[willamette-fcst] Forecast - Monday, June 22nd, 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: 
     Monday, June 22nd, 2009 at 10:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 7:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level low pressure system was centered over eastern
     Washington at mid-morning.  Satellite imagery showed an area of
     mostly clear skies, near the center of circulation, covering a
     fair portion of eastern Washington, with an impressive band of
     clouds whirling around the low-pressure center, across northeastern
     Washington, central Washington, and into northeastern Oregon.  
     Radar showed scattered showers embedded within that same circulation.

     Meanwhile, onshore flow was maintaining lots of marine low
     clouds over western Washington and northwestern Oregon, but
     the atmosphere is beginning to dry out over most of Oregon. 
     Mid-morning skies were mostly sunny over the southern half
     of the Oregon...including the coast.  Clearing skies
     overnight allowed temperatures to cool into the 40s across
     most of the Willamette Valley.  Corvallis and Eugene dipped
     into the upper 30s.  That is getting close to record cold
     temperatures for early summer.

     The Salem sounding this morning showed considerable warming
     aloft (above 7000 feet) since Sunday afternoon, in response
     to the eastward shift of the upper-level trough into eastern
     Washington. As a transitory upper-level ridge moves onshore
     today, continued warming aloft will help to stabilize the
     atmosphere over western Oregon.  There is still a slight chance
     of a shower through this afternoon...mainly along the north
     coast, over the north coastal range and over the extreme northern
     Cascades.  Otherwise, daytime heating will only produce some
     fair-weather cumulus cloud development over northwestern Oregon.

     The mid-morning ODA surface analysis showed high pressure centered
     over the central Oregon Coast with weak pressure gradients
     over western Oregon.  A thermal trough is forecast to begin
     building northward, into extreme southwestern Oregon, today,
     as the upper-level trough over eastern Washington shifts
     eastward into northern Idaho and western Montana.  That will
     increase the north-northwesterly gradients across western
     Oregon later this afternoon, with further drying and warming
     of the air mass.  After such a chilly start, for late June,
     high temperatures will still be below normal statewide this
     afternoon, even with some sunshine.  Rapidly clearing skies
     this evening will allow overnight temperatures to drop back
     into the 40s across most of the Willamette Valley.

Surface Winds:
     Var 5 this morning, NNW 8-15 this afternoon.
Transport Winds:
     WSW 5 this morning, N 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 50.
High Temperature:
     Salem\'s high temperature today will be near 72.
Humidities:
     Minimum relative humidity will be near 39%.
Sunrise/Sunset:
     Salem sunset tonight: 9:02pm; sunrise tomorrow: 5:26am.

Extended Outlook:
     A weak and transitory upper-level ridge will move over
     Oregon Tuesday for continued warming and drying of the air
     mass.  Temperatures should recover to slightly above normal
     by Tuesday afternoon across western Oregon.  The next
     weather system is forecast to be directed mainly at southern
     British Columbia and western Washington but may be strong
     enough to bring some light showers as far south as
     northwestern Oregon late Wednesday through early Thursday. 
     The main effect from this system will be an increase in the
     onshore flow Wednesday afternoon, along with more clouds. 
     Temperatures will most likely cool back below normal on
     Thursday, with considerable morning clouds.

     A weak ridge will shift the jet stream northward, to over
     southern British Columbia, on Friday.  Continued onshore
     flow will keep some morning clouds over western Oregon with
     afternoon sunshine lifting temperatures close to normal. 
     The jet stream is forecast to sag southward on Saturday,
     with another weak cold front possibly spreading light
     showers as far south as northwestern Oregon by late in the
     day.  The chance of showers will continue into Sunday with
     another weak ridge drying out the atmosphere a bit on
     Monday.  No major changes are forecast in the weather
     pattern through next week, with another trough forecast to
     come onshore around the middle of next week...keeping temperatures
     moderate and maintaining a threat of light showers.

Tomorrow (23 Jun):  AM Clouds. Mostly Sunny in the Afternoon.  Warmer.  47/79

Wed (24 Jun):  Increasing Clouds in the Afternoon. Chance of Showers North Late.  52/79

Thu (25 Jun):  Chance of AM Showers...Afternoon Clearing and Cooler.  56/73

Fri (26 Jun):  AM Clouds...Becoming Mostly Sunny.  53/76

Sat (27 Jun):  Increasing Clouds and Onshore Flow.  Chance of Showers North late.  52/76

Sun (28 Jun):  Mostly Cloudy.  Chance of Showers North.  51/75

Mon (29 Jun):  Morning Clouds.  Mostly Sunny in the Afternoon.  50/77

ODA Meteorologist
weather at oda.state.or.us