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January 12th-13th Cartopper Thread


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I wanted to say it, but didn't want to be labeled a weenie for talking about the NAM @ 60. 

 

I have clear eyes about Tuesday. Expectations are low, I'd be over the moon to see snow in the air, but I am prepared in case things fall apart. 

 

Question, why is it that the sim radar and winter radar progs are so different?

 

 

 

 

The scales are different - look at the right side - one starts at 12 other starts at 4dbz

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      I wouldn't worry too much about "the NAM @ 60".   Guidance seems to be locked in on the synoptic details, so it's worth looking here at a simulation that tries to resolve the mesoscale details.    Maybe that band would fall apart as it comes east if the run went another 6 hours, but the overall look there is encouraging for those who want to see a quick burst of snow.   

 

      As for those plots, the scales are different, but it still looks to me like the labels aren't right.   Almost seems like the second plot really starts at 20 and not 12.

 

I wanted to say it, but didn't want to be labeled a weenie for talking about the NAM @ 60. 

 

I have clear eyes about Tuesday. Expectations are low, I'd be over the moon to see snow in the air, but I am prepared in case things fall apart. 

 

Question, why is it that the sim radar and winter radar progs are so different?

 

 

 

 

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    Something isn't quite right.   If you look over Lake Superior, there is clearly some of the "3rd level of green" which corresponds to 12+ dbz, and the second plot then should have echoes there if it really starts at 12 dbz.   I wonder if the listed scale on the second plot is wrong.  On the other hand, I think it's more likely that the developer of that page is doing some processing of the original reflectivity field in order to convert the reflectivity to a precip type-based reflectivity plot;  whatever remapping is being done could be wiping out some detail.   The details of the features on the bottom map just don't quite match up with the features on the top plot.

 

The scales are different - look at the right side - one starts at 12 other starts at 4dbz

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    Something isn't quite right.   If you look over Lake Superior, there is clearly some of the "3rd level of green" which corresponds to 12+ dbz, and the second plot then should have echoes there if it really starts at 12 dbz.   I wonder if the listed scale on the second plot is wrong.  On the other hand, I think it's more likely that the developer of that page is doing some processing of the original reflectivity field in order to convert the reflectivity to a precip type-based reflectivity plot;  whatever remapping is being done could be wiping out some detail.   The details of the features on the bottom map just don't quite match up with the features on the top plot.

Yeah I took another look after my first glance and I agree. Seems wonky. 

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I'm interested in seeing what the REGM says once we're in range.

It's been very disappointing (as in accurate) with its poo-pooing of snows in the MA & NE this year. I still remember its 18z run on 2/14/15 when it showed the heavier qpf strip over mby. Dang if it wasn't right too. It did well last year. I'm so hoping that it show for us this winter a heavy event because it will mean it's gunna' snow!
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    The nest is going to resolve a mesoscale band better, just by resolution.

 

    In instability-driven convective events, the nest will also often do better since it is explicitly generating convective features, while the parent has to represent them using the convective scheme.   I doubt here that this is in play for the Tuesday evening feature, as I don't think this is convective, but I didn't have a chance to look.

 

Yep, but better to see a tick in the right direction than the opposite. 

 

Edit: question...Looking at the 18z GFS and this most recent run, the vort passes look identical. Are you saying that the nest is just doing a better job of showing how the vort pass translates to the mesoscale band, or that there are, in fact, subtle differences that develop this band as a result?

 

Thanks

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    True, but the nest still has a modest signal for a very narrow band of snow showers.   I think that the possibility of an hour or so of snow has pretty much faded, but the chance of 15 minutes of flakes in the air (and perhaps a brief burst) is still on the table.   The nest will resolve a feature like that;  the parent won't.

 

 

12z NAM does us no favors... snow for no one really as vort pass is in N PA

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NEAR TERM /THROUGH TUESDAY/...

LITTLE CHANGE TO THE TRANQUIL FORECAST TONIGHT WITH HIGH PRESSURE

SETTLING TO OUR SOUTH. CLEAR SKIES EARLY WILL CLOUD UP LATE AS

FRONTAL SYSTEM APPROACHES FROM THE WEST. ADJUSTED MIN TEMPS DOWN

SLIGHTLY IN A FEW LOCATIONS GIVEN CURRENT TRENDS. MOST AREAS WILL

BE BELOW FREEZING WITH WINDS HAVING BECOME LIGHT.

ISSUED WINTER WX ADVISORY 7AM-10PM FOR WESTERN UPSLOPE AREAS

EARLIER THIS EVENING. HIGHER RESOLUTION GUIDANCE APPROACHES A

QUARTER INCH QPF WITH FAVORABLE FORECAST ATMOSPHERIC SOUNDINGS

INDICATING A DEEP MOISTURE LAYER AND STEEP LAPSE RATES. MOST

INTENSE SNOWS WILL BE DURING THE AFTERNOON AND FOCUSED TIMING OF

ADVISORY DURING HIGHEST IMPACTS.

ARCTIC COLD FRONT AND POTENT VORT MAX ALOFT WILL MOVE THROUGH

DURING THE LATE AFTN/EARLY EVE WITH POTENTIAL FOR SNOW SQUALLS AND

SHOWERS ALL THE WAY TO THE CHESAPEAKE BAY. PLENTY OF LOW-LEVEL

INSTABILITY FOR THIS TIME OF YEAR WITH VERY STEEP LAPSE RATES AND

SUFFICIENT MOISTURE IN THE DGZ. WET BULB PROFILES ARE MOSTLY BELOW

FREEZING...SO ALTHOUGH SFC TEMPS MAY RISE INTO THE 40S...ANY

PRECIP WILL QUICKLY COOL THEM RESULTING IN SNOW SHOWERS. ANY

ACTIVITY WILL BE CAPABLE OF PUTTING DOWN A QUICK DUSTING AND

REDUCING VSBY. THE PROBLEM IS THAT CURRENT TIMING INDICATES

HIGHEST SNOW SHOWER POTENTIAL ALONG I-95 CORRIDOR DURING EVENING

COMMUTE. AT FIRST GLANCE THE RELATIVELY WARM TEMPS MAY PRECLUDE

SIGNIFICANT ROAD ACCUMULATIONS...BUT MY CONCERN WOULD BE THE

ACTIVITY OCCURRING AROUND DUSK...HAVING IT MELT ON CONTACT...THEN

REFREEZE AS TEMPS DROP...STRONG WINDS REMOVE THE HEAT...AND

WITHOUT ANY SOLAR INSOLATION TO HELP. NOT OUT OF THE QUESTION

THERE COULD BE SOME HALF INCH AMOUNTS...ESPECIALLY ACROSS THE

NORTHERN QUARTER OF THE CWA.

WINDS WITH THE FRONT MAY ALSO GUST QUITE STRONG WITH THE STEEP

LAPSE RATES AND PLENTY OF WIND ALOFT AVAILABLE TO MIX DOWN. WIND

ADVISORY CRITERIA IS POSSIBLE.

 

So basically a much much less exciting version of 2/14/15?

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