[willamette-fcst] Forecast - Monday, July 23rd, 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.

NOON UPDATE

Issued: 
     Monday, July 23rd, 2007 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 1:00pm until 7:00pm.
     Preparatory burning is allowed from 1:00pm until 2:00pm with a 100 acre limit.
     Propane flaming is not allowed.
     Straw stack burning is allowed from 1:00pm until 7:00pm.

Weather Discussion:
     The upper-level trough, responsible for the moist conditions the past several days,
     is weakening and lifting into Southern British Columbia today.  At midday, the
     associated surface front was stretching from near the northern tip of the Washington
     Coast to about two hundred miles west of the Southern Oregon Coast at midday.  This
     front is weakening as it accelerates northeastward.  It should move across the Willamette
     Valley this evening with only a chance of a light shower in the northern valley.

     Transport winds, which have been south-southwesterly are likely shifting to a more
     favorable, west-northwesterly direction, for burning.  Mixing heights should reach
     about 4500 feet.  However, it may be difficult to measure winds above 2200 feet, with
     pibals, this afternoon due to a broken cloud deck over the valley.  Onshore surface
     gradients should increase this afternoon, but they will not be as strong as they would
     have been, since the front is not coming onshore as quickly as was originally forecast.  

     The air mass remains very moist today.  We are closely watching the relative humidity,
     which may stay too high for open burning this afternoon. I have increased the high
     temperature forecast by a couple of degrees, since the front is not expected until
     after 5pm and Salem is already in the middle 70s. That will help lower relative
     humidities to below 50 percent this afternoon, but just barely. 

     Please contact your permit agent, if you think you have a dry field that is ready to burn.

     Preparatory burning is only being allowed from 1pm until 2pm
     due to high humidity levels and the potential for open
     burning this afternoon.  That burning window may be
     extended, if conditions favorable for open burning are not
     likely to develop.

Surface Winds:
     NW 6-10 this afternoon.
Transport Winds:
     WNW 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4500 feet.  Ventilation index 59.
High Temperature:
     Salem\'s high temperature today will be near 81.
Humidities:
     Relative humidity drops to 50% by 5pm.
     Minimum relative humidity will be near 47%.
Sunrise/Sunset:
     Salem sunset tonight: 8:49pm; sunrise tomorrow: 5:49am.

Extended Outlook:
     A more typical summer weather pattern is shown on today\'s
     medium and long-range computer models.  The pattern looks
     dry beginning Tuesday through this weekend.  There continues
     to be weak southwesterly flow aloft, which would bring weak
     onshore surface flow west of the Cascades and prevent
     temperatures from climbing much above seasonal normals.  

Tomorrow (24 Jul):  Morning Clouds...Afternoon Sunshine.  58/83

Wed (25 Jul):  Mostly Sunny and Warm.  54/88

Thu (26 Jul):  Mostly Sunny and Warm.  58/88

Fri (27 Jul):  Mostly Sunny and Warm.  58/88

Sat (28 Jul):  Mostly Sunny. A touch cooler.  58/85

Sun (29 Jul):  Partly Cloudy.  56/80

Mon (30 Jul):  Partly Cloudy. 55/80

ODA Meteorologist
weather at oda.state.or.us