[willamette-fcst] Forecast - Wednesday, July 30th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Wed Jul 30 07:55:17 PDT 2008
Daily Smoke Management Forecast
Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.
Wednesday, July 30th, 2008 at 9:00am.
Agricultural burning is not recommended.
Preparatory burning is allowed from 11:00am until 5:00pm with a 100 acre limit.
Propane flaming is allowed from 11:00am until 5:00pm.
Stack burning is not allowed.
A fairly active cold front, for late July, moved across
Western Oregon Tuesday evening and was falling apart east of
the Cascades this morning. Spotty light rain fell across
the Willamette Valley with the extreme north valley locally
picking up a few hundredths of an inch. Generally trace
amounts fell from Salem south to Eugene. Up to one-quarter
of an inch of rain fell along the Noorthern Oregon Coast
with about one-tenth of an inch along the central coast. A
few light showers also fell across North-Central and NE
Oregon with Pendleton picking up .01 inches.
The trace of rain that fell in Salem Tuesday was not enough
to offically end the long dry spell that has lasted for over
a month and a half. Today will be the 51st consecutive day
without measurable rain in Salem. That is not
extraordinary, since July is typically the driest month of
the year. The valley normally only gets about
three-quarters of an inch of rain in July.
The Salem sounding this morning showed quite cool air, for
late July, below 7000 feet. That is not surprising, since
high temperatures Tuesday were only in the low 70s...10-15
degrees below normal. Winds aloft were generally
westerly...indication that strong onshore flow was occuring.
Skies were mostly cloudy over the valley this morning,
which helped to hold minimum temperatures in the low to mid
50s (near normal). Daytime heating will combine with cool
air aloft and ample low-level moisture to keep a fair amount
of clouds around through early this afternoon.
A transitory upper-level ridge of high pressure is forecast
to move over the region today. That will promote sinking
air in the mid-levels of the atmosphere with considerable
warming aloft forecast by this afternoon. That will help
valley high temperatures recover into the mid to upper 70s
today...still well below normal. Transport winds are
forecast to turn northerly by early this afternoon and
north-northeasterly by late this afternoon, so open burning
is unlikely today.
NW 5-10 this morning, NNW 5-15 this afternoon.
NW 8 this morning, N 10 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 4500 feet. Ventilation index 45.
Salem\'s high temperature today will be near 77.
Relative humidity drops to 50% by 12pm.
Minimum relative humidity will be near 36%.
Salem sunset tonight: 8:40pm; sunrise tomorrow: 5:57am.
A dry westerly flow aloft is forecast through early Thursday
with the flow becoming more southwesterly Thursday
afternoon, in response to a system dropping down the British
Columbia Coastline. Transport winds are forcast to become
west-southwesterly Thursday afternoon with mixing heights
climbing to near or above 5000 feet. A significant open
burning opportunity now appears likely Thursday afternoon
and early evening.
The Gulf of Alaska system will move onshore across
Washington and Northern Oregon Thursday night and Friday.
It will likely bring some light rain the the northern and
central Oregon Coast Thursday night and possibly into the
Willamette Valley by Friday morning...especially north of
Salem. High temperatures Friday will likely be about 10
degrees below normal.
The parent upper-level low pressure area will stall and
weaken, over Southern British Columbia, with a drier
westerly flow aloft over Oregon this weekend. Strong
onshore flow Saturday will turn more northerly Sunday, as
temperatures recover to near normal. The upper-level low
pressure center is forecast to continue to weaken and drift
off the coast Monday. That would put southwesterly flow
aloft over Washington and Oregon with only slight warming
due to onshore surface winds.
The upper-level trough is further weaken and move over the
region Tueday and Wednesday of next week. That would
maintain onshore low-level flow and maintan near-normal
temperatures across Western Oregon. There is potential for
burning opportunities with this pattern, but it it way too
far out to be more specific at this time.
Tomorrow (31 Jul): Mostly Sunny...Increasing Clouds with a Chance of Rain North Late. 49/79
Fri (01 Aug): Mostly Cloudy and Cool. Chance of Showers...Mainly North. 53/73
Sat (02 Aug): Morning Clouds...Becoming Mostly Sunny. 51/79
Sun (03 Aug): Mostly Sunny. 51/82
Mon (04 Aug): Mostly Sunny. 52/85
Tue (05 Aug): Mostly Sunny. 52/84
Wed (06 Aug): Mostly Sunny. 53/82
weather at oda.state.or.us
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