The authors wish to thank B. Dugas, N. Gagnon, and M. Charron for help in preparing the data and developing the algorithm. A. Zadra thanks P. Bartello and M. Montgomery for insightful discussions and acknowledges support from the McGill's Faculty of Graduate Studies and Research, the “Fonds pour la Formation de Chercheurs et l'Aide à la Recherche du Québec,” and the Meteorological Service of Canada.
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