[willamette-fcst] Willamette Valley Field Burning Forecast - Noon Update

Tue Aug 12 11:48:26 PDT 2014

SILVERTON HILLS FIELD BURNING FORECAST

OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

11:45 AM PDT TUES AUG 12, 2014

BURN ADVISORY:

Agricultural burning is not recommended.

Prep burning is not allowed.

WEATHER DISCUSSION:

Upper level low in the eastern Pacific is combining with the low off the northern California coast bringing upper and lower level southerly flow over the state. Current radar imagery shows a line of thunderstorms moving toward Salem from the SSE. Currently, the event is moving through the Corvallis/Albany area. Temperatures are 13 degrees cooler at 11 a.m. than yesterday morning at this time. In addition, morning surface chart shows low pressure is moving east of the Willamette Valley and into the Cascades. Current pressure gradients are +3.1 mb from Newport to Salem and 0.0 mb from Salem to Redmond.

It appears the thunderstorm will move into the Salem/Sublimity area shortly after noon and provide a tenth to three tenths of an inch of rain. Expect continued cloud cover and chance of showers or thundershowers into the evening hours. Temperatures will likely struggle to get into the 80s.

TODAY'S FORECAST:

Mostly cloudy with increasing showers and/or thundershowers.

Salem's high temperature today will be near 80 degrees (average is 83).

Relative humidity: Will range from 50 to 80 percent this afternoon.

Surface winds: SE to WW at 4 - 8 mph, potentially gusty near the thunderstorm. Winds SW to NW at 5 - 10 mph later this afternoon and evening.

Transport winds: S to SW at 5 - 10 mph early this afternoon becoming SW to NW at 6 - 12 mph later this afternoon and evening.

Mixing height: Rising to near 2500 ft by 5 p.m.

Salem's sunset tonight: 8:23 p.m.

(Salem Airport data for Monday, Aug 11th: High 98°F; Rainfall: .00")

(Maximum Ventilation Index expected today: 25)

EXTENDED DISCUSSION:

Upper level low will move into the state on Wednesday bringing more showers and a chance of thundershowers over the area. The low will slowly exit to the east on Thursday but significant drying may not occur until Friday. Northwesterly onshore flow will continue into the end of the week and may provide a burn opportunity Friday.

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.

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

Nick Yonker

ODF Meteorologist

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