[willamette-fcst] Forecast - Friday, July 20th, 2007

[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.

Issued: 
     Friday, July 20th, 2007 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     A southwesterly flow aloft is steering a very moist weather
     system into the Pacific Coastline this morning.  Rain was
     already falling along the northern coastal strip by 7am,
     with doppler radar showing light rain bands pushing over the
     coast range and into the western sections of the Northern
     Willamette Valley.

     This weather system will progress very slowly eastward
     today, with light rain likely spreading east and south
     across the Willamette Valley this afternoon and evening. 
     Predicting rainfall amounts from this system is tricky,
     because Western Oregon is getting a glancing blow for this
     very moist storm.  Most of the rain will fall along the
     North Oregon Coast and across Western Washington, but the
     Willamette Valley could get a quarter of an inch by Saturday
     morning.  The greatest amounts will be in the northern
     valley.

     Some warming aloft has decreased mixing heights today, but
     burning advisory decisions were based on the need for
     another drying day, more light rain forecast for this
     afternoon, and south-southwesterly transport winds. 
     Southwesterly surface winds will increase this afternoon, in
     the Willamette Valley, as a cold front approaches the Oregon
     Coast.

Surface Winds:
     S 8 this morning, SSW 13 this afternoon.
Transport Winds:
     S 15 this morning, SSW 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 80.
High Temperature:
     Salem\'s high temperature today will be near 72.
Humidities:
     Minimum relative humidity will be near 55%.
Sunrise/Sunset:
     Salem sunset tonight: 8:52pm; sunrise tomorrow: 5:46am.

Extended Outlook:
     A damp weekend is in store, as a southwesterly flow aloft
     steers a couple of very moist weather systems up the Pacific
     Coastline.  The first system, which will bring rain into the
     Willamette Valley This afternoon and evening, will move into
     the valley and weaken Saturday, and the second system is
     forecast to approach the coastline Sunday morning. Both
     storms have tropical origins and are capable of producing a
     lot of rain.  The lastest computer guidance suggests that
     the Northern Willamette Valley could get as much as a
     half-inch of rain tonight and Saturday, if the front moves
     far enough inland.  A tenth to a quarter of an inch in the
     northern valley, and a tenth of an inch, or less, in the
     southern valley is more likely.

     Sunday\'s system not expected to push as far east, with the
     valley likely receiving less than a tenth of an inch of
     rain.  It will weaken considerably, as it moves inland
     Monday.  By Monday night, an upper level ridge of high
     pressure will build enough over the Pacific Northwest to
     weaken the storm track.  That will bring some drying and
     warming, but no prolonged dry or hot weather is forecast. 
     If significant rain falls between now and then, a couple of
     drying days may be required next week, before burning can
     resume.

Tomorrow (21 Jul):  Rain Likely.  59/75

Sun (22 Jul):  Cloudy.  Light Rain Likely at Times.  60/77

Mon (23 Jul):  Mostly Cloudy.  Chance of Showers.  60/78

Tue (24 Jul):  Partly Sunny.  56/80

Wed (25 Jul):  Mostly Cloudy.  Slight Chance of Showers.  57/75

Thu (26 Jul):  Morning Clouds...Afternoon Sun.  57/80

Fri (27 Jul):  Mostly Sunny.  55/83

ODA Meteorologist
weather at oda.state.or.us