This is the forecast for the foothills of the Northern Blue Mountains of Oregon, including the cities of Athena, Pendleton, and Pilot Rock issued at 8:16 AM on May 16, 2017:
Today will have rain in the morning, then numerous showers and isolated thunderstorms in the afternoon. Breezy, cooler. Some thunderstorms may produce small hail in the afternoon. Highs 51° to 56°. South wind 10 to 15 mph increasing to southwest 20 to 25 mph in the afternoon. Chance of precipitation near 100 percent. Tonight will be mostly cloudy. A chance of showers and a slight chance of thunderstorms early in the evening, then a chance of showers in the late evening and overnight. Breezy. Some thunderstorms may produce small hail early in the evening. Lows 38° to 43°. West wind 15 to 25 mph shifting to the southwest 10 to 15 mph overnight. Chance of precipitation 50 percent. Tomorow will be mostly cloudy with a 20 percent chance of showers. Highs 55° to 60°. West wind 10 to 15 mph.
An upper level low will move from Vancouver Island across Washington and Oregon to southern Idaho today and tonight. The associated cold front is moving through Washington and Oregon this morning with widespread rain. Behind the front precipitation will turn to showers as the upper level low passes over the region. Instability will increase as the cold pool and low move through this afternoon. A thunderstorm may pop up anywhere. West winds will pick up by midday due to tightening pressure gradients and higher winds aloft mixing to the surface behind the front. Funneling will also enhance the winds in the Columbia River Gorge and Kittitas Valley this afternoon. A wind advisory will be issued for the Gorge and Kittitas Valley. Snow levels will drop to around 3,000 feet tonight. There may be enough accumulation to warrant a late season snow advisory for the Ochoco John Day Highlands or the Blue Mountains but it may be difficult to accumulate snow due to the warm ground. Wrap around moisture from the upper level low in southeast Idaho will keep a chance of rain showers in the eastern mountains Wednesday while the showers gradually decrease from west to east. Wednesday night and Thursday an upper level ridge located offshore will build into Washington and Oregon behind the departing low. A weak disturbance moving riding over the ridge Thursday may have enough energy to trigger a few light showers from the Blue Mountains eastward.
Regional Weather Observations:
Pendleton Airport: Light rain. Temperature 49°, dewpoint 46°, relative humidity 89%, east wind 6 mph, air pressure 29.61 inches falling.
Adams: Temperature 47°, dewpoint 44°, relative humidity 89%, south wind 2 mph, air pressure 29.60 inches falling.
Athena: Temperature 47°, dewpoint 44°, relative humidity 89%, southwest wind 1 mph, air pressure 29.63 inches falling.
Helix: Temperature 47°, dewpoint 44°, relative humidity 89%, south wind 13 mph, air pressure 29.60 inches falling, wind chill 41°.
Milton-Freewater: Temperature 49°, dewpoint 43°, relative humidity 80%, south wind 3 mph, air pressure 29.64 inches falling.
Pilot Rock: Temperature 50°, dewpoint 44°, relative humidity 80%, southwest wind 2 mph, air pressure 29.63 inches falling.
Tutuilla: Temperature 48°, dewpoint 45°, relative humidity 89%, calm wind, air pressure 29.62 inches falling.
Umapine: Temperature 52°, dewpoint 47°, relative humidity 83%, south wind 3 mph, air pressure 29.59 inches falling.
Weston School: Temperature 46°, dewpoint 40°, relative humidity 79%, southwest wind 5 mph, air pressure 29.62 inches falling.