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November 11-12 Cold Front/Lake Effect Rain/Snow


Thunder Road

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There is significant model consensus that the first major cold shot of the season will hit next week as a >1044 mb High plunges southeastward into the Northern Plains.

 

It looks like there will be some rain and snow showers associated with the cold front Monday, but immediately following the frontal passage, northerly winds and sfc-850 mb delta T values over Lake Michigan of 20-22 C will likely support lake-effect snow showers consolidating into one main band by Tuesday morning, affecting at least part of Northwest Indiana.

 

Though at the very end of its run, the NAM currently suggests that most of the snow would be concentrated over LaPorte and South Bend, while the GFS and Euro show significantly less of a westerly component to the winds, and hence, much more snow for Porter County, and perhaps eastern Lake County (IN) as well.

 

Discuss.

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The 0z GFS is a little more bullish for some good snow showers and maybe even an inch in spots behind the front Monday afternoon across northern IL and northwest IN before the LES takes over.

 

Yup.  Very similar to the 18z run up through 18z Tuesday, then the new runs actually appears to increase the westerly component by 18z Tues.  As modeled, a nice spread-the-wealth event with Porter getting it at 0z and again at 12z, Lake Co. at 6z, and then finally LaPorte by 18z.  The transience of the band would probably keep totals down, but hey, any accumulating snow on November 12th is great in my book!

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Yup. Very similar to the 18z run up through 18z Tuesday, then the new runs actually appears to increase the westerly component by 18z Tues. As modeled, a nice spread-the-wealth event with Porter getting it at 0z and again at 12z, Lake Co. at 6z, and then finally LaPorte by 18z. The transience of the band would probably keep totals down, but hey, any accumulating snow on November 12th is great in my book!

I'm rooting for the stall scenario...I want to see what this thing can do if it parks in the same area, but I realize that wouldn't be good if it isn't over Valpo.

I wouldn't be surprised if there's thundersnow embedded given the magnitude of the instability and lake enduced EL heights near 10k.

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Zoomed in moisture map for the GFS. Approaching 0.40" in Valpo.

 

attachicon.gifLES_GFS96.png

 

The raw data is 0.40"  http://wxweb.meteostar.com/sample/sample.shtml?text=KVPZ

 

You can actually see the relative lull around 6z.

 

The KORD data spitting out 0.19" suggests that only ~0.21" of the Valpo QPF is actually LES, but that's pretty normal for a global-scale model.

 

(The other interesting note is that, yes, that 0.19" synoptic QPF at KORD, which with the temp profiles given, would be 1.5" of just synoptic snow there, assuming it all accumulates at 10:1.)

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12z NAM took a big step toward the GFS, backing off on the NW flow. It now has what the GFS had at 0z, with periods of LES for all three NW IN counties at one time or another.

Given all the data, if I had to guess, I'd say that the area most likely to receive 6" or more would be Porter county with parts of Lake and LaPorte also not out of it.

I'm not sure this will be the typical high ratio superfluff but the only part of the column near freezing is right near the ground so ratios may still be pretty decent with a possible exception being near the shore.

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Bo is going to get hammered, maybe 18 inches.

woo hoo! that would be great. APX is mentioning "significant accums" along and west of 131, in a NNW flow event.

that's one of the best flows for my specific area because you can get a single band connection to superior, rather than just moisture from superior.

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Bo is going to get hammered, maybe 18 inches.woo hoo! that would be great. APX is mentioning "significant accums" along and west of 131, in a NNW flow event.that's one of the best flows because you can get a single band connection to superior, rather than just moisture from superior.

My sled is done, got the call around noon. There won't be anything to track here, I will pay a bit more attention to this one. Usually +.75 inches of QPF verifies 18 inches LES.

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL

323 PM CST SAT NOV 9 2013

...

