SPRING SNOW , SAY IT AIN'T SO...
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SPRING SNOW, SAY IT AIN'T SO...
Temperatures around the region did make it into the low 50s Wednesday. Generally, that's northing to write home about. However, in this case I take exception as this is the first time since November many of have been able to string together three consecutive 50 degree days. Here's what the months temperatures look like so far in the Quad Cities.
Notice the dip we recently climbed out of. The morning of the 18th the low was 10 and by the 21st readings had climbed 48 degrees thanks to a high of 58. The ups and downs of March are quite evident in the meteogram.
Overnight showers and even a few thunderstorms fired in my southern counties close to a stationary boundary over far northern Missouri. With the addition of a 40kt low level jet and a cold front, some of the storms were efficient rain producers, especially near and south of HWY 34 in far SE Iowa and WC Illinois. Further north the rains were more stratiform and showery with much lighter amounts. North of HWY 30 little if any rain filled the bucket.
What happens with the cold front that has passed to the south is now a critical concern for what happens with a potential snow system Friday night. I say this because the depth of the cold air (where it stops), will lay the foundation for the weekend system to track. Over and over again we talk about the importance of the track, as well we should when it comes to snow. It's the NW quadrant, known as the cold sector where the deformation band necessary for heavy snow sets up.
Overall, the deterministic models are in good agreement that a deepening surface low will develop ahead of a short wave ejecting from the Rockies Friday. In fact, the EURO, GFS, and Canadian GEM all indicate a band of heavy wet snow. There's little disagreement there. Where issues develop is how far that cold air sinks Thursday before it stalls forming the track for the snow train to travel.
When you look at the ensembles, possible tracks produced by each of the models you see a multiple locations of where the surface low might end up. The wider the range in positions, the lower the confidence. We like to see tight clustering in a model. Taking it a step further, we then like to see similar clustering among the models. Then we get into a high confidence solution. Here's the ensemble tracks.
The EURO, honing in on the NW corner of Indiana Saturday morning.
The GFS is well southeast, closer to central Indiana.
The Canadian is clustered more towards NE Illinois.
The compromise solution would be the EURO with its track into NW Indiana. That does not mean it's correct but until I see tighter spreads among models, that is my starting place.
These are the individual surface maps depicting the surface low and the various precipitation types. Note the snow, always to the NW of the surface low.
The EURO
The GFS
The GEM
Basically, what we 're seeing at this point in the game is the snow shield further west into Iowa on the EURO and GEM due to tracks that are at least 150 miles northwest of the GFS. Even with it's further east track, the GFS still gets snow into the southeast half of my area. Here's what the snowfall projections currently look like. These are not forecasts, just raw model guidance the eventual forecast will be based on. They are very subject to change based on the uncertainty in track.
The EURO
The GFS
The GEM
As you can see, there is a significant range in snowfall amounts across my area depending on the model. The EURO is the furthest NW and keeps the area from the Quad Cities SE out of the significant snow. The GFS takes it right through the heart of my area and the GEM is sort of a middle ground approach. For what it's worth at this juncture, the EURO has a 70-90 percent chance of an inch or more of wet snow in roughly the northern half of my area.
Even once the track is nailed down these late season storms are very tricky to call, especially when transitions are involved and ground temperatures are warm. Unless snow really comes down, much of the accumulations occur on grassy and elevated surfaces. Additionally the snow melts from the bottom up so it can be hard to get an accurate assessment of how much actually falls. Needless to say, the harder it snows, the greater the chances for those accumulations of 6 inches or more. Last but not least, if the transition from rain to snow is slower than expected, several inches of accumulation is wasted as rain. I'll be blunt, there are still major questions to be answered that only time can clear up. However, I have seen enough to believe that at least the NW half of my area is under the gun for heavy wet snow. We'll see if new date later Thursday confirms that. I do expect winter storm watches will be issued for some portion of my area late Thursday if current trends hold. The area northwest of the Quad Cities is most likely to fit the bill.
If that's not enough conjecture, another chunk of energy rides into the region with a snow chance late Sunday night or Monday. It too has many of the issues we are dealing with from the first system but is not nearly as strong. That's all I will say on that issue for now other than the satellite image shows the firehose of moisture in the SW flow that will keep things hopping for awhile.
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CHILLY AROUND THE EDGES FOR AWHILE...
With threats of snow and lots of clouds, it goes without saying the next few days are going to be cool with highs mainly in the 40s, perhaps only the 30s in spots Saturday if snow is laid down from Friday's storm. Beyond that the future doesn't look much better on the GFS with 7 day average temperature departures well below normal in the period March 31-April 7th. Good grief.
That's where I will leave it for now. Thursday should be a telling day as far as trends go for the upcoming storm. I certainly hope so. I won't be able to sleep tonight with all the different outcomes spinning in my head. I always searching for the answers. It's what I do. Roll weather...TS
