[willamette-fcst] Forecast - Tuesday, June 30th, 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.

...State Fire Marshal Conditions May Be Reached Today Due To Brisk North Winds and Low Humidity...

Issued: 
     Tuesday, June 30th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 10:00am until 8:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level ridge over the Pacific Northwest is being
     flattened by a trough cutting across southern British
     Columbia.   With the main jet stream over Canada, Washington
     and Oregon are under a dry westerly flow aloft.  Weak
     onshore flow brought a band of low clouds into the
     Washington and extreme northern Oregon Coast overnight, with
     the remainder of both states staying clear.  Clear skies and
     relatively dry air over the region allowed temperatures to
     drop below normal across the region this morning.  Tillamook
     and Newport both dipped to a chilly 39 degrees this morning,
     while low clouds held temperatures in Astoria in the low
     50s.  Willamette Valley minimums dropped mostly into the
     40s, with McMinnville dipping to just 41 degrees.  Meacham
     was the cold spot in the state again this morning at 33 degrees.

     The surface analysis showed high pressure nosing into
     western Washington with a weak trough of low-pressure
     extending from eastern Washington to southeastern Oregon. A
     thermal trough was trying to build from Californais
     northward, into southwestern Oregon.  That was resulting in
     strong northerly pressure gradients which will intensify
     again this afternoon.  North winds gusted to 45 mph along
     the central and southern Oregon Coast Monday afternoon and
     to near 30 mph in the southern Willamette Valley.  Northerly
     winds relaxed overnight but were already increasing again at
     mid-morning along the southern coast and in the Eugene area,
     with gusts to around 15 mph.  Northerly winds should
     increase further this afternoon with gusts over 35 mph along
     the coastal strip and to around 25 mph in the central and
     southern Willamette Valley.  The combination of brisk
     northerly winds and low relative humidity levels will likely
     put much of the Willamette Valley into Fire Marshal
     conditions at times this afternoon.

     Temperatures aloft are similar to Monday, so surface
     temperatures today will also reflect those of Monday. 
     Willamette Valley highs will likely climb into the low 80s,
     after peaking Monday in the upper 70s.  Coastal highs will
     be in the 60s, along with those brisk northerly winds. 
     Temperatures east of the Cascades will range from the upper
     70s to the low 90s.

Surface Winds:
     N 5-15 this morning, N 10-17 G25 this afternoon.
Transport Winds:
     NNE 15 this morning, N 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 4000 feet.  Ventilation index 80.
High Temperature:
     Salem\'s high temperature today will be near 81.
Humidities:
     Relative humidity drops to 50% by 10.
     Minimum relative humidity will be near 25%.
Sunrise/Sunset:
     Salem sunset tonight: 9:02pm; sunrise tomorrow: 5:30am.

Extended Outlook:
     The weak upper-level trough to our north will shift east
     Wednesday, allowing an upper-level ridge to build over the
     region.  That will begin a warming trend across Washington
     and Oregon with only patchy morning low clouds restricted to
     the immediate coastline.  After morning minimums in the 40s
     to low 50s, afternoon highs should warm well into the 80s
     Wednesday.  State Fire Marshal Conditions may be reached
     again, in the afternoon, due to low relative humidity and
     brisk northerly winds.

     As the jet stream migrates even farther north on Thursday,
     the flow aloft will begin turning southwesterly.  A surface
     thermal trough will build northward into Oregon with
     northerly presure gradients relaxing.  That may warm valley
     temperatures to near 90 and will introduce a chance of
     afternoon thunderstorms to southern Oregon.  Increasing
     southwesterly flow aloft will likely shift the surface
     thermal trough eastward, into central and eastern Oregon,
     Friday and Saturday, along with the warmest temperatures. 
     The risk of afternoon thunderstorms will continue to migrate
     northward, from the Cascades, eastward across most of
     central and eastern Oregon.

     Southwesterly flow aloft is forecast to continue to
     strengthen Saturday, with increasng onshore flow cooling
     temperatures a bit west of the Cascades.  The thundershower
     threat will likely shift further east...mainly into Idaho. 
     By late Sunday, a strong upper-level trough is forecast to
     initiate a significant marine push and introduce enough
     moisture to the region for a chance of showers and
     thunderstorms statewide.  The cooling trend will continue
     into Monday with the chance of showers increasing, as the
     upper-level trough moves onshore.  The trough is forecast to
     stall and weaken over the region Tuesday.

Tomorrow (01 Jul):  Sunny and Warmer.  Brisk Afternoon Northerly Winds.  49/88

Thu (02 Jul):  Mostly Sunny and Very Warm.  52/90

Fri (03 Jul):  Mostly Sunny.  53/88

Sat (04 Jul):  Mostly Sunny and a Little Cooler.  Increasing Onshore Flow.  53/85

Sun (05 Jul):  Becoming Mostly Cloudy and Cooler.  Chance of Showers or T-Storms.  53/77

Mon (06 Jul):  Mostly Cloudy and Much Cooler.  Chance of Showers.  53/70

Tue (07 Jul):  Mostly Cloudy.  Slight Chance of Showers.  52/75

ODA Meteorologist
weather at oda.state.or.us