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When The Next Arctic Blast Hits DFW

By Chief Meteorologist Larry Mowry
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A man shelters under an umbrella as he walks through a rain shower. (credit: Getty Images/Armin Weigel/AFP)

A man shelters under an umbrella as he walks through a rain shower. (credit: Getty Images/Armin Weigel/AFP)

(credit: KTVT/KTXA) Larry Mowry
Larry joined the CBS 11 Storm Team in January 2008 from CBS affil...
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Many of you have probably heard about the next shot of Arctic Air that looks to be coming our way in North Texas.  I know a lot of people are tweeting about it and posting on Facebook their thoughts.  I love this blog we do on CBSDFW.com because unlike others, I get to show my work and show you what I am thinking.

This blast looks to hit sometime around Friday of next week + or – a day.  The question is will this be as strong and as bad as what we have just experienced.

So let’s talk about it.

WHY ANOTHER ARCTIC BLASTS

A few weeks ago, I blogged about how HIGH pressure over Alaska dislodges cold Arctic air and allows it to flow south.

Heading into next week (Dec. 16 thru Dec. 19) that high pressure relaxes over Alaska.  That will be one of the factors that warms us up in North Texas.  The early part of next week will find high temperatures in the 60s and possibly 70s.

But High Pressure becomes strong over Alaska late next week and here comes another shot of cold air.

Below is a look at the 500 mb wind pattern over North America on Saturday Dec. 21 (click on image to make it larger).  Basically what this shows, is what the upper level winds are like.  Note the high building over the northern Pacific and nudging its way into Alaska.  That creates a northerly flow coming straight out of northern Canada.  In fact, just like this past Arctic Outbreak, some of the cold air originates on the other side of the North Pole in Siberia.

500MBSATDEC_21AM

So here comes another shot of Arctic Air.  I look for the Arctic Cold Front to arrive sometime around Friday of next week + or – a day or so.  But how cold will it be this time.

It looks like we will have a period of cold air that could be comparable to what we have seen over the past 7 days.  There will be reinforcing shots of cold air as that high over Alaska strengthens.

Below is a look at the 500 mb flow on Christmas Day.  The thing to take from this map is how similar it looks to the map above 4 days earlier.  There won’t be much change in the pattern the week of Christmas.  This means once we get into the cold air, it will likely stay with us for a while.

500MB_Christmas_Day

WILL WE GET ANOTHER ICE STORM

At least with the initial blast of Arctic air around the end of next week, the setup is not as favorable for wintry weather.  Let me show you.

Below are the 3 different forecast models.

CANADIAN MODEL FOR 6PM FRIDAY, DEC. 20

CANADIAN6pmDEC20

The above map may be hard to see, so click on it to make it larger.  The green on the map represents precipitation.  Note how none of that is in North Texas.  This would just be a dry, strong cold front.

EUROPEAN MODEL FOR 6PM FRIDAY, DEC. 20

EUropean_6pm_FRI_DEC_20

The above map is a closer view of North Texas.  Again the greens/blues on the map represent precipitation.  A simple rule, look for the thick blue dashed line as the defining line of where we have rain vs. snow.  In meteorological terms, this is called the 540 thickness line.  Basically it can be used as a rough guide as to where the cutoff of rain to snow would be located.  During this time frame above, the European model shows the chance of wintry weather, most likely a change over to snow.  But it would likely be a brief changeover as precip would end later that evening and night.

GFS MODEL FOR 6PM SATURDAY, DEC. 21

GFS_SAT_6PM

The GFS Model, which is the main forecast model run by the US, shows precip lasting longer.  Again look for the blue, thicker dash line.  The GFS wants to keep an upper level disturbance to our west behind the cold air.  It then brings that disturbance over our area on Saturday.  That is what could bring us a chance of snow on Saturday.  I say that with a WORD OF CAUTION.  This is really the only model that shows that solution of snow.  But the ingredients are on the shelf for it to happen.

NEXT TWO WEEKS

Below is a summary of the next two weeks.

December Outlook

SO WHAT CAN I TELL YOU FOR SURE

I can tell you that we will see another blast of cold air coming next weekend.  More freezing temperatures.

The possibility is there for wintry weather.  Definitely not a certainty.

Will it be as bad as this ice storm? No, the setup right now does not favor an ice storm.  I’ll be keeping a close eye though on the pattern to see if that changes.

Thank you for taking the time to read this blog.

Larry Mowry

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