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Wx: 2010/2011 Winter Forecasts


jeffro

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our first direct hit of the season. this started out to our south with little precip, but has developed and shifted north putting us right in the bullseye. definitely a 3-6" event.

 

I thought they were saying it is a tues-thurs thing now though

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Models continue to come in more amplified and more intense with storm…

http://forums.accuweather.com/uploads/post-13166-1294635042.gif

A large closed low is dropping southeast through the northern Rockies while a sub-tropical shortwave slowly moves east-northeast over the Deep South. A polar vortex which is attempting to shear out the southern shortwave is moving out, which should allow heights to build over the east ahead of the northern shortwave, which should cause the southern shortwave to continue slowing down.

http://forums.accuweather.com/uploads/post-13166-1294635064_thumb.jpg

By tomorrow morning note how the southern energy has slowed down and is beginning to throw moisture west to the northern upper low. Also note how the –NAO block is over eastern Canada which is allowing the polar vortex to slide a little farther east. In addition, note the amount of vorticity rounding the western upper low which will result in that feature taking on a negative tilt and slowly pulling in the southern energy and associated moisture.

http://forums.accuweather.com/uploads/post-13166-1294635077_thumb.png

Note how when the energy rounds the trough over the west the trough takes on a negative tilt and how phasing with what’s left of the southern stream occurs. As this intense vorticity (also shown above) rounds a negatively tilted trough intense lift should occur and a surface low should form over the southern Plains. These dynamics should result in a slow moving area of moderate snow to continue dropping south out of the northern Plains.

http://forums.accuweather.com/uploads/post-13166-1294635100_thumb.png

As the storm continues to amplify impressive height falls and positive vorticity advection will occur which should result in the swath of moderate snow continuing east. Right now it appears areas north/east of western/southern IA into central IL will be a bit too far north of the better dynamics for the heavier snow, although some modest lift and deep moisture should result in a period of light snow well north of here.

http://forums.accuweather.com/uploads/post-13166-1294635125_thumb.jpg

Note how the SREFs valid for the same time show a solution just as amplified as if not more amplified than the 0z NAM, with an area of very strong voriticty indicating that mid level lift will be strong enough to generate moderate to perhaps heavy snowfall rates.

http://forums.accuweather.com/uploads/post-13166-1294635150_thumb.png

Note how our system has again closed off over IL with a clear negative tilt, which favors a primary tracking over the Ohio Valley. With a clear negative tilt and strong dynamics with a deepening system I would not be surprised if the primary ends up a little bit stronger than progged, causing a slightly heavier swath of snow from northern MO ENE into central IL, central IN, and central/northeastern OH.

http://forums.accuweather.com/uploads/post-13166-1294635172_thumb.png

Note also how there is clear upper level jet support with strong upper level divergence over the upper OV and lower lakes as the system moves through. This, combined with a solid Atlantic moisture feed should result in a decent snow across much of the upper OV and perhaps into the lower lakes, as decent mid to upper level lift combines with deep moisture through the snow growth region to result in moderate to heavy high-ratio snows. The best snows will likely fall near the 850mb low track where deformation snows will likely occur along with the strongest mid level frontogenesis/lift, and where snow ratios will be best (15:1 to 20:1 ratios should be good along north of the 850mb low track):

http://forums.accuweather.com/uploads/post-13166-1294635200_thumb.jpg

http://forums.accuweather.com/uploads/post-13166-1294635216_thumb.jpg

http://forums.accuweather.com/uploads/post-13166-1294635235_thumb.jpg

Right now models are printing out anywhere from .25-.5 (locally a tad more) in a swath from eastern MO through much of IL, IN, and OH grazing lower MI, with .5-.75” over western MO and western IA. Right now am not disagreeing with the western amounts. About a 12 hour period of moderate to heavy high ratio snow should allow 6 to locally 12” to fall here.

 

East, it appears that over IL into IN that the storm will feature a few hour (4-8) period of moderate snow with decent ratios and rates of .5-1” in the heaviest snow, with a few hours of lighter snow possible on either side. Those snow rates for 4-8 hours will put out a general 3-6” with locally more. It appears the heaviest snow will get into northern IL/southwest MI but just graze those areas. Farther east into northern OH/SE MI it appears that the deform may pivot over these areas as the low begins to transfer energy to the coast, so there may be a longer period, possibly 6-10 hours of moderate snow with rates of .5-1” per hour in the heaviest snow. This will put out slightly heavier amounts, generally 4-7” with locally more, especially if any lake enhancement occurs.

http://forums.accuweather.com/uploads/post-13166-1294635270_thumb.jpg

Right now it appears that with the 500mb low tracking over southeast MI that decent PVA will occur here as the 850mb low tracks just to the south and as heights quickly fall. This supports the heavier snow moving into lower MI, so will have to adjust amounts up there.

 

Updated map:

http://forums.accuweather.com/uploads/post-13166-1294635292_thumb.png

 

interesting.

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That's weird because at 4:15pm today the NWS posted this:

 

NOW WILL OVERSPREAD THE REGION FROM THE SOUTHWEST LATE TONIGHT

AND EARLY TUESDAY MORNING. THE SNOW WILL CONTINUE INTO TUESDAY

AFTERNOON BEFORE TAPERING OFF TO SCATTERED SNOW SHOWERS IN THE

EVENING. SNOW ACCUMULATIONS OF 4 TO 5 INCHES WILL BE POSSIBLE

THROUGH TUESDAY EVENING.

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