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calculus1

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  1. By the way, we’re heading to Black Mountain.  For many reasons:

    • Happy wife, happy life.  =)
    • Cousins with whom the kids can play in the snow.
    • (Who am I kidding?  I will also be playing in the snow.)
    • Pretty much guaranteed snow for the duration of the event.
    • 8-inch floor, according to the graphic posted above.
    • Monumental snowstorm experience.

    Let’s do this!  Can’t wait!

    • Like 10
    • Haha 1
  2. GSP AFD for those trying to figure out their thoughts:

    I love their candor in this.  The part about the 850mb low explains why their numbers are so high NW of I-85.

    The cat is out of the bag...

    Quote
    .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
    As of 245 pm EST Thursday: The 12Z model cycle has not changed
    our confidence that a significant winter storm will impact the
    western Carolinas and northeast Georgia this weekend. The model
    trend has been back toward more of a snow/sleet concern across
    a larger part of the region with more sleet/ice on the southeast
    fringe and the Charlotte metro area. Confidence is already high
    enough to issue a Winter Storm Watch for essentially the entire
    forecast area with wintry precipitation beginning in the Saturday
    night period. We don`t ordinarily jump at fifth period watches,
    but all the guidance points toward a significant event for at least
    the NC mountains/foothills with snow accum at double our warning
    criteria. Confidence is less outside the mtns/foothills in terms
    of the distributions of precip types and subsequent accumulations,
    and this has to do with the northward extent of an expected warm
    nose, but indications are that with the amount of liquid equivalent
    precip this system will have, even if our snow/sleet fcst amounts
    are wrong because the warm nose is stronger, the ice accums will
    be higher to overcome that deficiency, and we would reach warning
    criteria anyway. Thus, we will issue a Winter Storm Watch for the
    entire forecast area now.
    
    Winter storm scenarios are always complicated in this region
    because of concerns over precip-types, QPF, and temperatures.
    In this case, confidence is relatively high that we will have
    boundary layer temperatures cold enough to support wintry precip
    over the entire forecast area as the precip arrives from the west
    Saturday evening. The split upper flow pattern will essentially
    anchor a large continental sfc high in an ideal position to
    support the cold low level air mass. Precip may begin as a period
    of rain/sleet in many parts, especially east of the mtns, but a
    steady transition to wintry mixes and eventually to snow along/N
    of the I-85 corridor is likely toward daybreak Sunday. The mtns
    will be primarily snow for the duration. Excellent forcing spreads
    overhead Saturday night/Sunday morning in the form of strong
    upper divergence courtesy of coupled jet interaction, strong
    mid-level dpva as the upper low moves in, and a Trowal moving
    overhead Sunday morning. High confidence in categorical precip
    probs is the result. Getting back to the warm nose...the trend
    is toward a more southward track of the 850mb low...almost right
    over the fcst area. That may permit the warm nose to move only
    as far north as roughly I-85. What is interesting is the fairly
    steady movement of the 850mb low across the region, which will
    effectively limit the duration of the warm nose and allow colder
    air to wrap back down from the north during Sunday. As a result,
    we may see a somewhat rare switch back to light snow across the
    I-85 corridor as the system departs...while enough precip remains
    to produce accumulating snow in the afternoon. The area around CLT
    metro has the longest duration and the best chances of picking up a
    quarter-inch of ice accum Sunday morning, before the switch takes
    place in the afternoon/evening back to light snow. As the system
    departs Sunday night, we transition to a NW Flow snow situation
    along the TN border that may continue into Monday. Temps will
    be cold Sunday, remaining below freezing across large parts of
    the region, and will remain well below normal Sunday night with
    widespread black ice a strong possibility.
    
    Plenty can still go wrong with the details regarding snow/ice
    amounts and their distribution, so expect the fcst to drift over
    the next day or two one way or the other. However, confidence is
    high enough for a Winter Storm Watch now. The cat is already out
    of the bag at any rate...

