temperatures will remain well below
     normal with continued much-needed mountain snowfall.

Tomorrow (02 Apr):  Rain, Windy, and Heavy Mountain Snow.  Snow Level 2-3000 Feet.  40/51

Sat (03 Apr):  Showers and Very Cool.  Snow Level 1500-2500 Feet.  37/50

Easter Sun (04 Apr):  Increasing Rain and Mountain Snow Late.  Snow Level 3000 Feet.  38/52

Mon (05 Apr):  Showers Likely.  Continued Cool.  Snow Level Near 1500-2500 Feet.  38/51

Tue (06 Apr):  Mostly Cloudy.  Chance of a Shower.  Snow Level Rising to 3-4000 Feet.  37/57

Wed (07 Apr):  Increasing Chance of Rain and Mountain Snow.  Snow Level 3-4000 Feet.  40/52

Thu (08 Apr):  Mostly Cloudy.  Chance of Showers.  Snow Level Near 3000 Feet.  38/55

ODA Meteorologist
weather at oda.state.or.us