Tuesday, May 22, 2012

Considerable Forecaster Variability for Mem Day Weekend

Analysis: The Memorial Day Weekend forecast proved to be a challenge. The official high temperatures at MSP for Saturday, Sunday and Monday were 64, 92 and 80. None of the forecasters shined, though we'd say the Strib probably did the best, coming very close to nailing both Sunday and Monday temps. WCCO was out to lunch with the Saturday forecast, missing it by 15 degrees and standing out from the crowd in the process. This just in: long-range forecasts, particularly for this part of the country, is not quite an exact science!

A changeable forecast for Memorial Day Weekend means great variability in forecasts from your beloved local and national weather outlets. For Saturday, Sunday and Monday, there are spreads of 7 degrees, 14 degrees and 9 degrees respectively between forecasters. In general, the Star Tribune is the most bullish on weekend warmth (followed closely by KSTP) while WCCO is generally the coolest. Here are temperature forecasts as obtained at noon on Tuesday.


#4: 76/77/72
#5: 74/86/82
#9: 74/81/73
#11: 75/na/na
NWS: 74/83/73
Accuweather: 70/81/70
TWC: 69/85/72
Strib: 72/91/81

30 comments:

  1. Give or take a degree or two, I'm with KSTP and their forecast. These forecasts are tricky when you have a slow moving or stalled front, and the temperature gradient is fairly extreme from warm to cold sector. I'm sure these highs will be adjusted as the week goes on, but mid/upper 80's on Sun and low to mid 80's on Monday appear to be correct at the moment. If the timing or positioning of the incoming fronts changes, then the temps will have to be adjusted as well.

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  2. Yep, it appears to be a good challenging forecast, one that should separate the men from the boys.

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  3. SPC a bit bullish on severe weather for day 5.

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  4. @Bill,I believe the bigger concern for most folks is not the temps,but the rain falling from the sky.........most people at this time of year can enjoy the outdoors if there is a good deal of sunshine regardless of the temps,but if the weather is rainy then most outdoor plans are spoiled,like bbq's,parties,etc.......so if your long weekend starts Friday,then there will be two dry days(Fri/Sun)sandwiched around to wet days(Sat/Mon)so the weekend weather at best is 50/50,throw in some heat and humidity for Sunday,and one could argue we had much better Memorial Day weekends then the one forecasted for this weekend.

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    1. I heard you Big Daddy. Unfortunately, it's much easier to assess forecaster performance based solely on temps. Until each of them provides specific percent chances of rains for the various time periods, it's just a general "chance of rain for most of the long weekend."

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  5. Here's a question. The large amount of rain forecast for today and tomorrow is the result of a stalled cold front. Right now the front isn't stalled -- how do they know that it will stall?

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  6. Forecast models have been pretty consistent with it either stalling, or moving east very slowly. It is pretty evident looking at the wind profiles on the models that the front is very slow to move. At this point it looks like it will stall pretty close to the metro area, if not right overtop of it.

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  7. Yes, models are consistent. But I asked why. Is it because the winds are out of the south and so strong?

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  8. Ahh, ok. It's the ridge that is out to our east. The ridge is quite strong, and will pretty much slow the advancement of things behind it. This will be the case until the ridge breaks down. I'm sure there are others that can go into even more detail about the specifics, but that is pretty much the basic explination...strong ridge of high pressure out east.

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  9. Has the stall begun? Looks like storms have ceased to make eastward progress.

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  10. The rain started at 20:48 at my house. We'll see how long this lasts.

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  11. It came into western St. Paul about 15 minutes ago. Looks like it's more or less on schedule.

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  12. Per the RPM model, it looks like the stall won't really happen till near midnight.

    Here's the maps, with the line representing the approx. area of the front. Going from 06z to 09z, the line shifts slightly back to the west, which leads me to belive that is the stalling point.

    06z: http://i105.photobucket.com/albums/m203/duanewolter/RPM1.gif

    09z: http://i105.photobucket.com/albums/m203/duanewolter/RPM2.gif

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  13. Man did it rain last night and thru the overnight.........2.55 inches in the rain bucket here in Golden Valley,imagine if this situation occured in winter(of course we wouldn't be so lucky)but we would be sitting on about 30 inches of snow.........but hey at least we don't have to hear about drought anymore.

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    1. If only we got stalled cold fronts in winters lol.

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  14. Plymouth Weather LoverMay 24, 2012 at 10:58 PM

    Snow? I like any mention of snow. I will be dreaming of stalled fronts in winter!!

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  15. So Sunday appears to be the big day for us. Everybody seems to be in agreement that there will be an outbreak of some magnitude. I don't know a whole lot yet as far as reading models goes, but from what I do know I see a lot of ingredients coming together.

