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Good morning!

Enjoying this great weather? You get one more day of it before things begin to change. We've been locked into this zonal pattern for too long now, but the atmosphere is starting to get restless, and we'll start to see the start of those changes beginning this week. The morning map (850 mb winds and isobars/dewpoints/water vapor/radar) show moisture beginning to increase in advance of an area of low pressure. That low will drag a cold front across our area tonight and someone may see a shower, but probably not. That low is lifting northeast, and as it does it takes most of the mechanism's that would cause the rain to fall with it. 

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Latest satellite imagery early this morning shows mid and high clouds increasing across the area in advance of a fairly weak area of low pressure approaching the Ohio Valley. More clouds than sun today will result in temperatures a few degrees cooler than Saturday but it will still be another mild day for mid-late November with highs generally in the upper 60s to mid 70s area-wide.

The aforementioned low pressure system and trailing cold front will sweep across the area tonight bringing in a shot of cooler/drier air. Ahead of the front, a few showers will enter NW Georgia by later afternoon/early evening but lack of forcing will gradually diminish the showers before they advance any farther south/east overnight, tonight. Aside from some clouds and a wind shift to the NW late tonight, most areas will remain dry (especially south  of I-85). The sun returns Monday but it will be around 10F degrees cooler than Sunday for most areas which is more seasonal for this time of year.

Monday Night through Saturday

While quiet and dry ridge dominated regime starts out the first part of the work week, a more active pattern shift sets up midweek. An amplifying upper cutoff low developing in the Central Plains into the western Midwest will allow greater Gulf moisture advection into the southeast CONUS along the SW fetch aloft. The translated sfc front looks to push into the CWA late Wed into Thurs. As the stronger upper forcing ejects NEWD, the front looks to stall across the area late Thurs and possibly Friday (some evolution discrepancies in the guidance). Regardless of where any boundary could linger across the area, we stay susceptible to other possible rounds of precip with any weak impulses tracking along the upper open wave for the end of the work week.

The weekend looks to be even wetter as the western trough amplifies further and could break into another cutoff low bringing more enhanced moisture and stronger vorticity advection. Cannot rule out stronger storm potential just beyond the forecast period for late weekend but have plenty of time to watch. Given progged instability for the long term, still keeping Wed stable for just shower potential, then slight thunder chances Thu, more stable again for Fri, and nosed in some slight thunder for central GA again Sat.

Temps start out near normal in dry airmass Tue, then moderate to above climo for rest of week with aforementioned prolonged SW flow.

 

This is what they may be alluding to. The motherload. 🙂 The Holy Grail of winter storms. 🙂 In the winter, storms like this are what every meteorologist dreams of when it comes to cold and snow. This is a big deep upper level trough. The only thing better in the the winter would be for this to cutoff like a big bowling ball and slowly roll across the northern Gulf coast. Don't know that this is is going to happen the way you see it here because the GFS says no and the ensembles disagree as well. But when these start showing up within 10 days, it is time to start paying attention.

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Those troughs/lows bring their own cold temperatures, as the pull cold air down from the upper levels of the atmosphere. These are the corresponding anomalies.

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This is a cross section of temperatures, all the way from the surface to 38,000 feet or so for Blairsville. Notice around the 30th when the cold front passes, it looks like a funnel dumping cold air from above. 

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Sharp drop in temperatures.

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Combine the sharp drop in temperatures with a little moisture...

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I'll throw out the obligatory "THIS IS NOT A FORECAST" statement. At best this would be a dusting. A few days ago the GFS was showing 2-3". 🙂 Makes my heart beat faster. 🙂 

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It's not much right now, but it bears watching. Again, there isn't much support from the ensembles at he moment and no support from the GFS, so I'd just file this away as something interesting to keep an eye on. The models have been alluding to snow around this time period for several days now, especially the GFS, but it is still a long way off in weather days, so plenty of time to see what might happen.

Here in Big Canoe this morning, our temperatures are pretty homogenized so nothing special going on. The winds will be light all across the mountains today so no issues with wind.  

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The general forecast looks like this with slight variations for everyone. 

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I have the camera aimed toward the sunrise this morning and it may be a good one. This is the live YouTube stream. This is what it looks like right now.

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That's it for today, I hope everyone has a great Sunday!

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Meteorologist Larry Cosgrove

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As of Thursday in the past week, all of the longer term guidance was pushing the idea of a massive, continent-wide warm spell that would last through the upcoming winter. But as I have cautioned readers of this newsletter many times over the past 25 years (yes, it has been that long....), anytime a forecast series goes overboard with temperature extremes, the outcome will be (in some way, shape or form) wrong. This season I have pointed out that the analog set was firmly in a mixed-to-cold camp for North America. The most recent update of that comparison test was in stark contrast with the numerical model suites (CFS and ECMWF, shown here) that caused natural gas traders and winter weather enthusiasts unending depression. Add to this the presence of a La Nina episode, which many wrongly assume will eradicate cold air and snow outside of Canada and the Pacific Northwest.

Now we need to look at the ENSO signature. While it is true that the American equation has a very strong La Nina, other schemes such as the European and Columbia University (IRI) are in the moderate, and weakening over time, category. Those more conservative predictions match up well with the actual chart of sector 3.4, which in recent times is on a recurve-upward path. If the Kelvin wave complex over Sri Lanka and the equatorial Indian Ocean progresses into Malaysia and the Marianas Trench, downwelling could eradicate the cooler sea surface temperatures. In short, the resultant outlook is by no means a "gimme". Rather an "up for grabs" scenario that should allow for colder solutions as time wears on.

The forecast for the broad circumpolar vortex placement is vaguely favorable. While not split, expansive warming over Siberia and the northern Pacific Basin might allow for -EPO and -AP blocking signatures. Consider too that the snowpack is fairly contiguous and covering much of Canada. Both conditions imply southward drift of chilled air masses.

The Pacific Basin jet stream configuration is split, and is vaguely following the 2007 pattern of an organizing equatorial moisture axis. This gives the divergent flow, or greater contortion, a chance to a) bring storms into the southern and eastern U.S., and b) offer chances for cooler temperatures in the lower 48 states. Over the next 30 days or so, no real Arctic intrusions will come into the picture. Indeed, Canadian temperature anomalies would be warmer than normal, while American values would trend neutral-to-cool. That is the picture set up by the ECMWF and NAEFS 11 - 15 day outlooks, and would fit neatly with the 500MB outlines provided by those models. A system winding through the Deep South and Eastern Seaboard around December 6-7-8 could be a huge rainmaker, much like that predicted in the same vicinity in the medium range. Snow potential might be decent in higher elevations (Appalachian Mountains), but relatively minor in the Atlantic Coastal Plain.

It may take a while, but winter is coming. Patience is needed, even if that means waiting until January for some real action.
 
Prepared by Meteorologist LARRY COSGROVE on 
Saturday, November 21, 2020 at 10:45 P.M. CT

 

 

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And Larry once again

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Two important features are in view on the GOES WEST image. One is the well-developed Gulf of Alaska Low. The second (equally important to the forecast) is the equatorial moisture axis that runs from below Hawaii toward Baja California. If the two of these features were to combine (likely at this point, over the lower Intermountain Region in about three days), potential for significant rainfall will increase dramatically across the southern and eastern tier of the nation in the medium range. The numerical models suggest that would be a likely outcome.

 

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