[willamette-fcst] Forecast - Tuesday, March 30th, 2010

Tue Mar 30 09:11:41 PDT 2010

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: 
     Tuesday, March 30th, 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 strong cold front that brought heavy rain strong winds
     to western Oregon late Sunday and early Monday pushed east
     of the Cascades Monday afternoon.  It brought strong
     southwesterly winds to central and eastern Oregon, with
     gusts to around 50 mph common.  A developing wave of
     low-pressure formed along the front and stalled it over
     southeastern Oregon this morning.  Winds had decreased
     significantly across the entire state by this morning, with
     the strongest gusts, around 25-30 mph, from Klamath Falls to Rome.

     Colder air aloft was pouring onshore and across Oregon this
     morning, via a strong west-southwesterly flow aloft.  The
     freezing level over Salem was measured early this morning at
     just 2500 feet, which puts the snow level near 1500 feet. 
     Strong onshore flow was producing heavy upslope snow over
     the Cascades, with more than 6 inches of new snow creating
     winter driving conditions over the passes.  1-2 inches of
     snow was reported just east of Lyons, at only 1100 feet, in
     the western Cascade foothills this morning.  A Winter Storm
     Warning remains in effect until 11 a.m., above 4000 feet in
     the Cascades.

     Rainfall totals over the pass 48 hours have generally ranged
     from 1.5 to 2.5 inches along the coast and across the
     Willamette Valley.  Radar showed widespread mostly light
     rain continuing to circulate onshore.  The ODA surface
     analyis showed a weakening of the southerly gradients across
     the state, with a circulation center in central Oregon, near
     Redmond.  Satellite imagery showed more impressive cumulus
     cloud development moving onshore this morning, so numerous
     showers are in store for all of Oregon today.  Daytime
     heating should also help some thunderstorms to develop this
     afternoon.  Some storms could produce small hail.  Snow
     levels may drop low enough for wet snow over the coastal
     range passes...especially by tonight.

     Even with cloudy skies and showers overnight, cooling aloft
     dropped temperatures into the upper 30s and low 40s across
     western Oregon.  Highs today will not likely reach 50 in the
     Willamette Valley.  High mixing heights and continued
     blustery south-southwesterly winds will make for good
     ventilation conditions today.

Surface Winds:
     S 5-15 G20 this morning, SSW 7-17 G25 this afternoon.
Transport Winds:
     S 18 this morning, SW 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 100.
High Temperature:
     Salem\'s high temperature today will be near 49.
Humidities:
     Minimum relative humidity will be near 65%.
Sunrise/Sunset:
     Salem sunset tonight: 7:37pm; sunrise tomorrow: 6:55am.

Extended Outlook:
     A cold and unstable air mass will remain over Oregon
     Wednesday, with frequent showers and likely some afternoon
     thunderstorms.  Coastal and valley locations may get bursts
     of small hail.  Snow levels will be near the coastal range
     passes, with wet snow mixing with heavier showers in the
     higher hills around the Willamette Valley.  The main jet
     stream energy will sag southward, to over
     California...taking the main thrust of shower activity will
     it.  However, 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 cold Pacific storm is forecast to bring more valley
     rain and mountain snow on Friday, with snow levels well
     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 it appears as if it will be close enough for
     more rain and mountain snow to spread northward over Oregon.
     Temperatures will remain well below normal.

Wed (31 Mar):  Showers and T-storms with Small Hail.  Snow Level as Low as 1000 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 2-3000 Feet.  40/51

Sat (03 Apr):  Showers.  Snow Level 3000 Feet.  38/52

Easter Sunday (04 Apr):  Rain and Mountain Snow Likely.  Snow Level 3000 Feet.  38/52

Mon (05 Apr):  Showers Likely.  Snow Level Near 3000 Feet.  39/54

Tue (06 Apr):  Partly Sunny.  41/57

ODA Meteorologist
weather at oda.state.or.us