[willamette-fcst] Forecast - Wednesday, May 21st, 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: 
     Wednesday, May 21st, 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:
     A strong cold front swept across the entire Pacific
     Northwest Tuesday.  It dropped about one-quarter to one-half
     of an inch of rain along the northern and central coastal
     strip, and about one-quarter of an inch of rain in the
     Willamette Valley.  The front was strong enough to produce
     widespread rain east of the Cascades, with amounts ranging
     from a few hundredths of an inch to over one-third of an inch.

     The freezing levels over Oregon, which were above 15,000
     feet over the weekend, nosedived to near 4500 feet this
     morning.  A check of the ODOT road cameras revealed fresh
     wet snow, along the roadside, over the Cascade Passes this
     morning.  There was also an extreme temperature drop Tuesday
     in the wake of the cold front (on the order of 30 degrees)
     across Central and Eastern Oregon.  Ontario, near the Idaho
     Border, was the warm spot in the Oregon Tuesday...climbing
     to 85 degrees just ahead of the cold front early Tuesday
     afternoon.  Just 4 hours later, the cold front brought
     strong winds, locally heavy rain, and thunderstorms, with
     the temperature falling into the mid 50s.

     Much of Central and Eastern Oregon was buffeted by strong
     west winds gusting to near 40 mph on Tuesday with local
     blustery conditions continuing this morning.  Strong onshore
     flow west of the Cascades kept skies mostly cloudy with a
     few showers Tuesday.  Temperatures only climbed into the low
     60s across the Willamette Valley.  The ODA surface analysis
     this morning showed high pressure nosing into the Southern
     Oregon Coast and strong onshore pressure gradients across
     all of Oregon.

     An upper-level trough over the region will slide southeastward
     this afternoon and turn the flow aloft northwesterly over Oregon.
     That will keep things on the cool side of normal with strong
     onshore flow continuing at the surface.  Skies will stay mostly
     cloudy across Western Oregon with temperatures struggling to
     reach 60 this afternoon.  Eastern Oregon will also see mostly
     cloudy skies, with highs only in the 50s and low 60s.  The air
     aloft is quite cold, so daytime heating will act to destabilize
     the air mass and lead to the development of scattered showers
     across the state this afternoon...mainly near mountains.

     The showers and winds will die down overnight, but skies
     should remain mostly cloudy over the state.  Temperatures
     across the Willamette Valley tonight should be a few degrees
     colder than the mid to upper 40s we saw this morning.  a
     relaxing of the winds will combine with a cool air mass to
     send much of Central and Eastern Oregon into the 30s
     tonight, after holding up mostly in the 40s this morning.

Surface Winds:
     SW 10 this morning, WNW 10-15 G20 this afternoon.
Transport Winds:
     W 13 this morning, WNW 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 70.
High Temperature:
     Salem\'s high temperature today will be near 58.
Humidities:
     Minimum relative humidity will be near 57%.
Sunrise/Sunset:
     Salem sunset tonight: 8:42pm; sunrise tomorrow: 5:36am.

Extended Outlook:
     A very broad upper-level trough is forecast to center itself
     over Nevada this holiday weekend.  The counterclockwise
     circulation around it will continue to drive enough moisture
     into the Pacific Northwest to keep skies partly to mostly
     cloudy.  The flow aloft will turn northerly, or even
     northeasterly at times, which will act to inhibit widespread
     rainfall.  However, conditions will be moist and unstable
     enough to maintain a threat of showers...mainly from the 
     Cascades eastward and during the afternoons.  Temperatures
     will warm slightly but remain near to slightly below normal.

     The upper-level trough is forecast by computer models to
     drift westward, and eventually the California Coast, by Tuesday
     of next week.  That would put Oregon back under southwesterly flow
     aloft, which would increase the shower threat west of the Cascades.

Tomorrow (22 May):  Mostly Cloudy.  Slight Chance of Showers.  A Little Warmer.  43/61

Fri (23 May):  Mostly Cloudy.  Slight Chance of Showers...Mainly Afternoon.  43/65

Sat (24 May):  Partly Cloudy.  Slight Chance of Showers...Mainly Afternoon.  43/69

Sun (25 May):  Partly Cloudy.  Slight Chance of Showers...Mainly Afternoon.  44/70

Mon (26 May):  Partly Cloudy.  Slight Chance of Showers...Mainly Afternoon.  44/72

Tue (27 May):  Mostly Cloudy.  Chance of Showers.  46/73

Wed (28 May):  Mostly Cloudy.  Chance of Showers.  47/73

ODA Meteorologist
weather at oda.state.or.us