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Potential late season snow event for western NY and PA


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The mid level theta-e advection is off the charts. Given the amount of mid and upper level frontogenesis and the presence of -EPV with extreme deep height falls...there is a legit shot at some TSSN.

Hey Baro check this out. It's a crude way of taking things like -EPV together but works just as well. It's nailed the idea of TSSN before. Look at the pocket of LIs below zero just west of the tughill. Even where the LIs are near zero, that tells me the atmosphere is at least conditionally unstable. That will help form one of those -EPV bands right ahead of the dryslot where theta surfaces may fold and there is your TSSN.

post-33-0-03438600-1335036899.gif

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We will have to watch the evolution of the upper level low...you want the flow to turn due easterly with the 500mb low cut-off to your south and southeast. The tear drop shape on the NAM allows ESE flow in the mid-levels so warm air and the dry slot advances. I think that's why the NAM actually had sleet mixing in as 800mb temps rose to 1C in BUF.

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We will have to watch the evolution of the upper level low...you want the flow to turn due easterly with the 500mb low cut-off to your south and southeast. The tear drop shape on the NAM allows ESE flow in the mid-levels so warm air and the dry slot advances. I think that's why the NAM actually had sleet mixing in as 800mb temps rose to 1C in BUF.

Yeah sometimes these wrap up and the dryslot punches in further west. Part of me likes south of BUF for that reason, but verbatim euro looked nice.

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Hey Baro check this out. It's a crude way of taking things like -EPV together but works just as well. It's nailed the idea of TSSN before. Look at the pocket of LIs below zero just west of the tughill. Even where the LIs are near zero, that tells me the atmosphere is at least conditionally unstable. That will help form one of those -EPV bands right ahead of the dryslot where theta surfaces may fold and there is your TSSN.

post-33-0-03438600-1335036899.gif

That works for me! That is pretty much where I was thinking based off mid level theta-e plots.

Another crude and simple way to view the possibility is simply looking at upper level tropopause 1.5 PV and low level theta-e. Monday morning/afternoon looks prime.

post-999-0-31573700-1335037440.png

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We will have to watch the evolution of the upper level low...you want the flow to turn due easterly with the 500mb low cut-off to your south and southeast. The tear drop shape on the NAM allows ESE flow in the mid-levels so warm air and the dry slot advances. I think that's why the NAM actually had sleet mixing in as 800mb temps rose to 1C in BUF.

Lots of scenarios seem to be on the table, but guidance is hinting more at a rapid intensification than a slow intensification rate like the NAM. If anything I can see this going deeper than the ECMWF. Faster deepening would shunt WAA eastward.

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Lots of scenarios seem to be on the table, but guidance is hinting more at a rapid intensification than a slow intensification rate like the NAM. If anything I can see this going deeper than the ECMWF. Faster deepening would shunt WAA eastward.

right...I should have been clearer, too. I'm talking about partial T/partial t, not WAA. WAA is an obviously an important factor in getting the strong lift into the cold sector.

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That works for me! That is pretty much where I was thinking based off mid level theta-e plots.

Another crude and simple way to view the possibility is simply looking at upper level tropopause 1.5 PV and low level theta-e. Monday morning/afternoon looks prime.

Nice, looks like it gets down below 500mb. Should be some fun things happening.

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URGENT - WINTER WEATHER MESSAGE

NATIONAL WEATHER SERVICE BUFFALO NY

330 PM EDT SAT APR 21 2012

NYZ012-019>021-085-220330-

/O.NEW.KBUF.WS.A.0001.120423T0300Z-120423T2300Z/

WYOMING-CHAUTAUQUA-CATTARAUGUS-ALLEGANY-SOUTHERN ERIE-

INCLUDING THE CITIES OF...WARSAW...JAMESTOWN...OLEAN...

WELLSVILLE...ORCHARD PARK...SPRINGVILLE

330 PM EDT SAT APR 21 2012

...WINTER STORM WATCH IN EFFECT FROM SUNDAY EVENING THROUGH

MONDAY EVENING...

