[willamette-fcst] Forecast - Monday, August 18th, 2008

Willamette Valley Ag/Burning Forecast willamette-fcst at listsmart.osl.state.or.us
Mon Aug 18 08:03:48 PDT 2008




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, August 18th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     The strong upper-level ridge of high pressure that brought
     triple-digit heat to the Willamette Thursday-Saturday of
     last week shifted eastward to over over Idaho Sunday. 
     Increasing moist and unstable southerly flow aloft triggered
     shower and thundershower activity across the western half of
     Oregon Saturday night and Sunday.  The surface thermal
     trough, and 100+ temperatures, shifted east of the Cascades
     Sunday.  Pendleton was the warm spot in Oregon Sunday with a
     record shattering high of 108 degrees.  The old daily record
     was 104 degrees set in 1934.  Meanwhile, the increased
     cloud-cover and onshore flow held Western Oregon
     temperatures into the 80s Sunday afternoon.

     The ridge had shifted to over Montana this morning with a
     very moist and unstable southerly flow aloft continuing to
     produce numerous showers and thundershowers across Western
     and Central Oregon.  Doppler radar showed large areas of
     showers and thundershowers along the central Oregon Coast,
     the northern Willamette Valley, and from south-central
     Oregon through the northern Cascades this morning.  The
     storms were being carried northward by the southerly flow
     aloft.

     The morning ODA surface analysis showed a strong thermal
     low-pressure center over eastern Washington with a thermal
     trough extending through central Oregon to Sw Oregon. 
     Onshore flow was continuing to bring cooler low-level air
     into the Willamette Valley.  Western Oregon temperatures
     were only in the low 60s with numerous showers and a few
     lightning strikes.

     Satellite imagery showed cloud bands circulating northward
     around an upper-level disturbance, centered near the
     southern Oregon Coast.  That system will very slowly move
     onshore later this afternoon...maintaining the moist and
     unstable southerly flow aloft over Western Oregon today. 
     High humidities, damp fields, and continued showers makes
     open burning unlikely this afternoon.

Surface Winds:
     SW 5-15 this morning, WSW 5-15 this afternoon.
Transport Winds:
     SW 10 this morning, SW 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 35.
High Temperature:
     Salem\'s high temperature today will be near 76.
Humidities:
     Minimum relative humidity will be near 56%.
Sunrise/Sunset:
     Salem sunset tonight: 8:13pm; sunrise tomorrow: 6:19am.

Extended Outlook:
     The flow aloft will turn southwesterly by tonight, which
     will stabilize the air mass and push the thundershower
     threat east of the Cascades.  It will also maintain the cool
     onshore flow across Western Oregon.

     An unseasonably strong weather system is still forecast to
     move onshore late Tuesday afternoon or night for a general
     rain across Western Oregon.  Depending on the timing of this
     system, it may create a burning upportunity ahead of it
     Tuesday afternoon, if conditions are dry enough.  The valley
     will have a good chance of showers Wednesday.  The flow
     aloft is forecast to turn northwesterly and begin drying out
     Thursday afternoon.

Tomorrow (19 Aug):  Mostly Cloudy.  Good Chance of Rain Late.  59/76

Wed (20 Aug):  Rain Turning to Showers.  59/70

Thu (21 Aug):  Mostly Cloudy.  Slight Chance of Showers.  56/71

Fri (22 Aug):  Mostly Sunny.  51/80

Sat (23 Aug):  Mostly Sunny.  50/85

Sun (24 Aug):  Mostly Sunny.  52/85

Mon (25 Aug):  Moslty Sunny.  54/86

ODA Meteorologist
weather at oda.state.or.us












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