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    Series of Disturbances to Bring About Steady Shift to Cooler Weather

    10/15/2013, 8:10:48 AM

    Tuesday, 11:45 a.m.

    A potent storm has been moving steadily into the Midwest overnight and this morning. There has been quite a bit of rain with the storm so far, particularly in the Dakotas and Nebraska. It is a warmer storm overall that the one that brought heavy snow to the Black Hills about 11 days ago, but there has been some snow there this time around as well.

    From this point forward, the storm will be in a weakening phase. The intensity of the precipitation will drop off considerably in the ensuing 24 hours, as the upper-level low associated with the storm begins to open up and weaken. Rain will be more sporadic across the Great Lakes and Ohio Valley tonight.

    There may be an enhancement to the precipitation coming out of Texas, though, as some of the moisture associated with the decaying remains of Octave feed into heavier rains and some thunderstorms from central and northern Texas into northernmost Louisiana and southern Arkansas. That little wave will then ride along the front through the Tennessee Valley tomorrow and zip into New York state and northern New England tomorrow night before exiting Thursday morning.

    Right on the heels of that feature will come another around the base of the upper-level trough that is trying to become established in the middle of the country. Here's the 500mb forecast for tomorrow evening:

    The cold front itself will get hung up from southeastern New England through the mid-Atlantic down to the western Gulf Coast by Thursday morning, so as the next upper-level trough rounds the base of the trough, it will moisture right back to the front and cause rain and some embedded thunderstorms to break out tomorrow night and Thursday from the lower Mississippi Valley to the lower Ohio Valley and Appalachians. The same 12z Oct. 15 NAM model forecast for Friday morning has that wave bypassing southern New England:

    With the trough becoming more fully established by Friday, the ridge behind it will strengthen considerably, as you can see on the corresponding 500mb forecast:

    In response to that, there will be at least a couple of additional disturbances coming down in the north-northwest flow aloft into the Rockies and the Plains. One of these may bring some snow to Denver late Thursday night into Friday morning, and eventually it will cause more rain to break out in the southern Plains later Friday and Friday night.

    This wave of low pressure may come in two pieces, one tied more to the southern stream moisture and another that will roll across the Midwest and through the Great Lakes. Either way, it will delay the arrival of the truly cool air into the East by another day. However, as the entire trough finally rolls through Sunday, the cool air will follow, setting us up for a week next week that is likely to have a lot of cool air from the Rockies to the East Coast.

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


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