OREGON DEPARTMENT OF FORESTRY WEATHER OFFICE

9:50 AM PDT FRI AUG 1, 2025

TODAY’S DISCUSSION:

The upper-level trough that brought showers and thundershowers to much of central and eastern Oregon, and some sprinkles to the Madras area on Thursday, is moving off to the NE this morning. In its wake, clouds are clearing from Jefferson County. However, the wildfire smoke that got forced into the region will take longer to clear. Most of the smoke is aloft, but surface air quality sensors are elevated in Madras this morning.

More sunshine will allow temperatures to climb into the upper-80s this afternoon. There is still a threat of thundershower development over the Cascades later this afternoon and evening with a risk of one moving over the basin. Increasing onshore flow should improve air quality. The air aloft is slightly cooler today compared to yesterday, which should combine with more sunshine to provide excellent afternoon mixing.

TODAY’S FORECAST:

Partly cloudy and hazy this morning. Sunny and warmer this afternoon with improving air quality. Slight chance of an evening thunderstorm.

Madras’ Forecast High Today: 89°F (Thursday’s High: 83°F; Rainfall: Trace)

Transport Winds: S 5 mph this morning; turning NW 10-15 mph this afternoon...backing to SW at the mixing height. Winds could be erratic near thunderstorms this evening.

Mixing Heights: Rising to 3000 feet by noon and to 5000 feet by 2 p.m.

Relative Humidity: Dropping to near 30% around noon and to near 20% by 5 p.m.

EXTENDED DISCUSSION:

SW flow aloft and onshore flow at the surface is expected this weekend with generally NW transport winds in the afternoons. Skies should be mostly sunny on Saturday with high temperatures near 90°F. An upper-level disturbance increases the threat of showers or thundershowers on Sunday with temperatures cooling into the low-to-mid 80s. Wetting rains are possible Sunday evening.

A more stable westerly flow aloft should clear skies on Monday and cool temperatures to near 80°F. expect favorable burning conditions, but it may get breezy in the afternoon. Dry weather and moderate temperatures should continue through the middle of next week.

National Weather Service’s digital forecast is available at:

http://forecast.weather.gov/MapClick.php?lat=44.68&lon=-121.14861&site=pdt&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. Surface wind direction is the general expected wind direction.

at a specific point surface winds are highly dependent on local

terrain conditions.

4. Ventilation Index (if you want to calculate it) is the height of the

mixing layer times the transport wind speed divided by 1000.

This forecast is provided under an agreement between the Oregon Department of

Agriculture (ODA) and the Oregon Department of Forestry (ODF). For more information, contact ODA at 503-986-4701.

Pete Parsons

ODF Meteorologist