[willamette-fcst] Forecast - Wednesday, July 1st, 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 are likely this afternoon...

Issued: 
     Wednesday, July 1st, 2009 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:
     An upper-level ridge trying to build over the Pacific
     Northwest is still being flattened by a trough cutting
     across southern British Columbia and Alberta, Canada.   With
     the main jet stream over southwestern Canada, Washington and
     Oregon continue to be under a dry westerly flow aloft. 
     Surface gradients have completed a turn from onshore to due
     northerly, with no marine low clouds this morning...even
     along the Washington and Oregon coastlines.

     Clear skies and dry air over the region allowed temperatures
     to drop below normal across Oregon again this morning. 
     Tillamook and Newport both dipped to 41 degrees.  Willamette
     Valley minimums dropped mostly into the 40s, with
     McMinnville dipping to 42 degrees.  Meacham was the cold
     spot in the state, for the third straight morning, with a
     minimum at the freezing mark (32 degrees).

     Northerly winds increased again Tuesday afternoon, with
     gusts to near 40 mph along the central and southern coast
     and to 30 mph in the southern Willamette Valley.  The
     overall weather pattern is not much different today, except
     for several degrees of warming aloft, as seen on the morning
     sounding over Salem.  Therefore, daytime heating will, once
     again, force the increase of northerly winds this afternoon,
     with gusts over 35 mph likely along the coastal strip and to
     near 30 mph in the southern Willamette Valley.  North wind
     gusts in the 15-25 mph range are expected this
     afternoon in the northern Willamette Valley...much like
     Tuesday afternoon.

     The combination of low humidity levels and increasing
     northerly winds will likely put much of the Willamette
     Valley into Fire Marshal conditions this afternoon.  Warmer
     air aloft will also make for lower mixing heights today, so
     agricultural burning is not recommended.  With a full day of
     early July sunshine and warmer air aloft, valley highs
     should climb into the upper 80s, after peaking near 80
     Tuesday afternoon. Coastal highs will warm into the upper
     60s and 70s, along with those brisk northerly winds. 
     Temperatures east of the Cascades will range from the upper
     70s to the low 90s, with the warmest readings near the Idaho border.

Surface Winds:
     N 5-15 this morning, N 10-20 G30 south this afternoon.
Transport Winds:
     NNE 15 this morning, N 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 60.
High Temperature:
     Salem\'s high temperature today will be near 88.
Humidities:
     Minimum relative humidity will be near 22%.
Sunrise/Sunset:
     Salem sunset tonight: 9:02pm; sunrise tomorrow: 5:30am.

Extended Outlook:
     Not much change is forecast in the weather pattern Thursday.
     The jet stream is forecast to migrate slightly farther
     north, with another couple degrees of warming aloft.  A
     surface thermal trough will build northward into Oregon with
     northerly presure gradients relaxing.  Willamette Valley
     temperatures should climb to near 90 Thursday afternoon,
     with weak southwesterly flow aloft introducing a slight
     chance of late-day thunderstorms over extreme southern Oregon.

     Increasing southwesterly flow aloft will likely shift the
     broad surface thermal trough just far enough eastward to
     prevent western Oregon temperatures from warming much
     more...if any.  The threat of afternoon thunderstorms will
     increase across southern and eastern Oregon with continued
     warming temperatures there.

     A very weak upper-level trough will bring some westerly flow
     aloft to Oregon Saturday, with increasing onshore flow
     cooling temperatures a touch west of the Cascades.  It will
     still be a very warm day, however, with a chance of
     thundershowers continuing across southern and eastern Oregon.

     A stronger trough is forecast to approach the coastline
     Sunday, turning the flow aloft southwesterly and initiating
     a significant marine push late in the day.  There may be
     enough moisture introduced into the region for showers or
     thundershowers during this transition to a cooler air mass. 
     The cooling trend will continue Monday and Tuesday, with a
     chance of showers.  The trough is forecast to weaken, as it
     stalls over the region Tuesday and Wednesday.

Tomorrow (02 Jul):  Sunny and Very Warm.  50/91

Fri (03 Jul):  Mostly Sunny and Very Warm.  53/92

Sat (04 Jul):  Mostly Sunny and Very Warm.  53/89

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.  52/72

Wed (08 Jul):  Mostly Cloudy.  Slight Chance of Showers.  53/75

ODA Meteorologist
weather at oda.state.or.us