[willamette-fcst] Forecast - Monday, May 5th, 2008

Mon May 5 15:44:45 PDT 2008

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, May 5, 2008 at 4:45 pm.

Burn Advisory For Tuesday, May 6, 2008:
     Agricultural burning is allowed.  Suggested burn times are from 1:00 pm until 6:30 pm.
     Straw stack burning is allowed from 1:00 pm until 6:30 pm.

Weather Discussion:
     After a little rain Saturday, high pressure brought mostly
     sunny skies and above normal temperatures, for a change, to
     Western Oregon Sunday and today.  Willamette Valley
     temperatures only climbed into the upper 50s and low 60s
     Saturday but reached the low 70s Sunday and today.  Warmer
     air aloft pushed the freezing level above 10,000 feet over
     Salem early this morning.

     The afternoon ODA surface analysis showed onshore pressure
     gradients increasing along the coastline, where temperatures
     cooled from the low 60s Sunday to the mid 50s this
     afternoon.  Winds were still mostly northerly in the
     Willamette Valley but had turned northwesterly at about 15-25 mph
     along the coastline.  Cooler ocean air is forecast to penetrate
     into the Willamette Valley tonight in response to an increasingly
     strong westerly flow aloft.

     After fair skies this evening, low clouds should increase
     across Western Oregon overnight with low temperatures
     generally in the mid 40s.  Mostly cloudy conditions will
     prevail, from the coast to the Cascades, Tuesday with
     Willamette Valley highs cooling about 10 degrees from what
     we saw this afternoon.  There will also be a chance of
     morning drizzle and/or a light shower of two.  The snow
     level will remain quite high at around 7-8000 feet.

     Increasing onshore flow and cooling aloft will likely yield
     good ventilation conditions, for burning, later Tuesday
     afternoon across Western Oregon.

     A weak upper-level trough will slide across Oregon Tuesday
     night and early Wednesday.  That will further increase the
     onshore flow across the entire state with a slight chance of
     showers...mainly from the Cascades eastward.  On Wednesday,
     temperatures west of the Cascades will likley cool a few
     more degrees, from Tuesday, with partial clearing and highs
     only near 60 degrees in the Willamette Valley.  The snow
     level should drop to 5-6000 feet Wednesday, but very little
     precipitation is expected with this system.

Surface Winds:
     NNW 5-10 Tuesday morning, NW 10-15 Tuesday afternoon.
Transport Winds:
     N 10 Tuesday morning, NW 15 Tuesday afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height Tuesday will be near 5000 feet.  Ventilation index 75.
High Temperature:
     Salem\'s high temperature Tuesday will be near 63.
Humidities:
     Minimum relative humidity will be near 54%.
Sunrise/Sunset:
     Salem sunset tonight: 8:23pm; sunrise Tuesday: 5:54am.

Extended Outlook:
     Another weak upper-level trough is forecast to move over
     Oregon Thursday afternoon and night.  That will likely keep
     skies mostly cloudy over Western Oregon, with continued
     strong onshore flow at the surface holding temperatures in
     the mid 50s along the coast and near 60 in the Willamette
     Valley.  The trough should be just strong enough to produce
     a few showers across the state.

     A weak ridge of high pressure should begin to cear skies
     over Oregon Friday afternoon with temperatures recovering to
     near normal across the Willamette Valley. A stronger trough
     is forecast to approach the coastline Saturday afternoon
     with a good chance of showers over Western Oregon Saturday
     evening through Sunday.  Temperatures may climb above
     average, just ahead of the cold front, Saturday afternoon,
     before dropping well below normal Sunday.  The snow level
     could fall below the Cascade Passes Sunday.

     Some drying and warming is forecast for Monday and early
     Tueday.  The long-range models are in complete disagreement
     for late next week.  They were all indicating the
     development of a strong ridge over the Pacific Northwest,
     with 80-degree heat moving into the Willamette Valley in the
     7-10 day range, but the latest computer guidance is
     forecasting a rather cool and soggy westerly flow aloft.  Based
     on what we have seen so far this spring, I have kept the 
     forecast for the middle of next week cool and wet for now.

Tomorrow (06 May):  Mostly Cloudy and Cooler.  Slight Chance of Drizzle or a Shower.  43/63

Wed (07 May):  Mostly Cloudy and Continued Cool.  40/60

Thu (08 May):  Mostly Cloudy.  Slight Chance of Showers. Snow Level 4-5000 Feet.  39/59

Fri (09 May):  Becoming Partly Cloudy.  39/64

Sat (10 May):  Increasing Clouds and Continued Mild.  Chance of Rain Late.  43/67

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

Mon (12 May):  Mostly Cloudy.  Chance of Showers. 42/61

Tue (13 May):  Increasing Chance of Rain.  45/63

ODA Meteorologist
weather at oda.state.or.us