[willamette-fcst] Forecast - Wednesday, July 16th, 2008
Willamette Valley Ag/Burning Forecast
willamette-fcst at listsmart.osl.state.or.us
Wed Jul 16 08:02:06 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 16th, 2008 at 9:00am.
Agricultural burning is not recommended.
Preparatory burning is allowed from 12:00pm until 2:00pm with a 100 acre limit.
Propane flaming is allowed from 12:00pm until 5:00pm.
Stack burning is not allowed.
A weak upper-level disturbance was moving onshore this
morning and increasing the westerly flow aloft over
Washington and Oregon. The Salem sounding this morning
showed 5-10 degrees of cooling, from the surface up to
13,000 feet, since Tuesday morning. There was still a layer
of northeasterly winds from 2-4000 feet, but that should
switch to northwesterly by midday. The ODA surface analysis
showed high pressure building into the central coast with a
weak thermal trough extending from Eastern Washington
through Central and SW Oregon.
Onshore flow was increasing across Western Oregon this
morning with gradiant stacking and the Medford Draw
dominating this morning. Visible satellite imagery showed a
solid deck of low clouds and fog along the Washington and
Oregon Coastlines. The low clouds were banked up against
the coastal mountains and making their way up the coastal
river valleys at mid morning. Patchy low clouds had made it
up the Columbia River into the Portland area, with clear
skies over the remainder of the valley. Mostly sunny skies
covered the remainder of the state with only some mid and
high clouds over North-Central and NE Oregon.
Temperatures this morning were running about 10 degrees
cooler than Tuesday morning across he Willamette Valley.
Minimums dipped into the upper 40s and low 50s in response
to the increased onshore flow overnight. Onshore flow will
likely cap afternoon temperatures in the low 80s across the
valley, under sunny skies. Northwesterly surface winds may
approach or locally exceed 15 mph later this afternoon,
which could limit burning opportunities. Fire Marshal
conditions are not expected due to lower temperatures and
Cooling aloft will allow mixing heights to climb above 3000
feet in the early afternoon. Daytime heating may alleviate
the pressure-gradient-stacking and Medford-Draw issues later
this afternoon. We will begin taking pibal readings at
12:15pm for possibility of limited open burning. Transport
winds are forecast to become northwesterly, during the mid
to late afternoon, before turning back to northerly this
evening. Therefore, any burning opportunities will likely
WSW 5-10 this morning, NW 8-15 this afternoon.
NE 7 this morning, NNW 10 this afternoon.
Atmospheric Ventilation Conditions:
Maximum mixing height today will be near 5000 feet. Ventilation index 50.
Salem\'s high temperature today will be near 82.
Relative humidity drops to 50% by 11am.
Minimum relative humidity will be near 32%.
Salem sunset tonight: 8:55pm; sunrise tomorrow: 5:42am.
Another weak upper-level trough is forecast to reinforce the
onshore flow Thursday and Friday with increasing amounts of
marine clouds penetrating into the Willamette Valley. Even
with northwesterly transport winds,
pressure-gradiant-stacking issues may limit burning
opportunities Thursday, as the Willamette Valley become full
of cooler marine air. Areas of drizzle are likely by Friday
morning along the coast and western slopes of the coast
range. Transport winds may become northerly, again, as
early as Friday afternoon.
The upper-level ridge is forecast to rebuild over the region
Saturday with northerly transport winds and temperatures
warming back above normal. The long-range computer models
are not consistent in the timing of the ridge shifting
eastward and allowing a southerly flow aloft to move over
Oregon. That will likely happen either Sunday or Monday
with onshore flow and cooler temperatures returning to
Western Oregon. That transition may also bring showers or
thundershowers to much of the state.
Westerly flow aloft is forecast to stabilize the air mass
over the region by Tuesday with a more typical onshore flow
pattern at the surface.
Thu (17 Jul): Morning Clouds...Partly Cloudy in the Afternoon. Wind: NW 10-15 mph. 51/79
Fri (18 Jul): Morning Clouds...Mostly Sunny. Wind: NNW 10-15 mph. 50/80
Sat (19 Jul): Sunny and Warmer. 50/85
Sun (20 Jul): Mostly Sunny and Warm. 55/88
Mon (21 Jul): Mostly Cloudy and Cooler. Slight Chance of showers or Thunderstorms. 56/78
Tue (22 Jul): Morning Clouds...Mostly Sunny. 53/83
Wed (23 Jul): Patchy Morning Clouds...Sunny & Warm. 53/87
weather at oda.state.or.us
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