[willamette-fcst] Forecast - Friday, February 13th, 2009

[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.

.....Next scheduled update is not until Wednesday, February 18th, 2009 at 9am...

NOON UPDATE

Issued: 
     Friday, February 13th, 2009 at 12:00pm.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:30pm.
     Stack burning is not allowed.

Weather Discussion:
     A weakening cold front brought less than two-tenths of an
     inch of rain to the interior valleys of western Oregon last
     night and early this morning.  Areas of very light rain and
     snow pushed east of the Cascades this morning.  The bulk of
     the moisture from this latest weather system moved south of
     the region, into California.  Cloudy skies and areas of
     light rain kept valley temperatures above freezing overnight
     with most minimums in the mid 30s.  Late morning temperatures
     had warmed to near 40 degrees in the western valleys and
     locally into the mid 40s near Portland and along the coast.

     The air mass is still quite cold over Oregon.  The freezing
     levels over Salem and Medford were measured at just 2100 and
     1900 feet respectively early this morning.  That put the
     snow level near 1000 feet this morning.  It should only rise
     slightly this afternoon.  ODOT road cameras showed mostly
     wet pavement over the coastal mountain passes.  Slush was
     reported late this morning over Sunset Summit, on HWY 26
     over the coast range. The Cascade and Siskiyou passes looked
     they they were improving, as the snow showers let up. 
     Snowfall amounts in the mountains ranged from a trace in the
     northern Cascades to as much as 4 inches over the Siskiyous
     of southern Oregon.

     The late-morning ODA surface analysis put the low-pressure
     center about 100 miles off the northern California coast,
     with pressure gradients becoming more northerly across
     western Oregon.  As the low-pressure center continues to
     drift southeastward, pressure gradients will slowly turn
     even more northerly across western Oregon this afternoon. 
     Northerly transport winds are not conducive to good valley
     ventilation for stack burning, so it is not allowed today.

     Satellite imagery continued to show a significant
     cloud-shield circulating northward, around the low-pressure
     center off the northern California coast, into Oregon and
     most of Washington.  Doppler radar indicated a general
     decrease in showers across Oregon, with the main jet stream
     energy focused well south of the region.  The low-pressure
     center will continue to weaken and move inland, into
     northern California, tonight.  Partial clearing overnight
     may allow Willamette Valley temperatures to locally drop
     below freezing.  There will still be a slight chance of a
     light shower overnight with the snow level dropping back to
     near or below 1000 feet.

Surface Winds:
     N 5-10 this afternoon.
Transport Winds:
     NNE 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 20.
High Temperature:
     Salem\'s high temperature today will be near 46.
Humidities:
     Minimum relative humidity will be near 62%.
Sunrise/Sunset:
     Salem sunset tonight: 5:38pm; sunrise tomorrow: 7:14am.

Extended Outlook:
     A split-flow jet stream pattern is forecast this weekend
     through much of next week.  The southern branch of the jet
     stream, and main moisture feed, will continue to be directed
     into California.   A weak upper-level trough will maintain
     partly to mostly cloudy skies, cool temperatures and at
     least a few showers over Oregon...mainly south. The best
     chance of showers will be Sunday through Tuesday with more
     of a break during the second half of the week.  Another cool
     system is forecast to move into the region the following
     weekend.  Snow levels will rise a little but remain below
     the Cascade passes. Willamette Valley temperatures should
     remain slightly below normal.

Tomorrow (14 Feb):  Mostly Cloudy.  Slight Chance of a Shower.  Snow Level 1500 Feet. 30/46

Sun (15 Feb):  Chance of Showers and Cool.  Snow Level Near 2000 Feet. 32/46

Mon (16 Feb):  Mostly Cloudy.  Chance of Showers.  Snow Level 2500 feet.  32/48

Tue (17 Feb):  Decreasing Chance of Showers.  Snow Level 2-3000 Feet.  33/48

Wed (18 Feb):  Slight Chance of Showers.  Snow Level 3000 Feet.  33/50

Thu (19 Feb):  Partly Cloudy.  Slight Chance of Showers.  33/51

Fri (20 Feb):  Partly Cloudy.  Increasing Chance of Showers Late.  33/52

ODA Meteorologist
weather at oda.state.or.us