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MO/KS/AR/OK 2020-2021 "Winter" Discussion


JoMo
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Silly to analyze models with extreme scrutiny 7-8 day out, but I'm gonna do it anyways.

Before the event, we(NE OK/SW MO/NW AR) are at or below freezing for about 18 hours, then the event starts, temps surge to upper 40's and low 50's, and then plummet back below freezing as it exits.

Shallow cold air on this one, models do poorly in these situations and always underestimate the cold air's ability to linger, and want to let the warm air come push it out.

In this scenario, cold air comes in, get's entrenched, then models want 30-40mph winds(gusts) from the south to come in and push it all out during the duration of the rain/snowfall only to have in come back in full force less than 24 hour after it gets pushed out.

I'm not really buying that. That warm air would just go right over the top of the shallow cold air in that scenario. Which sets us up for sleet/freezing rain.

 

But hey, I'm obsessing over 1 run of the euro 7 days out...so you know....there's that.

 

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30 minutes ago, StormChazer said:

Silly to analyze models with extreme scrutiny 7-8 day out, but I'm gonna do it anyways.

Before the event, we(NE OK/SW MO/NW AR) are at or below freezing for about 18 hours, then the event starts, temps surge to upper 40's and low 50's, and then plummet back below freezing as it exits.

Shallow cold air on this one, models do poorly in these situations and always underestimate the cold air's ability to linger, and want to let the warm air come push it out.

In this scenario, cold air comes in, get's entrenched, then models want 30-40mph winds(gusts) from the south to come in and push it all out during the duration of the rain/snowfall only to have in come back in full force less than 24 hour after it gets pushed out.

I'm not really buying that. That warm air would just go right over the top of the shallow cold air in that scenario. Which sets us up for sleet/freezing rain.

 

But hey, I'm obsessing over 1 run of the euro 7 days out...so you know....there's that.

 

Yeah, southerly flow returns out ahead of the big system because the high pressure across the midwest is sliding off to the east quicker, due to the system in the northeast being faster, which results in the winds turning southerly, sooner. It's not just at the low levels, some kind of southerly flow happens throughout the atmosphere. 

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1 hour ago, StormChazer said:

FWIW, here is the mean 48 hour snowfall of the Euro members yesterday at noon to midnight last night.

BIG JUMP

 

12Z Yesterday

1609394400-ULm2dcdPx0Q.png

00Z Last Night

 

1609394400-wDS8KB4GrGs.png

I'd be interested in seeing the individual member breakdowns to see if they are as robust as the op run? My feeling is that the heft from the op run contributed to the big jump in totals in C KS. 

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4 minutes ago, StormChazer said:

Yeah, all the different models agree that this system should be very rich in moisture, so whoever gets the cold air should be in for a heavy snow!

At this rate on the 12z GFS, we may have to watch out for severe weather. Nice Nebraska snow though.

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7 minutes ago, JoMo said:

At this rate on the 12z GFS, we may have to watch out for severe weather. Nice Nebraska snow though.

Yep. Personally I think the chance of severe weather is higher than the chance of measurable snow around here. 

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17 minutes ago, JoMo said:

At this rate on the 12z GFS, we may have to watch out for severe weather. Nice Nebraska snow though.

In comparing the 12z GFS to the 00z Canadian and 00z Euro models, it appears the high pressure (modeled to be 1038-1042mb) is one of the keys to watch. All the models agree on a diffluent southwesterly flow with a lee-side low (modeled 999-1003 mb) developing, but, the degree of warmth is predicated on where the high pressure sets up and how strong that low is.  

If it's over MN, then we're looking at a big winter storm. Over southern Ontario, then we're looking at rain and storms. 

How have the models handled cold air masses so far this season?

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18 minutes ago, rockchalk83 said:

In comparing the 12z GFS to the 00z Canadian and 00z Euro models, it appears the high pressure (modeled to be 1038-1042mb) is one of the keys to watch. All the models agree on a diffluent southwesterly flow with a lee-side low (modeled 999-1003 mb) developing, but, the degree of warmth is predicated on where the high pressure sets up and how strong that low is.  

If it's over MN, then we're looking at a big winter storm. Over southern Ontario, then we're looking at rain and storms. 

How have the models handled cold air masses so far this season?

Wouldn't really make a difference, the storm system just wraps up too far west on the GFS. It needs to be more of an open positive tilted trough until it gets south of us, then it can wrap up. Anything else and the warm air is going to probably overwhelm the cold air sitting in place. 

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