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Kirk Mellish's Weather Commentary

Posted: 9:53 a.m. Sunday, Feb. 14, 2010

Not a puppy love, not a boring winter 

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By Kirk Mellish

I am beginning to wonder when I might get a weekend off or any chance at a personal life. Things are piling up on me because since the big rain storm pattern and flood began back in Sept. its been one weather threat after another and I am 24/7 on the job and nothing in my LIFE is getting done. I hate it.

I have no time so I'll post some discussions from elsewhere. My forecast has been updated on this site under 5-day forecast as always its updated daily as needed. This system is similar to the early January system that didn't cause problems until the day after it fell when temps plunged, actual accumulation if you recall was minor and more on grass than highways. Like that system this is not a storm (low pressure) moving through or South of Georgia but instead a strong front dangling down from the low storm center which started up Near Hudson Bay Canada then dropped into the USA from North of North Dakota making it a "Dakota Dasher" or "Manitoba Mauler" if you need to give it a nick-name as it tracks now from Southern MO to the DC area then up to Cape Cod, MA. In all the years I've worked here I can't remember a greater than one inch snow from a cold front but my memories not so great sometimes. And the way this winter has been going nationwide, if there were to be a "first time in memory" I guess this would be the winter for it. So while I am skeptical as of now, that doesn't mean I can't be convinced by later data. As the weather changes so will the forecast up down or completely different, whatever is needed.

MID MS VALLEY TO OH/TN VALLEYS...

A VERY DYNAMIC UPPER VORTEX MAKING ITS WAY SOUTHEAST INTO THE
REGION THIS MORNING FROM SD WILL MAKE ITS WAY INTO THE LOWER OH
VALLEY BEFORE TURNING EASTERLY. GIVEN HIGH SNOW TO WATER
RATIOS...THERE IS A POSSIBILITY OF 4 INCH AMOUNTS ACROSS
NORTHEASTERN MO IN A REGION OF MID LEVEL FRONTOGENESIS ALONG THE
TRACK OF THE LOW. INCREASED PROBABILITIES OF 4 AND 8 INCH AMOUNTS
ARE INDICIATED ALONG THE OH RIVER GIVEN THE TENDANCY FOR HIGHER
PCPN IN AREAS WHERE THE LOW PIVOTS AND MAKES ITS TUIRN. THE 13/18Z
AND 14/00Z RUNS WERE CONSISTENT IN SENDING THE MESSAGE OF A
NORTHWARD SHIFT TO THE TRACK OF THE LOW...BUT THE 14/06Z NAM
BACKED AWAY FROM THAT IDEA ALONG AND SHIFTED THE PRECIP MAX BACK
SOUTH OF THE OH RIVER. THE HPC MANUAL GRAPHICS WERE NOT ALTERED
SIGNIFICANTLY BY THE 06Z NAM STILL SHOWED SUFFICENT MESOSCALE
FORCING IN THE FORM OF FGEN IN AREAS COVERED BY THE PROBABILITY
MAPS...PLUS THE FACT THAT THE 00Z NAM HAD A LOT OF SUPPORT FROM
THE OPERATIONAL SUITE AND ENSEMBLES.

AS A SURFACE COLD FRONT ASSOCIATED WITH THE LOW PRESSURE SYSTEM
SWEEPS TO THE SOUTH AND EAST...COLD ADVECTION LOWERED LOW LEVEL
TEMPS/THICKNESSES SHOULD ALLOW FOR PCPN TO FALL IN THE FORM OF
SNOW AND PERHAPS SOME SLEET ACROSS THE TN VALLEY AND INTO PARTS OF
AL/GA FROM SUNDAY NIGHT INTO EARLY MONDAY MORNING. THERE SOULD BE
ENOUGH PCPN TO WARRANT A LOW END MDT RISK EXTENDING INTO NORTHERN
GA/AL WITH A SLGT RISK EXTNENDING SOUTHWARD BEHIND THE FRONT.
THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

The system we are watching is a strong upper level system which drops down from Canada and spread a swath of precipitation into the Deep South and Tennessee valley before turning east and likely bringing more precipitation to the upper southeast and eventually turning into a good snowstorm for the northeast. This storm has been intriguing to follow on the models, because if you just look at the 850mb T charts, it looks like the whole southeast is in for another round of snow tonight and Monday. However, you have to dig deeper than that. While this may be mostly snow and accumulating snows for parts of Tennessee and the mountains, most areas I think are going to struggle with a lack of boundary layer cool air and warm nose aloft plus a possible lack of moisture in the seeder-feeder zone for dendrite growth. Most areas will see southwesterly winds at the surface and through the lowest few thousand feet of the atmosphere which will melt the snow as it falls into it. Thus as of now, outside of the mountains, I am not expecting this to be a big deal. Areas in Tennessee, northern Alabama and Georgia, and western NC and NW SC, could see the precip change to snow and perhaps pickup a quick dusting or an inch, but I just don't see more than that from this, despite the cold temperatures at 850mb. As always the weather is constantly changing so logically forecast must constantly change, they are never written in stone. I see big BUST/FAIL written over this as there are things (warm nose aloft) that could keep it more rain than anything else with little moisture left by the time it gets cold enough so there is little or no snow accumulation OR CONVERSELY due to the steep lapse rates aloft and strong omega (vertical motions) the strong lift could create scattered elevated convection (thundersnow) which would dump VERY heavy amounts in a short time over a small and unpredictable area.
 
The pattern will remain cold and active the next 2-3 of weeks. The models are showing the potential for a threat next weekend sometime in the Friday-Monday time frame, and then perhaps the threat for a big storm around 2/26 give or take 4 days. I cannot nail down a specific storm or storms or their nature this far out,  but the amplifying ridge out west will send down more northern stream s/w and it looks like the southern stream will stay active as well, so we should not lack for threats. All part and parcel of what I've been talking about for weeks and months now. This late winter is closely paralleling 1958, 1964 and 1978 so check you history books for what might happen into April.