[willamette-fcst] Forecast - Tuesday, April 13th, 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: 
     Tuesday, April 13th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 10:00am until 6:00pm.
     Stack burning is not allowed.

Weather Discussion:
     The upper-level trough that was centered over southwestern
     Oregon and northern California on Monday is ejecting
     eastward, into the Rockies, this morning.  However, the
     counterclockwise circulation around it is spinning moisture
     back across western Oregon, from the northwest.

     At mid-morning, satellite imagery showed clouds continuing
     to cover most of both western Washington and western Oregon.
     Doppler radar and surface reports showed a fairly narrow
     band of light rain extending from southwestern Washington,
     just east of Kelso, across the northern Willamette Valley to
     just west of Corvallis.  The rain was moving slowly
     southeastward and should sweep across the Willamette Valley
     over the next couple of hours.

     The shower threat will not go away completely this
     afternoon, but the steady light rain should ease off by late
     this morning across the Willamette Valley.  Rainfall totals
     should be less than one-tenth of an inch.  The ODA surface
     analysis showed high pressure trying to build into
     southwestern Oregon and low pressure over eastern Washigton.
     That was resulting in weak southwesterly pressure gradients
     across western Oregon.  Winds were generally less than 10 mph
     at mid-morning and should not increase much through this afternoon.

     The freezing level dropped slightly overnight and was
     measured early this morning near 5000 feet over western
     Oregon.  That puts the snow level near 4000 feet, so some
     areas of minor snow accumulation are possible, over the
     Cascade passes, this morning.  In the wake of the rain-band
     moving across the Willamette Valley, skies are generally
     cloudy but dry along the coast this morning.  Mostly cloudy
     skies held temperautures in the 40s overnight across western
     Oregon and midday readings generally ranged from 45-50
     degrees.  After reaching highs Monday in the low to mid 60s,
     more clouds and slightly cooler air aloft will likely yield
     slightly cooler high temperatures this afternoon.

Surface Winds:
     SW 5-10 this morning, WSW 5-10 this afternoon.
Transport Winds:
     SW 10 this morning, WSW 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 50.
High Temperature:
     Salem\'s high temperature today will be near 58.
Humidities:
     Minimum relative humidity will be near 48%.
Sunrise/Sunset:
     Salem sunset tonight: 7:55pm; sunrise tomorrow: 6:29am.

Extended Outlook:
     Another upper-level trough is forecast to set up camp just
     off the Oregon and northern California coast by Wednesday,
     which will turn the flow aloft more southerly and warm
     temperaturs slgihtly.  Daytime heating will act to
     destabilize the moist air mass enough to maintain a threat
     of showers across western Oregon. Not much chance in the
     overall circulation pattern is forecast Thursday or Friday,
     with the upper-level trough finally moving onshore Saturday.     

     We may get a break from the showers by the second half of
     this coming weekend, with valley temperatures climbing
     slightly above normal.  However, a strong cold front is
     forecast to come onshore next Monday, with a return of cool
     valley rain and mountain snow.

Tomorrow (14 Apr):  Increasing Chance of Showers PM.  Snow Level Rising to 5000 Feet.  37/61

Thu (15 Apr):  Mostly Cloudy.  Chance of Showers.  Snow Level 5000 Feet.  38/63

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

Sat (17 Apr):  Showers Likely. Snow Level 5000 Feet. 45/62

Sun (18 Apr):  Partly Cloudy.  Slight Chance of Showers.  Snow Level 6-7000 Feet.  44/65

Mon (19 Apr):  Rain Developing. Cooler. Snow Level Dropping to 4000 Feet.  44/59

Tue (20 Apr):  Showers Likely...Decreasing Late.  Snow Level 3-4000 Feet.  41/57

ODA Meteorologist
weather at oda.state.or.us