Wednesday, October 23, 2013

Halloween Week Storm


This will be the first significant storm system of the season and confidence is increasing this will affect the state by the middle of next week.  One thing we must always keep watching this time of year is the severe weather possibility.  While I'm not calling for it at this time, we are in our secondary severe weather season and it's on the table.  There have been years when fall produces more severe weather than spring.  Let's hope this won't be the case.  Right now, it's fairly safe to say there will be the threat for heavy rainfall.

I'm going to follow the more superior European model.  Yesterday, it had one run that was completely out of touch, but I think the overnight run may have a decent handle on it now.  I fully expect temperatures to warm up later this weekend into next week.  Moisture levels will also be on the increase.  This warm up will be short lived as a blast of cold air will move in behind the front.  I would not be surprised to see snow with this dynamic system over portions of the OK/TX panhandle up to Kansas.  Remember, when you're dealing with the long range, it's very tough to get specific.  Just know things are likely to change in terms of strength, timing, etc.

Like I said above, I'm going to follow the European model.  This is valid next Tuesday at 7PM.  The black closed line over WY/CO is an area of high pressure at the surface.  Look at how the black lines drill south into northern and western Texas.  This is the high pushing very cold air (relative to average) south.  The boundary is draped from central Texas into western Arkansas.  In the upper levels, the energy I talked about in the previous blog post is pulling out of the southwestern United States.  The green and yellow blobs are precipitation amounts over the previous 6 hours.  You can see how much with the legend at the bottom.
By Wednesday morning at 7AM (October 30th). The upper low is located over New Mexico/West Texas.  In case you're wondering, that's the red and blue dashed lines making a circle over that area.  That's simply a reflection of the upper low position.  Remember, yesterday's run of the Euro was holding this upper level energy over the Pacific Northwest.  Now, it's pulling it out into the plains and that makes more sense!  The cold front is bisecting the state from PA into northeast Arkansas down into east Texas.  See the greens and yellows?  That's heavy rain surrounding the front.  As the upper level low pulls out of the southwest, you will see a surface low develop along the front.  That surface low will be responsible for more heavy rainfall.   Once it passes, the colder air will really get a push south.
Now we're looking at Wednesday, 7PM.  the surface low is over southeastern Arkansas.  See the black closed line (isobar)?  There's a cold front trailing from that low into LA.  The cold air is pouring into western Arkansas with very heavy rain over much of the state.  Now turn your attention to the upper level low over north TX/OK.  The red dashed line (circle) reflects its presence.  It's labeled "546".  This is a thickness value.  Once it reaches around "540" then we're watching for snow.  This is awfully close.  You must also consider surface temperatures too.  Are they cold enough?  So I think there's a chance for some snow on the north edge of this from the TX/OK panhandle into northern OK and southern KS.  Regardless, underneath the upper low, it's COLD!!!!!!
Now onto Halloween.  This is Thursday at 1PM.  The upper low is right over Arkansas with light rain.  THIS IS COLD!!!! The main front has moved into Alabama.  There's a dry slot from TX into LA up into eastern AR.  The counterclockwise circulation around the upper low is drawing in a dry, southwesterly wind aloft.  Then the upper low moves in and produces a cold rain.  The Euro suggests this could move out by sunset. 
In summary, remember this... IT'S IMPORTANT.  I have shown you above what one model says. IT WILL NOT BE PERFECT THIS FAR OUT!  This will change as far as timing, strength, and track.  But the modeling does agree on a significant storm system next week.  I will likely follow the more superior Euro in this situation.  It blew away the GFS last week when forecasting the Race For The Cure Weather.  I'll keep you updated.  Thanks for reading.  Stay tuned

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