[willamette-fcst] Forecast - Monday, July 30th, 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: 
     Monday, July 30th, 2007 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 7:00pm.
     Preparatory burning is not allowed.
     Propane flaming is allowed from 12:00pm until 7:00pm.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level low pressure area is moving eastward across
     Northern British Columbia this morning, with a weak trough
     extending southward into Northern Oregon.  The trough will
     lift northeastward through Eastern Washington this
     afternoon, with high pressure building across Oregon.  That
     is producing north to northeast transport winds over the
     Willamette Valley today, so preparatory burning is not
     allowed and open burning is unlikely.

     This morning\'s surface analysis showed fairly strong onshore
     flow across Central and Eastern Oregon, with gradients
     turning more northerly, west of the Cascades. The upper-air
     sounding, over Salem, showed north to northeast winds up to
     4000 feet, with a strong subsidence inversion at 5000 feet.
     The decreased onshore flow greatly reduced the formation of
     marine low clouds in the Willamette Valley, so a full day of
     sunshine will warm tempeartures to around 80 degrees this
     afternoon...or about 5 degrees warmer than on Sunday.

Surface Winds:
     N 10 this morning, N 10-15 this afternoon.
Transport Winds:
     NNE 15 this morning, N 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 75.
High Temperature:
     Salem\'s high temperature today will be near 80.
Humidities:
     Relative humidity drops to 50% by 12pm.
     Minimum relative humidity will be near 33%.
Sunrise/Sunset:
     Salem sunset tonight: 8:41pm; sunrise tomorrow: 5:56am.

Extended Outlook:
     A transitory upper-level ridge will build over the Pacific
     Northwest Tuesday and Wednesday, with continued sunny skies,
     northerly transport winds, and warming temperatures for the
     Willamette Valley.  A weak west-southwesterly flow aloft
     will allow a surface thermal trough to build into SW Oregon
     by Wednesday, which should be the warmest day of the week,
     west of the Cascades.

     On Thursday, the flow aloft becomes southwesterly, again, as
     an upper-level low pressure area approaches the coastline. 
     That system is forecast to shift the thermal surface trough
     east of the Cascades, with a marine push likely in the
     Willamette Valley.  This transition is too far away to time,
     but the forecast wind-shift does create a potential burning
     opportunity.  Right now, it appears that the most likely
     time will be Thursday afternoon.  We will continue to
     monitor this and keep you updated.

     The long-range computer models are beginning to forecast a
     fairly strong upper-level low pressure area, for this time
     of the year, to move into the Pacific Northwest Friday and
     stay here through the weekend.  That would result in strong
     onshore surface flow, cool temperatures, and the chance of
     drizzle or light showers across the Willamette Valley, which
     is rare for early August.  We will keep you updated on that
     outlook, as well... 

Tomorrow (31 Jul):  Sunny and Warm.  51/87

Wed (01 Aug):  Sunny and Hot.  55/93

Thu (02 Aug):  Sunny.  Increasing Clouds Late.  60/85

Fri (03 Aug):  Mostly Cloudy...Much Cooler.  Chance of Drizzle.  55/74

Sat (04 Aug):  Mostly Cloudy and Cool.  Chance of Drizzle or Light Showers.  54/73

Sun (05 Aug):  Mostly Cloudy and Cool.  Chance of Drizzle or Light Showers.  54/72

Mon (06 Aug):  Morning Clouds...Afternoon Clearing.  54/78

ODA Meteorologist
weather at oda.state.or.us