[willamette-fcst] Forecast - Tuesday, July 14th, 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, July 14th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from 1:00pm until 8:00pm.
     Preparatory burning is not allowed.
     Propane flaming is not allowed.
     Stack burning is not allowed.

Weather Discussion:
     Clearing skies overnight allowed for much cooler
     temperatures statewide.  Readings locally dropped into the
     30s across eastern Oregon this morning, with sections of the
     Willamette Valley dipping into the 40s.  Meacham and Burns
     both recorded the low in the state of 35 degrees and Baker
     City dropped to 38 degrees.  On the west side of the
     Cascades, Salem, Corvallis, and Eugene all fell to just 48
     degrees this morning, before low clouds and areas of fog reformed.

     Visible satellite imagery showed low clouds blanketing
     western Washington again this morning and extending south
     over most of the Willamette Valley.  Unlike yesterday,
     however, skies were already beginning to clear along the
     Oregon Coast, with onshore winds turning northerly.  Skies
     were mostly clear over southwestern Oregon and over all of
     central and eastern Oregon.

     The ODA surface analysis showed a trough of low pressure
     extending from east-central Washington into north-central
     Oregon with high pressure strongly building into western
     Washington and northwestern Oregon.  A thermal trough was
     beginning to build northward, from northern California, into
     extreme southwestern Oregon.  Pressure gradients were still
     onshore across western Washington and extreme northwestern
     Oregon but turned northerly across the southern half of
     western Oregon...including the central and southern Oregon
     Coast and southern Willamette Valley.

     An upper-level ridge is building just offshore with the
     Salem sounding this morning showing considerable warming and
     a much drier northwesterly flow aloft.  The ridge is
     forecast to remain offshore today, which will maintain the
     dry northwesterly flow aloft.  Northerly surface gradients
     will increase this afternoon across the western Oregon, as a
     thermal trough builds northward into extreme southwestern
     Oregon.  Areas of morning clouds should give way to sunny
     skies over western this afternoon with temperatures
     recovering to near-normal (low to mid 80s), after being
     below normal for 7 of the past 8 days.  In addition,
     relative humidities will drop to near or slightly below 30%
     by late this afternoon, which will aid in the drying of damp fields.

Surface Winds:
     N 5-12 this morning, N 7-15 G20 south this afternoon.
Transport Winds:
     NNE 10 this morning, NNE 14 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3700 feet.  Ventilation index 52.
High Temperature:
     Salem\'s high temperature today will be near 84.
Humidities:
     Relative humidity drops to 50% by 12pm.
     Minimum relative humidity will be near 28%.
Sunrise/Sunset:
     Salem sunset tonight: 8:56pm; sunrise tomorrow: 5:40am.

Extended Outlook:
     The upper-level ridge is forecast to slowly shift eastward
     to over eastern Oregon Wednesday and to over western Idaho
     Thursday, with slowly increasing southwesterly flow aloft
     over western Oregon.  That pattern would allow temperatures
     to continue warming over all of Oregon, with the possible
     exception of the immediate coastline, where there would be
     some increase in onshore flow.  Sunny skies should continue,
     along with drying northerly winds.

     A broad upper-level ridge is forcast to shift eastward, to
     over western Montana, by Friday with the associated surface
     thermal trough finally sliding east of the Cascades.  That
     would bring increasing onshore flow into western Oregon
     Friday afternoon and at least keep temperatures from warming
     any further.  That may also create a burning opportunity,
     but that is still way too far out to call at this time.

     Onshore flow will increase Saturday, as a weak upper-level
     trough moves onshore into southwest British Columbia.  No
     rain is forecast from this system, except for possible
     drizzle along the coast early Sunday, but temperatures
     should cool back to near-normal Saturday and slightly below
     normal Sunday.  Another weak trough is forecast to move by
     to our north Monday...maintaining onshore flow.

Tomorrow (15 Jul):  Sunny and Warmer.  51/90

Thu (16 Jul):  Sunny and Warm.  55/91

Fri (17 Jul):  Mostly Sunny and Warm.  56/88

Sat (18 Jul):  Partly Cloudy.  Near-Normal Temperatures.  54/80

Sun (19 Jul):  Partly Cloudy.  55/78

Mon (20 Jul):  Partly Cloudy.  54/79

Tue (21 Jul):  Mostly Sunny and Warmer.  52/85

ODA Meteorologist
weather at oda.state.or.us