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    Warmth Coming, but Strength and Length Still to Be Determined

    4/03/2013, 7:39:56 AM

    Wednesday, 11:30 a.m.

    It has been interesting to watch the models waffle back and forth with almost every run on the placement of various features across the country next week. One model brings the warm surge in, then turns it back with a cold front or back door cold front. The next run it pushes that front back and promotes even more warmth, even as another model goes in a different direction. There's a lot of volatility in the weather pattern, and how the various disturbances track from west to east across the country will have a huge bearing on how strong the warm surge becomes and how long it lasts.

    Take a look at just the GFS model. Here's yesterday's 12z run and its surface forecast for Wednesday morning next week:

    Notice the cool shot coming through the Northeast, with high pressure sliding off the New England coast, and the low-level chill likely down into eastern Virginia at that time, while a strong wave of low pressure is moving across the mid-Mississippi Valley. Compare that to the 18z Tuesday run for Wednesday morning:

    Suddenly the warmth is not just in play, but pushes all the way into upstate New York and New England, with virtually no sign of a back door cold front. There's still a strong wave of low pressure crossing the mid-Mississippi Valley at that time, with a pretty good chance of strong to severe thunderstorms ahead of that system. Now move ahead to the 0z Wednesday run, again, for Wednesday morning:

    That's somewhere in between, with a front having come through the Northeast, but not getting as far south as on the 12z run with a much weaker high to the north. There's still a strong storm, the worry of severe weather and a very strong surge of warmth into the Ohio Valley. Now the 6z model forecast for Wednesday morning:

    Now it looks like the old 12z run in many respects! All the while the operational GFS has undergone those changes, the European has gone from a chilly look on its 12z run to a decidedly warmer look on its 0z run. And the Canadian has a coldish look to its forecast for most of New York and New England Wednesday morning, with a clear frontal boundary stretching from the East Coast back to the mid-Mississippi Valley:

    So, what do you believe?

    The key to the outcome will probably come from the evolution of a trough digging into the West late this weekend and early next week. Some of the models are bringing this trough along slowly, which would allow one of two things to happen. One would be to bury it long enough over the Southwest to allow a northwest flow to develop from the Upper Midwest to the East Coast, which, in turn, would allow cooling and limit the extent of the warmth, with a second push of warmth ahead of the trough later in the week. On the other hand, the whole trough could hold together and, while moving slowly, could progress enough to push the warmth in and hold it there for several days before a cold front could reach the East Coast.

    If, however, the trough ends up being split into two or more pieces, as the European is suggesting, then the warmth would probably come in and stay in the absence of downstream blocking. Three different ways of resolving it, with each having a different outcome.

    So, in summary, it IS going to turn warmer this weekend and early next week. How long that warmth lasts in a given location is still up for debate, as is the strength of that warming at any place. If the t6z GFS ensembles provide any insight, then the warm card might be the one to play. Look at their forecast for Tuesday:

    Then for Thursday:

    Again, that's just one model run and its 'interpretation' of the events to come. Hang on to the steering wheel! There's a lot of warmth that is just waiting to bust out, but there's still plenty of cold air left in Canada that is not far away and can easily be drawn southward behind any storm or cold front. However, you can bank on it getting warmer, and there's probably going to be severe weather next week, if not a couple of rounds of severe weather.

    And probably some snow, too, particularly in parts of the central and northern Plains and Midwest. Nothing too unusual as we try to throw off the chill of winter and embrace the coming warmth of summer.

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


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