[willamette-fcst] Forecast - Tuesday, October 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.

Issued: 
     Tuesday, October 13th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 4:30pm.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     A major change in the weather pattern is taking place.  The
     northerly flow aloft that has brought cold and dry weather
     to the region for the past week has been replaced with a
     moist south-southwesterly flow aloft.  The first in a series
     of Pacific storms spread rain onto the Oregon Coast shortly
     after midnight and into the southern and central Willamette
     Valley during the pre-dawn hours this morning.  The bulk of
     the moisture from this system is being directed into
     northern California, but Doppler radar showed light rain had
     spread northward to about Olympia, Washington and eastward,
     across north-central Oregon, into south-central Washington.

     Low-level cold air remains trapped over eastern Washington
     and the northern half of central and eastern Oregon, where
     temperatures are near or below freezing at mid-morning.  The
     approaching storm system dropped the surface pressures
     offshore, forcing cold and dry low-level air, from east of
     the Cascades, westward across western Oregon.  Easterly
     winds, from the Columbia Gorge, were gusting to to around 40
     mph in the Portland area, with north-northeasterly winds
     funneling the cold and dry air southward across the
     Willamette Valley.  Temperatures west of the Cascades stayed
     in the 40s overnight, due to the increase in cloud-cover,
     but were still dropping at mid-morning due to evaporative
     cooling from the rain falling through the very dry low-level air.

     Increasing south-southwestery flow aloft will continue to
     bring rain at times to western Oregon today with
     northeasterly surface winds slowly turning southeasterly
     later today.  Willamette Valley temperatures should not drop
     below about 40 degrees this morning, before slowly warming
     into the mid to upper 50s this afternoon (about 10 degrees
     below normal).  The low-level air is cold enough this
     morning for precipitation to fall as freezing rain from
     north-central Oregon to the Pendleton area.  Temperatures
     will warm above freezing east of the Cascades this
     afternoon, and precipitation will turn to all rain below
     about 5000 feet.

Surface Winds:
     NNE 5-10 this morning, ENE 5-12 this afternoon.
Transport Winds:
     NE 8 this morning, ESE 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2300 feet.  Ventilation index 28.
High Temperature:
     Salem\'s high temperature today will be near 56.
Humidities:
     Minimum relative humidity will be near 62%.
Sunrise/Sunset:
     Salem sunset tonight: 6:30pm; sunrise tomorrow: 7:27am.

Extended Outlook:
     Westerly flow aloft will swing another weather system, and
     more rain, onshore across western Oregon Wednesday.  That
     should scour-out any remaining low-level cold air east of
     the Cascades...significantly moderating temperatures.  The
     snow level should hover around 7000 feet in the Cascades.  A
     warm front will likely bring some light rain to mainly
     northwestern Oregon Thursday, with the snow level lifting
     above 8000 feet in the Cascades.

     A transitory ridge will bring brief drying late Thursday and
     Friday, with another system forecast to swing onshore Friday
     evening.  Southwesterly flow aloft will direct the bulk of
     the rain from that system into southern British Columbia and
     western Washington.  A few showers could linger into Sunday
     with yet another weather system forecast to come onshore
     Sunday night and Monday.  Timing of weather systems that far
     out is next to impossible, but the latest guidance shows a
     possible break on Tuesday, with anther strom moving onshore
     next Wednesday.

Tomorrow (14 Oct):  Rain.  A Little Warmer.  Wind: S 5-15 mph.  47/60

Thu (15 Oct):  Mostly Cloudy.  Chance of Rain North. 51/65

Fri (16 Oct):  Mostly Cloudy.  Chance of Rain Late.  50/68

Sat (17 Oct):  Rain Turning to Showers.  49/63

Sun (18 Oct):  Mostly Cloudy.  Chance of Showers.  Increasing Rain Late.  49/62

Mon (19 Oct):  Rain Turning to Showers.  47/62

Tue (20 Oct):  Mostly Cloudy.  46/63

ODA Meteorologist
weather at oda.state.or.us