[willamette-fcst] Forecast - Monday, August 17th, 2009

[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.

...State Fire Marshal Conditions will likely be met in sections of the valley later this
   afternoon, due to low humidities and increasing northerly winds...mainly south...

Issued: 
     Monday, August 17th, 2009 at 8:40am.

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

Weather Discussion:
     A building ridge of high pressure, just offshore, will bring
     a dry and warmer north-northeasterly flow aloft to western
     Oregon today. Mid-morning satellite imagery showed only
     bands of high clouds streaming southward across Washington
     and much of Oregon.  There were some low clouds along sections
     of the immediate coastline.  Those should move offshore later
     this morning with sunshine statewide by this afternoon.

     The Salem sounding showed considerable warming aloft this
     morning, so temperatures will be about 10 degrees warmer
     across the Willamette Valley this afternoon.  Highs should
     warm into the upper 80s, as a surface thermal trough
     continues to build northward along the Oregon Coast.
     Offshore flow will drop relative humidities below 30% across
     the valley later this afternoon.  In addition, increasing
     northerly winds will likely put much of the south valley,
     and possibly areas of the north valley, into State Fire
     Marshal Conditions by late this aftenroon.  However,
     northeasterly transport winds may allow for the burning of
     fields on the extreme western side of the south valley late
     this morning. Other open burning is highly unlikely today.

Surface Winds:
     NNE 5-15 this morning, N 10-20 G25 south this afternoon.
Transport Winds:
     NE 17 this morning, NNE 22 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 77.
High Temperature:
     Salem\'s high temperature today will be near 88.
Humidities:
     Relative humidity drops to 50% by 11am.
     Minimum relative humidity will be near 28%.
Sunrise/Sunset:
     Salem sunset tonight: 8:15pm; sunrise tomorrow: 6:18am.

Extended Outlook:
     The strong upper-level ridge of high pressure is forecast to
     slide eastward, to directly over Washington and Oregon, by
     Wednesday.  Low-level winds will stay offshore Tuesday, with
     the surface thermal trough moving over the Willamette Valley
     Wednesday.  Temperatures will continue to warm, across the
     Willamette Valley, Tuesday and Wednesday, with some daily
     high temperature records in jeopardy.

     The upper-level ridge is forecast to move east of the
     Cascades Tuesday, with southerly or southwesterly flow aloft
     over western Oregon.  Some onshore flow, at the surface,
     will likely cool temperatures a few degrees across the
     interior valleys of western Oregon.  That may create a
     burning opportunity.  However, if the flow aloft becomes
     southerly, rather than southwesterly, that would decrease
     the chances for a burning opportunity and add a risk of
     thunderstorms...especially over the Cascades.

     The upper-level flow is forecast to become southwesterly by
     Friday, with increasing onshore flow at the surface
     continuing the cooling trend across western Oregon.  That is
     also a potential burning opportunity but too far out to be
     certain of at this time.  A weak trough is forecast to bring
     more cooling to western Oregon Saturday, but little to no
     rainfall.  A weak ridge may bring some minor warming to the
     region Sunday and Monday.

Tomorrow (18 Aug):  Sunny.  56/94

Wed (19 Aug):  Sunny.  58/97

Thu (20 Aug):  Mostly Sunny.  Slight Chance of PM T-Storms near the Cascades.  60/90

Fri (21 Aug):  Mostly Sunny but Cooler.  58/85

Sat (22 Aug):  Partly Cloudy and Cooler.  54/79

Sun (23 Aug):  Am Clouds.  PM Sunshine.   53/81

Mon (24 Aug):  Mostly Sunny.  53/85

ODA Meteorologist
weather at oda.state.or.us