[willamette-fcst] Forecast - Tuesday, July 22nd, 2008

[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 22nd, 2008 at 9:00am.

Burn Advisory:

     ...Preparatory burning time has been extended until 5:00pm...

     Agricultural burning is allowed.  Suggested burn times are from now until 7:00pm.
     Preparatory burning is allowed from now until 5:00pm with a 100 acre limit.
     Propane flaming is allowed from now until 5:00pm.
     Straw stack burning is allowed from now until 7:00pm.

Weather Discussion:
     An upper-level low pressure area moved onshore, across
     extreme Northern California, Monday evening and was centered
     over Southeastern Oregon late this morning.  Showers and a few
     thunderstorms were continuing along the Idaho border and over
     NE Oregon.  A more stable westerly flow aloft moved over
     Western Oregon Monday night and helped a significant amount of
     marine air spill over the coast range and into the Willamette
     Valley. Low clouds continued to blanketed most areas west of the
     Cascades at midday with areas of drizzle and very light rain.
     Eugene was still getting drizzle late this morning and had 
     accumulated .04 inches of rain this morning.     

     Thundershower activity will continue to shift eastward
     today, mainly into Idaho by late this afternoon, as the
     upper-level low pressure area lifts northeastward into
     Central Idaho later this afternoon.  Westerly flow aloft will
     stabilize the air mass, from west to east, across Central 
     and Eastern Oregon this afternoon.  Pilot reports indicate that
     the marine low clouds are up to 3500 feet thick, so burn-off will
     be slower than expected and not until mid to late afternoon.  The
     westerly flow aloft should help to clear California wildfire
     smoke from most of the state by this evening.

     The Salem sounding this morning showed considerble cooling,
     since Monday evening, below 13,000 feet, due to the
     intrusion of marine air overnight.  Valley temperatures will
     be 10-15 degrees cooler today with afternoon highs around 70.
     Mixing heights will climb to 3000 feet, when surface temperatures
     reach the mid 60s around 2 pm.

     The mid-levels of the air mass will be sinking today, in the
     wake of the system that moved through last night, so
     open burning is unlikely today in the Willamette Valley.  The ODA
     surface analysis showed strong pressure-gradient-stacking and
     Medford-draw condions that will likely persist through the day.

     A weak upper-level system, dropping down from the Gulf of Alaska,
     will help turn the tranport winds northwesterly this afternoon, which
     is a favprable direction for limited prep burning.  The prep burning
     time was extended to accomodate the later burn-off of the marine deck.

Surface Winds:
     NW 8-15 this afternoon.
Transport Winds:
     NW 8 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 5000 feet.  Ventilation index 40.
High Temperature:
     Salem\'s high temperature today will be near 73.
Humidities:
     Relative humidity drops to 50% by 3pm.
     Minimum relative humidity will be near 38%.
Sunrise/Sunset:
     Salem sunset tonight: 8:49pm; sunrise tomorrow: 5:48am.

Extended Outlook:
     A weak upper-level trough will maintaint the westerly flow
     aloft over Oregon Wednesday with the flow turning
     northwesterly by Wednesday evening.  That should turn
     transport winds more northerly, in the Willamette Valley,
     Wednesday afternoon with some drying and warming of the air mass.

     Near-normal weather conditions with are expected Thursday through 
     Tuesday with coastal low clouds and mostly sunny conditions over
     the interior of Western Oregon.  Southwesterly flow aloft is 
     forecast to strengthen slightly Friday, as a weak trough approaches
     the coast.  That may increase the onshore flow enough to create a
     limited open burning opportunity Friday afternoon.

Tomorrow (23 Jul):  Morning Clouds.  Sunny in the Afternoon.  Wind: N 10-20 mph.  49/78

Thu (24 Jul):  Patchy Morning Clouds...Sunny and Warmer.  Wind: NNW 5-15 mph.  49/85

Fri (25 Jul):  Mostly Sunny with Increasing High Clouds.  Wind: NW 5-15.  51/85

Sat (26 Jul):  Patchy Morning Clouds.  Sunny in the Afternoon.  52/83

Sun (27 Jul):  Mostly Sunny.  Increasing High Clouds.  53/82

Mon (28 Jul):  Morning Clouds.  Sunny in the Afternoon.  53/82

Tue (29 Jul):  Patchy Morning Clouds.  Sunny in the Afternoon.  52/83

ODA Meteorologist
weather at oda.state.or.us