Ah, March on Cape Cod...

Mon 3/17

We dodged a bullet this weekend. The powerful ocean storm spinning in place several hundred miles east of Cape Cod is now down to near 970 mb and is producing hurricane force winds. Had that system been tucked in a bit closer to the coast, we'd be cleaning up from one of our bigger storms in recent years. But, such is obviously not the case and instead we are on the far western periphery of the storm, with just some gusty north winds and cool temperatures in place. This storm has helped to drag down a fairly chilly air mass, with temperatures several degrees below the seasonal average. Thankfully, the March sunshine is doing its best to counter the wind and chill and make things feel a tad warmer than the actual air temperature.

Unfortunately for those looking for an extended period of nice weather, our next storm system is already on the charts and will be moving into the area by mid-week. This system is currently producing heavy rain and thunderstorms over the plains and into the Mississippi River Valley, with snow to its north. It's getting to that time of year where each one of these storm centers is a potential severe weather producer - and this will be no exception, with another outbreak of severe storms expected today, tomorrow and Wednesday over the central and southern US.

The big central US storm will head northeastward toward New England during mid-week, sending a sizable slug of moisture up into the region on Wednesday. Precipitation looks to come in two waves - the first very late Tuesday night into Wednesday midday, the second Wednesday afternoon and night. The initial surge of moisture will be in response to warmer air lifitng northward into New England and riding up and over the existing dry, chilly air mass in place. Should this precipitation arrive early enough, it's possible that it starts out as snow or a mix of snow and rain. In fact, some model guidance allows for a couple of hours of frozen precipitation. This will be highly dependent upon precipitation timing, however, as southeasterly winds will be taking hold and temperatures will be on the rise. At the current time, the worst I would anticipate would be an hour or two of snow, sleet and rain mixed before things switch over to all rain. The second round of rain (there may not be a real break in the action, just a decrease in precipitation intensity and coverage) will come later Wednesday afternoon and evening and will be associated with the low pressure center nearing the region and its attendant cold front. There could be a few downpours in there thanks to a good feed of moisture from the Gulf of Mexico. This looks like a 3/4 to 1 inch rainfall for the region.

The low pressure center responsible for the mid-week rain will intensify as it lifts into eastern Canada, becoming a fairly strong storm center to our north. It will also transition into a closed, vertically stacked storm center in response to high latitude blocking (essentially an atmospheric traffic jam that prevents systems from moving). This set-up will initiate a strong northwest flow across New England to close out the week, bringing down yet another chunk of chilly air from Canada. So chilly in fact, that despite dry air, highs Friday, Saturday and Sunday may only be in the upper 30s to near 40°F (by March 20th, average highs have reached 45°F). We'll have to track a clipper dropping through the base of the trough over the weekend, but current indications are this remains to our south. Either way, the high latitude blocking will be an interesting feature to watch evolve next week and through the second half of March as it could yield some potent east coast storm centers. This atmospheric set-up is actually favorable for early spring snow storms...