Thursday, February 26, 2009



"I keep working my way back to you, babe."
- Frankie Valli and the Four Seasons

UPDATED SYNOPSIS: THU FEB 26 - 6:45 AM. The period Saturday through Monday will feature several low pressure systems moving northeast from the Tennessee valley. As is being reflected in your NWS local forecasts, any or all of these systems have the potential to deliver rain, snow or both. The KEY factor raising concern is PLACEMENT OF THE HIGH. As quoted many times on this site, "predict the High and you predict the storm" a rule attributed to a legendary Penn State meteorology professor. Indications are that one of several high pressure cells in southern Canada may be positioned to supply adequate cold air as this projected system moves from the US southeast.

The forecasting rule to be applied for this storm is called "short range" which is a fancy term for "nowcasting" which is a euphemism for "we're not really sure what will happen, so just keep your eyes on the radar." I can understand the consternation facing NOAA forecasters, as this transition period into Spring is a historically tough time to accurately nail down snow potential. My analysis will have to wait until I complete several coursework projects this week. Until then, perhaps you can interpret these snippets from the HPC discussions of Feb 24-25 on our storm potential (edited for clarity):
HPC PREFERENCE IS TOWARDS AN BETTER AGREED UPON ENS MEAN OF BOTH 00Z/12Z GFS AND 00Z ECMWF AND 06Z GFS OF A MORE OFFSHORE SOLUTIONOF THE SFC LOW PRESSURE COMING OFF THE NC AND VA CAPES EARLY SUNDAY AND MOVING NWD TO THE NEW ENG BENCHMARK MON AND QUEBEC TUES. HIGHEST CONFIDENCE IN THE COLD AIR PLUNGE AND VERY WINDYCONDS BEHIND THE SFC LOW. THE MAIN BAROCLINIC ZONE WITH THIS SYSTEM WILL REMAIN OFFSHORE ONCE THE SFC LOW MOVES OFF THE MID ATLC COAST. HOWEVER DEFORMATION ZONE SNOW AND SNOW SQUALLS..WILL BE SHORT RANGE PROBLEMS FROM POSSIBLY AS FAR SOUTH AS ERN VA NWD INTO NEW ENG WITH THE SYSTEM WITH SURPRISES LIKELY SOMEWHERE IN THIS REGION. TYPICAL LARGE AMOUNT OF UNCERTAINTY FORECASTING THE LOCATION OF THE MID LEVEL CLOSED LOW CENTER AND THIS WILL TAKE ANOTHER DAY OR MORE TO HAVE ANY CONFIDENCE IN ITS LOCATION.
PREVIOUS SYNOPSIS: FRI FEB 20. No doubt takes some of our readers back a ways, and I select it to represent what this winter seems to keep doing. For the past 3 winters in the Mid-Atlantic, computer models (and indeed, the atmospheric trends which drive them) in an almost sadistic way keep throwing bones to the powderhounds... only to have those dream storms live on, but only in our dreams. While it's obvious winter conditions have returned, a never-say-die La Nina coupled with an unfavorable North Pacific trend compounded by a sporadically negative NAO mean the general rule still applies. What's the "general rule?" Easy: If there is potential for a storm to quench the Mid-Atlantic snowdrought, once curtain time arrives, the atmosphere will find a way to "misalign" and truncate that potential. I'm certain to be in good company with this philosophy among the skeptics! Of course if the PNA/NAO trend reverses, we're back in business.

WANT THE ONE SENTENCE SUMMARY? Except for the Saturday night-Sunday tease, there are no snow or rain threats on the horizon until next Friday: Just cold and windy trending to mild between now and then.

Powderhounds (a term coined here several years ago) are right to remain doubtful of any storm possibility right until they see the whites of it's eyes, er flakes. That said, the GFS and European models are again advertising another trip to Fantasyland from Friday 2/27 to Monday 3/01. Taken literally, the outcome would be no different than many PREVIOUS fantasy storms: The usual 24-36" of interior snow, with oh say 12 inches in the big cities. As with all previous storm monitoring this season, I'll take a closer look on Monday. Until then, you are welcome to track, analyze and comment accordingly on these comparable projections from the GFS, European.

In conclusion, Spring-a-lings know the true meaning of today's title: Regardless of what distractions winter continues to bring up, SPRING is working it's way back to you, babe.

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