Review of Winter Storm: February 23-24th, 2012

Epilogue 2/23-2/24/12 Storm:

Thursday 2/23 model runs on the system pivoted the storm further south than my initial projection across Northern Indiana and Northern Ohio.  In accordance; I raised snowfalls to 4" - 8" rather than the 2"- 4" with pockets of 3" - 6" forecast a day earlier on Wednesday. In retrospect, the low tracked closer to my original thinking; south of Tuesday's model projections over Illinois/Indiana but wound up further north of Thursday's model projections, over the corner of Southeast Lower Michigan early Friday. Just as important however, was the track of the upper air support which /vorticity max/ which tracked right across Southeast Lower Michigan. This was northwest of the surface low and provided maximum lift and dynamics for the system. Heaviest snow generally falls to the left (or north-northwest) of the vorticity center which was across Saginaw Valley into the Thumb (where 3" - 5" of snow with maximum pockets of 6" was observed). Heavier amounts were observed further northwest into central and northern Michigan.             
                                                      Snowfall Amounts & Map from DTX

What was learned in this event?

Just because they are the latest model runs (versions); doesn't mean they are the most accurate. Sometimes your earlier and initial analysis on a snow forecast is the better one and you must have faith to stick with it; even in the face of "model contrariness". On that premise, I failed by changing my original snowfall amounts Thursday. On the positive: I alerted the public of a storm that would impact Southeast Lower Michigan and the Great Lakes days ahead of the storm. The storm did develop and affected residents of Southeast Lower Michigan; in a winter that has been virtually "stormless"; see initial 2/21/12 blog below. 
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Blog: 2/23
Latest indications continue to show the winter storm first written about here on Tuesday will indeed affect all of Southeast Lower Michigan as she tracks eastward and then northeastward through the Northern Ohio Valley. Nearly all the models now paint an intensifying cyclone, shifting from southern Indiana northeast through central Ohio and then toward the Cleveland area by Friday afternoon. This more southerly track is in accord with earlier thinking and then some with the track now proficient for the likelihood of heavy snow across much of Southeast Lower Michigan.

While the track will be south of Southeast Lower Michigan, enough warm air will be drawn up ahead of the system to bring rain or rain mixed with snow up into the region toward sunset across the far south and this will move northeast;  encompassing all of Southeast Lower Michigan during the evening hours. Much of Southeast Lower Michigan should receive 4" to 8" of snow with this system with the highest amounts likely north of I-94. Heaviest snow inducing lower visibilities should occur toward the midnight hour and continue through the early morning hours.

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Earlier blog 2/22/12 of model and my positions:

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Initial Blog: 2/21

Latest model trends are converging on an intensifying Eastern Great Lakes low pressure system late Thursday into Friday. This system will be brought about as strong Pacific energy aloft aligns with/and phases with Polar energy diving in from central Canada.

On to the particulars; Strong energy aloft at varying levels is projected to dive east southeast from the Pacific into the Midwest by late Thursday. At the 250 MB /35,000 Ft/, the core wind max is expected to be at least around 130 knots! This upper level energy will proceed generally east and align itself along a potent stationary frontal boundary that will form and extend from the southern Great Lakes east into Pennsylvania and then, off the East Coast. At this time it looks a though a few waves of low pressure will be induced along the front while rippling east with time. As this scenario becomes more established across the southern Great Lakes and northern Ohio Valley; additional moisture will be drawn northward from the Ohio Valley and then subsequently, westward from the Atlantic. This moisture, in conjunction with the strong upper level dynamics and surface boundary, will be aiding and a betting with the development of the main Eastern Great Lakes cyclone or low pressure system by Friday. How quickly this above scenario takes place will have a lot to do with the final outcome of the weather to affect Southeast Lower Michigan.

On the projected 7 pm Thursday weather maps below; 

Map 1 from the GFS model denotes the 250 MB wind jet at 35,000 feet and speeds. The first jet core /1/ will help with the initial development of our frontal boundary and low pressure system as phasing commences; while the second jet core /2/ comes in from the rear to deepen and intensify the system during the day Friday. The second GFS map places the main developing low pressure near the tri-state area of Michigan-Indiana-Ohio also at 7pm Thursday. I feel the GFS may be too far north with the main surface low and its track could be further to the south; over the northern half of Indiana and Ohio rather than the border area.

                                                                          Map - 1

                                                                              Map - 2

Of course, this a projection of a few days out and therefore will be attentively watched and analyzed as updates from various models zero in on this system. Not only do the usual problematic winter storm specifics apply here; such as track and available moisture but also the temperatures in the lower levels of the atmosphere and surface which will dictate initially the amount of rain and snow and later, potential snow accumulation. At this time is does look as though the worst of the system will be east of Southeast Lower Michigan but it still bears watching, so stay tuned.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian