[willamette-fcst] Forecast - Friday, June 19th, 2009
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Fri Jun 19 11:47:15 PDT 2009
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:
Friday, June 19th, 2009 at 12:00pm.
Burn Advisory:
Agricultural burning is allowed. Suggested burn times are from 12:00pm until 8:00pm.
Preparatory burning is not allowed.
Propane flaming is not allowed.
Straw stack burning is allowed from 12:00pm until 8:00pm.
Weather Discussion:
A weak cold front moved onto the Oregon Coast early this morning and was over the
coast range late this morning. Ahead of the cold front, clouds and showers advanced
across most of the northern half of Oregon overnight. Locally more than a tenth of
an inch of rain fell along the northern and central coast and the northern Willamette
Valley. Rainfall amounts tapered off to just a trace in the southern Willamette
Valley around Eugene. Spotty showers dropped up to a few hundredths of an inch of
rain east of the Cascades.
Late-morning satellite imagery showed the leading band of clouds and showers had
pushed eastward and stretched from extreme western Montana and northern Idaho,
across northeast Oregon, to south-central Oregon. Doppler radar and surface
reports showed scattered areas of rain all along that line. The low-level cold
front was also producing some scattered light showers across western Washington
and western Oregon, north of a line from North Bend to Eugene. Westerly winds
aloft were creating upsloping conditions along the western slopes of the coast
Cascade ranges. That is where the bulk of the showers were falling. In contrast,
downsloping winds were creating areas of clearing on the eastern or lee side of
both ranges. One area with some sounbreaks was the western Willamette Valley,
and the other was west-central Oregon
The late-morning ODA surface analysis showed high pressure continuing to build into
the southern and central Oregon Coast with a low-pressure trough cutting across
east-central Washington. That was continuing to produce southerly winds in the
northern Willamette Valley, but winds had become westerly in the south valley.
Wind speeds had increased to the 5-15 mph range. Downsloping winds, off the coast
range, had warmed Willamette Valley temperatures into the mid to upper 60s, so I
have updated the high temperature forecast to include this warming effect. However,
cold air aloft will not support valley temperatures climbing much above 70 degrees.
The Salem sounding this morning showed the increasingly strong westerly flow aloft,
along with significant cooling from the surface all the way up to 35,000 feet. As
the weak cold front, and associated upper-level, trough move across the state today,
the air aloft should continue to cool. Daytime heating of the surafce will
destabilize the atmosphere this afternoon...leading to the development of scattered
showers...mainly over and on the western slopes of mountains. There is also a
chance of thunderstorms from the Cascades eastward.
There will be a mix of clouds, some sunbreaks and a few showers this afternoon
across western Oregon. Most of the sunbreaks will continue to be on the west side
of the Willamette Valley and most of the showers will be near the coast range and
over the Cascade foothills. Brisk westerly transport winds, along with mixing heights
slightly above 3000 feet, will provide adequate ventilation this afternoon for both
agricultural and stack burning.
Surface Winds:
WSW 8-15...becoming W 8-15 this afternoon.
Transport Winds:
W 15...becoming WNW 17 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 3700 feet. Ventilation index 63.
High Temperature:
Salem\'s high temperature today will be near 70.
Humidities:
Minimum relative humidity will be near 56%.
Sunrise/Sunset:
Salem sunset tonight: 9:02pm; sunrise tomorrow: 5:26am.
Extended Outlook:
Another weather system will bring a reinforcing shot of cool and moist air into
western Oregon later Saturday and across all of Oregon Sunday. It will also increase
the shower activity across the state. An upper-level trough is forecast to remain
over the region during the first half of next week, with temperatures staying below
normal. Onshore flow will maintain considerable morning clouds along the coast and
across the Willamette Valley, but the shower threat should decrease Monday.
The jet stream is forecast to push just north of Oregon Wednesday and Thursday of
next week, with a strong westerly flow aloft across Washington and southern British
Columbia. That would maintain onshore flow across western Oregon with plenty of
morning marine low clouds keeping temperatures near-normal. There is some indication
that the jet stream may migrate far enough north by the end of next week for
temperatures to climb back above normal.
Tomorrow (20 Jun): Mostly Cloudy. Chance of Showers...Increasing Late. 51/67
Sun (21 Jun): Cloudy and Quite Cool. Scattered Showers. 50/65
Mon (22 Jun): Mostly Cloudy. Slight Chance of Showers. 48/69
Tue (23 Jun): AM Clouds. Partly Sunny in the Afternoon. Warmer. 48/76
Wed (24 Jun): AM Clouds. Partly Sunny PM. Slight Chance of Showers North Late. 53/75
Thu (25 Jun): AM Clouds...Afternoon Clearing. 52/74
Fri (26 Jun): AM Clouds...Becoming Mostly Sunny and Warmer. 52/78
ODA Meteorologist
weather at oda.state.or.us
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