[willamette-fcst] Forecast - Wednesday, April 14th, 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.

     This daily Willamette Valley Agricultural Weather Forecast will become a seasonal product,
     as of Friday April 16th. The last broadcast and email of this forecast will be Thursday,
     April 15th. It will return as the \"Willamette Valley Field Burning Weather Forecast,\"
     issued daily via email and broadcast on WPOZ 585, beginning Thursday July 1st.

Issued: 
     Wednesday, April 14th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 11:00am until 6:00pm.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level trough is parked just off the west coast this
     morning with a southerly flow aloft over Oregon.  Two
     distinct circulation centers are rotating around in the
     trough.  The one of immediate concern is centered just off
     the northern California coast.  It is spreading considerable
     clouds over southwestern Oregon and as far north as Lane
     County. Mid-morning Doppler radar showed showers pushing
     northwestward, from northern California, to just west of
     Grants Pass, Oregon.

     Meanwhile, clearing skies and light winds overnight allowed
     temperatures to locally drop to the freezing mark in the
     Willamette Valley.  There were areas of valley frost, early
     this morning, with Hillsboro dipping to 31 degrees and
     McMinnville falling to 32.  Salem and Eugene both dropped at
     least down to 34 degrees.

     The ODA surface analysis showed high pressure over
     Washington and weak low pressure over southwestern Oregon. 
     That was bringing light northerly winds to western Oregon. 
     With some sunshine, mid-morning temperatures were warming
     into the 40s across northwestern Oregon.

     With the region under the influence of a cool upper-level
     trough, the freezing level is still fairly low today,
     measured over Salem this morning at just 4300 feet.  A lack
     of cloud-cover this morning, over the northern half of
     western Oregon, will allow the mid-April sunshine to warm
     Willamette Valley temperatures into the 50s by midday. Valley
     temperatures will likely climb into the low 60s this afternoon.

     The upper-level disturbance currently affecting extreme
     southwestern Oregon will slowly migrate northward this
     afternoon.  Clouds will increase, from south to north,
     across the Willamette Valley with daytime heating helping to
     make the atmosphere increasingly unstable.  Showers will
     likely push into the southern valley by late this afternoon
     and spread north across the remainder of western Oregon this
     evening.  There is also a chance of thunderstorm
     development.  Rainfall totals from the late-day showers
     could exceed one-quarter of an inch. Showers will taper off,
     from south to north, overnight, with mostly cloudy skies
     keeping minimums mostly in the 40s.

Surface Winds:
     N 3-8 this morning, N 5-12 this afternoon.
Transport Winds:
     NNE 8 this morning, N 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 48.
High Temperature:
     Salem\'s high temperature today will be near 61.
Humidities:
     Minimum relative humidity will be near 47%.
Sunrise/Sunset:
     Salem sunset tonight: 7:56pm; sunrise tomorrow: 6:27am.

Extended Outlook:
     We will likely be between upper-level disturbances Thursday,
     with southerly flow aloft warming temperatures back in the
     low to mid 60s.  Another impulse is forecast to rotate
     through the region Friday afternoon and evening for an
     increasing chance of showers.

     What little is left of the entire upper-level trough may
     finally move onshore Saturday but with only limited energy
     for shower development.  It still appears that Sunday will
     be the warmest day of the next 7, with highs possibly
     climbing into the low 70s.  The long-range models are still
     forecasting a cold front to come onshore late
     Monday...following by a cool trough on Tuesday. Some drying
     and warming is forecast for the middle of next week.

Tomorrow (15 Apr):  Chance AM Shower North.  Mostly Sunny.  Snow Level 5000 Feet.  41/64

Fri (16 Apr):  Mostly Cloudy.  Chance of Showers.  Snow Level 6000 Feet.  43/63

Sat (17 Apr):  Partly Cloudy.  Slight Chance of Showers. Snow Level 6-7000 Feet. 45/66

Sun (18 Apr):  Partly Cloudy and Warm.  46/72

Mon (19 Apr):  Rain Likely Developing. Cooler. Snow Level Dropping to 4-5000 Feet.  44/62

Tue (20 Apr):  Showers Likely...Decreasing Late.  Snow Level 4000 Feet.  41/57

Wed (21 Apr):  Partly Cloudy.  Slight Chance of Showers.  42/61

ODA Meteorologist
weather at oda.state.or.us