WITH THIS COLDER AIR BARRELING DOWN THE LAKE...MORE THAN FAVORABLE

THERMODYNAMIC CONDITIONS WILL PROVIDE A GOOD SETUP FOR LAKE EFFECT

PRECIP MONDAY NIGHT INTO TUESDAY...AND AM GROWING A LITTLE

CONCERNED FOR THE POSSIBILITY FOR SIGNIFICANT SNOW ACCUMULATIONS

ACROSS NORTHWEST INDIANA. A LONG FETCH DOWN THE LAKE WITH A

FAVORABLE SYNOPTIC PATTERN/CYCLONIC FLOW SHOULD ALLOW FOR AN

EXTENDED PERIOD OF LAKE EFFECT PRECIP TO PERSIST BEHIND THE SYSTEM

PRECIP...WITH A RAIN/SNOW MIX MORE PROBABLE LATE MONDAY AFTERNOON

BEFORE A QUICK TRANSITION TO ALL SNOW IS LIKELY TO BE OBSERVED

EARLY MONDAY EVENING INTO TUESDAY. BOUNDARY LAYER FLOW WILL KEEP

ANY PRECIP IN NORTHWEST INDIANA...WITH PORTER COUNTY THE MORE

PREFERRED LOCATION TO OBSERVE LES SNOW/SNOW BAND. DONT WANT TO GET

INTO ANY AMOUNTS SINCE SMALLER SCALE FEATURES/RESIDENCE TIME OF

ANY LES BAND WILL DICTATE SNOWFALL TOTALS...BUT THERE DOES APPEAR

TO BE A DEFINITE POSSIBILITY FOR ADVISORY TYPE SNOWFALL ACROSS AT

LEAST PORTER COUNTY WITH LOCALLY HIGHER AMOUNTS DEFINITELY NOT

OUT OF THE QUESTION.

RODRIGUEZ

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At least we are starting to get into the time range of some of the hi-res models, though they have their own biases to contend with.

IWX

AS COLD AIR DEEPENS MONDAY NIGHT AND FLOW QUICKLY BECOMES NORTHERLY...FOCUS SHIFTS TO LAKE EFFECT SNOW AND POTENTIAL FOR ACCUMULATIONS. MID LAKE TEMPERATURES HOVERING AROUND 10C PER MID LAKE BUOY AND THIS YIELDS SFC-850MB DELTA T VALUES AROUND 20C MONDAY NIGHT WITH SFC-700MB VALUES APPROACHING CRITICAL 30C LEVEL WHICH IS A GOOD INDICATOR FOR SIGNIFICANT ACCUMULATIONS. NAM12 SHOWING GOOD MOISTURE THROUGH 6-8KFT BUT THE ONE LIMITING FACTOR LOOKS TO BE SIGNIFICANT DRYING ABOVE 10KFT AS DRY CP AIRMASS BUILDS SOUTHWARD. HOWEVER...NORTHERLY TRAJECTORIES SUGGEST PRECONDITIONING OFF OF LAKE SUPERIOR A POSSIBILITY AND GIVEN ABUNDANT LOW LEVEL MOISTURE SHOULD STILL BE ABLE TO GENERATE A SIGNIFICANT SINGLE BAND MONDAY NIGHT INTO TUESDAY MORNING. NAM12 TRAJECTORIES SHOWING A MEANDERING NATURE TO BAND DEVELOPMENT WITH OFFSHORE FLOW LIKELY PUSHING BAND INTO EXTREME SOUTHWEST BERRIEN COUNTY AND WESTERN LAPORTE COUNTY. FOR NOW HAVE INCREASED POPS IN THESE AREAS TO HIGH END LIKELY WITH UNCERTAINTY LEFT TO ACTUAL BAND PLACEMENT. WITH JUST A BIT MORE VEERING OF LOW LEVEL FLOW...BAND COULD PUSH WEST INTO KLOT CWA. DID INCREASE SNOW AMOUNTS ACROSS WESTERN BERRIEN AND LAPORTE COUNTIES AS WELL AS WESTERN STARKE GIVEN FAVORABLE OVERNIGHT TIMING AND EXTREME INSTABILITY. MORE REFINEMENT LIKELY NEXT 48 HOURS AS HIGHER RES GUIDANCE COMES INTO PLAY. SEVERAL INCHES OF SNOW POSSIBLE WITH HEADLINES OF SOME TYPE NOT OUT OF QUESTION.

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For southern Lake Michigan, the most favorable parameters seem to occur early Tuesday before becoming less favorable with time, though these things often seem to wind down a bit slower than progged. Trajectories on Tuesday morning would seem to favor Porter county which is why I'm most bullish about that area. In addition, the band may spend the most amount of time there even with shifting.

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woo hoo! that would be great. APX is mentioning "significant accums" along and west of 131, in a NNW flow event.

that's one of the best flows for my specific area because you can get a single band connection to superior, rather than just moisture from superior.

 

Same with the area where our cabin is at. A 340ish wind direction is what we need for a good Lake Superior connection and have the wind strong enough to push that heavy "firehose" band inland enough to nail us. It happened last year when we got over a foot the day after Thanksgiving. Heck, I would be happy with just some tracking snow for opening weekend of firearm deer season.

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For LES, you can't really rely on the global models for the specifics; sure they have their purpose for general parameters, but for getting down to the nitty gritty, the hi-res models are the way to go. Once you learn their biases and account for those, you can really nail down accums and areas that will get hit.

 

Luckily, for those of us in the eastern lakes, the NWS in Buffalo has some great local models. So far for the two lake effect events that have hit Northeast Ohio this season (parts of eastern Cuyahoga County are already sitting at 9" for the season), they've been quite good. They might have done some upgrades over the summer:

 

http://www.erh.noaa.gov/buf/mm/mesomodels.html

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