EUREKA! FINALLY A STORM...

A SINCERE AND HOPEFUL MESSAGE

Friends and lovers of weather, it's imperative that you know I must reach my financial goal or it's time for me to hang it up after 50 years. I'm doing the best I can here to win your support, and rest assured there is no pleasure in asking for money. I get that its hard times and that's why I'm doing all I can to keep TSwails a no pay site. No matter what, I'm here through December, but the 14th year beyond is dependant on you. If you can help my cause, I'm making a humble plea for anything you can swing, it all adds up. Im $2,850 dollars (or 84% from my goal). Last but not least, I earnestly thank the 307 amazing individuals who have made such gracious contributions. You are all true treasures! Roll weather...TS

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A STORM WITH FLAKY IMPLICATIONS

Some radical changes have taken place that now put my area squarely in the path of a storm with rain and accumulating snow in the northwest. The past 36 hours, models have been slowly trending southeast with a compact but potent storm. That's particularly important in this case because the beneficial precipitation falls northwest of the circulation center in what's known as the deformation band. I noted in my post 24 hours ago that there could be some 1/4 to 1/2 inch precipitation totals northwest of the Quad Cities. That was with the low tracking just NW of the Quad Cities towards Freeport in NW Illinois. Now it may be further SE.

The latest EURO ensembles have now clustered their 51 member solutions on a track that's al least 30 miles southeast of the Quad Cities Thursday night.

The mean of the EURO ensembles now shows the NW 2/3rds of my area in a spot ripe for 1/4 to more than a 1/2 inch of precipitation.

Now, because this is based on the ensembles, keep in mind some of the 51 members take the low further NW or SE. So the model is working on an average track that to me is southeast of the Quad Cities that curls up NW of Chicago. Even though its less than 24 hours before the storm hits, there is a chance the center deviates north or south another 30 more miles. Much of that depends on how intensification and phasing takes place, a mesoscale issue that won't be certain until late morning Thursday. However, we seem to be moving in that direction.

That said, by morning we can put more reliance on the operational EURO relying on the more defined details that a single run produces. In fact, the latest operational is very close to the track that its ensembles indicate southeast of the Quad Cities. That could be entirely correct. (If nothing else it will be very close).

Using the EURO operational solution (which is most likely better than anything else), it produces a precipitation swath just NW of the center that looks like this regarding amounts. Totals of .40" to .90" are pretty widespread over EC Iowa. Amounts well over an inch show up in my far northwest counties, especially in Dubuque, Jones, and Jackson County. Again, that's all in the deformation band northwest of the surface low track. Unfortunately, southeast of there and the Mississippi, amounts taper off rapidly where the dry slot is in play.

An even bigger challenge will be the possibility of significant snow in my northwest counties. Due to the track of the system, locations NW of the Quad Cities will be substantially cooler than areas to the southeast. The EURO indicates this for highs Thursday. Note readings in NC Iowa don't get out of the mid to upper 30s.

As the low grinds northeast Thursday, rain breaks out in the far south ahead of the low towards evening. With temperatures still mild, rain is ongoing much of the evening, especially over my Iowa counties. By now the circulation east of the Quad Cities is beginning to tap into the cold air to its north. With precipitation increasing, strong vertical velocities (lift) are causing evaporative cooling in my northwest counties. This dynamic process draws down cold air and the freezing line (0 C) gets into my northwest counties mid to late evening. In this animation ending Friday morning you can watch the freezing line sweep across eastern Iowa Thursday evening towards the Great Lakes. It doesn't reach my southeast counties soon enough to encounter heavy precipitation there, thus just rain or a brief change to snow is expected. However, it does catch the northwest third of my region for a changeover to snow that could last 6-10 hours, enough in the far northwest to produce some healthy wet accumulations with snow rates over an inch per hour.

Before it ends, stiff north winds could exceed 30 mph making things rather difficult where snow is involved after later Thursday eveing into early Friday. The EURO shows this for snow accumulations. Bang, that's a major big shift south. 24 hours ago it had 1/2" on Dubuque. Often it's the other way around, more of a push toward the north.

I will be the first to tell you, even 24 hours before the event, this is a difficult snow forecast in my NW counties. Just a 30 mile shift in track could alter all the dynamics involved, such as where the heaviest precipitation falls, and when and where the rain-snow line sets-up. Take that blob of snow and move it 20-30 miles either way and you can imagine the implications that has on my northern counties.

Notice how going back to the ensembles, there is still enough spread in the 51 member average that amounts are not as heavy due to smoothing and uncertainty in some of the outliers. Also, the one inch line is past the Quad Cites close to I-80. Instead of the 12 inches of snow the operational shows in Dubuque, the ensemble mean only has 3.5". Tuesday the value of the ensemble will be minimal and the forecast will be based on the operational run which is much more detailed, and likely heavier.

By the way, other models are jumping on the snow ship fast in my NW counties. Here's some raw snowfall output from them.

The GFS

The HRRR

The 3K NAM

What this all leads me to surmise is that the NW half of my area (NW of the Quad Cities) is likely to see a healthy precipitation event with rain eventually changing to snow from EC Iowa into NW Illinois. Amounts of .50" to as much as an inch seem quite possible. 3-5 inches of snow (perhaps 6"+ in local spots NW) is also a concern depending on track and the timing of the change-over. It's likely that if trends hold, a winter weather advisory will be issued for roughly the area north of a line running from Cedar Rapids, Iowa to Freeport, Illinois later Thursday night and Friday morning. If the EURO is right, warning criteria would easily be met in some of that region. Southeast of the Quad Cities, rain will develop but diminish in the evening as the dry spot invades. Amounts here should be more in the range of .40" to .20", lighter as you go deeper into my southeast counties.

One other thing to keep an eye on is the possibility of some thunderstorms popping up towards Thursday evening in my counties from extreme SE Iowa into WC Illinois. There is some CAPE and shear, but its much more pronounced from EC Illinois into central Indiana.

SPC does have a slight risk of severe storms that could include a few tornadoes from Peoria southeast.

Much colder air and snow showers plow through the region Friday on strong NW winds ending the above normal temperatures we've enjoyed much of the month. This is the meteogram for the Quad Cities showing thermal trends into early next week. Readings could be significantly colder than this in my NW counties if there is a decent snow cover.

I must say this system has really evolved rapidly the past 24-48 hours and went from a minor rain event, to heavy precipitation, accumulating snow, wind, and even a few storms in the south. It certainly has the feel of a spring storm with all the moisture and dynamics involved. Hopefully, those of you who come up on the lower end of the precipitation spectrum get another chance soon. Big changes are in the works Thursday night, especially in the north where flakes will fly. More tomorrow around mid-day. Roll weather...TS ON A SERIOUS NOTE, IF I CAN'T MEET MY FINANCIAL GOALS, THIS WILL BE THE LAST YEAR OF THE SITE. IF YOU LIKE THE CONTENT, THE FUTURE IS UP TO YOU. T.S. 84% to my goal.

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