[willamette-fcst] Silverton Hills Forecast - Fri Jul 2, 2010

[Willamette Valley Ag/Burning Forecast]

SILVERTON HILLS FIELD BURNING FORECAST
OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE
9:00 A.M. PDT FRI JUL 02 2010
TODAY'S BURNING ADVISORY:
Prep burning is not allowed.
Propane flaming burning is not allowed.
TODAY'S WEATHER DISCUSSION:
An upper level trough will bring cool and showery weather to the northern Willamette Valley today. Fields are not ready for burning.
TODAY'S FORECAST:
Mostly cloudy and very cool with a few showers likely.  Surface winds will be S at 5-12 mph this morning; becoming W 5-15 mph this afternoon.  Transport winds will be SW at 8 mph this morning; becoming W at 10 mph this afternoon.  Maximum mixing height today will be 4000 feet.  The ventilation Index will rise to 40 this afternoon.  Salem's high temperature today will be near 65 degrees.  The relative humidity will drop to 50% around 2 p.m.
Salem's sunset tonight is at 8:57 pm
EXTENDED DISCUSSION:
A drier northwesterly flow aloft is forecast for Saturday and Sunday.  An upper-level ridge will build over the region late Monday through Wednesday.  A surface thermal trough will build northward along the coast with the transport winds turning offshore Tuesday and Wednesday.  Sinking air aloft and plenty of July sunshine will warm northern Willamette Valley temperatures to well above normal.  The ridge may begin to back off the coast as next Thursday with increasing northwesterly flow aloft.  That is still a dry pattern, but the low-level flow would turn back onshore...likely cooling temperatures back closer to normal by Friday.
EXTENDED  FORECAST:
Sat  July 3rd:  Chance of a morning shower...becoming partly sunny.  49/71
Sun July 4th:  Morning clouds.  Partly sunny in the afternoon.  49/73
Mon July 5th:  Morning clouds...becoming mostly sunny in the Afternoon.  50/75
Tue July 6th:  Sunny and much warmer.  Northeast winds.  50/87
Wed July 7th:  Sunny and very warm.  Northeast winds.  57/92
Thu July 8th:  Sunny.  Increasing onshore flow late.  60/90
Fri July 9th:  Patchy morning clouds.  Mostly sunny.  55/85
Notes:
     1.  Mixing height, as used here, is the lowest height at which the
         potential temperature exceeds the potential temperature at the surface.
         As a practical matter it is the approximate height to which a
         smoke plume will rise assuming good ignition, dry fuels, and
         winds less than about 15mph.
     2.  Transport winds are a layer average through the mixing height,
         weighted slightly toward the winds at the top of the layer.
     3.  Ventilation Index is the height of the mixing layer times
         the transport wind speed divided by 1000.
     4.  Surface wind direction is the general expected wind direction.
         At a specific point surface winds are highly dependent on
         local terrain conditions.
This forecast is provided under an agreement between the Oregon Department of
Agriculture and the Oregon Department of Forestry.  For information contact ODA
at 503-986-4701.
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