Snowstorm Still Looking Good for Parts/Possibly Most of NE

[donsutherland1]

Earlier today, when the evil duo of the GFS and UKMET were conspiring to dash the hopes of snowlovers in the northern Mid-Atlantic and Northeast against the sharp rocks of suppression, I had <b>noted</b>:

<i>While there has been a decided trend on some models in favor of suppression, one would do well to recall that a similar trend had seemed to establish itself a few days prior to the Presidents Day Snowstorm e.g., 2/12 18Z GFS--ironically at roughly a similar distance from the event in terms of timing. Moreover, bear in mind that this was also a question of two waves. Of course, there were some differences, too, but the important point is that there is uncertainty and fluctuations in the modeling might not be revealing much of value at this time.

Overall, at this time of uncertainty, one is probably better served by holding with the more consistent models than those that have been most erratic especially as some model support (e.g., the GGEM) for a decent event in the Mid-Atlantic and Northeast remains intact.</i>

A look at the new runs of the ECMWF and GGEM assert that the idea of at least several inches of snow for the big cities from Philadelphia to Boston (though I still believe at least some of the precipitation there will fall in the form of mixed precipitation or rain) and 6" or more in interior sections continues to look good. If anything, odds for the big cities receiving an invitation to the party of heavy snowfall are increasing.

In the same camp of signficant snowfall also is the 0Z run of the ETA Model.

So, there remains plenty of model support for the snowstorm idea.

Perhaps even more important are some developments taking place in the actual weather:

1) A look at the 500 mb height anomalies suggests that there will be no overpowering suppression of the potential snowstorm, meaning that the ECMWF track is about where one would reasonably expect the storm to track.

2) Above normal temperature anomalies have cooled to near normal in eastern Canada. This is important as this will be the source region for cold air to feed the possible snowstorm. The important point here is that there will be sufficient cold air but not so much that the storm would be suppressed too far to the south.

3) From an evolutionary standpoint, the scenario is beginning more and more to resemble in a rough fashion the scenario of the Presidents' Day 2003 snowstorm--two waves, similar track, etc. There are some important differences, but none of those differences argues for suppression.

4) The 500 mb pattern is quite different from that which prevailed during the March 4-6, 2001 event. First, the low height anomalies are not anywhere near as elongated as existed at that time. Second, the above normal height anomalies over central Canada are somewhat farther to the west and lower than those of March 4-6, 2001.

All in all, my confidence that at least parts of the northern Mid-Atlantic and Northeast will see significant snowfall is good. My confidence that the aforementioned big cities will see at least several inches of snow is also good.

Thus, for some, to borrow from Po Fei Huang's "After A Heavy Snow," "A bank of whiteness" is all that some will see by the time the snow stops falling.

[Dave C]

It's been interesting watching local mets in Boston area. They flip-flop each day with models leaning one way then another. :-? I remember many storms in our past (Jan 96, Presidents day storm etc.) which models picked up on systems 5-7 days in advance then would flip-flop each day until about 48hrs. till game time before coming together. One local met (Tim Kelly NECN news) has been staying consistent, not writing it off then doing 180 deg. turn the next day.

[donsutherland1]

Dave,

The situation has been very complicated and the risk of error is therefore quite high. Some of the models will have difficulty in assessing given situations. That's why the synoptic pattern is important to study (as is recognizing normal model biases). That way, one can better judge whether the model guidance is/is not reasonable (to me, the idea of suppression seemed to be a low probability matter hence I didn't buy into yesterday's GFS/UKMET arguments for suppression). Time, though, can be a constraint especially as an event nears.

In such complex situations as the upcoming event (a tale of two systems), in general it is better to stick with the model that has been consistent than those that have performed erratically. From days out, there's sufficient time to evaluate the situation and less need to make a call with each model run. Rather, treating each model run as providing evidence to back/reject a preliminary idea and not making the decision to accept/reject that idea until later can be useful. At a minimum, it can avoid the shifting forecasts that can occur if one places undue reliance on any single model, suite of models, etc.

