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Fabulous February Arctic Outbreak

DaculaWeather

By DaculaWeather,
in Tennessee Valley

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Stovepipe

Stovepipe

Posted
Posted

its about time we start relying on a NW trend. Amazing considering it was looking to go hundreds of miles to far north 2 days ago

 

I'm not sure I'd wish the GGEM/EURO/UKIE much north at this point personally.  I could be way wrong but I don't think the jog south on the 18z gfs is of any concern. 

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jaxjagman

jaxjagman

Posted
Posted

CPC tends to agree with a southward push:

 

hazards_d3_7_contours.png

Valid Sunday February 15, 2015 to Thursday February 26, 2015

US Hazards Outlook

NWS Climate Prediction Center College Park MD

300 PM EST February 12 2015

Synopsis: At the start of the period, surface low pressure moves away from the New England coast. Cold, surface high pressure builds in behind the departing storm over the central and eastern U.S. Areas of low pressure are expected to form over the southern Plains and move eastward across the lower Mississippi Valley and then northeastward along and off the east coast. Another area of cold surface high pressure moves from the Northern Plains to the west-central U.S., then gradually spreads eastward. Areas of surface low pressure are anticipated near the Aleutians and Gulf of Alaska.

Hazards

Periods of high winds for parts of the northeast and coastal sections of the Mid-Atlantic and southeast, Sun-Thu, Feb 15-19.

High winds for parts of the Central Great Basin, southwest, central and southern Rockies, and central and southern Plains, Mon-Wed, Feb 16-18.

Periods of high winds for parts of the Aleutians and western Alaska, Sun-Thu, Feb 15-19.

Heavy snow for extreme eastern parts of coastal Massachusetts and Maine, Sun, Feb 15.

Heavy precipitation for parts of southeastern Alaska, Mon, Feb 16.

Heavy snow spreads southward across the Rockies, Sun-Mon, Feb 15-16.

Heavy rain for parts of the southern Plains, lower Mississippi and Tennessee Valleys, and southern Appalachians, Mon, Feb 16.

Freezing rain and sleet for parts of the southern Plains, lower Mississippi and Tennessee Valleys, southern Appalachians, southeast, and Mid-Atlantic, Sun-Wed, Feb 15-18.

Heavy precipitation for parts of the central and southern Plains, lower and Middle Mississippi Valleys, Tennessee Valley, central and southern Appalachians, and Mid-Atlantic, Mon-Wed, Feb 16-18.

Heavy snow for parts of the Central Mississippi, Tennessee, and Ohio Valleys, central and southern Appalachians, Mid-Atlantic, and coastal New England, Tue-Thu, Feb 17-19.

Periods of much below normal temperatures for much of the eastern two thirds of the CONUS (except Florida and western Texas), Sun-Thu, Feb 15-19.

A slight risk of much below normal temperatures for much of the eastern two-thirds of the country, Fri-Thu, Feb 20-26.

A moderate risk of much below normal temperatures for most of the eastern half of the CONUS, Fri-Thu, Feb 20-26.

A high risk of much below normal temperatures for much of the northeastern CONUS, Fri-Mon, Feb 20-23.

Severe drought for the Central and Southern Great Plains, Southwest, Great Basin, California, the Pacific Northwest, and Tennessee Valley.

Detailed Summary

For Sunday February 15 - Thursday February 19: Low pressure is forecast to move off the New England coast. As the low deepens, heavy snow (in excess of 4 inches in 24 hours) is possible for extreme eastern sections of Massachusetts and Maine Feb 15. High winds (in excess of 30 knots) are forecast for parts of the northeast and coastal sections of the Mid-Atlantic and southeast Feb 15-17.

Heavy snow (in excess of 4 inches in 24 hours) is expected to spread southward across the Rockies due to upslope flow Feb 15-16.

