ARE YOU KIDDING ME...
A MESSAGE FROM TSWAILS
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CONFOUNDED AND CONFLICTED...
For over a week, models have strongly pointed to a harsh winter pattern beginning this weekend that lasts well into February. Over the past 24 hours, guidance has veered to less in the way of cold and snow, especially the GFS. Honestly, I was jolted by some of the trends as everything was well teleconnected, supported, and consistent on the major models 2 days ago. Before I get into it, let me show you what has me so frustrated with the GFS.
First, the 500mb jet stream Monday night on the GFS for February 18th. That's a wickedly cold shot of air.
The latest run Wednesday evening for the same period. The whole trough is gone, completely vanished, replaced by ridging! Compare the two, there's no similarity.
This was snow shown on the GFS Monday through February 17th.
Now the latest run of the GFS through February 20th. That's a full on nothingburger! A microcosm of the whole winter to date.
I've been around long enough to know you don't hit something as hard as I have, unless you're feeling extremely confident you are on the right road. Even tonight, I still have teleconnections in favor of a healthy winter weather pattern coming up.
The negative AO (Arctic Oscillation)
The Negative NAO (North American Oscillation)
The negative PNA (Pacific North America Oscillation)
THE MJO (Madden Julien Oscillation) headed to the cold phases of 8 and 1. You can see the U.S. temperature analogs for both phases at the top of the phase diagram.
There's also a stratwarm at 10mb and the splitting of the Polar vortex that more often than not forces Arctic air into the mid-latitudes.
All of these teleconnections are cold signals, except for the negative PNA. In this case, it can actually be a good thing because the dominance of cold signals provide some resistance to the western trough it represents. That keeps the pattern active but allows the cold to push enough to create snow systems. The opposite, the positive PNA can be cold, but is generally dry with NW flow.
So what is the problem, Houston? The only thing I can see that might be driving this flip is the EPO which is shown turning positive.
That could mean the ridge off the west coast that funnels cold into the country is eventually weakened or eliminated. That in turn can get Pacific air into the pattern despite the negative Arctic Oscillation resulting in a more moderate pattern. This development was not shown yesterday, but it may be the fly in the ointment.
The ridge is still intact at 144 hours, as you can see in red over Alaska. That implies the EPO is still negative. The question is does it get wiped out, allowing the positive EPO to develop and replace it.
I would say the key to us avoiding what looked like a high impact period of winter weather next week is how the EPO responds in the 7-14 day period. I just haven't seen enough of the GFS trend yet to get fully on board with its milder and less snowy solutions. The EURO has backed off on the intensity of cold air intrusions, but still remains cold enough to produce some healthy snows, especially February 13-16th. Until models can pull data from the West Coast, what's available is sketchy in the Pacific and Arctic regions. Long range, that keeps things very much in flux. I flat out did not see these conflicts coming!
Despite a more moderate brand of cold, snow forecasts remain highly varied and what I would classify as very low confidence. Look what the GFS indicates for snow through the 21st. Massive amounts are shown to the north in Minnesota and Wisconsin. In my area, the black hole effect has reduced amounts to peanuts.
However, the EURO says forget that nonsense and shows a far more robust representation much further south for the same period.
What can I say other than my left hand is empty, and my right loaded. I have to figure out the winning play, and that is far from certain tonight. I'll deal with that tomorrow.
A LITTLE ICE GOES A LONG WAY
Meantime, a fresh batch of cold air settled into the region Tuesday, bringing temperatures down to more seasonal levels. Warm air advection is already underway, with clouds increasing. Eventually, enough warm moist air will ride up and over the cold dense surface air to produce saturation and some icing issue. This upglide process, will create enough lift to provide some minor precipitation in the form of light freezing rain and drizzle. The north could see some snow or sleet mixed. The speed of the system continues to slow meaning any icing holds off until the afternoon in the south and Wednesday evening in the north. Amounts won't be much, generally less than .05", but that would be just enough to create some slick spots. The NWS has a winter weather advisory in effect for the entire area from noon to 9:00PM.
The EURO indicates this for freezing rain totals. Not much more than a glaze, but that's all it takes to go sliding.
The 3k NAM has a dusting of snow possible north of I-80 where all snow or a mix of light freezing rain and snow is possible.
Another system is aimed at the area Saturday, with a bit of light snow north or a snow freezing rain mix south. Despite a nice track for snow, forcing and moisture is not well aligned locally and precipitation amounts look very light. That won't be the case further north, where heavy snow appears likely. Here's what the GFS indicates for snow totals Saturday.
The EURO is in general agreement on the position of the snow band but higher on amounts. Another near miss!
Needless to say, I have a throbbing migraine. We'll see where tomorrow takes us. Hopefully in a better direction than today. Roll weather and if you can spare a donation, I will see to it that it's money well spent....TS
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