Thanksgiving Week Arctic Outbreak

[Jonathan Whitehead]

Surprised no ones has started a thread on this yet as this appears to be the first major arctic outbreak of the season for much of the US. While there doesnt appear to be any sig frozen precip with this outbreak (at least across the Plain and South), it does appear it will make for cold Thanksgiving travels.

Here is a look at this mornings MSLP forecast from the GFS beginning at 12 UTC this Saturday.

 

[rdale]

Most long-range forecasters are throwing out the GFS and using GFS ENS / ECMWF instead, which are nowhere near as cold.

 

[Jeff Miller]

To add to this, for those who have frequently been observing the GFS Model, it has consistently been far too cold and far too strong with arctic outbreaks in the long range patterns. What you will see is a strong arctic blast, then it will moderate and weaken as the actual event gets closer. Reading one specific model for winter weather predicting and using this as a forecast is like trying to make a cake with just eggs. You have to add the other ingredients (models and ensembles) to make your forecast cake and have it be edible, so to speak.

Though it is certainly true that there will continue to be a cold build up of canadian air over the next few weeks and an increase in snow cover, the true arctic blasts will likely hold off for at least a few more weeks. Believe me when it happens, the ensembles and models will yell about it and it will be very hard to ignore.

 

[Jonathan Whitehead]

I completely agree with both of you but I challenge you to find a long range model that offers as clear a surface forecast analysis as the GFS. Last I checked the Euro and Canadian are available only thru AWIPS and GEMPAK and not readily available online like the GFS so someone like myself with no forecasting job is on outside using only what I can use. Its frustrating. And dont even get me started on winter cross sections.

 

[rdale]

Just because it's available doesn't mean it's valuable... I can show you some 1km models that show so much detail you'd think it was showing live radar. But if the forecast stinks, what good is it?

 

[Patrick Marsh]

Most long-range forecasters are throwing out the GFS and using GFS ENS / ECMWF instead, which are nowhere near as cold.

Monday's 00 UTC run of the ECMWF had high temperatures in the 30s (F) for Oklahoma on Wednesday of next week. In fact, the 00 UTC run of the ECMWF was colder than the 00 UTC run of the GFS, and the ensemble did support the solution. I'm not saying it will happen like this, but the ECMWF is showing a significant cool down next week.

While on the topic, both the ECMWF and GFS are suggesting a wintry mess from Kansas City, MO to Chicago IL from late Tuesday into Wednesday. The ECMWF has the surface 32F line meandering through Chicago during this time period, with precipitation, with what could potentially be a significant snowfall across Kansas City, MO into Iowa, and then into far southern Wisconsin. I'll also point out, that at least based on the 00 UTC guidance suite, the ECMWF was significantly wetter than the GFS.

 

[rdale]

You're looking at the EC Ensemble?

 

[Patrick Marsh]

Yes. Now, I'm not looking at postage stamp type plots, but ensemble fields like mean, spread, standardized anomalies, etc. are available for viewing.

 

[Kelly Sugden]

Most long-range forecasters are throwing out the GFS and using GFS ENS / ECMWF instead, which are nowhere near as cold.

Actually the GFS and EC have been similar on the synoptic scale of cold air/high pressure build up over Canada. They do have differences in the surge southward across the Central Plains. Any high plains forecaster knows that models do not handle the shallow cold air mass that well. Gravity will eventually dominate. Thanksgiving week does look cold.

 

[jdrenken]

Here is the Euro Ensembles and the "Deterministic" from the source now that we don't have Allan Huffman's website available.

 

[jdrenken]

By the way...the HPC is throwing out the 00Z GFS per their extended forecast discussion.

 

[Kelly Sugden]

850 hPa temp anomalies

There is no question it will be colder next week. The problem is the boundary of the Arctic air will be fighting against southwest flow aloft...with the baroclinic boundary shuffling south and north with minor upper air disturbances. This is until the upper level trof finally traverses east allowing the Arctic air to complete surge southward across the rest of the Central Plains into Texas. Next week, particularly towards Thanksgiving looks cold for Kansas and Oklahoma, and hopefully shifts south into Texas as well.

 

[Jonathan Whitehead]

Tru arctic air outbreak are characterized by NW flow aloft to northerly flow due to Gulf of Alaska ridge and/or NERN Pacific ridging. However next week will feature a SW flow. Now that doesnt mean u still cant have arctic outbreaks b/c gravity is gravity, once it breaks off its Katy bar the door. Having said that, with next week featuring a SW flow does that mean the arctic air wont be as deep or as long lasting if the flow aloft was a true Siberian Express setup? My experience living in Plains is Arctic air with SWRLY flow tend to be quite shallow, which in dead of winter makes for the first stage of ice storm event.

 

[Chris Carter]

The only thing that is really certain, is that its going to be very cold over most of the nation during the holiday break (Tuesday - Sunday) and someone is going to get a lot of snow and a lot of wind, and tornadoes.

Latest runs have switched from a track and takes it northeast along the East Coast, to a more westward track that pulls it over the Great Lakes and really cranks up the lake effect snow machine. But now there is an issue of timing, in fact I have seen a few GFS runs where there are two parts of the system where one part breaks off over the Great Lakes during Thanksgiving and a second part heads off the East Coast a few days after that.

It seems like a lot of flip flopping back and forth between the models. But there is a good week before whatever comes out from the rockies impacts the travel for the holidays.