As areas of low pressure form over the southern Plains, high winds (in excess of 30 knots) are anticipated for parts of the central Great Basin, southwest, southern and central Rockies, and southern and central Plains Feb 16-18. At the same time, Arctic high pressure is forecast to move from the Northern Plains to the central CONUS. As the areas of low pressure move east-northeastward towards New England a wide variety of precipitation is expected across the central and eastern CONUS. Heavy rain (in excess of 1 inch in 24 hours) is expected for parts of the southern Plains, lower Mississippi and Tennessee Valleys, and southern Appalachians Feb 16. Freezing rain or sleet is anticipated for parts of the southern Plains, lower Mississippi Valley, Tennessee Valley, southern Appalachians, southeast, and Mid-Atlantic Feb 15-18. Heavy mixed precipitation is forecast for parts of the central and southern Plains, lower and Middle Mississippi Valleys, Tennessee Valley, central and southern Appalachians, and Mid-Atlantic Feb 16-18, and heavy snow (in excess of 4 inches in 24 hours) is expected for parts of the Central Mississippi, Tennessee, and Ohio Valleys, central and southern Appalachians, Mid-Atlantic, and coastal New England Feb 17-19. High winds (in excess of 30 knots) are anticipated for parts of the east coast Feb 18-19.

Areas of arctic high pressure moving across the eastern CONUS lead to periods of much below normal temperatures (12-24 degrees F below normal) for much of the eastern CONUS (except west Texas and Florida) Feb 15-19.

Low pressure near the Aleutians/Gulf of Alaska is forecast to lead to high winds (in excess of 30 knots) for parts of western Alaska and the Aleutians Feb 15-19. Heavy precipitation (rainfall in excess of 2 inches in 24 hours at lower elevations, snowfall in excess of 6 inches in 24 hours at higher elevations) is anticipated for parts of southeastern Alaska Feb 16.

For Friday February 20 - Thursday February 26: The numerical models are in relatively good agreement on the upper-level pattern over North America consisting of a ridge over the eastern Pacific and Alaska, and a trough over the central and eastern CONUS. This pattern favors above normal temperatures for the southwestern CONUS with below normal temperatures favored for the central and eastern conus. Because of an expected amplified trough, a slight risk of much below normal temperatures exists for much of the eastern two-thirds of the country Feb 20-26, a moderate risk exists for most of the easterh half of the CONUS Feb 20-26, and a high risk exists for parts of the northeast CONUS Feb 20-23. It should be noted that multiple areas of cold high pressure are expected to cross the central and eastern CONUS during the period with brief warm-ups preceding each fresh delivery of arctic air. For this reason it needs to be noted that the various areas of probability for below normal temperatures during week 2 will not cover the entire areas denoted for the entire period specified.

The most recent U.S. drought monitor, valid on February 10, 2015 indicates a very slight increase in the areal coverage of severe to exceptional drought (D2 to D4) from 16.04 to 16.18 percent across the continental U.S. 40 percent of California remains designated in the exceptional drought category.

Forecaster: Randy Schechter

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Stovepipe

Stovepipe

Posted
Posted

I hope you are right. If the over night runs dont correct I will start to worry. JB seems to to think it will correct northwest.

 

JB also said this was a "Deep South" storm a couple of days ago.  I take his thoughts with a huge grain of salt.  He often times seems more interested in arguing with people on social media than paying attention to the geography of his calls.

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ShawnEastTN

ShawnEastTN

Posted
Posted

Actually after looking at the track on the GFS, it's a great track for a large snow event here. New Orleans to Tallahassee to SE Georgia is a classic Gulf track and I believe we'd see a precip shield up to at least I-64 in Kentucky with that track.

I agree John.  As we have seen many many times especially with the GFS and NAM an under modeled precip shield.  I also agree that track of the low is pretty dang close to a perfect track for most all of the Tennessee Valley Region to receive some sort of measurable snow, and likely the majority of folks better than their seasonal average. 

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1234snow

1234snow

Posted
Posted

18z DGEX (previous one I posted was 6z, sorry, copied it from the SE forum without checking):

5YWNhb4.gif

Someone remind me, is this an extension of the NAM or are GFS parameters used to initialize it? Or both? I forget every season.