Can it be difficult avoiding the temptation to follow the latest run of models? You bet!

[Guest]

Dave,

The situation has been very complicated and the risk of error is therefore quite high. Some of the models will have difficulty in assessing given situations. That's why the synoptic pattern is important to study (as is recognizing normal model biases). That way, one can better judge whether the model guidance is/is not reasonable (to me, the idea of suppression seemed to be a low probability matter hence I didn't buy into yesterday's GFS/UKMET arguments for suppression). Time, though, can be a constraint especially as an event nears.

In such complex situations as the upcoming event (a tale of two systems), in general it is better to stick with the model that has been consistent than those that have performed erratically. From days out, there's sufficient time to evaluate the situation and less need to make a call with each model run. Rather, treating each model run as providing evidence to back/reject a preliminary idea and not making the decision to accept/reject that idea until later can be useful. At a minimum, it can avoid the shifting forecasts that can occur if one places undue reliance on any single model, suite of models, etc.

Can it be difficult avoiding the temptation to follow the latest run of models? You bet!

Very well stated Don and agree 100%! Great advice!

[donsutherland1]

Thanks. I'm still kicking myself over my Sunday idea. Although by early in the week I had discounted it, it does scar things, nevertheless in spite of my avoiding the GFS/UKMET's efforts to bait me into a trap of suppression. Needless to say, things could still go wrong.

[JCT777]

Don - excellent post. I have put most of my doubts aside and I now believe that my area will at the very least see a moderate snow accumulation (and perhaps a heavy snow accumulation) between early tomorrow morning and Saturday evening.

[Heady Guy]

JCT, I am not to far away from you. I am wondering where we stand on a change to rain or not on Friday. What do you think?

[JCT777]

Heady Guy - My thinking is that we change over to rain by noon or so tomorrow, but only after getting 2 or 3 inches of snow. I think temps will max out at about 34. Once the 2nd storm starts affecting us late Friday night, any light rain/mix will quickly change to snow as colder air gets pulled in and the precip gets heavier. I would not be surprised to see over 6 inches accumulate by Saturday evening from the 2nd storm.

[Heady Guy]

Mt Holly seems to be out of the loop again.

[JCT777]

Mt. Holly is being overly cautious. I expect to see some major forecast changes and a winter storm watch issued (for Friday night through Saturday) by mid-afternoon today.

[Heady Guy]

That is what I am hoping for today. I am hoping the new models come out good for PHL area.

[JCT777]

I think they will. If you don't mind me asking, Heady Guy, what town do you live in?

[Heady Guy]

north wales

[JCT777]

I lived in North Wales for 5 years. Nice area. I am currently 2 minutes away from Spring Mountain. They have been making snow for the past 2 evenings, getting ready to open up for the season on December 13. It gets me in the mood for Christmas and for a nice snowstorm whenever I drive by and see them making the snow.

[donsutherland1]

A quick update...

Based on the latest GFS and ETA guidance, the "sex appeal" of the ECMWF's remarkable consistency only looks more alluring against the backdrop of the earlier wild fluctuations of some of the other guidance.

Overall, a possible love affair with its snowfall ideas appears to be heating up. Put plainly, the ingredients continue to fall in place for an early-season significant snowfall for parts of the northern Mid-Atlantic and Northeastern regions.

This evening after the ECMWF's run is out, I'll post some detailed ideas on the upcoming system. As a quick note, my accumulations will be for the second system and not the first one, as I see the second one as having the greater snowfall potential.

Briefly, I'll also note that should the early-season significant snowfall develop, it will have implications for the remainder of the winter season given past instances. I'll mention some of those later today, as well.

[Stephanie]

Mt. Holly is being overly cautious. I expect to see some major forecast changes and a winter storm watch issued (for Friday night through Saturday) by mid-afternoon today.

They just have a Winter Weather Advisory out right now and don't anticipate that it'll be necessary to issue a warning: :-?

