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Author Topic: 3/4/15 Winter Storm Potential - Because Why Not?  (Read 124709 times)

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Offline Charles L.

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #30 on: March 01, 2015, 01:23:15 PM »
Too much silence. GFS and EURO must not be good?


Sent from my iPhone using Tapatalk

???????? Kevin and Eric posted what the 12z GFS showed for Memphis and Nashville.

And chat is talking about the Euro, which was a solid hit.
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Kevin Terry

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #31 on: March 01, 2015, 01:46:23 PM »
OK...let's talk about this setup in general...then about the 12z ECMWF solution...

As mentioned days ago...the make or break here is where does the arctic front slow and/or stall...and no longer allow for a push of continued CAA before/as the second round of precipitation arrives. The second round appears pretty sure at this point...but for who and just what is way up in the air. As discussed above...we have a camp of the NAM/UKMET that are looking to stall early...and thus would keep wintry weather northwest of the region. Meanwhile...the GFS is the most aggressive...while the GGEM and ECMWF have slowed a bit since last night but still plenty speedy enough to bring winter precipitation into the region.

So Question 1: Is this the beginning of a "Northwest Trend"? No...not really...because there's no organized system to even trend NW here. This is all dependent on the timing of that front. If the front continues to slowly significantly...then yes...the swath of significant winter precip potential goes NW but that's not a NW trend in the traditional sense. And of course we have no idea if the models have latched onto the frontal speed yet for sure anyway...which means trends in any directions are possible...and that changes not only the character of the surface cold air but the depth of cold air aloft. Usually...arctic fronts move faster than modeled...and slowing trends are rare...but that doesn't mean it couldn't happen here.

Now...onto the Euro...as said the Euro is slower than last night...though not by a significant amount and not enough to change the character of significant winter precip into the region versus the 00z run. What has changed...that slight slowing trend has warmed the temperatures aloft some...so there is more freezing rain and sleet that would be dealt with vs. pure snow than we saw on the 00z Euro run...as both 850 and 700 mb temperatures have moved up to borderline to unfavorable levels for pure snow...though there's a decent period of snow to end the event that would result in appreciable accumulation. What's very weird about the ECMWF solution here...like the 00z run...it has a very thin stripe of intense QPF that literally sits on I-40 for 6-12 hours...dropping ~1.5" amounts in that time. No other model is anything near aggressive like this...and I'm not sure if that's because the Euro shows a band of enhanced frontogenesis there or something else. I'm not even sure it's realistic given there is no other model support for something at this level at this time.

But Question 2: If those intense precip rates verify...is the cold air going to get hung up ala March 2, 2014...refusing to move the freezing line South? Well...I would be stupid if said "No" to this...that was a lesson I promised myself I would learn after that event last year. If those heavy precip rates verified in those initial hours...the 850mb temps in that corridor are 7 to 10C. That would be ZR...and with those rates you have to assume latent heat release processes would be going on and have some effect. And if that band were to sit on top of I-40? Well...you can connect the dots. But for all of that to happen you have to put in a lot of assumptions in the 12z ECMWF verifying *exactly* as modeled...which is a bad bad assumption to make right now.

So...here's where we stand...we need to pin down the progression of the front in the days to come. That's going to determine what happens and where. There's basically two camps at this point though IMO...1) The front is rather fast and TN is within a significant ice/sleet/snow (just how much of what TBD) or 2) The front is slow and gets hung up north of I-40...and the second round of moisture just tracks well northwest anyway...and there's not much if any winter precipitation locally. Basically...WSW or bust? I think so...

Offline Susan

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #32 on: March 01, 2015, 02:03:24 PM »
Thank you Kevin for taking the time to write that up. 
All my misspelled words, typos, and grammatical errors, are intentional, and intended to troll and provoke.

Offline JayCee

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #33 on: March 01, 2015, 02:18:26 PM »
It appears this system is like every one we follow for the most part in our neck of the woods--borderline--and we'll just have to see how the models trend the next few days.  Comes down to the speed of the cold front, which is somewhat dependent on the strength of the big blue H pushing it southward. 







"For many years I was self-appointed inspector of snowstorms and rainstorms, and did my duty faithfully, though I never received one cent for it.." 
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Offline Eric

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #34 on: March 01, 2015, 03:03:21 PM »
OHX is on-board:

