[willamette-fcst] Forecast - Friday, July 13th, 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 13th, 2007 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 6:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     The strong upper-level ridge of high pressure, that has been
     responsible for the hot weather this week, has shifted
     eastward to over Idaho.  Oregon is on the western flank of
     this ridge and under the influence of south to southeasterly
     flow aloft.  That is circulating middle and high level
     moisture into the region, which has combined with daytime
     heating to produce shower and thunderstorm development the
     past three nights in parts of the Willamette.  Last night
     the storms were focused on the north valley, near Portland,
     producing considerable lightning and about a tenth of an
     inch of rainfall.

     Not much change is expected in the overall weather pattern
     today, with the southerly flow aloft continuing to feed warm
     and unstable air into the region, with above normal
     tempertures a risk of a valley thunderstorm today.  This
     pattern also inhibits the seabreeze from developing, so
     transport winds will be extremely light today, with a south
     to southeast flow at the top of the mixing layer.  On the
     other hand, winds could become locally strong and gusty near
     thundersorms.

     The flow aloft will become more southwesterly tonight, which
     will likely confine thunderstorm activity to the Cascades
     and points eastward.

Surface Winds:
     SW 3 this morning, W 5 this afternoon.
Transport Winds:
     SW 3 this morning, SW 5 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 25.
High Temperature:
     Salem\'s high temperature today will be near 87.
Humidities:
     Relative humidity drops to 50% by 2pm.
     Minimum relative humidity will be near 35%.
Sunrise/Sunset:
     Salem sunset tonight: 8:57pm; sunrise tomorrow: 5:39am.

Extended Outlook:
     A series of weather systems will make their way into the
     Pacific Northwest over the next seven days.  A southwesterly
     flow aloft will swing a weak cold front onto the Pacific
     Coastline Saturday night.  This system will increase the
     onshore flow across Western Oregon Sunday for significant
     cooling and bring a slight chance of light shower activity
     to the northern valley.  A transitory ridge of high pressure
     will bring warmer and dry conditions Monday.

     The long-range computer models are now more consistent in
     their solution for next week.  They show the next
     upper-level low pressure area approaching the coastline
     Monday night.  That will turn the flow aloft southerly to
     southeasterly again Tuesday and Wednesday, which brings a
     renewed chance of thunderstorm development to Western Oregon
     and decreases the likelyhood of a burn opportunity on those
     days.  Southwesterly flow aloft is forecast to keep
     tempertures cooler than normal with onshore surface flow
     next Thursday and Friday.

Tomorrow (14 Jul):  Partly Cloudy.  57/85

Sun (15 Jul):  Mostly Cloudy and Cooler.  Slight Chance of Showers.  57/77

Mon (16 Jul):  Morning Clouds...Sunny Afternoon.  52/85

Tue (17 Jul):  Increasing Clouds.  Chance of Showers and Thunderstorms.  57/80

Wed (18 Jul):  Mostly Cloudy.  Chance of Showers and Thunderstorms.  56/75

Thu (19 Jul):  Partly Sunny.  52/72

Fri (20 Jul):  Partly Sunny.  50/75

ODA Meteorologist
weather at oda.state.or.us