     

    • Like 1
  3. 36 minutes ago, Blue_Ridge_Escarpment said:

    Yep. Actually has a form of downsloping there. Mountains circling on either side. 

    Yep, that's what I was mentioning earlier.  Fortunately for me, it seems Black Mountain is too far east to feel the severe effects of it.  If you ever get a chance to see it, the Visitor Center at Gorges State Park has a great exhibit demonstrating the differences in precipitation for the SW mountain counties.  Buncombe County is almost a desert by comparison to Jackson, Transylvania, and Henderson.  The Visitor Center's 3-D image of the area shows the high peaks all around Buncombe with Asheville nestled down in the bottom.  They also have video demonstrations of how the storms travel up and over the mountains, skipping the Asheville bowl.  It's quite informative, if you are into weather, and I assume we are, if we are on this site.  :D

    • Like 1
  4. 6 minutes ago, BlueRidgeFolklore said:

    That “V” of lower totals on the GFS coming into Asheville from Madison County, is due to the French Broad River Valley funneling in warmer air from TN. That’s always a battleground area with CAD. In these setups, AVL isn’t Black Mountain. Black Mountain will do well.

    That's most helpful with the local topography, @BlueRidgeFolklore.  Thanks for explaining that.  I think I'm pretty near set on heading up the mountain.

    • Like 1
  5. 10 minutes ago, calculus1 said:

     

    Hmm...

    That map paints Hickory in a better spot than Asheville...

    Making my decision tougher...  :D

     

    But the Black Mountains (including Mt. Mitchell), just to the NE of the town of Black Mountain, get clobbered in this scenario (more than two feet).  So, being just to their SW could be beneficial too.

    • Like 1
  6. 7 minutes ago, NavarreDon said:


    What’s the timeline, when does a decision have to be finalized? If you have time follow the model trends. Depends on what part of Hickory & what part of Black Mountain. I’d wait as long as possible to gather the most info then make the call. The great thing is either way will be a win!


    .

    My wife wants to let her mother know as soon as possible.  Probably by tomorrow afternoon we should have it finalized.

    • NW Hickory, approximately one mile from Alexander County line.
    • Between Black Mountain and Swannanoa, near Owen HS.
  7. I would love your guys' perspective on this.  Here's my dilemma:

    • There's nothing like seeing it snow/sleet/whatever in your own backyard, and Hickory has a good chance to get walloped.
    • My in-laws have welcomed us to come spend the weekend with them in Black Mountain (due east of Asheville on I-40, just up Old Fort Mountain).

    I think Black Mountain has a much better chance of remaining snow for the entire event (2400 feet elevation), with little chance of mixing in sleet (at least at this point in the forecast).  However, Buncombe County traditionally is the driest county in the state and often has precip minima there compared to surrounding areas.  Ignoring other factors such as my kids playing with cousins in the snow in Black Mountain, which experience would you prefer?

    1. Staying at home and seeing 6+ inches of snow, with an inch or snow of sleet, followed by a deform band with more snow IMBY, OR
    2. Traveling to in-laws and seeing a pure snowstorm with likely 12+ inches of snow on the ground, but they might get downsloped a bit by surrounding mountains.

    As you can probably guess, my wife doesn't even understand why it's a dilemma, and she's like, "Let's go to my parents and have fun with the family there".  But there's something so special about seeing it snow, during the day, all day, below freezing, in your own backyard.  And, I'm a sucker for taking records and measurements IMBY, as you can see from my signature line.  :D

    What are your thoughts?

     

    • Like 1
  8. 1 hour ago, ILMRoss said:


    TBH those ensemble graphics are manna from forecasting gods at this range. There’s a shape, you get to communicate a pseudo-snowmap well before it’s responsible to put together an actual map but you also get to absolve blame to the model in case things go wrong. I can blame them. I interned there back in the day and one of my good met friends (no comment on who) is on the team; they’re smart cookies and I generally think they thread the needle pretty well of tipping their hand while also being responsible with what they put out.

