Sunday, February 1, 2009

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PRE-GAME UPDATE: SUN FEB 1 - 6:45 PM. There is much going both in atmospheric analysis and in the Foot household. I have reviewed some data, HPC discussion and current upper air 500 mb charts. There's no change to the forecast posted below, the game is still on, but I have one suggestion: send someone from your household to the store DURING the Superbowl. Why? No NWS office is anywhere close to raising a Watch, and today's false warmup will completely remove any suspicion of significant snow in less than 48 hours. This will not be similar to March 1993 as originally feared, but it could be quite a surprise to some on Tuesday morning! Especially those who plowed through their food supply at the ballgame party. Teachers: Lesson plan info posted, links to be added shortly, thanks for being patient.

KICKOFF STATEMENT: SUNDAY, FEB 1 - 6:45 AM. Welcome to the start of what may be a "Fabulous February" for powderhounds and storm watchers alike. Changes in official forecasts over the past 2 days demonstrate the value of relying on the laws of physics, because despite what mathematical formulas may project about the future, one must never abandon the most important source of data: reality. That being said, I believe that physics has turned in our favor. Result: the GAME is ON, and I'm not talking about that other game.

WEATHER AND IMPACT SYNOPSIS: Several upper level factors are converging on a solution that many on this site have been anticipating for some time:
(1) Deep tropical moisture ejecting from the East Pacific into the Gulf of Mexico (could this in fact be the arrival of the MJO Phase 1 that I never explained?)
(2) A negatively-tilted upper level trough over the Eastern seaboard US, due in part to a decreasing North Atlantic Oscillation, a slightly rising Pacific-North American Index.
(3) Several short-waves embedded in the upper level flow moving southeast from western Canada. These short-waves will travel the flow, and begin interacting with a surface low which has formed in the Oklahoma panhandle.

The combined effect of these three factors will use the Gulf moisture to moisten the surface low that was touched off by the short-wave. (6:45 PM update: I realize some forecasters are discounting the Gulf moisture, I but think based on even just general cyclonic can this moisture go anywhere but up into the flow. It's not just going to sit there. Indeed, I believe you can see it interacting with the flow already on the water vapor. )
6:45 PM clarifications: A new low pressure should take shape in the northern Gulf of Mexico Monday, and direct newly energized moisture into the upper level flow. With the base of the trough located over the coastal Mid-Atlantic, ANOTHER new surface low should form there as a reflection of the short-wave and incoming moisture. Just like an old Joe Paterno play, this low goes "straight up the middle" but in the process dumps moisture westward in doing so, partly because is caught at base of the trough.

Result: Slow-moving and localized coastal storm. Thus, my original forecast posted yesterday remains intact: Rain Monday mixes with and changes to snow, becoming heavy overnight before ending Wednesday. Liquid equivalents could be anywhere between .75 and 1.00 inches for much of the region. You can do the math to determine snow amounts. As for school, this scenario suggests Tuesday may have to be punted, but I would not put Wednesday on the bench just yet.

WHY THE BIG CHANGES? It has been hypothesized by Accuweather forecasters that an air traffic restriction over parts of Alaska due to an impending volcano eruption may have led to a gap in data. Concurrently, shortwaves that would be responsible for spawning the storm in the Gulf were moving across this area at the very same time. It is coincidence? Certainly other factors could explain the huge 300 mile shift in many computer models since Friday, but there do not seem to be any the NWS is willing to acknowledge. I guess we can just chalk it up to physics. Note to the analysis team: I am out today until at least 12:30 PM, so no updates until after that. So enjoy THIS game, and the "other one!"