2 Major Cold Fronts This Week ... Let's Talk Temperatures
This has been an interesting summer from a Meteorologist's perspective. We all know it was a hotter than normal summer, but I will say if the drought had not been present then it could have been a colder than normal summer. The drought in summer time is such a powerful influence that it normally overcomes anything. We have seen the drought reduced significantly in the last two weeks and I think we are seeing a return to the natural order of the atmosphere. A dip in the jetstream or "northwesterly" flow is now beginning to dominate our pattern and this has big ramifications!
Jetstream Amplification
When we see a big dips in the jetstream it means we are allowing the colder air in Canada to filter into the US. East coast dips in the jetstream mean colder weather for the Ohio Valley. This is the exact setup that is evolving for our area.
Major Dip In The Jetstream Late Tuesday
Major Dip In The Jetstream Late Saturday
Notice the dip in the jetstream is even larger than the first one on Tuesday.
When you amplify the jestream like this, we get large areas of cold air surging to the south. This is what we will see on Tuesday and again on Saturday. As we look at temperature anomolies (departures from normal), you can see these chunks of cold air push toward the Ohio Valley.
Temperature Anomolies Wednesday Morning
Notice temperatures 10-15 degrees below normal move into our area on Wednesday.
Temperature Anomolies Late Friday
Notice the temperatures will warm to slightly above normal on Friday ahead of the next big front that you can see organizing late Friday.
Temperature Anomolies Saturday Morning
Notice the cold temperature anomolies are heading in our direction with the major front moving in early Saturday.
Temperature Anomolies Early Sunday
Notice the cold temperatures take hold again on our area early Sunday morning.
My Thoughts On The Cool Week
The first major cold front will move across the area tonight. The temperatures will be colder than we have seen since April 27th of this year. I think some locations outside the city could drop into the lower 40s to upper 30s! You will need that coat by Wednesday morning. Here is a look at some of the computer models by Wednesday morning. Notice the top right part of each image where shows the computer model name and time.
With the second front blasting through the area early Saturday, we will see temperatures falling through the day on Saturday. By Sunday morning, we will likely have even colder temperatures than what I expect on Wednesday. The GFS in particular is pretty bullish with lows on Sunday where the EURO is a bit warmer.
The GFS has had a very good track record lately and I see no reason to discount it at this point. I think it is quite likely that a few will fall into the 30s by Sunday morning!
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marc, can you give a precip % on the following this week? fri pm, sat am, sat pm, sun am. i have big outdoor weekend plans. are most models in agreement on this weekend?
Posted by: chrisb | 09/17/2012 at 05:43 PM
chrisb, the accuracy on something like that is under 5%. I would rather give you an accurate forecast later this week then throw darts. If you can, check back with me Friday.
Posted by: Marc Weinberg | 09/17/2012 at 06:10 PM