[willamette-fcst] Forecast - Thursday, May 8th, 2008

[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: 
     Thursday, May 8th, 2008 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 6:30pm.
     Straw stack burning is allowed from now until 6:30pm.

Weather Discussion:
     The Pacific Northwest is under the influence of a very cool
     but generally dry northwesterly flow aloft.  Marine low
     clouds were persistent across the Willamette Valley
     Wednesday and held afternoon temperatures in the mid 50s (10
     degrees below normal).  The low clouds also held up
     temperatures overnight with valley minimums this morning
     generally in the low 40s.  The air aloft is even colder this
     morning than it was Wednesday morning with the freezing
     level over Salem measured at just 3100 feet.

     The ODA surface analysis showed high pressure centered just
     off the Central Oregon Coast this morning with onshore flow
     continuing across Washington and Oregon.  However, the
     onshore flow is weaker than it was Wednesday morning and
     visible satellite pictures confirm that the marine low
     clouds are not as extensive this morning over Western
     Oregon.  Small breaks in the clouds were already showing up
     over the coastal range and just offshore.

     Skies should transition from overcast to partly sunny over
     the Willamette Valley today with temperatures warming a
     couple of degrees from what we saw Wednesday.  Another dry
     but cool upper-level trough is forecast to move onshore
     later today and will combine with surface heating to keep
     skies mostly cloudy.  There is a slight chance of a light
     shower near the mountains this afternoon, but the clouds
     over the valley should top out at the mixing height around
     6000 feet.  Skies will stay mostly cloudy overnight, but
     valley minimums should dip a few degrees lower than they
     were this morning.

Surface Winds:
     WNW 3-6 this morning, NW 7-12 this afternoon.
Transport Winds:
     NW 6 this morning, NW 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 6000 feet.  Ventilation index 72.
High Temperature:
     Salem\'s high temperature today will be near 58.
Humidities:
     Minimum relative humidity will be near 45%.
Sunrise/Sunset:
     Salem sunset tonight: 8:27pm; sunrise tomorrow: 5:50am.

Extended Outlook:
     After a mostly cloudy start Friday, a weak ridge of high
     pressure should clear skies in the afternoon with
     temperatures recovering to near normal across the Willamette
     Valley.  A weak cold front is forecast to approach the
     coastline Saturday with a chance of light rain moving
     onshore by late afternoon.  Temperatures will likely be
     mild, ahead of the front, Saturday and then drop back below
     normal with a cool trough bringing a chance of showers Sunday.  

     Showers are forecast to taper off Monday, as the upper-level
     trough pushes east of the region.  A warm front is forecast
     to bring clouds and perhaps light rain as far south as
     Northwestern Oregon Tuesday, but that may be the last threat
     of rain for awhile...

     The long-range computer models are still showing a strong
     ridge building over the Pacific Northwest for much warmer
     and dry weather during the second half of next week.  We
     could be in for a taste of summer-like weather with strong
     offshore surface flow and Willamette Valley temperatures
     shooting well into the 80s as early as next Thursday.  Record
     highs for the valley this time of the year are in the low 90s,
     and that is not impossible around Friday or Saturday of next week.

Tomorrow (09 May):  Becoming Partly Cloudy.  37/65

Sat (10 May):  Increasing Clouds.  Chance of Light Rain Late...Mainly North.  40/67

Sun (11 May):  Chance of Showers and Cooler.  Snow Level Dropping to 3-4000 Feet.  43/58

Mon (12 May):  Mostly Cloudy.  Chance of a Shower Early...Afternoon Clearing.  40/63

Tue (13 May):  Chance of Light Rain North.  Partly Cloudy South.  45/65

Wed (14 May):  Becoming Mostly Sunny and Warmer.  46/73

Thu (15 May):  Sunny and Very Warm.  49/82

ODA Meteorologist
weather at oda.state.or.us