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    Cold Blast to Fade by Week's End

    4/23/2013, 7:18:24 AM

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    Tuesday, 11:30 a.m.

    You've heard the old saying: 'If I had a nickel every time I heard someone say...' To finish out that saying, I'd use the phrase something like this: '...I'm tired of the cold! When is it going to warm up?' Any amalgamation of that phrase will do, as the message is the same: most everyone is really, really done with the cold (and snow). They've had it, and really would like some nice, warm, sunny days to enjoy!

    I have some good news, and I have some bad news. First, the good news. As the headline says, the cold blast now shivering much of the Rockies and Plains into the Midwest will fade by week's end. Let me show you four charts that I think capture very well the essence of the change that is coming. First, the morning 850mb analysis of heights and temperatures as depicted by the 12z NAM Model:

    Note the area with below 0C cold over the northern and eastern Rockies, the central and northern Plains and parts of the Midwest, the core of which is colder than -10C. Now the GFS ensemble temperature anomalies for tomorrow:

    That's a huge area with temperatures at least 10 below normal tomorrow, the core of which is nearly 20 below average in the southern Plains, and even more so in the northern Plains!

    Compare that to the projected 850mb temperature forecast for Friday evening:

    That is a dramatic turnaround in just 84 hours, particularly over the northern and eastern Rockies and western Plains! In terms of the temperature change aloft, that's a 20 to 25C change, which is anywhere from 36 to 45 degrees warmer aloft! That will obviously have some impact on the temperatures below, and, indeed, the projected temperature anomalies for Friday and much, much different:

    You don't see as big of a change at the surface as you might expect, as there is some delay or 'lag' between the arrival of the warm air aloft and how that translates into warming at the surface. Remember, there's quite a bit of snow on the ground, and where there isn't a lot, it's still pretty much from the most recent storms, either rain or snow. Now, if I present you the Saturday GFS ensemble 2-meter temperature anomaly forecast for Saturday, you can better see that warming showing up:

    At least the Rockies and Plains will see a significant change in the weather from what it is and looks like now to what it will be come Saturday! How well does this translate into the East? Unfortunately, the bad news is 'not quite as well.' That doesn't mean they can expect cold and snow, but there will first be a couple of chilly days coming up behind the cold front on Thursday and Friday. Then, after some warming this weekend, it's looking more and more like there will be some sort of slow-moving feature in the East during the early and middle part of next week that will prevent the really warm, beautiful weather from settling in. Look at the GFS height anomalies for next Wednesday evening:

    Some of the operational runs of the GFS, and especially the European, have been going with the idea there will be some sort of cut off or closed low in the East for a time next week. It's getting to be that time of the year for closed lows to become more frequent, as the jet stream finally retreats, and puddles or pools of cold air are left behind, often in the form of these closed lows. And if you get caught near one, especially under it and to the north and east of one, the weather tends to be lousy - cloudy, wet, sometimes breezy to windy and often wet. That's not the sunny, 70-degree weather that I suspect most everyone would like to see.

    Maybe we're done with the brutal cold and snow after the next couple of days, but I have a feeling the month of May won't exactly look like the middle of summer, either. No, the atmosphere is probably going to have the memory of the past three months, which have been, on average, cold and wet. We may have to wait several more weeks before a truly warm pattern takes hold in a much broader part of the country.

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com


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