[willamette-fcst] Forecast - Monday, October 20th, 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: 
     Monday, October 20th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 8:00am until 4:30pm.
     Straw stack burning is allowed from 8:00am until 4:30pm.

Weather Discussion:
     A weakening frontal system brought some sprinkles to the
     Willamette Valley Saturday morning, with many areas not even
     getting measurable rain.  Aurora, Salem, and Corvallis all
     received just one-hundredth of an inch.  A transitory ridge
     brought a return of stagnant weather conditions Sunday with
     areas dense morning valley fog.  Clouds began increasing
     late in the day, Sunday, in reponse to an approaching cold
     front.  That helped lift the fog from the valley Sunday
     afternoon, with a few sprinkles moving in the region by
     early this morning.

     The ODA surface analysis showed a cold front moving onto the
     Washington and Oregon coastlines at mid-morning.  Doppler
     radar showed a band of light rain extending from Western
     Washington through the northern Willamette Valley with the
     back edge of the precipitation already making it the the
     coast range.   Surface reports indicated light rain from
     Portland southward, through Salem, with the south edge of
     the rainfall, on radar, pushing south to Eugene. 
     Temperatures were near 50 degrees with southerly winds
     between 10 and 20 mph.

     The cold front, and associated steady light rain, should
     quickly move east of the Willamette Valley by this
     afternoon.  Cooling aloft will help mixning heights climb to
     near 5000 feet this afternoon with morning southerly
     transport winds becoming west-southwesterly.  However, the
     main pool of cold air, in the wake of this system, will come
     onshore north of Oregon, so only a few showers are likely in
     the Willamette Valley this afternoon and evening.  Snow
     levels, in the northern Cascades, will drop to near 4000
     feet by this evening with a little snow possible over the
     passes.  Snow levels may remain higher than pass levels in
     the southern Cascades.

     Breezy south winds, this morning, will turn more westerly
     this afternoon and taper off by this evening.  With cooler
     air aloft moving over the region this afternon, high
     temperatures will have a tough time making it over 60
     degrees.  Partial clearing tonight will help temperatures
     drop into the upper 30s across most of the valley, with
     areas of fog forming by Tuesday morning.


Surface Winds:
     S 10-20 this morning, W 7-15 this afternoon.
Transport Winds:
     S 20 this morning, WSW 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 100.
High Temperature:
     Salem\'s high temperature today will be near 59.
Humidities:
     Minimum relative humidity will be near 62%.
Sunrise/Sunset:
     Salem sunset tonight: 6:18pm; sunrise tomorrow: 7:36am.

Extended Outlook:
     Another upper-level ridge is forecast to build over the
     region Tuesday.  Areas of moring fog could be locally
     dense...especially in the south valley.  A weak warm front
     will likely spread some middle and high clouds across NW
     Oregon during the day.  The upper-level rideg will amplify
     on Wednesday with increasing offshore flow clearing the fog
     from the valleys and mixing warmer air aloft down to the
     surface.  That could push afternoon temperatures into the
     70s, which would be at least 10 degrees above normal.  This
     very warm forecast to supported by the top seasonal climate
     analog year of 1929, which also had very warm weather at
     this time.  In fact, Salem\'s record high this Wednesday, of
     83 degrees, was set in 1929.

     A weak cold front will bring a chance of light rain Thursday
     afternoon...mainly to the north valley.  The long-range models
     are all showing a strong ridge of high pressure building over
     the region, beginning Friday, with a prolonged period of dry
     and very mild weather lasting well into the following week.
     Offshore flow may develop enough by next Monday for valley
     temperatures to, once again, climb into the low 70s.

Tomorrow (21 Oct):  Areas of AM Fog...Mostly Sunny Afternoon.  39/62

Wed (22 Oct):  Patchy AM Fog South...Otherwise Sunny and Very Mild.  37/72

Thu (23 Oct):  Chance of Light Rain...Mainly North.  45/61

Fri (24 Oct):  Areas of AM Fog.  Partly Sunny in the Afternoon.  39/62

Sat (25 Oct):  Areas of AM Fog.  Partly Sunny in the Afternoon.  40/64

Sun (26 Oct):  Areas of AM Fog.  Mostly Sunny in the Afternoon.  41/66

Mon (27 Oct):  Areas of AM Fog...Mainly South.  Sunny and Mild in the Afternoon.  41/71

ODA Meteorologist
weather at oda.state.or.us