SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

8:45 AM PDT THU SEP 26, 2019

 

BURN ADVISORY:

 

Recommended times for agricultural burning are from 10 a.m. until 5:00 p.m.

 

Prep burning is not allowed.

 

WEATHER DISCUSSION:

 

The weather pattern is becoming less stable as an upper-level disturbance drives a weak frontal system south into Oregon today. Onshore flow will build up as isolated rain showers push into Marion County this afternoon.

 

TODAY’S FORECAST:

 

Mostly Cloudy with Rain Showers.

 

Salem's high temperature today will be near 69°F (average is 74°F).

Relative humidity: Remaining above 65% throughout today.

Surface winds: S-SW 4-7 mph this morning; SW-W 5-10 mph this afternoon.

Transport winds: W-NW 10-15 mph this morning; NW 7-13 mph this afternoon.

Mixing height: Rising to 3,000 feet by 10:00 a.m. and reaching 5,000 feet by 1 p.m.

Salem’s sunset tonight: 7:02 p.m.

 

(Salem Airport data for Wednesday, September 25th: High 72°F; Rainfall: .00”)

(Maximum Ventilation Index expected today: 65)

                                                                           

EXTENDED DISCUSSION:

 

Friday will see a major shift in the atmosphere, as the jet stream dips down over the Cascades, bringing cold & dry air south from Canada. A series of frontal systems will keep the atmosphere unstable and well-mixed, with isolated showers and mountain thunderstorms possible over the Cascades. The Snow Line will drop rapidly, and may bring occasional rain/snow mix to eastern Marion County over the coming weekend. Breezy conditions are likely throughout the Willamette Valley through the end of September.

 

The National Weather Service’s digital forecast is available at:

http://forecast.weather.gov/MapClick.php?lat=44.90549606158295&lon=-122.8106689453125&site=pqr&unit=0&lg=en&FcstType=text

 

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 15 mph.

                                                            

     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 (ft) times

         the transport wind speed (mph) 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.

 

     5. In accordance with OAR 837-110-0090, all field burning shall be

         banned when any two of the following criteria are present:

         A. Temperature of 95 degrees Fahrenheit or above

         B. Relative humidity of 30 percent or below                

         C. Wind speed of 15 miles per hour or higher

 

This forecast is provided under an agreement between the Oregon Department

of Agriculture (ODA) and the Oregon Department of Forestry (ODF).  For

information contact ODA at 503-986-4701.

 

To add/remove your email address from this list, please go to:

 

http://listsmart.osl.state.or.us/mailman/listinfo/willamette-fcst

 

Tom Jenkins, AEM

ODF Meteorologist