[willamette-fcst] Forecast - Thursday, November 12th, 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: 
     Thursday, November 12th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:00pm.
     Straw stack burning is allowed, for dry stacks, from now until 3:00pm.

Weather Discussion:
     A small but intense upper-level disturbance was centered
     near the mouth of the Columbia River at mid-morning.  An
     associated area of cold showers extended from southwestern
     Washington across much of western and central Oregon.  The
     air aloft is quite cold with this system.  The freezing
     levels over Salem and Medford were measured at just 3500 and
     3800 feet respectively early this morning.

     Late-morning imagery from ODOT road cameras confirmed
     sticking snow over the Cascade passes with wet snow sticking
     on the trees and rooftops as low 1670 feet, near highway 22,
     in Detroit. Sticking snow also fell, from Bend to Chemult,
     in central Oregon this morning.  ODOT road cameras showed
     just wet pavement over the coastal range passes.

     The mid-morning ODA surface analysis also showed a weak
     low-pressure center near the mouth of the Columbia River. 
     South-southeasterly pressure-gradients were producing 5-15
     mph winds from the coast across the Willamette Valley. 
     Doppler radar showed the bulk of the shower activity had
     pushed east of the Willamette Valley, but a few showers were
     still rotating onshore, in a westerly flow aloft, around the
     center of the upper-level disturbance.

     Even with quite cold air aloft, shower activity kept
     temperatures above freezing across western Oregon overnight.
     Morning minimums ranged from the mid 30s to the low 40s
     across the Willamette Valley.  The center of the upper-level
     disturbance is forecast to slide southeastward, to over
     central Oregon, by late this afternoon.  Showers should
     taper off across western Oregon with some sunbreaks. 
     However, cold air aloft will keep surface temperatures
     mostly in the 40s across western Oregon today.  Partial
     clearing this evening will allow temperatures to drop back
     well into the 30s overnight, before clouds increase from the
     next weather system by early Friday morning.

Surface Winds:
     S 5-15 this morning, S 5-12 this afternoon.
Transport Winds:
     SSW 12 this morning, SSW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3200 feet.  Ventilation index 38.
High Temperature:
     Salem\'s high temperature today will be near 49.
Humidities:
     Minimum relative humidity will be near 68%.
Sunrise/Sunset:
     Salem sunset tonight: 4:46pm; sunrise tomorrow: 7:07am.

Extended Outlook:
     A cold front is forecast to drop into the region, from the
     Gulf of Alaska, on Friday.  It will likely bring a few hours
     of locally heavy snow to the Cascades.  Snow could fall as
     low as 1500 feet in the northern coast range and the Cascade
     foothills.  More rain is in store, for the coast and the
     Willamette Valley, Friday morning, with showers Friday
     afternoon.  Clearing skies Friday night could allow valley
     temperatures to locally drop below the freezing mark, with
     areas of fog forming.

     A warm front is forecast to increase clouds across
     northwestern Oregon Saturday afternoon and lift the snow
     level to near 4000 feet.  Rain is likely across western
     Washington and northwestern Oregon by Sunday morning, with
     the snow level rising above 5000 feet in the Oregon
     Cascades.  The warm front is forecast to push north of the
     region by Sunday night with rain tapering off. Temperatures
     should be quite mild Monday and Tuesday, ahead of a cold
     front forecast to come onshore Tuesday evening.  More valley
     rain and mountain snow is forecast for the second half of
     next week.

Tomorrow (13 Nov):  Rain and Mountain Snow.  Snow Level Dropping to 1500 Feet.  36/47

Sat (14 Nov):  Areas of AM Fog. Increasing Clouds.  Snow Level Rising to 5000 Feet.  32/48

Sun (15 Nov):  Rain...Mainly North.  Snow Level Rising to 6-7000 Feet.  37/53

Mon (16 Nov):  Mostly Cloudy and Mild.  43/57

Tue (17 Nov):  Increasing Clouds.  Rain Developing in the Afternoon.  44/54

Wed (18 Nov):  Rain Turning to Showers.  Snow Level Dropping to 3000 Feet.  42/49

Thu (19 Nov):  Rain Developing With Mountain Snow.  Snow Level 3000 Feet.  39/49

ODA Meteorologist
weather at oda.state.or.us