NO PAIN, NO GAIN...
The next several days we are going into full fall mode with significantly colder temperatures returning to the Midwest on gusty NW winds. In fact, by Monday of next week the coldest weather of the season will give us an unwanted taste of what awaits us in the months ahead. However, if you can take the short term pain, the long term gain may be worth it. More on that in a minute.
First, a deep trough is in the process of creating a cold core 500mb cut-off low that meanders around the upper Midwest into next Tuesday. Watch it all come together in this animation that extends from Wednesday evening through next Tuesday. Look at that bowling ball spin. Such energy is a definitive sign that the seasonal increase in temperature disparity is well underway and it's impacting the strength of the jet stream and storm systems within it.
With the cold core 500mb low in close proximity, temperatures October 14th through the19th are shown averaging 10-12 degrees below normal per day.
Here's a closer view of the central Midwest.
The worst of the chill arrives Monday and Tuesday when temperatures at times could be 20-24 degrees below normal.
Get a load of these low temperatures the GFS is depicting next Tuesday morning. Low to mid 20s are widespread in my area with a hard freeze throughout the Midwest.
Preceding the big chill next week, weekend temperatures Friday through Sunday will likely hold in the low to mid 50s. Thursday will be no peach either as strong cyclonic flow within a tight pressure gradient keeps winds howling and the temperatures scowling. Highs will struggle to surpass 50 in the north with low to mid 50s elsewhere. Deep mixing is expected to produce gusts of 30-40 mph in the afternoon. Some spotty instability showers or sprinkles will also dot the area (mainly in the north, most likely in the afternoon).
The cyclonic flow the next few days will promote lobes of vorticity (energy) that rotate around the stubborn cold core low. One of these could spark a few brief light showers later Friday and another arrives Sunday bringing the worst of the cold air this set-up has to offer.
By the way, I was awakened by thunder late Wednesday night as a cold front punched into the area. Some spots had some small hail and a narrow swath of moderate rains fell from Williamsburg and Cedar Rapids to just NW of Dubuque. You can see it on the radar estimates below. The other green areas were the result of rain that fell Tuesday. Bottom line, some areas picked up needed rain, others barely enough to settle the dust. Some is better than nothing!
After the rains ended Wednesday morning, the true cold front blasted into the area during the afternoon. It brought a smattering of showers with its main impact being powerful winds and colder temperatures. Gusts at the Cedar Rapids airport reached 54 mph. Iowa City was close behind with a max of 51 mph. By midnight evening temperatures were back in the low 40s as the cool air that dominates the weekend gets firmly established.
THE PROMISE OF WARMER AIR
The pain of the coming chill ends with the gain of warmer temperatures in the 6-10 day period, perhaps even longer. A classic flip in the pattern is expected that is well signaled by the MJO (Madden Julien Oscillation). Currently we are in phase 5, known for a temperature analog in October that favors cooler than normal readings (right where we are heading)
A few days after that we enter phase 6 which in October points to warmer temperatures.
The EURO operational and ensemble are in sync with that idea showing week 1 temperature departures that look like this. That mirrors a phase 5 MJO analog.
Week 2 we go to this. That certainly looks like a phase 6 analog.
Neither phase 5 or 6 is a great precipitation producer and the 15 day rainfall departures reflect that with a continuation of below normal rainfall through October 27th.
I'm one of those guys that would take the pain before the gain. So I'm fine with the way this looks to be playing out. The other take away is not to be too disheartened with the premature cold early next week. It's just that, premature, and there's more Indian Summer weather to come. Stay strong my friends! Have a stellar day and roll weather...TS