*SIGNIFICANT NOVEMBER SNOWSTORM* 7:00PM Sunday, Nov 9 2014 An early season significant-impact snowstorm will arrive in Wisconsin tomorrow morning. Models once again have trended stronger, snowier and further north with the heaviest accumulations over the last 24 hours. RIGHT NOW: Not much is happening yet. The 850 mb 0C temperature line will move into Wisconsin as precipitation develops Monday morning. North of this isotherm precipitation in the form of snow is expected and south of it, rain. Snow accumulations of 8-15” are forecast across most of northern Wisconsin Monday morning and ending Tuesday evening. The heaviest accumulations will likely be along or slightly north of an axis from Cumberland to Park Falls to Land O Lakes to Marquette where 10-15” are expected. Locally higher accumulations are possible. Precipitation is expected to start Monday morning around 6AM in the west and spread quickly across the rest of Wisconsin (snow north, mix/rain south). Northern Wisconsin will stay as snow all day Monday and it could come down fast with snow rates approaching 1.5” per hour. Dry air will sneak in at times Monday late afternoon and evening before filling in for the second and final round of accumulation. The duration of the evening weakening trend due to dry air, location and movement of the main snow band, and distribution/balance of snow outside of the main band are factors that could reduce/enhance accumulations. A sharp gradient in snow accumulation is anticipated over central Wisconsin as the precipitation moves in from west to east. Warmer air will tickle the southern edge of the precipitation shield leading to a mix of snow and rain south of an Eau Claire-Marinette line. This line could shift slightly north as we tippy toe closer to the event. Southern Wisconsin will see scattered rain showers much of Monday and early Tuesday before switching over to snow later Tuesday. Little to no snow accumulation is expected until Tuesday evening where one or two inches of additional accumulation are possible. Other problem areas include the lake Michigan shoreline where warmer air will lead to more mix/rain precipitation. This is especially problematic on shoreline north of Green Bay where snow accumulations could really be cut down. DISCUSSION I was concerned Saturday evening that the map I had made earlier was a bit too conservative. It was, however I’m still not convinced that we will see widespread super high 18”+ accumulations advertised by some models with this system. Quite often we see the “models bloat” in terms of QPF within the last 24 hours of the event resulting in very generous estimations. I have a feeling current snowfall predictions will hold down and will likely need to increase them along a very narrow corridor coinciding with the most preferential movement of the snow band. One more thing, the operation 11/8-12ZGFS was STILL on the southern end of the ensemble spread suggesting a northern trend may still occur. NEXT UPDATE: 6:30AM MON AUTHOR - JUSTIN POUBLON
Posted on: Mon, 10 Nov 2014 01:17:50 +0000
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