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Saturday, February 7, 2009

Mild weather clashes with negative NAO and makes for a tough call for Feb 12

This is a date we have been singling-out for a few posts as a time in which the pattern will turn active. By the looks of things this appears to be a good prognostication but the specifics regarding the storm on February 12th remained veiled in a cloud of fog and all we can do is lay out a few possibilities and wait a day or two. Until then we can expect temperatures to take a few very sharp up and down turns. It will start when the mild weather gives way to snow showers and a gusty and chilly wind on Sunday. The ski day Sunday could very well start with a little corn and end with a little powder if we are lucky enough to get a heavy snow shower or two during the middle part of the day.

February 12th and the varying scenarios
Temperatures will remain chilly Sunday night, Monday and Monday night but will make a quick recovery Tuesday as readings by then approach the freezing mark. Wednesday could the turn out quite balmy with temperatures reaching the 40's on mild southwesterly breezes. We have made mention of the most dominant feature on the North American weather map - a block in the jet stream which encompasses the vast area from eastern Canada through the Davis straights and into Greenland. This block represents an expansive area of unseasonably warm and stable weather in that part of the world but it also has significant ramifications on our part of the world. It is a feature partly to blame for the mild weather but west to east moving weather systems will have a tough time penetrating this feature with any success and they are thus forced to take "the Holland Tunnel" and dive underneath. Such will be the case with the February 12th case or at least I think. The actual specific track remains important and is still very much up in the air. The amount of available cold is also very important this too remains a question since only a limited amount will be present upon the storms arrival on Thursday. A few days ago I made a guess that the storm may produce some rain then some wet snow and then powder snow and our trusted friend the European model is suggesting such a scenario or something close to that anyway. Guidance from other models have varied from run to run but have been somewhat more pessimistic including more warmth and more rain.

President's Day and the week that follows
February 12th will mark a temporary end to the mild weather. The cold that follows will be far from severe as the above mentioned block will actually act as an arctic blockade. The mostly Canadian air that will cover the region should ensure that precipitation through February 21st stays in the form of snow. The track of storms in this period could be rather suppressed since weather systems will be forced to go farther and farther underneath the large jet stream blocking feature. Since there will be multiple systems crossing the country between the 14th and 21st of February it is reasonable to expect a fruitful outcome from one of them at least either during the President's day weekend or the week that follows. We have gotten some late inning drama from a few storms this year and perhaps Presidents week will provide an opportunity for more.

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