ON YOUR MARK, GET SET...
Every November we have a reckoning of sorts. It's the point of no return where a new season comes to the table, (invited or not). After a monumental meal topped with stimulating conversation, the wind switches and the warmth gives way to the chilling reality, the dude on the other side of the table is a stranger from another world. His name is winter, and he's not here for dinner, he's here for 4 months. Welcome to your new reality.
Okay, that's a bit dramatic, but there is some truth to the fact that each year there is an event that flips the switch to winter. Next week may be one of those times, thanks to a re-alignment of the jet stream that brings a strong upper air low and its associated trough into the Midwest. The culprit looks like this on the GFS November 22nd.
At the surface, you can see the surface low is stacked under the upper air low, indicating that pressures are low from the surface all the way to the jet stream at 30,000 ft. The system is also cut off from the westerlies, which would normally push the energy along in a progressive way. That makes this a slow moving disturbance that will impact the Midwest for several days beginning next Monday, and lasting the remainder of next week.
Initially, the storm tracks into western Iowa next Tuesday on a path that takes it into Minnesota. That means most of the central Midwest will be in the warm sector of the system, and the first wave of precipitation falls as rain Monday night and Tuesday morning. Highs will be mild in the 50s and low 60s into midday Tuesday.
Eventually, the circulation gets closed off, causing the surface low to rotate counter-clockwise around the upper air low. The cyclonic circulation will take the surface low in a loop from NW Iowa, to eastern Nebraska and finally back into northern Missouri, a trip that takes 3 days.
At this point, the EURO shows the remaining energy being transferred to a new slug of vorticity, wrapping into the deepening upper air circulation from the SW. The hand-off generates another surface low that shoots northeast out of Arkansas into Illinois. After a break in precipitation later Tuesday and Wednesday, this development causes a new round that overspreads the region Thursday into Friday. At this point, the potential is there for rain to mix with or turn to snow, especially in my western counties in Iowa. Eventually, as the low passes, snow showers will push across the rest of the region Friday morning. With cold air aloft and bouts of vorticity spinning through the region Saturday and Sunday, additional snow showers look likely next weekend.
Needless to say, this is a very complex atmospheric realignment involving multiple spokes of energy. Models are still trying to grasp the depth of phasing and where it occurs. I still like the Midwest as the cornerstone of where the energy consolidates. That said, important details remain unresolved that will dictate the timing and location of precipitation, as well as any transition to snow around November 22nd. While I can't be specific with any snow totals, I do see the first snowflakes of the year later next week and potentially the first accumulations for many. On top of that, the EPO (eastern Pacific Oscillation) takes a big dive into negative territory, giving me high confidence that the coldest temperatures of the season are on their way in a week. Here's what the meteograms of the GFS and EURO are showing for temperatures the next 2 weeks. Note the plunge after the 21st.
The GFS
The EURO
Back to the short term, the rain the fell overnight is over, aside from some pockets of drizzle Thursday morning. Clouds will likely be a factor much of the day before they break out for sunshine Friday and Saturday. Highs Thursday look cool, ranging from the upper 40s north to the low 50s south. The additional sunshine Friday pops readings into the mid 50s, while Saturday and Sunday, upper 50s to low 60s are on the table. This may very well be the best weekend we see for several months to come, so enjoy it! Roll weather...TS
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