[willamette-fcst] Forecast - Friday, October 31st, 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.

...Next Update Tuesday, November 4th, at 9 a.m.

NOON UPDATE

Issued: 
     Friday, October 31st, 2008 at 12:00pm.

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

Weather Discussion:
     The first in a series of weather systems ended the extended
     dry spell with rain coming onshore Thursday night.  Rain
     continued to fall across the Willamette Valley through most
     of the morning but was tapering off to lighter showers at
     midday.  Rainfall totals generally ranging from one-quarter
     to one-third of an inch.  Doppler radar showed the main area
     of rain had moved north into Washington with a trailing band
     of showers stretching from the north coast to the northern
     Willamette Valley.  The rain had come to a halt south of
     about Salem.  However, valley temperatures had only warmed
     into the mid 50s with continued light southeasterly winds.

     A developing storm system, about 600 miles off the northern
     California coastline, will maintain southerly flow aloft and
     offshore surface winds this afternoon. That will maintain
     low mixing heights with south-southeasterly low-level winds.
     Satellite imagery was showing a few breaks in the clouds
     over the south valley that will likely move north this
     afternoon.  A touch of sunshine would help lift valley
     temperatures to near 60 degrees. There is still a chance of
     a light shower this afternoon, but things are drying out.

     Skies will likely stay mostly cloudy this evening, but there
     is a ghoul chance of dry conditions for the trick-or-treaters.
     It will also be a relatively mild evening, with temperatures
     staying in the mid 50s, witch is good.

Surface Winds:
     SE 5-10 this afternoon.
Transport Winds:
     S 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1800 feet.  Ventilation index 22.
High Temperature:
     Salem\'s high temperature today will be near 60.
Humidities:
     Minimum relative humidity will be near 69%.
Sunrise/Sunset:
     Salem sunset tonight: 6:01pm; sunrise tomorrow: 7:51am.

Extended Outlook:
     The next weather system will split as it moves onshore late
     Saturday, with the jet stream aimed at central California. 
     It will still bring increasing rain to western Oregon, with
     total rainfall amounts around one-quarter of an inch
     (similar to today).  Offshore surface winds will likely keep
     high temperatures in the upper 50s Saturday afternoon.

     An upper-level trough will bring cooling aloft Sunday and
     Monday with the flow aloft, and at the surface, turning
     onshore.  That should promote better mixing of the air mass
     and improve ventilation conditions.  The jet stream will
     still take the bulk of the rain into California, with
     lighter rain at times across Western Oregon.  Rain and snow
     will be enhanced over the mountains, due to upslope flow. 
     Some rain will also make it east of the Cascades.  Colder
     air aloft will drop the snow level to about 5000 feet, in
     the Cascades, by late Sunday and to between 3500 and 4000
     feet Monday.

     The upper-level trough is forecast to push east of the
     region Tuesday afternoon with the flow aloft turning
     northwesterly and beginning to dry out.  A warm front will
     likely bring steady rain to western Oregon Wednesday, as it
     pushes the snow level back above the Cascade passes.  The
     long-range computer model forecasts diverge late next week,
     with some calling for dry conditions and others maintaining
     a damp westerly flow aloft.  The ODA Seasonal Climate
     Outlook favors drier conditions returning, so I have leaned
     the forecast in that direction for next Thursday and Friday.

Tomorrow (01 Nov):  Increasing Light Rain in the Afternoon. 50/59

Sun (02 Nov):  Showers Early...Increasing Rain Late.  Snow Level Dropping to 5000 Feet. 48/57

Mon (03 Nov):  Rain Likely...Mainly South.  Snow Level 3500-4000 Feet.  43/54

Tue (04 Nov):  Decreasing Showers.  Snow Level 3500-4000 feet.  42/52

Wed (05 Nov):  Rain Likely.  Snow Level Rising to 6000 Feet Late.  38/52

Thu (06 Nov):  Mostly Cloudy.  Areas of Fog.  Slight Chance of Light Rain.  40/55

Fri (07 Nov):  Mostly Cloudy.  Areas of Fog.  Chance of Light Rain...Mainly North.  40/55

ODA Meteorologist
weather at oda.state.or.us