Quote
MODELS ARE NOT IN GOOD AGREEMENT IN THE TIMING OF THE FRONT MOVING
THROUGH THE MID-STATE ATTM.  NAM IS SLOWEST...GFS IS THE FASTEST AND
THE EURO SITS SOMEWHERE IN THE MIDDLE.  OVERALL...I HAVE GONE WITH
SOMETHING SIMILAR TO THE EURO TIMING REGARDING FRONTAL PASSAGE. 
POST-FRONTAL PASSAGE COULD VERY WELL BE THE STORY OF THIS SYSTEM
THOUGH.  MODELS ARE...AND HAVE BEEN IN GOOD AGREEMENT WITH A LARGE
AMOUNT OF LIFT BEHIND THE FRONT ASSOCIATED WITH WHAT SEEMS TO BE AN
EXTREMELY STRONG UPPER LEVEL JET.  WITH MIDDLE TN RESIDING IN THE
RIGHT ENTRANCE REGION OF THIS 140-170 KT JET...MODELS CONTINUE TO
SPIT OUT AN INORDINATE AMOUNT OF QPF IN A ENVIRONMENT SOLIDLY
SUPPORTIVE OF SNOW ON THE BACK SIDE OF WEDNESDAY'S FRONT.
IF WE
WENT WITH A 10 TO 1 RATIO...AND EVEN ACCOUNTED FOR LATENT HEAT
RELEASE FROM TUESDAY NIGHT'S LIQUID RAINFALL...WE WOULD BE IN LINE
FOR 4 TO 6 INCHES OF SNOW ACROSS A GOOD PORTION OF THE MID-STATE.
THE GOOD NEWS IS...THIS SET UP IS TYPICALLY NOT CONDUCIVE TO THAT
KIND OF SNOW ACCUMULATION.
WE USUALLY ONLY GET THOSE KIND OF SNOW
TOTALS WITH A SURFACE LOW PASSING US TO THE SOUTH...MUCH LIKE LAST
WEEK. THAT SAID...DUE TO MODEL CONSISTENCY...I HAVE TO START
TALKING ABOUT MINOR SNOW ACCUMULATIONS WEDNESDAY AND WEDNESDAY
NIGHT BUT I'M NOT GOING TO ATTACH ANY MORE THAN 1-2 INCHES TO THE
FORECAST ATTM.
PLENTY MORE TO COME REGARDING THIS SYSTEM.
EXPECTATION IS FOR THE MODELS TO FINALLY REALIZE THEY'RE OVERDOING
THE QPF AND BACK OFF OVER THE NEXT SEVERAL RUNS.
#tSpotter Coordinator for Rutherford and Warren Cos. (@WarrenSevereWx and @RuthSevereWx)

Offline JetJock

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #35 on: March 01, 2015, 05:00:29 PM »
Very informative write up Kevin. Thanks for taking the time and effort to provide your insight.

Well done!  ::applause::
All Thrust!  No Vector!

Offline Eric

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #36 on: March 01, 2015, 05:33:24 PM »
18z GFS Cobb data for BNA:

2.1" SN
.44" IP
.61" ZR

No thanks. 
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Offline pirates1

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #37 on: March 01, 2015, 06:36:28 PM »
Eric---what does that translate to?

Offline Eric

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #38 on: March 01, 2015, 06:40:07 PM »
Eric---what does that translate to?

One helluva mess.
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Offline Coach B

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #39 on: March 01, 2015, 07:05:37 PM »
Paducah's AFD had this to say concerning the new GFS:
Quote
IT IS IMPRESSIVE TO NOTE THAT THE DETERMINISTIC GFS GUIDANCE DURING
THE MIDDLE OF LAST WEEK ACTUALLY PICKED UP ON THE ORIENTATION AND
STRENGTH OF THE MID-WEEK COLD AIR SURGE BEING DEPICTED IN THE
CURRENT RANGE OF NUMERICAL MODEL SUITE. THE LATEST CHANGES IN THE
CONSTRUCTION OF THE PHYSICS AND RESOLUTION OF THE GFS APPEAR TO BE
SHOWING BETTER IMPROVEMENT.


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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #40 on: March 01, 2015, 07:52:13 PM »

Offline Clarksville Snowman

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #41 on: March 01, 2015, 07:52:53 PM »
It's COMING!!!! ::popcorn:: ::snowman:: ::snowman:: ::snowman::!!!

Offline JayCee

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #42 on: March 01, 2015, 08:46:31 PM »
Well, if Eric's Cobb data is any indication of what this system is bringing, then I'm not excited.

Here's hoping that east TN stays on the warm side of this thing.  I really, really don't want more ZR.  Nothing enjoyable about it, whatsoever.  In fact, give me 60 and thunder.  It is March, after all. 
"For many years I was self-appointed inspector of snowstorms and rainstorms, and did my duty faithfully, though I never received one cent for it.." 
Henry David Thoreau

Offline Charles L.

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #43 on: March 01, 2015, 09:11:40 PM »
Simulated radar of the 0z NAM valid for late Wednesday night.

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Everything you see in orange and red is, more than likely, heavy sleet.

Look at how expansive the precip field is BEHIND the front.

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Offline pirates1

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Re: 3/4/15 Winter Storm Potential - Because Why Not?
« Reply #44 on: March 01, 2015, 09:21:21 PM »
Crap!  What happened to the snow scenario?

 

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