3/27/12 Forecast Update

Mar 27, 2012

The forecast for storm initiation due to weak forcing is still the big issue with todays setup. Shear is there, and instability (albeit in a very narrow corridor) is also there. The big fly in the ointment continues to be the lack of any real appreciable forcing. There is not much of a wind shift with the front. Still, if a storm can ignite, CAPE values approaching 2000 should compensate for the lack of forcing. Overall the previous forecast written here still looks to be on track.

Here are some various model solutions for simulated relfectivity. As often is the case with “big if” scenarios such as what we are dealing with today, the solutions vary wildly.

12Z NAM valid 3z (10pm:)

14z RUC valid 2z (9pm:)

12z 4km wrf valid 3z (10pm)

14z HRRR valid 4z (11pm)

Which one will win out? It is tough to say, each model has its strength and weaknesses. It is up to a forecaster to understand the setup, analyze the data and make their own call. However typically you would see better model agreement than this during the day on a setup. This lends to an overall low forecast scenario. I tend to side on the more conservative solutions due to issues with the setup. I have seen these occluded low/weakly forced cold front setups under-produce more often than not. Still though, the potential for severe storms is there, and everyone needs to pay attention to rapidly weather changing conditions.

Should storms form, they will likely do so near the IA/IL border and slide eastward. A thin band of storms close to the front can be expected with hail and winds being the primary threats. This would probably take place closer to dark. Storms will probably only have a short window to produce severe weather as instability will decrease with the sunset. Currently the best chance for severe appears to be west of I-39 and south of I-88 (see map in previous forecast.)

Stay tuned to the facebook page fore more updates as the event progresses.



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