Sunday, April 28, 2013

A Truly Amazing Weather Pattern Evolving


3:15 PM Monday update...   There are still questions as to how this evolves later this week in terms of where and how strong the upper low will be.  Therefore, I have no changes to my thinking.  I still think several record low temperatures will be challenged.  Both the GFS and the Euro shows readings into the mid and upper 30s Saturday morning across central Arkansas and temperatures below freezing across the west.  The GFS model is even going so far still as to show snow over portions of western and northern Arkansas.  Several runs over the past few days have done the same thing.  However, at this time, I'm not buying that idea.  IF that were to happen, it would likely be the latest snowfall ever recorded in Arkansas.  I'll have to look into that.  The magic number late this week is 39 degrees.  That's the all time coldest May temperature in Little Rock.  Remember, temperature records date back to the 1870s.

With a transition from 80s to 30s/40s, you would think severe weather would be possible especially in May.  Right now, there could be a few strong storms, but I just don't see any major severe weather with this right now.  If that changes, I'll let you know.

Here's the Monday morning run of the GFS showing record low temperatures early Saturday morning around 7AM.  Look at that, it's in the mid 30s in Little Rock and below freezing over the west.
The Euro is almost on the same page next Saturday morning with temperatures well into the 30s, but not as cold as the GFS.  AMAZING for the beginning of May.
 
And the GFS even shows snow accumulation over western Arkansas.  Amazing, but I don't believe it... at this time.
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I really can't believe what I'm seeing on the computer models over the next 7 days.  The opening of May could look more like the beginning of March.  There are plenty of questions as to how this will evolve, but no matter what model you believe, the underlying theme is simple.... COOL!  Temperatures could be anywhere from 15-20 degrees below average by the end of the week.  This will all come AFTER we soar into the 80s during the beginning of this week.  Get ready for a major ride on the "Weather Roller Coaster"!

Like I said, there are several variables at play here.  A deep trough of low pressure will develop over the central and eastern United States.  This will eventually evolve into a "cut-off" low.  Simply put, this sort of isolates it from the main flow aloft.  When this happens, you can get unsettled and cool weather for an extended period of time.  It's not one of those situations where the cool comes in and exits quickly.  The model differences deal with WHERE the low sets up and HOW STRONG will it be?  There will be the potential for several types of record lows to be broken such as, overnight lows, daytime low maxes, and even the coldest temperature for the month of May.  However, I must caution you that while this potential exists, there are questions.  The main ones for me are how much cloud cover is present, precipitation, and how strong will the winds be around the area.  Any of these 3 factors can PREVENT lows from dropping to record levels.  HOWEVER, these 3 factors will also prevent daytime highs from climbing and it's a good bet we'll be way below average.

Here are the records I'm watching for May 3rd, 4th, and 5th in Little Rock

Friday May 3rd records:
Coldest high temperature 52 degrees set in 1994
Low temperature 41 degrees in 1929

Saturday May 4th records:
Coldest high temperature 53 degrees set in 1935 and 1907
Low temperature 40 degrees set in 1971

Sunday May 5th records:
Coldest high temperature 56 set in 1935
Low temperature 43 set in 1945

Top 10 coldest May temperatures in Little Rock
  1. May 1, 1903 39 degrees
  2. May 4, 1971 40 degrees
  3. May 2, 1963 40 degrees
  4. May 12, 1960 40 degrees
  5. May 2, 1909 40 degrees
  6. May 2, 1994 41 degrees
  7. May 9, 1976 41 degrees
  8. May 1, 1963 41 degrees
  9. May 3, 1929 41 degrees

I have available the RAW low temperatures from both the 06Z Sunday GFS and the 00Z Sunday Euro for next Friday, Saturday, and Sunday:

                                 GFS      Euro
Friday May 3rd         36          39
Saturday May 4th     36           40
Sunday May 5th       39           47

This cut off low presents a couple forecasting challenges.  This type of storm system means there will be extremely cold air aloft. If the atmospheric conditions are right, thunderstorms could develop and pose a hail threat.  This COULD also be a situation where "cold air funnels" develop as well.  These are typically harmless, but cause quite a stir if you happen to see one.

The GFS is even going so far as to show snow accumulations across much of northern Arkansas on a few of its model runs.  Do I buy this? NO!!!!!  However, I think it's telling us something.  While the chance is very small, I would not doubt if someone reported a sleet pellet or a snowflake near the Missouri border.  We'll see. 

Here are the maps.


The GFS shows the strong low aloft over northern Arkansas and southern Missouri late Friday.  If you're underneath it, it's COLD!!!!!!  See the black lines closed around this.  This is indicating it's closed off from the main jet stream flow.

The Euro at the same time shows basically the same thing, but stronger!  This is amazing to see in early May!
The Canadian has it too, but it's further to the west so you see at least one computer model differing with the placement.
In summary, IF THIS PLAYS OUT THE WAY THE DATA SAYS, IT COULD BE ONE OF THE MOST TALKED ABOUT WEATHER EVENTS OF THE YEAR .  It's still several days away and can change, but the models have shown remarkable consistency with this evolving pattern.  Stay tuned.

2 comments:

Mitchell McDill said...

Well Todd says the weather pattern is amazing but I call it more annoying. I mean we didn't even have that cold of a winter- that's when we want to see the below normal temps- not March thru May! I'm going to check but I bet there were days in January and February warmer than we what we've had lately.

Raj said...

I never will understand why other's say "That's Arkansas weather for you." People from other states will tell you "That's [insert state name] weather for ya." Nothing special about Arkansas. The old saying for Minnesota was "If you don't like the weather, just wait 15 minutes." We must spread awareness about this! Too long have I witnessed others thinking that Arkansas weather is unique to erratic weather changes. Not so!

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