NEW THOUGHTS ON THE HALLOWEEN SNOW EVENT...
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WINTER WEATHER ADVISORY #6
As we talked about earlier a fast moving snow system will bring a slushy round of snow to most of my area tonight. Accumulations should generally end up in the 1 to perhaps 2" range. Just enough to let you know the reality of a long winter is ahead of us.
The focus of this post is actually more centered on the second wave of energy which promises even more snow just in time for Halloween. Unfortunately there are still some details to resolve in terms of the location and eventual amounts.
The trends the past 24 hours are this.
There are issues regarding the phasing and intensity of the energy which forms the Halloween system. On the satellite you can see two distinct pieces of energy. The one in question is dropping in from Canada and the northern Rockies.
The EURO and CANADIAN show less phasing which results in a system that's sheared and weaker. While the EURO has a closed low the trough has a positive tilt. The impacts of this are rather complex but in essence it means QPF is down meaning less potential for heavy snow. The snow is also further south because of a weaker surface low limiting the push of the deformation band.
The GFS on the other hand has been showing a more intense upper air low (nearly negative tilt) and better surface reflection. The system is venting more. That makes a difference with heavier a heavier snow band that falls a bit further northwest. You should be able to see it here.
As you can see it's a pretty subtle difference but it will end up being an important one. Here's what the GFS is showing for snow. A tight Iowa and regional perspective. This includes what falls tonight.
Now the less aggressive and further southeast forecasts of the EURO.
As you can see the differences are not huge but they do make a big difference as to where the heavy snow band sets up in my region.Something else to account for is that the GFS tends to be too wet and I think its solution is high on totals. In fact, i think both the EURO and GFS are high on amounts due to marginal temperature and warm ground that will cause quite a bit of settling.
With more than 60 hours to go before the event I would lean more toward the EURO output. I think we will see some movement towards that on the GFS in the next 24 hours.
I'll have something new on the trends this evening. One last thing, the NWS ins La Crosse did issuer a winter weather advisory for parts of NE Iowa and Wisconsin tonight. If you are traveling up that way there could be some tricky travel. I'm not expecting any serious issues this far south. Maybe a few slick spots. Something to watch.
That's if for the here and now. More to come. Isn't if great to talk about snow for Halloween! Roll weather...TS
P.S. Here's the latest radar showing precip. beginning to develop out west.