The Balance of September for the Upper Mississippi River Valley Center on Minnesota

[Minnesota Meso]

I posted this on the Minnesota Forecaster page. Even though it is set up to grade the local met's I gave the site owner a heads up to get ahead of local guys.

So here are the stats through Sept. 11th.

Our average high temp is 84.3°

Our average low temp is 59.7°

This leaves us with a average temp for the month of 72° which is +5.9° above the 30 year average through the first 11 days of the month.

But what is on the horizon? Another warmer than normal weekend is setting up. After that all bets are off. All of the indices that meteorologist's look at are showing a major cooling trend. The Pacific North American Oscillation (PNA) is showing signs of going strongly positive which means a ridge on the west coast, thus higher than normal temps out there. The Arctic Oscillation (AO) is showing signs of going strongly negative which means cooler air could be released from the arctic and be transported down to us. The North American Oscillation (NAO) is also showing signs of going strongly negative which means blocking over eastern Canada to Greenland, thus slowing down the progression to the east of troughs and ridges.

So what does that mean? Without any ridges (warmer than normal temps) being able to work into our area, the troughs (cooler than normal temps) will continue to dive into Minnesota without much moisture to work with, keeping the storm track to our south. Because of this I suspect that we will see some much below normal highs next week, after that they will tend to modify. But without much cloud cover I think that over night lows could be lower that what the models are showing.

So even though we are sitting at +5.9° as I type this, I think this month has a good chance of seeing below normal temps overall. That would break our streak of 15 consecutive months of above normal temps. What do I think of the chances? My head says 50/50, my gut says 60/40 chance of below normal temps for the month.

[phlwx]

MSP is +1.7, MPX is +0.2...heat island is a killer!