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The Jan 9-10 Storm Part 4


Cheeznado

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So FFC waits until right before the storm to tweak amounts DOWN based on latest Models? Huh? Are they looking at the same models we are? Why deviate the forecast that's been in there for days. Ride it out baby! A good forecaster would stick to their guns, and I see no reason to change anything based on the latest model runs. If anything, it's colder longer and there's more QPF on many of the models. Worry warts.

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So why is the GFS showing so much less precip than the NAM/RUC/WRF and all the3 shorter range models? I have seen where this is the case and sometimes the NAM and others are right, and other times the GFS is correct or closer to the final solution. What is the Nam picking up on (or GFS picking up on) that the other may be incorrectly interpreting?

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There is an excellent powerpoint presentation titled The Effects of Upstream Convection on Downstream Precipitation by Kelly Mahoney and Gary Lackmann. It explains how convection in different orientations can either increase or decrease downstream precipitation. It is a long power point but is you kind of skim over the main points it can help you know what to look for. Here is the link below.

Effect of Upstream Convection on Downstream QPF - Slide 1

I posted that paper last night...yea I just looked through the abstract, intro, and conclusion. I briefly remember a quick discussion on this in a lecture when I had Lackmann for synoptic.

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Also of note on the 12z NAM, there is ONE single layer above freezing at hour 42 so theoretically, if the heavier precip rates continue until 42, you could see us holding onto a colder profile.

By 42 the storm should nearly be over. 42 hours from 12z today would midday tuesday.

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I think, based on the NAM ans SREF there will be a very tight gradient between where I live in WC Dekalb county and the northern/NE burbs- I may only get 2-3" here then a fair amount of sleet. But up I-85 watch out. So I am contemplating getting a hotel room up in that area- I would hate it if I missed the snow by only a few miles.....

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Here's what I don't understand, from FFC, new update

There will be a quicker changeover in atlanta but I don't agree at all with their amounts here. Breaking the soundings and precip output down by 3 hour intervals clearly show the changeover will occur after the main brunt of heavy snow. Especially for athens, gainesville, etc.

I expect 5 to 7 here before it's all said and done. But there is potential for more. We'll see.

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I think, based on the NAM ans SREF there will be a very tight gradient between where I live in WC Dekalb county and the northern/NE burbs- I may only get 2-3" here then a fair amount of sleet. But up I-85 watch out. So I am contemplating getting a hotel room up in that area- I would hate it if I missed the snow by only a few miles.....

Come on out to Dacula! thumbsupsmileyanim.gif

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I will add that the shift in the short range models to a climotologically more accurate precip spread which looks remarkably similar to Jan 88 is encourging for folks in the TN valley, through N GA and up I-85. We could see widespread 12"+ amounts like the 88 event as well.

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I will add that the shift in the short range models to a climotologically more accurate precip spread which looks remarkably similar to Jan 88 is encourging for folks in the TN valley, through N GA and up I-85. We could see widespread 12"+ amounts like the 88 event as well.

And this is where FFC ust drop the ball as always....So every Short Range guidance including Nam are showing the NW section recieving more than the 5-7 they had so they decide to lower totals!? What am I missing here?

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MESOSCALE DISCUSSION 0012NWS STORM PREDICTION CENTER NORMAN OK1055 AM CST SUN JAN 09 2011

AREAS AFFECTED...PORTIONS NE TX...EXTREME SERN OK...SWRN/S-CENTRALAR...NWRN/N-CENTRAL LA.

CONCERNING...HEAVY SNOW VALID 091655Z - 092300Z

POTENTIAL IS INCREASING FOR HEAVY SNOW RATES 1-2 INCH/HOUR FROM ERN PORTIONS TX/OK BORDER REGION...SWD TO NEAR I-20...THROUGH ABOUT 20Z. HEAVY SNOW POTENTIAL THEN SHOULD SHIFT ENEWD ACROSS ARKLATEX REGIONINTO S-CENTRAL AR BY 00Z. THIS WILL OCCUR ALONG NRN EDGE OF LARGE REGIONAL PRECIP SHIELD...WITH SOME AREAS NOW EXPERIENCING RAIN OR MIX OF SLEET AND FREEZING RAIN UNDER GOING TRANSITION TO SNOW.SFC ANALYSES INDICATE SUBSTANTIAL COOLING ACROSS TX PORTIONS OF DISCUSSION AREA DURING LAST 3-4 HOURS...WHICH WILL CONTINUE TO COOL LOW-LEVEL AIR MASS AND SHUNT SFC FREEZING LINE FARTHER SWD IN ASSOCIATION WITH THREE PROCESSES...

1. SUBLIMATIONAL/EVAPORATIONAL WET-BULB EFFECTS IN PRECIP CASCADE

2. DYNAMIC COOLING OF DEEP COLUMN RELATED TO LARGE-SCALEDCVA/ASCENT...AS MID-UPPER LOW AND ACCOMPANYING SHORTWAVE TROUGHAPCH...AND

