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March 28, 2011

Can the Tuesday/Wednesday Storm Produce Snow???

The big topic over the weekend had the be the "white stuff" falling from the sky. What a week we had last week... highs in the 80s, severe weather, then ending the week officially with 0.3" of snow. To say the last week of March was wild would be an understatement. One more storm to end March, let's talk about whether it is a rain or snow scenario.


Forecast Discussion


We are watching a weak storm move across the area today. The humidy is very low, so I am not concerned about too many problems from this storm. We will go between storms later today, then wait for our next storm late tomorrow. Ahead of the storm, we will see pretty warm conditions tomorrow, but like our last storm the dry atmosphere will allow temperatures to drop quickly once the precipitation begins. The question is can they drop low enough. In this scenario, it would take about 35 degrees to 37 to support snow, so let's begin our look.  

The NAM and GFS look very similar in their setup for this system with very similar amounts of precipitation. Note where the blue line is located on the following maps. Keep in mind that is a "rough and dirty" rain/snow line on the computer models. We will look at the computer models from 1 am Wednesday through 7 am Wednesday.


NAM Forecast for 7 AM on Wednesday

Note the NAM holds things a bit warmer on this next storm. Seymour would see a quick transition to snow or go all snow late Tuesday to early Wednesday..


Nam precip totals 1 


NAM Forecast for 7 am Wednesday

Note by the time the cold air arrives in Louisville, the precipitation is shutting down.


Nam precip totals 2 


GFS Forecast for 1 am Wednesday

Note the GFS says it is way too warm to support snow in Louisville by 1 am on Wednesday, but shows a near or all snow scenario for Seymour, IN.



GFS Forecast for 7am Wednesday

Note, the GFS (like the NAM) is shutting down the precip by the time it gets cold enough to support much snow in Louisville.




HPC Forecast for 2"+ of Snow

Note the negligable numbers near the river up to 40% near Seymour, IN.


HPC 1 



My Snowfall Forecast


The GFS is again my forecast model of choice. It has done very well with the precipitations amounts and temperature profile of the atmoshere. I like that it is showing on a few flakes as the storm ends Wednesday morning from Louisville to E-town. Clearly this is primarily a rain event for the Louisville metro and points south.


The only area that I feel could pick up an accumulation would be near Seymour, IN to North Vernon, IN to Bedford and maybe as far south as Scottsburg, IN. The last storm cooled the pavement temperatures considerably near Seymour, IN. Take a look at the 35-37 degree pavement temperatures near Seymour, IN.




I think those colder pavement temperatures could support up to a 1" accumulation from Bedford, IN, to Seymour, IN, to North Vernon, IN on the pavement and 2" on the grassy surface over this area.



Full Forecast


Today we could see some flurries early near Louisville and snow showers are likely south of E-town, KY early. We will all see decreasing clouds late this afternoon with a high near 50.




With our next storm approaching very quickly, we will see a return to mostly cloudy skies tonight with a low near the freezing mark.




Finally your 7-day. Rain appears likely late tomorrow through early Wednesday and will possibly mix with a couple of wet flakes as it ends in Louisville. Stray showers are possible on Thursday and Friday, but temperatures will start to moderate. By the weekend, the weather pattern will start to change to a "high amplitude" jetstream. This should allow significantly warmer weather with the occasional "2" day spurt of colder air, but the warm should out number the colder days starting late this week.




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