Severe Weather Alert from the National Weather Service

...ATLANTIC NJ-BUCKS PA-CAMDEN NJ-CECIL MD-CHESTER PA-CUMBERLAND NJ- DELAWARE PA-GLOUCESTER NJ-HUNTERDON NJ-KENT MD-MERCER NJ- MIDDLESEX NJ-MONTGOMERY PA-NEW CASTLE DE-NORTHWESTERN BURLINGTON NJ- OCEAN NJ-PHILADELPHIA PA-SALEM NJ-SOMERSET NJ- SOUTHEASTERN BURLINGTON NJ-WESTERN MONMOUTH NJ-
... WINTER WEATHER ADVISORY FOR TONIGHT INTO FRIDAY...

THE NATIONAL WEATHER SERVICE HAS CONTINUED A WINTER WEATHER ADVISORY FOR MUCH OF CENTRAL AND SOUTHERN NEW JERSEY... SOUTHEASTERN PENNSYLVANIA... NORTHERN DELAWARE... AND EXTREME NORTHEASTERN MARYLAND. THIS INCLUDES THE FOLLOWING COUNTIES...

IN NEW JERSEY... HUNTERDON... SOMERSET... MERCER... MIDDLESEX... SALEM... GLOUCESTER... CAMDEN... BURLINGTON... CUMBERLAND... AND INLAND SECTIONS OF ATLANTIC... OCEAN AND MONMOUTH.

IN PENNSYLVANIA... BUCKS... MONTGOMERY... CHESTER... DELAWARE... AND PHILADELPHIA.

IN DELAWARE... NEW CASTLE.

AND IN MARYLAND... CECIL AND KENT.

SNOW WILL SPREAD ACROSS THE AREA FROM SOUTHWEST TO NORTHEAST TONIGHT. THE SNOW WILL BEGIN CHANGING TO RAIN ALONG THE NEW JERSEY SHORE LATE TONIGHT... AND THE RAIN WILL SPREAD OR MIX FURTHER INLAND DURING THE DAY FRIDAY. AN INCH OR TWO OF ACCUMULATION IS POSSIBLE IN THE ADVISORY AREA BY FRIDAY MORNING. ANOTHER INCH IS POSSIBLE DURING THE DAY FRIDAY... MAINLY TO THE NORTH AND WEST OF PHILADELPHIA WHERE THE RAIN WILL MIX IN LAST.

THE RAIN OR MIXED PRECIPITATION SHOULD CONTINUE INTO SATURDAY... BEFORE TAPERING TO SNOW SHOWERS LATE IN THE DAY AS THE STORM HEADS OUT TO SEA.

REMEMBER THAT A WINTER WEATHER ADVISORY IS ISSUED WHEN SNOW OR OTHER WINTRY PRECIPITATION IS FORECAST THAT WILL CAUSE SIGNIFICANT INCONVENIENCES. WHILE THE PRECIPITATION IS NOT EXPECTED TO REACH WARNING CRITERIA... CONDITIONS COULD... IF CAUTION IS NOT EXERCISED... LEAD TO LIFE THREATENING SITUATIONS. CONTINUE TO MONITOR THE LATEST FORECASTS... AND LISTEN FOR LATER STATEMENTS.

...

[Stephanie]

A quick update...

Based on the latest GFS and ETA guidance, the "sex appeal" of the ECMWF's remarkable consistency only looks more alluring against the backdrop of the earlier wild fluctuations of some of the other guidance.

Overall, a possible love affair with its snowfall ideas appears to be heating up. Put plainly, the ingredients continue to fall in place for an early-season significant snowfall for parts of the northern Mid-Atlantic and Northeastern regions.

This evening after the ECMWF's run is out, I'll post some detailed ideas on the upcoming system. As a quick note, my accumulations will be for the second system and not the first one, as I see the second one as having the greater snowfall potential.

Briefly, I'll also note that should the early-season significant snowfall develop, it will have implications for the remainder of the winter season given past instances. I'll mention some of those later today, as well.

Will look forward to the additional information!!