[willamette-fcst] Forecast - Wednesday, March 17th, 2010

[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: 
     Wednesday, March 17th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 10:00am until 4:30pm.
     Stack burning is not allowed.

Weather Discussion:
     A weak cold front moved across western Oregon late on
     Tuesday and was cutting across Montana and Idaho this
     morning.  The storm produced lots of clouds, and blustery
     southerly winds, but not very impressive rainfall.  Winds
     gusted to around 50 mph along the coast and to near 40 mph
     in the Willamette Valley, as the cooler air began pouring
     into the region.  The freezing level over Salem dropped from
     more than 8000 feet Tuesday morning to just 4000 feet this
     morning.  Rainfall totals were generally only a few
     hundredths of an inch across the Willamette Valley.  The
     coast picked up from one-tenth to about two-thirds of an inch.

     A few showers are lingering across northwestern Oregon this
     morning, with light snow over the Cascade passes. 
     Mid-morning temperatures were in the upper 30s and low 40s
     across western Oregon.  The showers will give way to mostly
     sunny skies this afternoon, as high pressure strongly builds
     into the region.  Cool northerly surface winds will increase
     this afternoon, capping high temperatures in the upper 50s. 

Surface Winds:
     N 5-15 this morning, N 10-20 G 25 this afternoon.
Transport Winds:
     N 15 this morning, N 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 80.
High Temperature:
     Salem\'s high temperature today will be near 57.
Humidities:
     Minimum relative humidity will be near 49%.
Sunrise/Sunset:
     Salem sunset tonight: 7:21pm; sunrise tomorrow: 7:19am.

Extended Outlook:
     A dry northwesterly flow aloft is forecast for Thursday, as
     an upper-level ridge of high pressure begins building just
     off the west coast.  Drier air filtering into the region
     will allow morning minimums to dip to near the freezing mark
     across the Willamette Valley.  Even with a lot of afternoon
     sunshine, cooling northerly winds will not allow high
     temperatures to get much above normal (normal highs are in
     the upper 50s).

     The upper-level ridge is forecast to move over Oregon Friday
     and Saturday.  A building surface thermal trough, along the
     coast, will turn low-level winds offshore on
     Friday...further drying the air mass and leading to a large
     spread between morning minimums and afternoon maximums. 
     After a possible frosty start Friday morning, afternoon
     highs should climb into the low to mid 60s in the Willamette
     Valley.  Coastal highs could locally hit 70 degrees.

     The upper-level ridge is forecast to slide over central Oregon
     Saturday, with onshore flow bringing cooler temperatures to the
     immediate coastline.  The thermal trough will shift to over the
     Willamette Valley, where highs should climb into the mid 60s.
     The upper-level ridge will continue to shift eastward, to over
     Idaho, by Sunday afternoon with increasing southwesterly flow
     aloft over western Oregon.

     A weak cold front will bring cooler temperatures and a chance
     of light rain by Sunday afternoon.  Some light rain will
     likely spread across most of western Oregon by Sunday
     evening.  High temperatures will likely drop back below
     normal Monday and Tuesday with snow levels lowering below
     the Cascade passes.  Rain will turn to showers on Monday
     with the showers ending on Tuesday.  Another weak weather
     system may bring back a chance of rain by later Wednesday.

Tomorrow (18 Mar):  Cool Start, With Possible Areas of Frost...Becoming Mostly Sunny.  33/60

Fri (19 Mar):  Possible Frosty Start...Sunny and Mild in the Afternoon. Offshore Flow.  31/62

Sat (20 Mar):  Cool Morning...Sunny and Very Mild in the Afternoon.   33/65

Sun (21 Mar):  Increasing Clouds. Chance of Rain by Afternoon.  37/60

Mon (22 Mar):  Rain Likely and Much Cooler.  Snow Level Dropping to 3000 Feet.  39/52

Tue (23 Mar):  Decreasing Showers.  Snow Level 2500 Feet.  37/54

Wed (24 Mar):  Increasing Chance of Rain Late.  Snow Level Rising to 4-5000 Feet. 36/56

ODA Meteorologist
weather at oda.state.or.us