AgWeatherNet Weekly Weather Outlook for October 21, 2011

Frost Likely in Central Washington on Tuesday Morning

Nic Loyd, Meteorologist, 509-786-9357
Gerrit Hoogenboom, Director. 509-786-9371

Important Points about Next Week's Frost Event

  • Frost is likely next Tuesday morning, October 25th, especially in typically colder locations such as Moxee and Ellensburg. Frost is also possible Wednesday morning.
  • Many areas will be near or below 32 degrees Tuesday morning. Cold locations will experience temperatures in the 20s.
  • The coldest areas would be valley locations in rural areas and away from steep slopes and bodies of water.
  • The danger will be greatest if the skies are clear and conditions are dry and calm on Monday night and Tuesday morning.
  • This will be a radiation frost, and so there is likely to be spatial variability in low temperatures and frost danger on Tuesday morning. The expected stable conditions can cause differences in temperature over short distances which are influenced by small scale features like local terrain and elevation.
  • Wind machines could be an effective warming mechanism on Tuesday morning.
  • This will not be a significant cold air outbreak associated with an arctic air mass. Temperatures will warm into the 50s during the day on Tuesday.

Weather Overview
Periodic cloudiness and weak weather systems will dominate the weather through the weekend along with periods of light rain for western Washington, although little rain is expected in eastern Washington during the period. Mild southwesterly flow will keep temperatures above normal, especially at night, with highs generally in the 60s, and lows in the 40s. Cooler and more seasonal weather should return early next week with northerly flow over the area on Monday. Low temperatures on Tuesday morning should drop below freezing in many areas and into the 20s in the coldest spots as skies clear and drier continental air moves into central Washington. Later in the week, as a strong ridge builds over the region, warming in the upper atmosphere should bring stable conditions and strengthening inversions with mild temperatures in the mountains. However, limited warming will occur in the low elevations since shorter days and a weaker sun will limit the mixing potential of the warm air down to the surface in the valleys and basin. High temperatures early in the week will be mainly in the 50s.

Washington State University