     

    46 minutes ago, Cold Rain said:

    They heavily use ensembles, which have been been trending from flatter and weaker to stronger and more wintry as the Ops have trended from adequately strong and favorable to more amped warmer aloft.  If the Ops continue to trend in that direction, you can expect the ensembles to follow and WRAL to follow that.

    If you guys think I am arguing against using ensembles in forecasting, I am not.  I am arguing against displaying a map that gives precision probabilities.  If WRAL derives their “probabilities” from ensembles, I still disagree with their language.  If they said “14 out of 50 ensemble members indicated 3 inches or more of snow for Clinton” or even “28% of ensemble members indicated 3 inches or more of snow for Clinton”, I would have no issue with those statements.  Those are indisputable facts based off model output.  But equating such fractions of ensemble members to probabilities is a misuse of statistics, in my opinion.

    The probability of a success (getting three inches of snow or more, in this case) is equal to the number of successes divided by the number of possible outcomes (failures + successes).  The ensemble members do not represent all the possible outcomes; they only represent approximately 50 of the infinite number of possible outcomes.  Thus, we can’t really say there is a 28% probability of something happening based off ensemble members.  In fact, I would argue there’s really no way to calculate such a probability, because it’s impossible to account for all the possible outcomes that arise from tweaking just one minuscule atmospheric condition somewhere over the entire globe.

    It’s the language that I take issue with, not the use of ensembles.  If they were to change their title to “Percent of Ensemble Members that Predict 3 Inches of Snow”, I would see that as much more transparent.  As it is, I think it’s a misleading graphic.

    • Like 2
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  9. 25 minutes ago, EarlGrey said:

    Here are the chances for 3'' of snow from WRAL.

     

    There's a 32% chance that Raleigh could see three inches of snow!

    This is such a crazy graphic.  I understand perhaps giving general ranges of 10, 20, 30, etc. percent chances of snowfall of X amount (and even those are questionable).  But, how could anyone offer that degree of precision even 12 hours out, much less 4-5 days?  For instance, Clinton has a 21% chance of seeing 3 inches of snow?  Not 20% and definitely not 22%, but exactly 21%?  So, if the atmospheric conditions were exactly the same as they are right now, and we play them out 100 times, then exactly 21 of those times Clinton would receive 3 inches of snow?  No way could we possibly know that or perform that experiment.  And there’s definitely not empirical evidence that we can fall back on to know this probability to this degree of precision.  This is such a horrible use of statistics and probability…

    • Like 3
  10. 37 minutes ago, buckeyefan1 said:

    HKY

    Thanks for posting these meteograms, Buckeye.  I just can't fathom all the pretty colors on these charts for Hickory -- there are so many pinks and purples, on both the ECMWF and the GFS ensembles.  We aren't supposed to get nice things.  I love the bonus bump in snow on the GFS too.  As if 12 inches with the first one isn't enough, let's tack on an additional 8 inches a week later.  Yessir!

     

    13 minutes ago, buckeyefan1 said:

    GSP  :lol:

    The track of the low will determine how strong
    of a warm nose might develop from the south, which would greatly
    affect the precip-type distribution. The QPF blend right now is
    especially modest, and the conservative approach is preferable
    for a system that is still out on Day 4/5. In spite of the trend,
    readers are cautioned to manage their expectations...at least for
    the time being. Stay tuned.
    
    

    My favorite part of the GSP AFD is the bolded here.  We are cautioned to manage our expectations.  Yeah, we're not too good at doing that on weather boards.  :D

    • Like 3
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  11. 31 minutes ago, BooneWX said:

    I was just about to say. I’d kill for a legit Miller A right about now. Pain is seeing snow the west and east but nothing here. The Dec 2018 and Feb 2014 storm truly were magical for the foothills. I’m not close to being ready to throw in the towel yet. Climo will eventually be in our favor - the quick hitters are rarely our storms but that’s ok. 

    Yep, that's the tough part.  It's amazing how much they got in the W-S area this morning.  The lee of the Apps is a tough place to live if you like snow.  Really need those classic Miller A storms, but those are few and far between now, it seems.

    • Like 1
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