A strong positively tilted low pressure trough will push in the western part of the country over the weekend and slow the progression of a cold front sliding across the mid part of the country by early next week. The recent model trend from the 12/2&3 - NAM /12z and latest 00Z/ indicate the front will push just east of Southeast Michigan and then stall or slow to a crawl while extending southwest into eastern Oklahoma and western Arkansas.
Weak waves of low pressure along with a surplus of moisture will ignite a streak of snow and rain which will extend from Texas into the southern Great Lakes by early next week. Snow accumulations could be notable if the front stalls long enough as it gets hung up under the strong southwesterly jet. The latest 12/3 - GFS /00Z/ model also has the front slowing but the best moisture still hangs just to the south and east of Southeast Michigan. Stay Tuned.
This is a very recent development in this system as the models had for several days, pushed the entire boundary further east with little overrunning precipitation under the baroclinic zone. This system is a "sling-shot" type of system I talked about in my Outlook and were one of the more prevalent type of snow makers for Southeast Lower Michigan during my analogue winters.
From the Outlook
I mentioned the "sling-shot" pattern in my earlier discussion in regard to the jet stream. Plain and simple, by looking at the storm track map you can see how the Arctic/Polar jet prefers to take a dive southward (southeast or even southwest) to the lee of the southern Rocky Mountains in these analogue winters. This in turn, loads the storm "sling-shot "and shoots it east northeast toward the Great Lakes and then "somebody gets stung in the....";-). Who gets stung remains to be seen as the pattern evolves.
Check out the 500MB and Surface and you can visualize these vort maxs pivoting around the Southwest Trough and being "shot" northeast toward the Lakes. It is still very early to run for the snow shovels and also (like stated in my most recent post), the models have some trouble with forecasting the jet that feeds these systems from the Pacific, so this is just a heads ups at this time!
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**Update**
From above-
The latest 12/3 - GFS /00Z/ model also has the front slowing but the best moisture still hangs just to the south and east of Southeast Michigan. It is still very early to run for the snow shovels and also (like stated in my most recent post), the models have some trouble with forecasting the jet that feeds these systems from the Pacific, so this is just a heads ups. Stay Tuned.
**All recent models trends have now (12/4) shifted back to the earlier GFS/Euro trend consensus of keeping the axis of precipitation pushing slowly east as colder but drier air infiltrates Southeast Lower Michigan. While some light snow is still expected on the backside of this system, amounts will be light. The upper low spun up over the Southwest will also shift east with time and will be moving into the Ohio Valley later in the week but at this time, the system is slated to stay south of our region.**
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Earlier NAM 12/3-00Z Model Run Fri Night for Monday Night @ 72hrs
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian
