[willamette-fcst] Forecast - Tuesday, January 19th, 2010

Tue Jan 19 11:59:00 PST 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.

NOON UPDATE

Issued: 
     Tuesday, January 19th, 2010 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:00pm.

              ...The rules for stack burning have changed...

     In 2010, the total number of acres that can be stack-burned in the Willamette Valley
     is 1000 acres.  Pre-registration is now required, and stack burning permits must be
     obtained from an ODA staff member. 

Weather Discussion:
     A very typical \"El Nino\" weather pattern has set up across
     the Pacific Ocean.  A strong jet stream is directing a
     series of potent storms into California, with an extremely
     mild south-southwesterly flow aloft over Washington and
     Oregon.  The bulk of the rainfall from the incoming weather
     systems will stay south of the Willamette Valley, this week,
     but some rain and blustery winds can be expected at
     times...mainly south.

     At the surface, low-pressure centers have been approaching
     the northern California coastline and then turning north,
     and moving across the offshore waters of the Oregon Coast. 
     A fairly impressive system moved northward, along the Oregon
     Coast, Sunday night, bringing damaging south winds to the
     coast and sections of the Willamette Valley.  Coastal wind
     gusts were generally in the 60-80 mph range with local gusts
     to around 50 mph in the Willamette Valley.

     The \"parent\" surface low-pressure center had moved to well off of the
     northern Oregon Coast by late this morning, but a weaker, secondary
     low-pressure area formed along the frontal boundary and moved northward,
     just off the Oregon Coast, overnight.  It brought another round of
     blustery winds to western Oregon, in the early morning hours, but winds
     were not as strong with this system as they were with the previous one.
     Southerly winds, gusting to about 45 mph, swept across the coast and
     into much of the Willamette Valley shortly after midnight.  Winds
     rapidly slackened off across the Willamette Valley, by mid-morning as
     the low-pressure center moved northward, to off the Washington Coast.

     Another low-pressure center was forming along the frontal
     zone and was centered near the southern Oregon Coast late
     this morning.  It was bringing farily strong southerly winds
     to southwestern Oregon.  Medford has been getting brisk
     southerly wind-gusts, to around 50 mph, since 7am.  The
     low-pressure center was helping to increase the offshore
     gradients across the Willamette Valley, with easterly
     wind-gusts increasing to around 35 mph in the Portland area.
     Winds in the central and southern Willamette Valley were
     light.  Some increase in south-southeasterly winds is likely
     this afternoon, along the coast and in the Willamette
     Valley, as this low-pressure wave continues northward.

     Satellite imagery showed cloudy skies covering most of
     Oregon, with some filtered sunshine over the northeastern
     corner of the state.  Radar showed only a few sprinkles
     north of Roseburg, with spotty rainfall over southwestern
     and south-central Oregon.  Some showers will rotate
     northward, into the Willamette Valley, later today, but
     rainfall amounts are not expected to be significant.  The
     bulk of the rain is expected to remain south of the
     Oregon/California border.

     The air aloft remains unseasonably mild.  The freezing
     levels over Salem and Medford were measured at 5300 and 5800
     feet respectively this morning.  ODOT road cameras showed
     just wet pavement over the Cascade passes, with pass
     temperatures in the mid 30s late this morning.  As a broad
     upper-level trough slowly approaches the coastline, the air
     aloft will cool...lowering the snow level to below the
     passes by tonight.  However, significant snow accumulations
     are not likely, due to a lack of precipitation.

     Slight cooling aloft and southerly transport winds will make
     for good ventilation conditions today.  Midday temperatures
     were already well into the 50s across the northern
     Willamette Valley, and along the north coast, where easterly
     winds were mixing warm air aloft down to the surface. 
     Temperatures were in the mid to upper 40s across the
     southern Willamette Valley, where winds were light.  Skies
     should remain mostly cloudy across western Oregon with an
     increasng chance of light showers this afternoon...mainly
     south.  Mild easterly winds will continue across the north
     valley, with increasing south-southeasterly winds also
     helping temperatures climb well into the 50s across the
     south valley this afternoon (about 10 degrees above normal).

Surface Winds:
     SSE 5-15 G25 this afternoon in the south valley.  E 15-25 G35 in the north valley.
Transport Winds:
     S 20 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2500 feet.  Ventilation index 50.
High Temperature:
     Salem\'s high temperature today will be near 55.
Humidities:
     Minimum relative humidity will be near 55%.
Sunrise/Sunset:
     Salem sunset tonight: 5:02pm; sunrise tomorrow: 7:43am.

Extended Outlook:
     The next low-pressure system, in the latest series of
     storms, is forecast to approach the northern California
     coastline on Wednesday.  That should keep skies mostly
     cloudy across western Oregon with increasing offshore
     low-level flow.  Rain will likely spread northward, at least
     into the southern Willamette Valley, by Wednesday afternoon.

     Once again, the bulk of the rain from this system is
     forecast to push into California.  As the low-pressure
     system tracks northward, near the Oregon Coast, Wednesday
     night and early Thursday, it may bring a burst of strong
     southerly winds to sections of western Oregon.  Tis system
     has the potential to produce locally damaging winds,
     especially along the coast and across southwestern Oregon,
     depending on its exact track.

     The broad upper-level trough is forecast to move onshore
     Friday, with showers and slightly lower snow levels.  A
     transitory upper-level ridge will likely bring some drying
     over the weekend.  The next weather system is forecast to
     come onshore Sunday night.  It also has the potential to
     bring strong winds to mainly the coastal strip. Another
     upper-level ridge is forecast to dry things out Tuesday
     night and Wednesday.

Tomorrow (20 Jan):  Mostly Cloudy. Rain Spreading North. Snow Level 4000 Feet.  39/50

Thu (21 Jan):  Rain and Windy Early...Turning to Showers.  Snow Level 3500 Feet.  38/50

Fri (22 Jan):  Showers.  Snow Level 3000 Feet.  36/48

Sat (23 Jan):  Mostly Cloudy.  Chance of Showers.  Snow Level 3000 Feet.  35/49

Sun (24 Jan):  Increasing Clouds.  Rain Late.  Snow Rising to 4000 Feet.  34/48

Mon (25 Jan):  Rain Likely.  Snow Level 4500 Feet.  39/50

Tue (26 Jan):  Mostly Cloudy.  Decreasing Chance of Showers.  Snow Level 4000 Feet.  37/50

ODA Meteorologist
weather at oda.state.or.us