[willamette-fcst] Forecast - Thursday, October 30th, 2008

[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: 
     Thursday, October 30th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 12:00pm until 4:00pm.
     Stack burning is not allowed.

Weather Discussion:
     The protective upper-level ridge of high pressure that
     brought an extended period of dry and mild weather to the
     region is continuing to shift eastward with increasing
     southwesterly flow aloft over Oregon.  The Salem sounding
     this morning showed further warming aloft, compared with
     Wednesday morning, and a strong low-level temperature
     inversion from about 1000 to 1800 feet.  Transport winds
     were southerly at about 8 mph.  Increasing southwesterly
     winds aloft were blowing at over 50 mph above 8000 feet...an
     indication of major changes on the horizon.

     Satellite imagery showed cloudy skies covering virtually all
     of Washington and Oregon this morning, due to the moist
     southwesterly flow aloft.  However, Doppler radar was not
     showing more than perhaps a few sprinkles from those clouds,
     with the mid-levels of the air mass still quite dry.

     The ODA surface analysis showed offshore gradients
     increasing across western Oregon, in response to the
     approaching cold front.  Increasing southeasterly winds will
     help mix warmer air aloft down to the surface, which should
     raise valley temperatures into the low 60s this afternoon
     (Salem only reached 54 degrees Wedneday, due to light winds
     and a low-level temperature inversion).

     The offshore frontal boundary will slowly move closer to the
     coastline today with the flow aloft turning southerly and
     continuing to increase.  That will keep the air mass aloft
     warm and mixing heights quite low again today.  Skies will
     remain cloudy with a few sprinkles possible...mainly along
     the coast.  Rain will spread inland by Friday morning with
     between one-tenth and one-quarter of an inch of rain likely
     during the day Friday.  There may be a break in the rain
     Halloween night.

Surface Winds:
     SE 4-8 this morning, SE 5-10 this afternoon.
Transport Winds:
     S 8 this morning, S 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1800 feet.  Ventilation index 18.
High Temperature:
     Salem\'s high temperature today will be near 61.
Humidities:
     Minimum relative humidity will be near 58%.
Sunrise/Sunset:
     Salem sunset tonight: 6:02pm; sunrise tomorrow: 7:50am.

Extended Outlook:
     A few showers should also make it east of the Cascades
     Friday, but this cold front will weaken considerably, as it
     attempts to push into the ridge of high pressure over the
     western half of the country.  Another weather system is
     slated to come onshore late Saturday, but the main jet
     stream energy is aimed at Northern California, which will
     help to split and weaken this system.

     Showers will give way to a more steady rain Sunday, as a
     stronger system moves onshore.  Colder air aloft will drop
     the snow level to about 5000 feet in the Cascades.  A strong
     westerly flow aloft will keep some rain in the forecast on
     Monday with the snow level dropping to near 4000 feet late.

     Another system is forcast to come onshore Tuesday with
     showers lingering into Wednesday.  A warm front will
     increase clouds on Thursday, but the bulk of the rain
     appears as if it will stay north over Oregon.  A transitory
     ridge of high pressure may bring brief late Thursday into
     Friday, but the overall weather pattern will likely remain damp.

Tomorrow (31 Oct):  Light Rain Likely...Decreasing by Halloween night.  48/61

Sat (01 Nov):  Increasing Rain in the Afternoon. 46/59

Sun (02 Nov):  Showers Early...Increasing Rain Late.  Snow Level Dropping to 5000 Feet. 45/54

Mon (03 Nov):  Rain Turning to Showers.  Snow Level Near 4000 Feet.  42/53

Tue (04 Nov):  Increasing Rain.  Snow Level Rising to Above 5000 Feet.  42/53

Wed (05 Nov):  Decreasing Showers.  38/56

Thu (06 Nov):  Mostly Cloudy.  Chance of Light Rain...Mainly North.  41/54

ODA Meteorologist
weather at oda.state.or.us