    However, since I'm still pretty novice when it comes to all this I'm curious as to what the experts on this site are thinking. Anybody have any thoughts yet?

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  16. Sunday could be a very active day, with the main threat for severe coming with a cold front moving east across MN during the evening and overnight hours. All three modes of severe should be possible with it, however I think the hail and damaging winds will be a bigger factor than tornadoes. At this time, I believe areas of SW MN up into central MN will stand the best shot at perhaps seeing a tornado or two, since initiation should be somewhere in that vicinity. At the evening goes on, it should form into a nice line and become a damaging wind threat. Unless some overnight storms really screw with Sunday's temps, temps should easily get into the 90's. That will be plenty of instability for some nice storms to get going. The NWS mentioned a greater tornado threat if a mesolow could form...which is quite common with convective complexes. Stay tuned to forecasts, as many will be outside and perhaps away from TV's or radios.

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  17. Well in regards to temps we got into the low 90's,so Mr. Douglas takes the cake on that,in terms of weather(precip) this weekend....Friday was nice,Saturday I wouldn't call a washout but it rained enough of the time to spoil any outdoor activities,Sunday was just plain disgusting out,unless your one that loves high heat and humidity,it has stayed dry the whole day,but now as we head into the evening hours storms are gathering and firing from NW Nebraska,NE Iowa and So. MN,moving NNE,it should be a rainy/stormy night in and the metro.....but this should all clear out for a beautiful Memorial Day with less humidity and heat..........Happy Memorial Day everyone and stay sky aware tonight!

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  18. Seems like an odd line keeping most of the rain west of the 35E line.... last 3-4 major rains I've watched it all go by just to the west of Rosemount. I hope this doesn't continue on into winter. (yes, I am already looking forward to snow)

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    1. Looks like the stuff to the SW of the Twin Cities is starting to push to the east as the line continues to develop. So those of us in the eastern metro will likely get something a little later tonight.

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  19. 64/92/80...those were the official temps at MSP for Sat, Sun, and Mon. So, Saturday no one was really that close (The Weather Channel was closest, and was still off by 5 degrees). Sunday goes to the Trib (good call by P. Douglas), and Monday both the Trib and KSTP were pretty close. I wouldn't be too harsh though since these were forcasts several days out. Still though, props to those who got it pretty damn close.

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  20. Yea, good assessment, Duane. The Saturday forecast was 4-days-out as of Tuesday so that was a legitimately poor forecast (or the models did a poor job). In fact, the morning forecast on Saturday (for Saturday) was not very good. Some, including MPR, said the afternoon would be "relatively pleasant." I'd say it was just this side of a washout.

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  21. Duane I agree as well, kind of a complicated forecast for that time period, when would it rain, how much and where would the heaviest precip's be. I was calling for some places to get 5-7" through Memorial Day, I was a little shy in some spots, (well ok a lot shy in some spots). I ended up with 6" in my backyard, for the week.

    Turning my attention to next weekend, Saturday looks to see some sun with a high of 72° a 20% chance of rain, totals should be less than a 1/10 of a inch. Sunday look fabulous with sunny skies and a high 77° Dew points should stay south of 55 for the weekend.

    Monday should see a return of 80°+ along with higher dew points as it looks like we could once again get into a period of disturbed weather.

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    1. check that on Sunday, Temps now look like they could be above 80 with dew points as high as 65° based on the 5/29 0z and 12z runs of the euro. Precip chances 20%

      GFS is about 6 hours slower bring in the higher DP's

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  22. @randyinchamplin, any thoughts on the longer range? my sister gets married june 9th and i will be coming down from ND from the 6th-10th. hoping for some good severe weather days.

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    1. 1st of all thanks for asking, 2nd of all I hope your sister gets 80° temps with the dews in the low 50's, that would be prefect for a wedding day. But to answer your question, at this time it's way to earlier to tell. I don't know where you will be at in MN, so my best advice would to monitor the Area Forecast Discussion from the various offices that cover MN. Another source would be to monitor the Storm Predictions web site under Convective Outlooks, while often time's for the day 4-8 daily outlook they will show "predictability to low," they often in their text portion give a idea of what they think.

      As a amateur weather nut, I like forecasting, but please refer to the pros.

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  23. Bill,

    I'm still impressed that you are rating the media and NWS based on their day 7 forecast and think that rating has meaning. How was the day 2 forecast for the holiday weekend?

    --Kevin.

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    1. Yea, I think I'm pretty much done with this whole rating stuff. I've got a lot of "in conclusion" thoughts to share on the subject at some point soon....

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  24. Hey Bill severe threat close to home on Sunday,with all this heat and humidity forecasted on Sunday....storms could be big,hope tornadoes stay away though......as they always say keep an eye to the sky.

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