Frost Situation Update – September 17, 2012

Synopsis: Last week below normal temperatures saw frost developing across most of the agricultural areas of the province. Several stations recorded temperatures below -5C.

Frost Areas September10 to September 11 2012-See map

Frost Areas September15 to September 16 2012-See map

• Province wide, cooler than normal temperatures over the past week have brought frosts to most areas. • Generally, two episodes of frost were seen. One spanned the two nights from September 11 and 12, and struck several locations across southern , with the coldest temperatures recorded at Blackie AGCM (-8.4 C) south of and at AGCM (-7.4 C) south of the Cypress Hills. • A second major episode of frost occurred between September 15 and 16th, with many areas north of Red Deer seeing temperatures dip below -2 C. During this time the coldest temperatures recorded at the AGCM station (-5.5C) in the central Peace Region, followed by AGCM station (-4.8C), just northwest of the town of Westlock. • It is likely that some low lying areas will have experienced temperatures even lower that what is represented on the attached maps.

Perspective: Frosts of this magnitude, this early in the season are generally quite rare. The following are estimated probabilities that each of the following stations will have a frost down to -5 C on or before September 15: • La Glace AGCM ...... once in 16 years • Dapp AGDM ...... once in 50 years • Blackie AGCM ...... once in 20 years • ACGM ...... once in 50 years • Manyberries AGCM ...... once in 50 years

Additional Maps can be found at www.agriculture.alberta.ca/maps

Near-real-time hourly station data can be viewed/downloaded at www.agriculture.alberta.ca/stations Note: Data has about a two hour lag and is displayed in MST (add one hour for daylight savings time)

Ralph Wright Soil Moisture Specialist Head, Agrometeorology Applications and Modelling Section, ARD