3. LOWER-ORDER PROCESS OF SENSIBLE COOLING OF AIR MASS FROM COLDER PRECIP GENERATED ALOFT.ELEVATED/LOW-LEVEL WAA CONVEY OR...SAMPLED IN LOW LEVELS BY 30-40 KTSELY LLJ IN VWP/PROFILER WINDS OVER LA AND SE TX...IS SUPPLYING MOISTURE FOR PRECIP GENERATION AND WILL OFFSET THAT COOLING SOMEWHAT ABOVE BOUNDARY LAYER. HOWEVER...PRIND TEMPS WILL REMAIN COLD ENOUGH TO KEEP PREDOMINANT PRECIP TYPE AS SNOW IN THIS CORRIDOR. RATES SHOULD INCREASE AND SNOW AREA SHOULD EXPAND OVER NEXT FEW HOURS...IN RESPONSE TO MOISTURE TRANSPORT INTO NWRN PORTIONS OF REGIME CHARACTERIZED BY JUXTA POSITION OF NWRN FRINGES OF STRONGEST 294-303K ISENTROPIC LIFT...WRN PART OF ZONE OF MAX 600-750 MB LAYERFRONTOGENESIS...AND THERMAL LAYERS SUPPORTING OPTIMAL DENDRITE GROWTH.

mcd0012.gif

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Updated my map and discussion today... might make one more update this evening before things get underway.

http://blizzard.atms.../local_jan.html

24ovne8.png

33arnrm.png

Phil, You think just a trace-1 inch here N.Foothills (Surry county) That seems low from what i've been reading, Or unless alot has changed since I went to church ?

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And this is where FFC ust drop the ball as always....So every Short Range guidance including Nam are showing the NW section recieving more than the 5-7 they had so they decide to lower totals!? What am I missing here?

I agree, that call map they have is horrible. NW GA, looks like it might be in the sweet spot. After doing well all week FFC might be back to par for the course..

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I agree, that call map they have is horrible. NW GA, looks like it might be in the sweet spot. After doing well all week FFC might be back to par for the course..

I think they have Cedric and my totals waaaay underdone and then I checked Cherokee Cty and I really think they are off for your area too Kevin. This really shouldn't surprise anyone. Maybe Steve Nelson will pop in and give us their logic behind this forecast?

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I agree!

Just got home from church and trying to sort thru the lastest model runs.

MAN, the NAM said HELLO.

Loving the short range model posts folks...

THanks

I will add that the shift in the short range models to a climotologically more accurate precip spread which looks remarkably similar to Jan 88 is encourging for folks in the TN valley, through N GA and up I-85. We could see widespread 12"+ amounts like the 88 event as well.

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I think they have Cedric and my totals waaaay underdone and then I checked Cherokee Cty and I really think they are off for your area too Kevin. This really shouldn't surprise anyone. Maybe Steve Nelson will pop in and give us their logic behind this forecast?

From Nashville: (Huntsville was also talking bout this but oh no not crazy FFC)

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE NASHVILLE TN

1042 AM CST SUN JAN 9 2011

.DISCUSSION...

A MAJOR WINTER STORM CONTINUES TO DEVELOP THIS MORNING IN THE LOWER

MISSISSIPPI VALLEY WITH WINTRY PRECIP ALREADY PUSHING INTO CENTRAL

MISSISSIPPI...SOUTHERN ARKANSAS AND SOUTHEAST OKLAHOMA. EXPECT THIS

TREND TO CONTINUE NORTHEAST WITH SNOW REACHING SOUTHWEST MIDDLE

TENNESSEE AFTER 6 PM AND INTO THE NASHVILLE AREA BEFORE MIDNIGHT

AND OVERSPREAD THE NORTHEAST AND PLATEAU AFTER MIDNIGHT. HAVE

ISSUED A WINTER STORM WARNING FOR ALL OF MIDDLE TENNESSEE FROM

MIDNIGHT TONIGHT THROUGH MONDAY. WILL NOT REGURGITATE THE CONTENTS

OF WSW HERE.

COOKS METHOD HAS BEEN VERY CONSISTENT FOR THE LAST SEVERAL RUNS IN

BRINGING THE STRONGER WARM ADVECTION PATTERN ACROSS SOUTHERN MIDDLE

TENNESSEE/NORTHERN ALABAMA WITH 6 TO 8 INCH AMOUNTS. MY FEELING IS

THAT WE MAY BE LOOKING AT SLANT WISE CONVECTION (THUNDER SNOW)

ACROSS SOUTHERN AREAS OF THE MID STATE AND SOUTH END OF PLATEAU

(GRUNDY...WARREN AND VAN BUREN COUNTIES) WITH THIS EVENT. IF THAT

HAPPENS THERE COULD BE POCKETS OF HIGHER AMOUNTS THAN WHAT I HAVE

CURRENTLY HAVE IN THE WSW.

Yet FFC says hey this is a good time to lower totals? :whistle:

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Phil, You think just a trace-1 inch here N.Foothills (Surry county) That seems low from what i've been reading, Or unless alot has changed since I went to church ?

I based my results on the 12z nam... it does seem like they give you guys about .2" before the changeover... so its possible you might get into the 1-3 or 2-4 range. My map surely isn't perfect, but I still thing there is a lot of cold damming air to overcome.

One thing to watch is how deep is the moisture plume. The air is so cold and dry in the NC foothills that by the time the precipitation starts to fall at the surface, the moisture aloft is already starting to leave. So there is no guaranteeing that the .2" is all snow.

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always nervous here. But I'm not worried on our temps. The RUC has our temps in the damming region dropping even more, probably good rates and a little upslope cooling going on right at the time we're getting into the good moisture, speaking of CLT to GSP and AVL region...your triangle of doom. I imagine the ratios would be pretty good here at -6 or so.

post-38-0-84092000-1294590531.gif

I SMELL Jan 1988 with a little blend of Feb, 2004 folks!! :whistle::lightning:

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