FLIRTING WITH A WINTER STORM...
Well, it's a bit early for March Madness but the models are are exhibiting that trait later this week with a potential winter storm coming out of the southwest. There's always plenty of model discrepancy with any winter storm regarding snowfall, especially in the early stages. However, in this case we are less than 36 hours away from the event and we have a huge discrepancy in solutions from a major impact snowstorm to one with little if any pop.
Here's the system on satellite Monday night. The energy is just beginning to enter the Pacific Northwest. Eventually it rounds the Southwest and takes aim on the Midwest Wednesday and Thursday.
The strength and track of the storm is tied to a process called phasing. The polar jet containing cold air is generally separate from the sub-tropical jet which carries moisture. When the two streams can hook up and bundle their energy, you get yourself a good old fashioned storm. That's a fully phased system.
In this case, the GFS is stronger with phasing allowing a strong wave to form along a cold front that passes Wednesday and then stalls until the wave rides it northeast to St. Louis Thursday. That scenario generates a heavy deformation snow band that catches much of my area. The EURO, with much less phasing is weaker. That allows a more progressive wave that only clips or passes just southeast of my area.
Look at the difference that makes in snow totals. Discrepancies between the two models at this short time frame are quite significant...(24 inches significant) in the Quad Cities between the GFS and EURO in the same run, 36 hours before the event!
The GFS
The EURO
Examining other models, it's clear the GFS is the furthest north with its snow band. However, the 12K NAM not too much further southeast.
The GEM though is more in the ballpark of the EURO sparing the majority of my area.
Personally, I still think there's still enough time for any model to make significant corrections and adjustments. My hope is that the gaps close Tuesday and we can tighten this baby up. Trends the next 12 to 24 hours will be important to monitor. For now confidence is still far lower than what I would like to see. I'll summarize later in this post.
The Weather Prediction Center is showing this for its 1" snowfall probabilities.
Due to limited confidence, the winter storm severity index shows nothing more than minor impacts in any location. I'm sure this will go up to at least moderate impacts in some part of the central Midwest once the track and intensity is clearer.
No matter what the outcome, precipitation will start as rain. That's due to an influx of warm air ahead of the storm system. Tuesday under partly cloudy skies highs will reach the mid 30s north where there's snow cover to the mid to upper 40s south without it. Clouds thicken Tuesday night and temperatures will hold fairly steady or even go up. Wednesday the cold front enters the picture late in my northern counties. That allows another mild day with highs ranging from the low 40s north to perhaps the low 50s far south.
As the front arrives Wednesday afternoon, showers develop that continue into the evening. Around midnight colder air turns the rain to snow in the north and eventually that reaches the remainder of the south by daybreak. There could be some minor accumulations Wednesday night but if there's going to be anything significant it holds off until Thursday and Thursday night.
To wrap this up, I'm still leery of what the GFS is showing. There's no way 24" of snow falls in the Quad Cities. No matter where the heavy snow band develops, I doubt amounts would exceed 15 inches and for most it would be in the 8-10 inch range in the max band. Where that will be is anybody's guess but I suspect it ends up in the area of far SE Iowa, NE Missouri, and central Illinois. Again, it all comes down to phasing and I think by Tuesday night we should have a far better handle on how this all pans out. I do think winter storm watches will be issued for some part of the region later Wednesday (especially the far SE). Until then, all we can do is watch, wait, and hope for a more consistent look to the models. Stay tuned and roll weather...TS
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