Thursday Update

Frost tonight

High pressure will build over eastern Canada and the Northeast U.S. tonight. The combination of clear skies, low dewpoints and light winds will lead to strong radiational cooling overnight, sending temperatures in some areas to near or below freezing for a few hours at most.

Most areas near large rivers and lakes, along with urbanized locations will not have frost.

I made some slight adjustments to the above map since yesterday.

If any readers have frost early Friday morning please let us know through the comment section below.

------- Another chance for frost....

A second shot of unseasonably cool air will sweep down into eastern Canada and the Northeast U.S. this weekend and early next week with another strong high pressure area building in behind the front. This will likely setup the possibility of more frost Saturday night/early Sunday over northwest Ontario then Sunday night/early Monday over southern/eastern Ontario (away from large bodies of water and cities) and down into the Appalachian region of the Northeast U.S.

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Western rainfall

I have no significant changes to the rainfall forecast map that I issued yesterday for the Pacific storm system tracking northeastward across the region through Friday night. I still like an average of 12-25 mm for Calgary with more to the southwest.

For Canada, it still looks like the heaviest rainfall will be over extreme southwestern Alberta and extreme southeastern BC (higher terrain) later Friday and through Friday night.

The good news is that this system will be slowly weakening as it tracks northeastward and it will be moving along. The system which brought the flooding to southern Alberta earlier in the summer was a stronger, more compact system and barely moved for 2 days.

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