[willamette-fcst] Forecast - Monday, March 29th, 2010

[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: 
     Monday, March 29th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from now until 5:30pm.
     Straw stack burning is allowed from now until 5:00pm.

Weather Discussion:
     The moderate to strong El Nino, in the eqatorial Pacific
     Ocean, is weakening but expected to last at least through
     this spring.  Typical of El Nino, our early spring weather
     looks more wintry than spring-like. 6-10 inches of snow fell
     over the Cascades passses late last week, with about
     one-half inch of rain in the Willamette Valley.  After a
     brief break, with some sunshine on Saturday, rain spread
     back across western Oregon on Sunday.

     It seems more like November or December overnight, with
     southerly winds, gusting to over 80 mph along the coast and
     to nearly 50 mph in the Willamette Valley, accompanied by
     heavy rain.  The National Weather Service wind tower, at
     Garibaldi, recorded a wind gust early this morning of 85
     mph.  77 mph winds were clocked at the Yaquina Bay Bridge,
     in Newport.  Mt. Hebo, in the northern coastal range,
     recorded a peak gust of 96 mph.  In the Willamette Valley,
     southerly winds gusted to 46 mph in Salem and to 38 mph in
     Portland.  Rainfall totals of more that one-half inch were
     common along the coast and across the Willamette Valley,
     during the past 24 hours.  Troutdale, Hood River, Newport,
     and Brookings all picked up around an inch of rain.

     The mid-morning ODA surface analysis showed southerly
     pressure gradients beginning to relax across western Oregon,
     while strengthening slightly east of the Cascades. 
     South-southwesterly winds were still gusting to around 30
     mph across western Oregon, with local gusts to about 35 mph
     in the Willamette Valley and to over 40 mph along the coast.
     Southerly winds had increased across central and eastern
     Oregon, with 25-40 mph gusts.  The strongest winds, east of
     the Cascades, were from Klamath Falls to Rome.

     The strong cold front, responsible for the stormy weather,
     was just moving onto the Oregon coast at mid-morning. 
     Satellite imagery showed solid cloud-cover across the entire
     state, with a back edge to the overcast skies nearing the
     coast.  Doppler radar and surface reports showed locally
     heavy rain falling across all of western Oregon, with only a
     few areas of light rain making it east of the Cascades.  The
     freezing level jumped to 6-7000 feet, ahead of the cold
     front, Sunday afternoon and was holding there this morning. 
     ODOT road cameras showed wet pavement over Cascade passes,
     where temperatures were several degrees above freezing.

     The cold front is forecast to slowly progress eastward,
     across western Oregon, this morning and push east of the
     Cascades this afternoon.  In its wake, the steady rain will
     turn showery, with colder air aloft rapidly dropping the
     snow levels in the Cascades.  Satellite imagery shows
     impressive cumulus cloud development approaching the
     coastline, so scattered thunderstorms are likely to move
     onshore later this afternoon.  With lowering snow levels
     today, the National Weather Service has issued a Winter
     Storm Warning, for elevations above 4000 feet, where more
     than foot of new possible is possible later this afternoon
     and tonight.  That is much-needed snowfall but could cause
     serious travel delays over the Cascade passes. 
     Thunderstorms will likely produce bursts of small hail along
     the coast and across the western valleys later this
     afternoon and this evening.

     Stormy conditions held overnight temperatures mostly in the
     mid to upper 40s across western Oregon.  Mid-morning
     readings ranged from the upper 40s to the low 50s.  Highs
     this afternoon should only warm into the 50-55 degrees
     range.  Pressure gradients are forecast to turn more
     southwesterly, in the wake of the cold front, this
     afternoon.  Continued blustery southwesterly winds and
     cooling air aloft will provide excellent ventilation
     conditions today for agricultural and stack burning.

Surface Winds:
     SW 15-25 G35 this morning, SW 10-20 G30 this afternoon.
Transport Winds:
     SW 35 this morning, SW 30 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3000 feet.  Ventilation index 105.
High Temperature:
     Salem\'s high temperature today will be near 54.
Humidities:
     Minimum relative humidity will be near 61%.
Sunrise/Sunset:
     Salem sunset tonight: 7:36pm; sunrise tomorrow: 6:56am.

Extended Outlook:
     A cold and unstable air mass will move over Oregon Tuesday
     and Wednesday, with frequent showers and likely some
     afternoon thunderstorms.  Coastal and valley locations will
     likely see more bursts of small hail.  Snow levels will
     remain well below the Cascade passes and could drop as low
     as the coastal range passes by Tuesday night.  The main jet
     stream energy will sag southward, to over California, by
     Wednesday.  However, plenty of cold air aloft will combine
     with daytime heating to trigger plenty of showers across Oregon,
     with the mountains continuing to pick up much-needed snowfall.

     A transitory ridge of high pressure is forecast to move
     onshore Thursday and warm the air aloft enough to stabilize
     the atmosphere and decrease the showers across the state. 
     Clearing skies could allow temperatures to approach the
     freezing mark across the Willamette Valley Thursday morning.
      Partly sunny skies and warmer air aloft will help daytime
     highs climb closer to normal Thursday afternoon, with only a
     slight chance of a shower.

     Another cool Pacific storm is forecast to bring more valley
     rain and mountain snow on Friday, with snow levels staying
     below the Cascade passes.  Showers will follow the cold
     front on Saturday, with more snow expected in the mountains.
      The next system may take aim more at California, on Easter
     Sunday, but that is getting too far out to call.

Tue (30 Mar):  Showers and T-storms with Small Hail.  Snow Level Dropping to 2500 Feet. 40/51

Wed (31 Mar):  Showers and T-storms with Small Hail.  Snow Level Dropping to 1500 Feet. 36/50

Thu (01 Apr):  Decreasing Showers.  Becoming Partly Sunny.  Snow Level 2500 Feet.  34/54

Fri (02 Apr):  Rain and Mountain Snow.  Snow Level 3-4000 Feet.  40/53

Sat (03 Apr):  Showers.  Snow Level 3000 Feet.  40/55

Sun (04 Apr):  Chance of Rain...Mainly South.  Snow Level 4000 Feet.  40/55

Mon (05 Apr):  Chance of Rain.  Snow Level 3-4000 Feet.  39/55

ODA Meteorologist
weather at oda.state.or.us