Fun Forecasts Ahead

Thursday 1/24/08

1. Snow Tonight - It's not the developing Mid-Atlantic storm system that raises concern but the northerly wind it generates tonight. This wind, in combination with a brief shot of cold arctic air moving in behind the storm, raises the concern for ocean effect snow. What are the parameters we see? Well a north to even north-northeast wind will extend from the surface all the way up to nearly 10,000 feet in the atmosphere for a solid 8 to 12 hour window of time tonight (beginning near dinner time and lasting until dawnish.) This well-aligned wind will coincide with cooling temperatures both at the surface and aloft - with temperatures at 850 mb (5000 feet) dropping to -13C to -14C overnight. This will generate a 16 to 17 C difference in temperature from the ocean surface to the air aloft, well above the required thrreshold for ocean induced clouds and precipitation. We've certainly seen ocean effect snow across the Cape with less favorable conditions. While computer guidance only shows a few hundreths of an inch of precipitation, when talking about ocean effect snow, that miniscule forecast can be a good signal for a healthy event. Oh, and this go around, the snow should work further west than the past few times, as a more northerly component to the wind will allow snow bands to drift westward to the canal for a time. Don't be surprised to see the National Weather Service issue a Snow Advisory for the Cape later today.

2. Something interesting for later in the weekend? - It appears as though an ocean storm will form southeast or east of Cape Cod this weekend and sit and spin into early next week as the feature becomes becomes vertically stacked and stalls somehwere in the western Atlantic. The question is where exactly this happens. Is it far enough east to not pose a problem or is farther west and place us more squarely under its influence? The European model is now sitting at 3 consecutive runs with a low placement that would bring unsettled weather westward and very near the Cape as the northwest side of the storm brushes the region. With high pressure locked into to our north and west, this set up would favor gusty north to northeast winds and perhaps some periods of snow. The GFS model is further east as is the Canadian model and neither would be a major problem. The often overlooked (perhaps for good reason) NOGAPs model is quite threatening and would be a flat out walloping for us here on the Cape. So could this be one of those "surprise" situations where the weather is far different down here on the Cape (stormy) as compared to Boston and points north and west (quiet and pleasant)? We shall see...