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Winter Speculation 17/18 -December Thread

AMZ8990

By AMZ8990,
in Tennessee Valley

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John1122

John1122

Posted
Posted

GFS once again with a big ice storm on the far western areas that trends to a nice snow event from Clarksville to the northern plateau and into Kentucky. Sleet, up to 1/2 inch of freezing rain from Nashville west. 1-2 inches of snow across the 40 corridor in Middle TN with 3-5 inch amounts along the Kentucky border. 

Canadian is 2-5 inches from Nash west to the Mississippi River.  

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Blackbearvol

Blackbearvol

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Nws Memphis, very  conservative, Has gone with the Euro. Said the gfs was too fast. Cmc is too slow. They’re forecast discussion is really good this afternoon. Even talking about next Tuesday. 

Good read  funny thing is they pretty much skipped over the next two days  

.DISCUSSION... Primary forecast concern remains late week wintry precipitation chances, associated with an upper lifting across the southern plains into the lower MS River valley. In the interim, mild and relatively humid conditions will prevail in the warm sector ahead of the approaching low. 12Z medium range models were a little better agreement with respect to the evolution and track of the late week low. The ECMWF model appeared to be good timing and track compromise between the faster GFS and slower Canadian. The ECMWF did deepen the upper low more than the NAM, GFS and Canadian, leading to a slightly slower exit and slightly greater QPF. Expect a transition from rain to sleet to snow behind the upper low. Still too early to determine transition precip type and duration with confidence, but ECMWFsuggests the elevated warm layer to result in a period of sleet- not sufficiently deep to completely melt snow from above, limiting the freezing threat at ground level. Best snow chances should occur in the deformation zone along the north and northwest side of the 500mb low, where NAM depicts fairly strong trof of warm air aloft (TROWAL) wrapping around the top side of the low. This would place areas north of a Forrest city to Oxford and Corinth line in the best position for receiving measurable snow. Accumulations will be dependent on boundary layer temps Friday afternoon. Models have trended colder for the weekend, a likely scenario following measurable snow. ECMWF depicts another snow event next Monday night, developing a baroclinic leaf ahead of an upper trof diving south through the plains. GFS depicts a similar pattern, but with the baroclinic leaf forming over southeast TX and northern LA. Canadian model isn`t too far off the GFS. With the lack of model consensus, have lowered snow chances early next week below the model blend. In any case, below normal temps likely to continue early next week. 

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AMZ8990

AMZ8990

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9 minutes ago, Blackbearvol said:

Nws Memphis, very  conservative, Has gone with the Euro. Said the gfs was too fast. Cmc is too slow. They’re forecast discussion is really good this afternoon. Even talking about next Tuesday. 

Good read  funny thing is they pretty much skipped over the next two days  

.DISCUSSION... Primary forecast concern remains late week wintry precipitation chances, associated with an upper lifting across the southern plains into the lower MS River valley. In the interim, mild and relatively humid conditions will prevail in the warm sector ahead of the approaching low. 12Z medium range models were a little better agreement with respect to the evolution and track of the late week low. The ECMWF model appeared to be good timing and track compromise between the faster GFS and slower Canadian. The ECMWF did deepen the upper low more than the NAM, GFS and Canadian, leading to a slightly slower exit and slightly greater QPF. Expect a transition from rain to sleet to snow behind the upper low. Still too early to determine transition precip type and duration with confidence, but ECMWFsuggests the elevated warm layer to result in a period of sleet- not sufficiently deep to completely melt snow from above, limiting the freezing threat at ground level. Best snow chances should occur in the deformation zone along the north and northwest side of the 500mb low, where NAM depicts fairly strong trof of warm air aloft (TROWAL) wrapping around the top side of the low. This would place areas north of a Forrest city to Oxford and Corinth line in the best position for receiving measurable snow. Accumulations will be dependent on boundary layer temps Friday afternoon. Models have trended colder for the weekend, a likely scenario following measurable snow. ECMWF depicts another snow event next Monday night, developing a baroclinic leaf ahead of an upper trof diving south through the plains. GFS depicts a similar pattern, but with the baroclinic leaf forming over southeast TX and northern LA. Canadian model isn`t too far off the GFS. With the lack of model consensus, have lowered snow chances early next week below the model blend. In any case, below normal temps likely to continue early next week. 

I saw this too.  Their confidence factor is at a 3 out of 5 on Friday for wintry weather in the mid south.  They were at 2 this morning.

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Carvers Gap

Carvers Gap

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Posted
1 hour ago, Blackbearvol said:

Nws Memphis, very  conservative, Has gone with the Euro. Said the gfs was too fast. Cmc is too slow. They’re forecast discussion is really good this afternoon. Even talking about next Tuesday. 

Good read  funny thing is they pretty much skipped over the next two days  

.DISCUSSION... Primary forecast concern remains late week wintry precipitation chances, associated with an upper lifting across the southern plains into the lower MS River valley. In the interim, mild and relatively humid conditions will prevail in the warm sector ahead of the approaching low. 12Z medium range models were a little better agreement with respect to the evolution and track of the late week low. The ECMWF model appeared to be good timing and track compromise between the faster GFS and slower Canadian. The ECMWF did deepen the upper low more than the NAM, GFS and Canadian, leading to a slightly slower exit and slightly greater QPF. Expect a transition from rain to sleet to snow behind the upper low. Still too early to determine transition precip type and duration with confidence, but ECMWFsuggests the elevated warm layer to result in a period of sleet- not sufficiently deep to completely melt snow from above, limiting the freezing threat at ground level. Best snow chances should occur in the deformation zone along the north and northwest side of the 500mb low, where NAM depicts fairly strong trof of warm air aloft (TROWAL) wrapping around the top side of the low. This would place areas north of a Forrest city to Oxford and Corinth line in the best position for receiving measurable snow. Accumulations will be dependent on boundary layer temps Friday afternoon. Models have trended colder for the weekend, a likely scenario following measurable snow. ECMWF depicts another snow event next Monday night, developing a baroclinic leaf ahead of an upper trof diving south through the plains. GFS depicts a similar pattern, but with the baroclinic leaf forming over southeast TX and northern LA. Canadian model isn`t too far off the GFS. With the lack of model consensus, have lowered snow chances early next week below the model blend. In any case, below normal temps likely to continue early next week. 

Outstanding disco.  Great find.  

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