[willamette-fcst] Forecast - Thursday, February 12th, 2009

Willamette Valley Ag/Burning Forecast willamette-fcst at listsmart.osl.state.or.us
Thu Feb 12 09:19:06 PST 2009




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, February 12th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 11:00am until 3:30pm.
     Straw stack burning is allowed from 11:00am until 3:30pm.

Weather Discussion:
     Clearing skies last night combined with light winds and a
     cold air mass over the region to drop temperatures well
     below freezing across most of western Oregon.  Willamette
     Valley minimums fell into the 20s, with areas of icy fog
     forming.  Hillsboro was at least as cold as 22 degrees this
     morning, approaching their record low of 20 degrees, set in
     1948.  McMinnville dipped to at least 24, Salem and Aurora
     hit 26 degrees, and Eugene dipped to 27.  Some wet road
     surfaces may have turned icy overnight, especially in foggy
     areas, so travel with caution this morning. Temperatures
     were still at or below freezing, across most of western
     Oregon, at 8am.

     Satellite imagery showed high clouds already increasing over
     western Washington and western Oregon, in response to the
     next in a series of cold weather systems dropping into the
     region from the Gulf of Alaska.  A surface low-pressure
     center was developing about 300 miles west of the central
     Washington coast.  The associated cold front was still a
     couple of hundred miles offshore and extended south to off
     the northern California coast.  This storm is forecast to
     take a slightly more of a southerly track than the system
     that moved through the region Tuesday and Wednesday, with
     the bulk of the precipitation headed for California.

     As the low-pressure center slowly drifts southeastward, the
     associated cold front will bring increasing clouds to
     western Oregon today with rain moving onto the coast later
     this afternoon.  Valley highs will climb into the mid 40s
     with increasing south-southeasterly winds.  The air mass
     remains very cool over the region with the freezing levels
     over Salem and Medford measured at just 2300 and 2900 feet
     respectively early this morning.  Increasing offshore
     low-level flow will maintain quite low snow levels tonight
     and Friday.  Expect sticking snow, above about 1000 feet, in
     the coastal range tonight with a 2-4 inches of new snow
     likely.  Snow totals will increase to the south.

     Rain will move into the western valleys this evening with
     snow levels dropping to around 500 feet in the north valley,
     by early Friday, and to about 1000 feet in the south valley.
     A few inches of new snow are also likely over the Cascade
     passes...especially across the southern half of the state. 
     Some wet snow may locally mix to the valley floors tonight
     and Friday, but accumulations below 500 feet are not
     expected.  Total precipitation amounts, tonight and Friday,
     will likely be less than one-quarter of an inch across the
     Willamette Valley, with most of the moisture from this
     system moving into southwestern Oregon and northern
     California.  Cloudy and damp conditions should keep most
     valley minimums slightly above freezing tonight.

Surface Winds:
     SSE 0-7 this morning, SSE 5-15 this afternoon.
Transport Winds:
     S 7 this morning, 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 45.
Humidities:
     Minimum relative humidity will be near 59%.
Sunrise/Sunset:
     Salem sunset tonight: 5:36pm; sunrise tomorrow: 7:15am.

Extended Outlook:
     Clearing skies Friday night should allow valley temperatures
     to, once again, drop well below freezing.  Saturday will be
     a break-day between storm systems with partial clearing and
     just a slight chance of a shower.  The next weather system
     is forecast to take an even more southerly track, Sunday and
     Monday, with the bulk of the moisture rotating across
     southern Oregon and northern California.  That storm track
     will maintain a cool offshore low-level flow across western
     Oregon, so snow levels will remain between 1000 and 3000 feet.

     Tuesday, a weak upper-level trough over Oregon will maintain
     low snow levels and a chance of showers.  The chance of showers
     will decrease Wednesday and Thursday with more clearing.
     Temperatures should moderate closer to normal by Thursday.

Tomorrow (13 Feb):  Decreasing Rain and Snow.  Snow Level Near 1000 Feet.  33/44

Sat (14 Feb):  Partial Clearing and Cool.  Slight Chance of a Shower.  27/47

Sun (15 Feb):  Chance of Showers and Cool.  Snow Level Near 2000 Feet. 30/46

Mon (16 Feb):  Mostly Cloudy.  Slight Chance of Showers.  Snow Level 2500 feet.  30/48

Tue (17 Feb):  Chance of Showers.  Snow Level 2-3000 Feet.  33/48

Wed (18 Feb):  Slight Chance of Showers.  Snow Level 3000 Feet.  33/50

Thu (19 Feb):  Partly Cloudy.  Slight Chance of Showers.  33/51

ODA Meteorologist
weather at oda.state.or.us



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