I first starting talking about this in my blog on Monday this week. I felt there was enough data to support mentioning that there is going to be a major cool down for part of Derby week and the data continues to suggest part of the week may not be very nice at all. In tonight's blog, I want to start to look at the computer model's temperatures for next week.
A Major Pattern Chance Is Beginning
The weather pattern for 4 of the last 5 days has been a warmer than normal pattern. That has been very nice and quite frankly will continue through early next week, but when the change comes it will be sharp! The weather pattern right now has broken down into what we call an "omega block". Notice how the jet stream resembles the greek letter omega (Ω) now.
Blocking patterns act as a road block for all storms. That means the storm over Billings, Montana will not just move slowly, but it will really drag its feet over the next week. Notice that same storm by Monday has only moved to near eastern Kansas.
By Thursday of next week, this is now sitting over eastern KY. That means in 204 hours, this storm has only moved 1,200 miles. That is an average storm motion of 5.8 mph for the next 9 days! Talk about a turtle!
What Does This Slow Moving Storm Mean For Our Area?
This slow moving storm means sustained weather on both sides of the low. In front of the low, it means sustained warm weather that lasts through around Monday, then a sharp turn toward sustained colder weather. Looking at the EURO and GFS temperatures for next week, you can see the problem this potentially means for Wednesday, Thursday, Friday, then it gets a bit unclear beyond that point. As you look at the data, note the timestamp and computer model name is in the top right part of each image. Please remember this is NOT my forecast, but a look at the computer model temperature forecasts for next week.
EURO Computer Model Temperature Projections
Notice the EURO keeps us "mild" on Tuesday, but beyond goes cold for this time of the year.
GFS Computer Model Temperature Projections
Notice the GFS also doesn't bring the front through on Tuesday, but it turns sharply colder on Wednesday.
My Thoughts On Our Cooldown Next Week...
I have been pretty convinced this pattern was a lock for days now. The exact time when we turn colder is still not locked at all. I do feel it will occur in the middle of next week. If it ends up in the Tuesday timeframe, then it will likely warm by Derby day, but if it occurs later like Thursday, then we would have a colder Derby. Right now, the data suggests the front gets here on Tuesday night meaning Wednesday through Friday would be chilly days for this time of the year.
The slow moving nature of this storm means rain is likely from Sunday night through at least Wednesday and showers will likely continue on Thursday. While this is not ideal for Derby week, it seems the most likely at this point. The heaviest rain would likely be Monday or Tuesday as things stand right now. Here is one of the interesting tidbits, both the EURO and GFS gets it cold enough to mix a few snow flakes or sleet pellets with the precipitation next week. This is nothing to worry about from a travel standpoint, but an interesting footnote. Here is a look at the GFS for Wednesday morning. To be honest, I would not be surprised to see a little sleet mix in with some of the showers if they came in the early part of the day on Wednesday or Thursday of next week.
The Climate Prediction Center continues to bite hard on this cooldown in their 6 - 10 day forecast and their 8 - 14 day forecast. Notice they have a 50% - 60% chance of below normal tempertures in this period which covers April 28 through May 6. That is obviously a significant chance of colder than normal temperatures!
CPC Forecast For Monday, April 28 - Friday, May 2.
CPC Forecast For Wednesday, April 30 - Tuesday, May 6.
How this affects Oaks and Derby remains a bit unclear considering those days are still 9 and 10 days into the future. This kind of pattern moves so slow and with slow moving storms, they can be erratic. I would say in the next 3 - 5 days, we should be able to dial in Oaks and Derby, but not yet. I will be watching and updating...
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