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Central PA Late January Thread Part III


Rick G

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As I look at the storm for wednesday, I am, wondering if there will be a change over to sleet and IP. In my area, the schools hear Ice storm, they go into a panic. I don't blame them because the wyoming valley area has a lot of hills.

Right now light to moderate squall. Visiblitiy is down to under 3 miles.

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THE NAM AND GFS HAVE POTENTIALLY SIGNIFICANT INITIALIZATION ERRORSOVER BRITISH COLUMBIA...WITH THE NAM TOO WEAK AND NORTHEAST WITH THE CENTER OF THEDEVELOPING SHORTWAVE TROUGH...AND GFS TOO STRONG AND SOUTH. THESE DIFFERENCES CONTRIBUTE TOGROWING SOLUTION DIFFERENCES OVER TIME...WITH THE GFS LESSAGGRESSIVE IN DIGGING THE TROUGH INTO THE ROCKIES...A SOLUTIONWHICH IS DISCOUNTED DUE TO INITIALIZATION ERRORS AND ITS RELATIVEPOSITION WITHIN THE GUIDANCE ENVELOPE. MEANWHILE...THENAM...ALTHOUGH WITH INITIALIZATION ISSUES OF ITS OWN BUT NOT ASMUCH AS THE GFS...PRODUCES A FORECAST CLOSE TO THE MODEL CONSENSUSINCLUDING ENSEMBLES.

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That map looks absolutely beautiful, the problem is how much sleet cuts into the totals? If we could stay snow that equates to about 13-17" of snow!! Just depends on how much the HP to the north influences the area and how much WAA we get

Yes, since this is a mean it can be deceiving. Looking at the individual members, lots of them show warming at 850mb through much of PA. A lot of sleet and freezing rain would occur after a decent thump of snow. A handful of members pass the Low right through CPA, so a change to rain cannot be ruled out either.

Individual 12z ensemble members:

http://www.meteo.psu.edu/~gadomski/ENSPRSNE_12z/ensprsloopmref.html

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In terms of the upcoming week in the Harrisburg area, it looks to me as if a bout of moderate overrunning snows, then ice, will lay the groundwork for a rather wintry week of weather. I believe, having observed this type of event over my years, the warmer and more humid air will override the arctic air that is in place from these clippers that have brought it south to us by Sunday evening. Keep an eye on the strength of the High based on the obs over the next 2 days. If that (southern Ontario/northern NY) High is greater than 1030 mb on Monday, I would expect a large amount of wintry precip falling as snow, then sleet, then freezing rain, then ending as some backlash snows as the true arctic high spills east. The origin of that high is cP and cA...that is important. Regardless what the modeling suggests, it is very difficult to erode the low level dense cold that gets dammed east of the mountains. Over the years, I have seen models send surface temps to very "warm" levels only to see the surface remain at/below freezing. The modeling simply struggles with the density of the cold air dammed east of the mountains. Thus, I look for a glacier being formed by Thursday here in the lower Susq. Valley as the true cA air advects east later in the week. I did see that the synoptic set-up is analogous to the Valentine's Day 2007 storm as determined by CIPS analog packages ( Cooperative Institute for Precipitation Systems) which synoptically and climatologically makes perfect sense. Just my 2 cents......

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Yes, since this is a mean it can be deceiving. Looking at the individual members, lots of them show warming at 850mb through much of PA. A lot of sleet and freezing rain would occur after a decent thump of snow. A handful of members pass the Low right through CPA, so a change to rain cannot be ruled out either.

Individual 12z ensemble members:

http://www.meteo.psu...rsloopmref.html

yeah it sure looks like the majority of pa will change over at some point, well for me there was only 1 member showing a change over to sleet and the rest says I stay all snow well that can change mighty fast! I live practically right on the PA/NY border, we normally do very well with these types of events

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THE NAM AND GFS HAVE POTENTIALLY SIGNIFICANT INITIALIZATION ERRORSOVER BRITISH COLUMBIA...WITH THE NAM TOO WEAK AND NORTHEAST WITH THE CENTER OF THEDEVELOPING SHORTWAVE TROUGH...AND GFS TOO STRONG AND SOUTH. THESE DIFFERENCES CONTRIBUTE TOGROWING SOLUTION DIFFERENCES OVER TIME...WITH THE GFS LESSAGGRESSIVE IN DIGGING THE TROUGH INTO THE ROCKIES...A SOLUTIONWHICH IS DISCOUNTED DUE TO INITIALIZATION ERRORS AND ITS RELATIVEPOSITION WITHIN THE GUIDANCE ENVELOPE. MEANWHILE...THENAM...ALTHOUGH WITH INITIALIZATION ISSUES OF ITS OWN BUT NOT ASMUCH AS THE GFS...PRODUCES A FORECAST CLOSE TO THE MODEL CONSENSUSINCLUDING ENSEMBLES.

Where's this from?

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In terms of the upcoming week in the Harrisburg area, it looks to me as if a bout of moderate overrunning snows, then ice, will lay the groundwork for a rather wintry week of weather. I believe, having observed this type of event over my years, the warmer and more humid air will override the arctic air that is in place from these clippers that have brought it south to us by Sunday evening. Keep an eye on the strength of the High based on the obs over the next 2 days. If that (southern Ontario/northern NY) High is greater than 1030 mb on Monday, I would expect a large amount of wintry precip falling as snow, then sleet, then freezing rain, then ending as some backlash snows as the true arctic high spills east. The origin of that high is cP and cA...that is important. Regardless what the modeling suggests, it is very difficult to erode the low level dense cold that gets dammed east of the mountains. Over the years, I have seen models send surface temps to very "warm" levels only to see the surface remain at/below freezing. The modeling simply struggles with the density of the cold air dammed east of the mountains. Thus, I look for a glacier being formed by Thursday here in the lower Susq. Valley as the true cA air advects east later in the week. I did see that the synoptic set-up is analogous to the Valentine's Day 2007 storm as determined by CIPS analog packages ( Cooperative Institute for Precipitation Systems) which synoptically and climatologically makes perfect sense. Just my 2 cents......

yeah I can't imagine with a powerful HP to the north this changes many areas over to plain rain, definetly looks like a slop storm with WAA over spreading the area. The faster we get the development of the secondary the better some areas can see quite a bit of snow. Your right models typically don't handle CAD very well and thus don't always sense the potentially for very bad icing sometimes. All of places should still manage to get a very good front end thump of snow before the change over to sleet and ZR

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CMC run at least gives us an idea what the precipitation is gonna be.

http://collaboration...pe_gem_reg.html

That run is an example of the worst case scenario for the I-80 corridor. That would be a long duration of snow and ice with a 1036mb high sitting over Eastern Canada. With the high and the snowcover, it will be very difficult to warm up north and east of the mountains.

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