NOTHING MORE THAN A NUISANCE...
When we last talked, the topic of the day was sorting out the impacts of a potential winter storm. We knew one was coming but there was some serious doubt about where its snow would occur and how much would fall. With another 24 hours of data to look at and the storm well into the western United States, we have begun to see trends that lend themselves to a higher level of confidence with regards to the storms performance. Even so, there's some critical fine tuning that needs to be done finalizing the track and the amount of snow that falls. A period of freezing rain is also a concern.
The number one challenge with this system since the git-go has been the amount of phasing between the northern and southern branch of the jet stream. To the point, the more phasing the stronger the storm and the further north it tracks. The further north it tracks, the more snow reaches and falls in my area.
Looking at the water vapor imagery by way of the GOES satellite, you can see a strong sub-tropical jet driving energy into the southwestern U.S. Moisture is readily seen surging into the Midwest out ahead of the developing storm.
Wednesday evening at 500mb you can see the energy in the sub-tropical jet entering the Texas Panhandle. You can also pick out a broad fetch of energy in southern Canada associated with the Polar Jet. What this indicates is that the system is not fully phased which makes it tougher for the surface low to really explode and track north. Instead, it's forced to travel more east/northeast and maintains less intensity than if the two streams were fully phased.
What that means is that the heavy snow producing aspect of the system Thursday is going to travel southeast of St. Louis, and very much like the system two weeks ago, the NW half of my area is under the influence of dry air and will not be impacted by the snow shield who's northern fringe will have a very hard cut-off somewhere through the southeast third of my area.
No matter what the outcome, precipitation will start as rain Wednesday. That's due to an influx of warm air ahead of the storm system. Clouds thicken Wednesday morning as a cold front enters my northern counties around noon. That allows another mild day with highs ranging from the low 40s north to perhaps the low 50s far south. The front will also be the catalyst for showers which develop and spread southeast as the afternoon progresses. Later in the evening and overnight, colder air turns the rain to freezing rain and sleet that eventually goes over to all snow. This happens first in the north but in this location precipitation ends shortly after the transition. That points to minor accumulations of ice and snow. Further south, the switch takes place after midnight but a longer duration of ice and snow could create slightly higher accumulations and more in the way of travel issues. The GFS indicates some freezing rain totals up to 1/4 inch. These are on the high end in my opinion but there could be a few totals up to 1/10 of an inch.
Overall, anything really significant in terms of snow holds off until Thursday when the primary energy sweeps out of the Plains. Snow that develops in the morning makes very little inroads into my southern counties if my gut feeling is correct. This is looking more and more like a nothing burger, even in the south.
For now, a a winter storm watch remains in effect for the southeast third of my area late Wednesday night through Thursday as the primary energy tries to activate snow in this part of my area. Currently these counties under watches which at some point are likely to be cancelled or downgraded to winter weather advisories way down south.
The winter storm severity index now includes moderate impacts for some of my far southern counties. That's subject to change as well.
Here's the official snowfall forecast from the NWS in the Quad Cities. I think this is very unlikely to verify.
The U.S. Models are the furthest north but have made significant shifts southeast in the past 24 hours, closer to what the EURO has been indicating. I think these will drop even further southeast in later runs Wednesday. Even if the positioning were correct, amounts are highly inflated and some of this is likely sleet and ice so don't take any of these numbers literally. In fact, I need to mention all of the models below are nothing more than raw guidance. They are all incorporated into the big picture to ascertain trends and ultimately forecasts like the one the NWS has issued. Also, (AND THIS IS VERY IMPORTANT), there is still a decent spread between the EURO, GEM, and the U.S. models so the track could very well shift even further south and that would leave places like the Quad Cities, which is on the northern edge of the snow shield currently with little if any snow accumulation. I'll have a summary of my expectations following the snow output below.
The 3K NAM
The 12K NAM
THE TRUTH AS I SEE IT...
Now it's time for the models which I believe are handling the storm best, the ones which I will base my forecast on.
My take is that the U.S. based models are experiencing some sort of convective feedback issue and are too far north. They should correct southeast. Aside from that they are too strong and generate too much precipitation which contaminates rain and snow totals. Much like the EURO depicts, I expect the brunt of the storm Thursday to miss my area. Totals southeast of a line from Burlington to Kewanee could reach 1-3 inches, heaviest the further southeast you go. I don't look for much northwest of that line which takes the Quad Cities completely out of potential warning and advisory criteria as far as snow is concerned. Outside of the icing issue Wednesday night, this again appears to be a close but no cigar scenario for most of my area. Ugh...
Winds however will become rather stiff Wednesday night and Thursday out of the northeast which may create some blowing and drifting limiting visibility in those areas where snow occurs way down south. They also usher in much colder air and temperatures Thursday will slip into the teens and hold there all day. Wind chills in the range of zero to 10 will be common.
Behind the storm the weekend starts out cold but a nice warm-up is expected Sunday ahead of our next weather maker when highs may push 50 in the south where snow cover is not a factor. 40's certainly look widespread.
Looking out a ways, the 6-10 day outlook includes near normal temperatures (although I think there will be significant fluctuations. Precipitation is expected to be above normal which is one of the first times I've seen that indicated in quite some time.
That's all I have for you for now. Stay tuned for further updates as the storm begins to show its hand even more Wednesday. Until then, roll weather...TS
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