I think it uses both. The DGEX initializes from the data from the NAM(84 hrs) and then uses the GFS' equations for the rest of the run. Well that's what it used to do. I'm not sure if they changed the DGEX when the GFS got the upgrade. The DGEX has the wild solutions because the NAM at 84 hours out doesn't verify very well.

Edit: here is the link for the DGEX: http://www.emc.ncep.noaa.gov/mmb/mmbpll/dgexops.conus/

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Stovepipe

Stovepipe

Posted
Posted

I think it uses both. The DGEX initializes from the data from the NAM(84 hrs) and then uses the GFS' equations for the rest of the run. Well that's what it used to do. I'm not sure if they changed the DGEX when the GFS got the upgrade. The DGEX has the wild solutions because the NAM at 84 hours out doesn't verify very well.

Edit: here is the link for the DGEX: http://www.emc.ncep.noaa.gov/mmb/mmbpll/dgexops.conus/

 

Thanks yes that makes sense!

 

Here's Robert's thoughts, copied from SE forum:

 

 

From Robert on FB:Just a quick touch on next week's storm system. First, this is the best chance yet this season for the South and MidAtlantic, but there's never a guarantee, just because its all agreed upon. Things can and do change. I do think though for someone, this is going to be a big hit just not sure where yet. The energy for the Storm will take a unique path , going from the Gulf of Alaska, dropping into the Southwest States, picking up a "Baja low" and then merge with it, all in tandem with a Long Wave trough axis that is gradually. This means the moisture will proliferate with time, blossoming from Texas, the Deep South and then work up the coast, and train along for the same areas for more than 24 hours in some cases. There will be a lot of jet streak enhancement to the precip development in the South and East by Monday (and may start Sunday initially). By Monday night the whole Gulf is opening up quickly and pouring moisture north toward the Carolinas and Virginia where cold air is in place, and by Wednesday morning it should be coming to an end along the East Coast. Its too early for the specifics, who gets what, but if you're north and west of the low, at some point you should get some Winter precip. It is possilble the southwest low doesn't get picked up and that would change things toward less precip--but most of the time, it gets picked up. With time I can draw rain, snow , ice lines. For wherever there is snow and ice, with the upcoming cold air , it should stick easily. And there will be vicious cold following this storm next week too.

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Bango

Bango

Posted
Posted

I am finding it hard to define a sweet spot period.  I think I'd like to be a couple of hours north/northeast of Chattanooga but even then your affected hugely affected by a tick north or south.  I am also hating the trend downward in QPF, we've gone from weenie runs to less and less (GFS yikes).  Today I felt like TRI might have a 200 miles of wiggle room with all the model consistency we were seeing earlier in the day but stating the obvious, this southern track may kill us.  Heck, let's blend the UKMET and GFS, see what happens.

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1234snow

1234snow

Posted
Posted

Just got a look at the 0z GGEM. It looks a lot like the GFS does to me. The Baja low does not phase with the trough. The northern extent of the precip shield only makes it as far north as a line from Memphis to Chattanooga. Chatty gets around 4". Memphis gets close to 6". Nashville and KTRI gets less than an inch. Knoxville barely gets to 2 inches maybe. Just an amazing difference from the 12z run of the GGEM to tonight's run. Some places that got over a foot on the 12z run gets nothing on this run. One of the wildest swings I've ever seen.

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ShawnEastTN

ShawnEastTN

Posted
Posted

I am finding it hard to define a sweet spot period.  I think I'd like to be a couple of hours north/northeast of Chattanooga but even then your affected hugely affected by a tick north or south.  I am also hating the trend downward in QPF, we've gone from weenie runs to less and less (GFS yikes).  Today I felt like TRI might have a 200 miles of wiggle room with all the model consistency we were seeing earlier in the day but stating the obvious, this southern track may kill us.  Heck, let's blend the UKMET and GFS, see what happens.

Well by Sweet spot I mean our region in general.  There will always be nuances in amounts from one location to another but the Tennessee Valley Region as a whole are still in prime territory.  There will be wiggles in tracks, and i'm sure we will see varying solutions over the next 36 hours, before a more consistent solution begins to form. 

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