Un extrait sur le forum d'ACCU..cela pourrait expliquer en partie ce qui se trame : The 00Z NAM and GFS tonight are showing the potential for a major to history winter storm over the forecast area Monday night into Wednesday morning. So what caused the change in the models? The introduction of the additional energy from the northern Pacific in the form of the jet streak that I discussed this morning has been introduced. This has profound changes in the way the atmospheric pattern develops. The ridge over the West is more amplified, which leads to a sharper and more concentrated trough. The position of the trough produces less interference for the 50/50 low and negative NAO blocking influence on southeastern Canada. As a result, the high can now ridge into the Northeast and northern Mid Atlantic on Monday night, which drives the low level cold air into the Coastal Plain. Good bye boundary layer issues. Meanwhile, the 50/50 low slows down the entire pattern and allows the short wave to tilt negative at a near perfect timing. The result? A significant snow storm with the potential of 6 to 12 inches or more of snow. Now, thats what the two models say. I think that this solution IS valid, however I would like to see some more satellite data and model date before making a major update. There is a good chance that I issue an upgrade in the Alert Status tomorrow morning.