[willamette-fcst] Forecast - Tuesday, April 28th, 2009

[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: 
     Tuesday, April 28th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 6:00pm.
     Straw stack burning is allowed from now until 6:00pm.

Weather Discussion:
     A strong upper-level ridge of high pressure in the Gulf of
     Alaska brought a northern flow aloft to the Pacific
     Northwest over the weekend.  A series of weather
     disturbances dropped into the region, from Canada,
     eventually carving out a fairly vigorous trough over
     Washington and Oregon by Monday.  Showers spread across most
     of western Oregon by Monday evening with some locally heavy
     rainfall in the north valley.  CoCoRaHS reports indicate up
     to three-quarters of an inch of rain fell, in the past 24
     hours, in sections of Clackamas County with nearly
     two-thirds of an inch in the Cascade foothills of Marion
     County.  One-half inch of rain was reported at the Aurora Airport.

     Most areas along the coast, the central and southern
     Willamette Valley, and across southwestern Oregon have
     picked up from a few hundredths to around one-tenth of an
     inch of rain since Monday, with the northern Willamette
     Valley generally getting between one-tenth and one-quater of
     an inch.  Rain and snow has also been falling from the
     Cascades eastward locally more than one-quarter of an inch
     of rain reported from central Oregon to the Idaho border. 
     Meacham, in the Blue Mountains of northeast Oregon, has
     picked up over one-half inch of precipitaion in the past 24
     hours...a mixture of rain and wet snow.

     The air aloft of Oregon is quite cold this morning with the
     freezing levels over Salem and Medford measured at just 4000
     and 3900 feet respectively.  Satellite imagery showed cloudy
     skies covering vitually the entire Pacific Northwest with
     Doppler Radar indicating multiple bands of showers rotating
     across the entire region.  Snow showers were falling over
     the Cascade passes with an inch or two of new snow and some
     snow on the roadways.  Light to moderate showers were
     falling in the Willamette Valley.

     The mid-morning ODA surface analysis showed onshore flow
     across Oregon with southerly gradients in the Willamette
     Valley.  Valley winds were generally less than 10 mph. 
     Temperatures were mostly in the mid to upper 40s west of the
     Cascades and in the 30s and 40s across central and eastern
     Oregon.  Showers will continue statewide thoughout the day,
     with well below normal temperatures.  Some showers could
     produce brief locally heavy rainfall and small hail.

Surface Winds:
     S 5-10 this morning, SSW 5-12 this afternoon.
Transport Winds:
     S 12 this morning, SW 14 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3700 feet.  Ventilation index 52.
High Temperature:
     Salem\'s high temperature today will be near 55.
Humidities:
     Minimum relative humidity will be near 59%.
Sunrise/Sunset:
     Salem sunset tonight: 8:14pm; sunrise tomorrow: 6:04am.

Extended Outlook:
     The upper-level low pressure area over the region will
     slowly weaken Wednesday and push eastward to over Idaho by
     Thursday afternoon.  Showers will taper off with moderating
     temperatures.  A warmer westerly flow aloft will send a weak
     weather system into southern Oregon and northern California
     Friday with an increasing chance of light showers moving
     northward, into the southern Willamette Valley, late in the day.

     A stronger system is forecast to come onshore by Saturday
     night with rain becoming likely by Sunday across western
     Oregon.  An even stronger system is slated to move onshore
     Tuesday, in a strengthening westerly flow aloft.

Tomorrow (29 Apr):  Mostly Cloudy.  Decreasing Showers.  40/58

Thu (30 Apr):  Slight Chance of AM Showers.  Becoming Partly Sunny.  39/62

Fri (01 May):  Increasing Clouds and Warmer.  Slight Chance of Showers Late.  42/69

Sat (02 May):  Mostly Cloudy.  Increasing Chance of Rain Late.  45/68

Sun (03 May):  Rain Likely.  47/64

Mon (04 May):  Mostly Cloudy.  44/66

Tue (05 May):  Rain Likely.  47/63

ODA Meteorologist
weather at oda.state.or.us