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

Thu Apr 1 12:08:48 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.

NOON UPDATE

          Next Update Scheduled For Monday, April 5th, 2010 at 9 a.m.

Issued: 
     Thursday, April 1st, 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:
     Showers rapidly tapered off Wednesday evening, with clearing
     skies and a cold air mass allowing overnight temperatures to
     drop to near the freezing mark across much of western
     Oregon.  The exception was along the northern coast, where
     mostly cloudy skies, and continued light showers, held
     overnight temperatures near 40 degrees.  The remaining
     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 and McMinnville both recorded minimums of
     a frosty 29 degrees this morning.  Corvallis and Eugene
     dipped to 32 degrees, while Salem officially bottomed out at
     33 degrees.

     By late this morning, temperatures had warmed into the mid
     to upper 40s across western Oregon.  Satellite imagery
     showed considerable convective cloud development over
     northwestern Oregon, due to the combination of cold air
     aloft aloft and surface heating by the sun.  However, a weak
     upper-level ridge is beginning to build onshore and turn the
     flow aloft more northwesterly.  Slight warming aloft is
     acting to cap the convection and limit shower development. 
     Doppler radar only shows scattered light showers north and
     west of a line from Newport to McMinnville to Hillsboro. 
     The showers were moving northeastward, with the flow aloft
     still out of the southwest.

     The late-morning ODA surface analysis showed high pressure
     building into western Oregon with continued weak southerly
     gradients from the coast across the Willamette Valley. Wind
     speeds were in the 5-12 mph range.  As the weak upper-level
     ridge of high pressure continues to push over the region,
     the flow aloft turn progressively more northwesterly this
     afternoon.  Further drying and slight warming of the air
     mass should be just enough to counteract the destabilizing
     effects of daytime heating, so afternoon and evening shower
     activity will be far less expansive than it was on
     Wednesday. Partly sunny skies will lift afternoon
     temperatures 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:
     SW 5-12 this afternoon.
Transport Winds:
     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.  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

Sun (04 Apr):  Increasing Rain and Mountain Snow Late.  Snow Level 3-4000 Feet.  38/52

Mon (05 Apr):  Rain Turning to Showers.  Continued Cool.  Snow Level 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.  38/54

ODA Meteorologist
weather at oda.state.or.us