[willamette-fcst] Forecast - Monday, August 25th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Mon Aug 25 07:54:38 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.
Monday, August 25th, 2008 at 9:00am.
Agricultural burning is not recommended.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Stack burning is not allowed.
After a warm weekend, with valley highs Saturday in the mid
to upper 80s and Sunday in the low 80s, another moist cold
front spread rain into the Willamette Valley late Sunday
afternoon. The slow moving front cold front dumped between
one-quarter and two-thirds of an inch of rain across the
valley by 5am this morning. The clouds and rain held valley
temperatures up overnight with minimums in the mid to upper 50s.
The soundings from Salem on Sunday showed a large tongue of
warm air aloft capping mixing heights below 2000 feet all
day. The sounding from this morning showed considerable
cooling from the surface all the way up to 25,000 feet.
That will make for higher mixing heights today, but relative
humidtiy levels will stay over 60% for most of the day and
fields are wet.
The ODA surface analysis showed high pressure across Western
Washington and Western Oregon with onshore flow west of the
cold front that was moving into Eastern Oregon. Satellite
imagery showed the leading edge of the clouds from the cold
front reaching Union County in NE Oregon and stretching
southeastward into northern Klamath County, in South-Central
Oregon. The back edge of the solid clouds had moved across
the western side of the Willamette Valley, where some
patches of blue sky were breaking through.
An upper-level trough will further chill the air aloft today
and keep a few showers going across Western Oregon. With
strong onshore flow and cold air aloft, valley high
temperatures should stay in the upper 60s (normal for today
is 80 degrees). The upper-level trough will slide east of
the Cascades this evening with the flow aloft becoming
northwesterly and drying out. That will help skies to clear
overnight, which will allow most valley temperatures to drop
into the 40s. With high humidity levels near the surface,
areas of fog and low clouds are likely by Tuesday morning.
NW 5-10 this morning, NW 8-15 this afternoon.
NW 10 this morning, NW 13 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 4500 feet. Ventilation index 59.
Salem\'s high temperature today will be near 68.
Minimum relative humidity will be near 57%.
Salem sunset tonight: 8:01pm; sunrise tomorrow: 6:28am.
A flat ridge of high pressure will continue the
northwesterly flow aloft Tuesday. Surface winds across the
valley will turn northerly with slow drying and warming of
the air mass across Western Oregon. A weak cold front is
forecast to slide across Southern British Columbia and
Western Washington Wednesday. The southern edge of this
system may be strong enough to to bring some drizzle fromt
he north coast to the extreme Northern Willamette Valley.
Transport winds may back from northerly to northwesterly
Wednesday, especially in the north valley. That would
normally present a possible burning opportunity for the
north valley, but fields may be too damp from the recent
rains. Weak ridging aloft will dry the air mass Thursday
with transport winds likely turning northerly again.
Another weather system is forecast to swing into Southern
British Columbia and NW Washington Friday afternoon. The
flow aloft is forecast to become more westerly over Oregon,
in response to an approaching weak upper-level trough.
Transport winds and mixing heights could become favorable
for open burning of dry fields. The upper-level trough is
forecast to move over the region Saturday with increasing
onshore flow cooling valley temperatures back into the 70s.
Some morning drizle is possible...especially along the coast.
A flat transitory ridge will turn the flow aloft
northwesterly Sunday, for drier and warmer weather. The
ridge if forecast to shift east of the region Monday with
the flow aloft becoming southwesterly. A cold front is
forecast to approach the coast late Monday, but that is
getting too far out for the forecast models to time accurately.
Tue (26 Aug): Areas of Morning Fog and Low Clouds...Mostly Sunny in the Afternoon. 47/76
Wed (27 Aug): Partly Sunny. Slight Chance of Sprinkles or Drizzle North. 48/78
Thu (28 Aug): Sunny and Warmer. 48/83
Fri (29 Aug): Mostly Sunny. Increasing High Clouds. 52/82
Sat (30 Aug): Morning Clouds. Afternoon Clearing. 53/76
Sun (31 Aug): Mostly Sunny. 50/80
Mon (01 Sep): Mostly Sunny. Increasing Clouds late. 51/78
weather at oda.state.or.us
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