[willamette-fcst] Forecast - Tuesday, May 19th, 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, May 19th, 2009 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:
     An increasing southwesterly flow aloft shifted the surface
     thermal trough into central Oregon Monday, with the warmest
     weather also moving east of the Cascades.  Under sunny
     skies, highs across central and eastern Oregon Monday
     climbed into the 80s and lower 90s.  Monday highs across the
     Willamette Valley cooled mostly into the middle and upper
     70s, although Portland and Eugene both managed to reach 81
     degrees. Strong onshore flow kept most of the coastline
     blanketed in low clouds Monday with temperatures only in the
     upper 50s and low 60s.

     A sharp cold front swept across western Oregon Monday night,
     dropping up to one-half inch of rain in the extreme northern
     Willamette Valley, mainly near the Cascades foothills.
     Rainfall totals south of the Portland area were generally
     from one-tenth to one-third of an inch, with the lowest
     totals in the south valley.  Only about one-tenth of an inch
     of rain fell along the northern and central coast.  Less
     than one-tenth of an inch fell along the south coast and
     across southwestern Oregon.

     The cold front produced only a few light showers, as it
     pushed east of the Cascades early this morning.  At
     mid-morning, the ODA surface analysis showed the cold front
     stretching from northern Idaho to southeastern Oregon, with
     onshore flow spreading cooler air across all of Oregon. 
     Visible satellite imagery showed a fairly narrow band of
     clouds, associated with the cold front, extending into
     northeastern Oregon with partly to mostly sunny skies
     elsewhere east of the Cascades.  Strong onshore flow was
     producing considerable marine low clouds over western Oregon
     with some showers...mainly over the coast range and the Cascades.

     A farily vigorous upper-level trough will cut across
     Washington and northern Oregon this afternoon...dropping
     snow levels in the northern Oregon Cascades to near 4000
     feet and enhancing the shower activity over northwestern
     Oregon.  Daytime heating may combine with cold air aloft to
     produce a thunderstorm or two over the north valley this
     afternoon.  Mostly cloudy skies and continued strong onshore
     flow should hold temperatures mostly in the upper
     50s...about 20 degrees cooler than on Monday.


Surface Winds:
     SW 5-10 this morning, SW 5-15 G20 this afternoon.
Transport Winds:
     WSW 10 this morning, W 15 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 75.
High Temperature:
     Salem\'s high temperature today will be near 59.
Humidities:
     Minimum relative humidity will be near 55%.
Sunrise/Sunset:
     Salem sunset tonight: 8:39pm; sunrise tomorrow: 5:38am.

Extended Outlook:
     The shower activity should taper off tonight across western
     Oregon, as the upper-level trough pushes eastward. 
     Scattered showers may continue, over the mountains of
     northeastern Oregon, through early Wednesday. A weak
     upper-level ridge is forecast to move onshore Wednesday with
     a drier northwesterly flow aloft spreading from west to east
     across the state.  Surface winds will turn northerly, and
     increase, over western Oregon Wednesday afternoon, with
     temperatures recovering to near-normal.

     The flat ridge is forecast to shift east of the Cascades
     Thursday afternoon, with the flow aloft turning more
     westerly.  That will induce a weak surge of cooler ocean air
     into the Willamette Valley Thursday evening.  A very weak
     upper-level trough is forecast to move over Oregon Friday,
     with continued onshore flow but little to no rainfall.  The
     main storm track is still forecast to move well north of
     Oregon, over the Memorial Day Weekend, with weak westerly
     flow aloft.  An upper-level ridge is forecast to build over
     the region early next week with the flow aloft turning more southerly.

Tomorrow (20 May):  Morning Clouds...Becoming Mostly Sunny.  39/68

Thu (21 May):  Mostly Sunny.  Increasing High Clouds Late.  40/75

Fri (22 May):  Partly Cloudy.  Slightly Cooler.  45/72

Sat (23 May):  Morning Clouds...Becoming Mostly Sunny.  46/74

Sun (24 May):  Mostly Sunny and Warmer.  46/78

Mon (25 May):  Mostly Sunny and Warmer.  47/82

Tue (26 May):  Mostly Sunny And Warm.  50/85

ODA Meteorologist
weather at oda.state.or.us