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Sunday's Snow - A Difficult Forecast!

Sunday's Snow - A Difficult Forecast!

Current predictions as of Friday morning

by Monty Webb

Posted on March 21, 2013 at 11:37 PM

Updated Friday, Mar 22 at 6:16 AM

Snow Chances For Sunday

Everybody is talking about it -  A Spring "Snow Storm"...  Let me be completely honest with you, this is an extremely difficult forecast!  We have weather models that are giving us a range from zero to 12 plus inches.  How's that for consistency!  Let's take a closer look at the data and see if we can make any sense out of this mess.

No Real Agreement

First lets look at the GFS...  It has the northern most track of all the models. 

Sunday morning the Low is over western TN.  We would wake up to some cold rain with the snow over IL and MO (in the cold air northwest of the low)

By midday the Low is centered over the TN/KY border.  We start seeing some cold air pulled into the region and transitioning from rain to snow.

And by Sunday evening the cold air is firmly in place with the Low sitting to our east in E. KY.  Notice the heaviest snow in over SE IN, SW OH and N. KY.

The GFS paints out 2-4" over the Metro with the snowfall quickly dropping off south of Bullitt Co.  The bulls-eye of 6-8" is to our northeast.

 Now, lets take a look at the NAM, which is tracking the Low a little farther south.

Sunday morning the NAM has the Low centered over south central TN and we still wake up to some cold rain.  But, with the Low tracking farther south and east the cold air would arrive sooner.  thus, we would transition to snow during the morning hours.

By midday the Low is over southeast KY.  and the NAM is showing a nice band of snow along the Ohio River.

Sunday Evening the NAM has the Low sitting off the east coast and we are cold with snow showers.

So how much snow is the NAM trying to dump on us...  A lot!  I think the NAM is way over doing the snowfall totals!  (Sorry snow lovers)

Finally the RPM is tracking the Low way south and doesn't give us any rain or snow!  I also believe this model is out to lunch.

NOAA's Weather Prediction Center - 24hr Probability of Snow Accumulating (Sunday)

WPC has the Metro in a 40-50% chance of greater than 2" and you can see that increases to a 60-80% chance over south central IN.

We (Metro) are in a 20-30% chance of seeing 4" or greater, while south central IN is looking at a 40-60% chance

As we move to the greater then 6" probability the chances really drop off.. 5-10% for areas north/south of the Ohio River and a 20-30% over south central IN.

Finally the greater that 8" probability is very low... 1% north and south of the Ohio River and around 5 maybe 10% for south central IN.  It is obvious that WPC is not buying into the NAM solution.

My Snow Forecast

As I stated earlier the is a pain in the neck to forecast, but everyone likes to see the numbers.  Just remember this forecast is Not Set in Stone and will likely change over the next couple of days!

Final Thoughts

There are many pieces of this puzzle that needs to come together just right for us to see the snow...  How much warm air advection will we see out ahead of the low on Sunday; how fast will the cold air move in behind the low; will we get dry slotted Sunday evening; the final track of this low...  The models are simply having a difficult time with this system.  Another challenge to the models is a short wave (upper level disturbance) over the Gulf of Alaska.  This short wave will not hit the upper air network until Friday night.  Once it does the models will be able to add that data to the forecast.  Hopefully we will have a much better handle on this system Friday night/Saturday morning.  Stay tuned I'm sure the forecast will be changing!