[willamette-fcst] Forecast - Thursday, November 19th, 2009

Thu Nov 19 11:58:19 PST 2009

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: 
     Thursday, November 19th, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 2:30pm.
     Straw stack burning is allowed from now until 2:30pm.

Weather Discussion:
     An active frontal system, stalled out over western
     Washington and extreme northwestern Oregon, is slowly
     pushing to the north today.  Heavy rain continued to fall
     this morning, with an additional inch coming down, since
     4 a.m., along the coast, from Astoria, OR to Hoquiam, WA. 
     About one-half inch of rain has fallen, in the last 8
     hours, across much of the interior of western Washington,
     including the Seattle area.  Southerly winds are also
     increasing, with another low-pressure center forming, along
     the front, about 500 miles off the northern Oregon Coast. 
     It is forecast to track northeastward and come inland just
     north of Vancouver Island, British Columbia by late tonight.

     The National Weather Service has issued a High Wind Warning,
     valid until midnight, for the Oregon Coast.  South winds
     were gusting from 40-50 mph along the northern and central
     coast late this morning, with some local gusts over 60 mph. 
     South wind gusts will likely increase to as high as 75 mph,
     over exposed headlands and beaches, this afternoon and
     evening.  In the Willamette Valley, southerly winds will
     continue gusting to around 35 mph this afternoon and evening.

     Oregon is in the warm-sector of the storm today, with the
     blustery southerly winds making for mild temperatures.  Most
     of western Oregon was in the mid 50s, with highs today likely
     climbing into the upper 50s.  Some 60-degree readings are
     possible, which would be about 10 degrees above normal.  The
     freezing level over Salem was measured at 7000 feet this morning
     and may rise slightly more this afternoon.  ODOT road cameras
     showed wet pavement over the Cascade passes late this morning,
     with temperatures well above freezing.

     Doppler radar was showing the main area of rainfall starting
     to lift north of Oregon at midday, with surface reports
     confirming a decrease in rainfall intensity along the extreme
     north coast.  This afternoon will be cloudy, windy, and mild
     across Oregon, with some light rain still likely along the
     north coast.  The remainder of western Oregon will only have
     a chance of light rain...mainly north.  The break from the rain
     will be brief, with a cold front forecast to move onshore tonight.
     Rain will spread back onto the entire length of the Oregon Coast
     overnight, with continued strong southerly winds.

Surface Winds:
     S 15-25 G35 this afternoon.
Transport Winds:
     S 35 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 58.
Humidities:
     Minimum relative humidity will be near 40%.
Sunrise/Sunset:
     Salem sunset tonight: 4:39pm; sunrise tomorrow: 7:17am.

Extended Outlook:
     The cold front is forecast to finally come onshore during
     the pre-dawn hours Friday.  There will likely be a few hours
     of locally heavy rainfall, across all of western Oregon,
     with the cold frontal passage.  However, it is not expected
     to stall, while moving across the region, so total rainfall
     amounts should not become excessive.  The greatest rainfall
     totals will likely be along the immediate coastline and in
     the coastal range.

     Strong southerly winds overnight will turn more
     southwesterly, and begin decreasing, after the frontal
     passage Friday morning.  The rainfall will turn showery
     Friday afternoon, with the snow level dropping back to
     around 2500 feet by Friday night.  Accumulating snow is
     expected over the mountain passes, beginning Friday
     afternoon and continuing through Friday night.

     Showers will taper off Saturday, with yet another weather
     system forecast to renew the steady rain, and increase the
     southerly winds, across western Oregon Saturday evening. 
     Snow levels will only climb to around 4-5000 feet, ahead of
     the cold front, so significant snow accumulation is likely,
     over the Cascade passes, Saturday and Saturday night.  The
     steady preciptation will turn to showers, in the wake of the
     cold front, on Sunday, with the snow level dropping back to
     around 3000 feet. 

     A warm front is slated to spread more rain across western
     Oregon Monday...along with rising snow levels.  A weak cold
     front will follow Monday evening, but the snow level should
     only drop back to around 5000 feet Monday night.  There may
     be a few lingering showers Tuesday, but a building upper-level
     ridge of high pressure may send the next warm front just north
     of Oregon.  That would give the state a break from the rain,
     along with continued mild temperatures.  The first in a new
     series of storms is forecast to come onshore next Thursday.

Fri (20 Nov):  Rain and Windy...Turning to Showers.  Snow Level Dropping to 2500 Feet.  45/50

Sat (21 Nov):  Showers Early...Increasing Rain and Wind Late.  Snow Level 3-4000 Feet.  39/47

Sun (22 Nov):  Showers.  Snow Level near 3000 Feet. 40/49

Mon (23 Nov):  Rain Likely.  Snow Level Rising to 5-6000 Feet.  42/54

Tue (24 Nov):  Mostly Cloudy.  Slight Chance of Rain North.  Mild.  41/53

Wed (25 Nov):  Areas of AM Fog...Partly Sunny and Mild.  38/55

Thu (26 Nov):  Rain Ceveloping.  Snow Level 6000 Feet.  43/52

ODA Meteorologist
weather at oda.state.or.us