AM All Zones Update on Potential Snowstorm Late Wednesday Night into Thursday

A storm system tracking over the Great Lakes, will bring some periods of rain with possibly freezing rain over Interior this morning. Some very mild and record breaking temperatures also possible on Wednesday. But more attention is already on possible snowstorm starting late Wednesday night and last into Thursday. Details are still yet to be ironed. But confidence is growing on moderate to significant snowfall for parts of the area.

The general trend on much of the model and ensemble guidance over overnight and early Tuesday, is for a deeper trough with polar jet and pacific jet disturbances phasing, along the East Coast. This largely due a stronger ridge over the Western US. This will result in a wave of low pressure develop to the south, along cold front that will push through the region on Wednesday. Latest ECMWF and GFS models show a more intense low further north bringing a more significant snowfall to much of the region. Latest ECMWF ensemble guidance has 40%> probability for more than 3″ of snow near the I-95 corridor and areas south east

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A dual upper-level jet and mid-level shortwave energy will support a lot lift some precipitation to expand further northwest. So a moderate snowfall still occur especially near the coast. These synoptic features also causes us to believe a little more, that the surface and mid-level lows will wind up closer to coast, with a stronger thermal gradient somewhere likely along or on either side of the I-95 corridor. This could lead to some strong frontogenesis and heavier banding with dynamic cooling by Thursday morning. At this time, we are thinking preliminarily, snowfall totals 4” to 8” could be widespread over the region, with some locally higher totals up to 10” possible.

Although as usual there are some uncertainties, that may keep us from forecasting bigger snowfall totals. First one is in regards to how much phasing will occur, close to coast. Less phasing, will lead to weaker/farther south storm and thus lower snowfall totals. A large east-based blocking ridge will be over parts the Kara Sea to Greenland. This not quite an ideal pattern for huge east coast snowstorm. But as this will be sufficient for some slowing down of the flow, more phasing closer to region.

Early morning 6z NAM model strong mid-level frontogenesis just west and along of the I-95 corridor, with low pressure hugging the coast more.

Early morning 6z NAM model very strong mid-level frontogenesis, just inland with low pressure hugging the coast more.

Another uncertainty, is some rain or wintry mix that could occur at the onset of precipitation, with a warmer antecedent airmass. This could lead some lower snowfall totals, in parts of the area. However, more phasing with the low near or just inside the  40/70 benchmark, will likely lead to more cold-air advection and dynamics for heavy snowfall rates, across the region by Thursday morning.

Will be monitoring model runs later today and tonight for more trends tonight. This storm should exit the region by Thursday evening. Friday appears to be cold and dry. A weak clipper passing through the Northeast, may bring some snow showers on Friday night or Saturday. Stay tuned for another zone forecast update on this system, later today. A snowfall map with more details on snowfall totals across the region,  may be issued with the zone forecast by this afternoon or evening.