AgWeatherNet 4/17/2013 Special Outlook

Cold Temperatures Possible Again on Monday Morning

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

Time Period
High risk: Monday morning
Moderate Risk: Sunday and Tuesday mornings
Low risk: Friday and Saturday morning, and next Wednesday morning and beyond

Locations Affected
Possibly much of central and eastern Washington.

Mid 20s in colder locations to the 30s in warmer areas on Monday morning.

Inversion Strength
Sunday: Moderate and Variable
Monday: Strong
Tuesday: Very Strong

Extent of Monday Morning Frost
Isolated Frost: Very Likely
Scattered Frost: Somewhat Likely
Widespread Frost: Uncertain but Possible

The potential exists for areas of frost to return on Monday morning. While this frost event will not be as long lasting or widespread as the recent episode, many areas will still have the potential for subfreezing temperatures due to expected dew point temperatures in the 20s.

It is important to note that this upcoming event will differ in several significant ways from the cold temperatures earlier this week, which could influence which areas experience the coldest temperatures, and what methods of frost protection will be effective. Rather than a cold air mass, Monday morning's potential frost would be the result of stable conditions, clear skies, and light winds.

The inversions associated with the coming event will be strong, and wind machines should be increasingly effective by Monday and especially into Tuesday morning. Also, the coldest areas are likely to be more strongly tied to low lying areas after Sunday, such that exposed slopes and hilltops like Snipes will be much warmer than valley areas. By Tuesday, sunny skies will promote very warm day-time temperatures compared to recent days.

Despite a return to generally milder weather in the coming days, a brief shot of cool air will arrive later this weekend from the north. As Washington transitions from a slightly unsettled pattern this weekend to a building ridge of high pressure next week, the risk for frost will temporarily return on Monday morning. The colder areas could drop into the mid to upper 20s, while other areas will remain in the 30s.

The potential for isolated frost exists on Sunday morning, although wind and clouds should keep most areas above freezing. By Tuesday morning, conditions should be very stable and clear, although the warmth of the air mass by that point precludes the mention of anything beyond isolated frost. By Wednesday morning, further warming should mean the return of frost free conditions.

Other weather features in the coming days will include windy conditions on Friday, followed by the warmest day-time weather of the year next week. High temperatures in central Washington may reach the mid 70s to mid 80s by Wednesday or Thursday, and warm conditions will be felt state wide.

Although the details are subject to change, this situation bears watching. Please continue to monitor AgWeatherNet for weather forecast updates during this variable time period. The Frost Risk page is update daily, and additional detail about the frost risk and other hazards will be available in the Friday outlook. For questions or further information, please contact Nic Loyd, (509)786-9367,

Washington State University