THE NATIONAL WEATHER SERVICE IN BUFFALO HAS ISSUED A WINTER STORM

WATCH...WHICH IS IN EFFECT FROM SUNDAY EVENING THROUGH MONDAY

EVENING.

* LOCATIONS...SOUTHERN ERIE AND WYOMING COUNTIES AND THE WESTERN

SOUTHERN TIER

* TIMING...SUNDAY EVENING THROUGH MONDAY.

* HAZARDS...ACCUMULATING HEAVY WET SNOW.

* ACCUMULATIONS...10 TO 16 INCHES.

* WINDS...NORTHEAST TO 40 MPH.

* VISIBILITIES BELOW A HALF MILE AT TIMES.

* IMPACTS...WIDESPREAD DOWNED TREES AND POWER LINES CAUSING POWER

OUTAGES. HAZARDOUS DRIVING CONDITIONS DEVELOPING.

* FORECASTER CONFIDENCE...HIGH.

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3" or more will start causing damage here for sure. If we saw 6" or more you can be positive we will start seeing serious outages. For those south of here all i have to say is get ready and yes WNYLakeeffect you better have your camera ready as will i. Got my sony bloggie 1080p video camera. Can get up to 2 hours of 1080p video.

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KBUF:

IN TERMS OF HOW POTENTIALLY UNUSUAL THIS WHOLE EVENT COULD BE (ESP

THE SNOW ASPECT OF IT)...NEARLY ALL OF THE MAJOR FORECAST PARAMETERS

(500MB AND 700MB HEIGHTS...MSLP...850MB TEMPS...AND WIND COMPONENTS)

ARE 4 TO 5 STANDARD DEVIATIONS FROM NORMAL. IT IS CERTAINLY

SIGNIFICANT WHEN A COUPLE FORECAST PARAMETERS ARE THAT ANOMALOUS...

BUT WHEN NEARLY ALL OF THE MAIN FACTORS ARE THIS FAR FROM

NORMAL...THEN THE EVENT STARTS TO RISE TO THAT OF A MEMORABLE OR

EVEN HISTORIC STATURE...IF ALL OF THESE FACTORS REMAIN IN PERFECT

ALIGNMENT.

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I only have an iPhone to take pics, but if it gets interesting enough, I'll take some.

If we were to get >12" of snow, it would be the 2nd latest on record, just beating April 20-21, 1901, which was the largest April snowstorm on record (22.5"). The only later date was April 30-May 1, 1908.

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I would love to be in the high terrain in western NY. I guess it is possible for some of those snow amounts to verify given the combo upslope and intense deformation/frontogenesis if everything comes together perfectly.

Yeah looking at progs and seeing temps falling into the upper 20s at that elevation... plus any enhanced cooling from forced orographic lift, they may be able to get away with somewhat decent ratios all things considered in the hills SW of BUF.

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KBUF:

IN TERMS OF HOW POTENTIALLY UNUSUAL THIS WHOLE EVENT COULD BE (ESP

THE SNOW ASPECT OF IT)...NEARLY ALL OF THE MAJOR FORECAST PARAMETERS

(500MB AND 700MB HEIGHTS...MSLP...850MB TEMPS...AND WIND COMPONENTS)

ARE 4 TO 5 STANDARD DEVIATIONS FROM NORMAL. IT IS CERTAINLY

SIGNIFICANT WHEN A COUPLE FORECAST PARAMETERS ARE THAT ANOMALOUS...

BUT WHEN NEARLY ALL OF THE MAIN FACTORS ARE THIS FAR FROM

NORMAL...THEN THE EVENT STARTS TO RISE TO THAT OF A MEMORABLE OR

EVEN HISTORIC STATURE...IF ALL OF THESE FACTORS REMAIN IN PERFECT

ALIGNMENT.

The AFD pretty much says it all.

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