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April 29, 2011

Rain in the weekend forecast, but the question is how much???

With swollen rivers across much of the area, we really need to think about how much rain could fall from the chances this weekend. There is a bit of a spread on rainfall totals coming from the computer models this morning, but I think we can get a good grasp on the amounts in our morning discussion.


Rain Forecast Discussion


A storm is going to approach the area this Sunday and we will see a quasi-stationary front get stuck near the river. This setup is vastly different from what we saw over the last 10 days. That system had a huge amount of moisture to work with, where this system has marginally moist air to work with and not near the warmth. That still means heavy rain could fall, but I don't see a way it could rival what we saw over the last 10 days. The GFS is going with smaller rain totals than the NAM, but that is commonly the case as NAM has a better grasp of convective events.


GFS Rainfall Forecast Rainfall Through Monday AM

Note the GFS  is indicating 1" to 1.5" for most of the area.



NAM Rainfall Forecast Rainfall Through Monday AM

Note the NAM is showing 1.5" of rain from Louisville through southern Indiana and up to 3" for southern Kentucky.




HPC Rainfall Forecast Rainfall Through Monday AM

Note HPC is indicating around 1.5" to 2" of rain for most of the area.


HPC 1 


Remember much of the area remains under a flood warning with all the rain from our last system. The Ohio River has crested in most locations and it is falling, but this rain could delay falling below flood stage.




River Flooding 1 



My Rainfall Forecast


There is definitely a difference in how the NAM and GFS are dealing with this system. I do find some of the NAM info a bit unreliable right now because it seems to be moving the front too far south of the river. I think the problem with the NAM is overestimating the initial t-storms and their ability to shift the front south. I like the placement of the front and rainfall totals from the GFS. I think a widespread 1.5" rainfall total will occur Sunday and into early Monday. Some isolated totals further south could approach 2".



Full Extended Forecast


With so many outdoor events coming up, I wanted to touch on the extended. I love the weather tonight for the US Bank Great Balloon Glow with temps in the 60s - 70s. :)


KDF 1 


Tomorrow for Opening Night at Churchill Downs for the Spring Meet 2011, we should have a very warm afternoon and mild temperatures through the night. I have introduced a small 30% chance late, but it does look like rain won't start until late.


KDF 2 


On the longer range, I think showers look possible for the Pegasus Parade and Oaks could include a morning shower then partly cloudy in the afternoon. A chance does exist for showers late on Derby, but there remains some uncertainty still in that time frame. We will continue to dial in these forecasts as we get closer.





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Any chance of severe before derby?

John, nothing stands out at this point.

When is this rain going to be falling on Sunday. We have a Birthday Party at 2 outside :(

The rain chance is really all day on Sunday, but most likely in the morning. It will be hard this far out to determine the exact timing of each wave right now.

Thank you Marc!

Marc, what is going on with the wind just west of Salt Lake City? This is the same area that the last front developed and caused all of the flooding. Look back on the radar screens and see the donut yourself. I think that it is a haarp location in this area and all the flooding and storms are at the hands of our government. Thanks for your time and no I am not a nut case, just concerned grandpa.

Robert, remember that is likely a relic of the code that creates the composite radar imagery. Unfortunately we do not have 100% coverage across the US because of blocking from terrain and other things, so I suspect that is just an artifact.

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