Absolute Vorticity

The Euro is keeping in tack with the nam of keeping temps warmer at the ground so takes a few more hours before changeover to frozen and then to snow. Track wise not much different than the Ukie but again how the models play out the temperature of the atmosphere at different levels makes all the difference in p-types.

50 miles can make such a huge difference with this system on Thursday and you could get a foot of snow and 25 miles away 1/2 inch of ice and another 25 miles southeast mainly rain with switchover to ice late.

With such a sharp and tight gradient, a shift in the track of this system say by 25 miles in one direction or the other, will have major impacts on our sensible weather.

EDIT: What you said Tim!

tron777 wrote: ↑Mon Jan 31, 2022 1:39 pm With such a sharp and tight gradient, a shift in the track of this system say by 25 miles in one direction or the other, will have major impacts on our sensible weather.

EDIT: What you said Tim!

Exactly Les and we are on the same page. I just wanted that couple of extra hours between waves and hopefully this will allow the cold dense air to move an extra 50 miles southeast. If there is little in the way of a break then you could get stuck with hours of rain and 34 degrees.

tpweather wrote: ↑Mon Jan 31, 2022 1:41 pm

tron777 wrote: ↑Mon Jan 31, 2022 1:39 pm With such a sharp and tight gradient, a shift in the track of this system say by 25 miles in one direction or the other, will have major impacts on our sensible weather.

EDIT: What you said Tim!

Exactly Les and we are on the same page. I just wanted that couple of extra hours between waves and hopefully this will allow the cold dense air to move an extra 50 miles southeast. If there is little in the way of a break then you could get stuck with hours of rain and 34 degrees.

One solution that no model is showing is all rain with both systems. We've got rain to some ice / sleet to heavy snow or we've got more rain then a lot of ice then light snow or just rain a later changeover to ice then a touch of snow at the end. So three basic ideas with timing and precip type is what I have seen on todays guidance. Changeover times at CVG from rain to wintry precip varies from Wed after midnight to midday Thurs. That is quite a spread still and need to narrow it down to make a proper forecast.

Temps are key as well especially if we have frz/rain. Having temp at 30-32 especially after being mild a couple of days before hand can keep the ice down somewhat but if you lower that temp to 26-28 or lower then the ice becomes more of a problem and especially if we are still seeing frz/rain after dark on Thursday. Like Les mentioned the timing of the changeover is key and again models may not be able to really nail that down until Wednesday.

tpweather wrote: ↑Mon Jan 31, 2022 1:48 pm Temps are key as well especially if we have frz/rain. Having temp at 30-32 especially after being mild a couple of days before hand can keep the ice down somewhat but if you lower that temp to 26-28 or lower then the ice becomes more of a problem and especially if we are still seeing frz/rain after dark on Thursday. Like Les mentioned the timing of the changeover is key and again models may not be able to really nail that down until Wednesday.

For AV land the amount of snow we get versus ice is really dependant on how strong the artic high is. If it's strong enough to push the second, more intense, wave south we will cash in. If not, we will get mainly ice with a little back end snow. The GFS has the Arctic high stronger, thus more snow. Whichever model is correct, the first wave will not put down any snow in AV land so we are counting on the GFS/UKmet being right as opposed to the other models. Tomorrow at this time we should know which model camp will win out. As was alluded to earlier by Les, warm air at the upper levels should not be a warm tongue of death kind of a problem. Sometimes models don't have these Arctic air far enough south in this type of set up and hopefully that truly is the case for that second wave.

15Z SREF wants to change CVG over from rain to ice mid to late morning Thurs. 1.2" of snow on the mean ending Thurs night around 1am (that is when the model stops) 2" mean for I-70 Crew.

12Z EPS Mean for snow - 10:1 Ratio

tron777 wrote: ↑Mon Jan 31, 2022 2:26 pm 12Z EPS Mean for snow - 10:1 Ratio


EPSSnow.png

Funny how the Euro was the south model a couple days ago and now the GFS is the south model, while the Euro went north.

mainevilleweather wrote: ↑Mon Jan 31, 2022 2:34 pm

tron777 wrote: ↑Mon Jan 31, 2022 2:26 pm 12Z EPS Mean for snow - 10:1 Ratio


EPSSnow.png

Funny how the Euro was the south model a couple days ago and now the GFS is the south model, while the Euro went north.

Yep. CMC and RGEM are back north to go along with the Euro. NAM has been dropping south so will it do so again to join the GFS or not. We will know shortly...

the suspense is killing me.

Winter Storm watch just hoisted for me. .2 to .4 ice accretions and 4 to 6 inches of snow.

18Z NAM looks more south at Hour 36.

snowbo wrote: ↑Mon Jan 31, 2022 3:06 pm Winter Storm watch just hoisted for me. .2 to .4 ice accretions and 4 to 6 inches of snow.

Seems like a conservative call thus far

cloudy72 wrote: ↑Mon Jan 31, 2022 3:14 pm

snowbo wrote: ↑Mon Jan 31, 2022 3:06 pm Winter Storm watch just hoisted for me. .2 to .4 ice accretions and 4 to 6 inches of snow.

Seems like a conservative call thus far

Yeah, I thought it might be a little low too!

Eric's Hood has a watch out for 0.10-0.40" of ice and 6-11" of snow. Then the one along the I-70 Corridor that Bo mentioned for the Dayton and Columbus area posters. For Cincy, we wait. Lots of uncertainty... I can see an expansion of the watch coming tonight and tomorrow in more areas.

I hope everyone who has been snow starved this winter cashes in. We've been lucky in my hood. I don't see this one being a terror down here.

NAM matching GFS advancement of surface temps with both reading at INDY 32 degrees at hr 48

snowbo wrote: ↑Mon Jan 31, 2022 3:17 pm

cloudy72 wrote: ↑Mon Jan 31, 2022 3:14 pm

snowbo wrote: ↑Mon Jan 31, 2022 3:06 pm Winter Storm watch just hoisted for me. .2 to .4 ice accretions and 4 to 6 inches of snow.

Seems like a conservative call thus far

Yeah, I thought it might be a little low too!

Just to early to start out with a high number , they'll bump it up tomorrow if need be

Darke county (Eric) is 6 to 11 inches and it's southern neighbor, Preble county is 4 to 6 inches.

Louisville NWS has WSW out for counties in KY and IN that border the river.

So far a few minor changes in the nam. The second piece of energy looks to be a tad further south at hour 54 but I will let the model finish its run. A key area is called ice accretion that was mentioned. Many times we see these storms and it shows 2 inches of frz/rain but that does not mean 2 inches of ice on the ground and usually much less than that. Getting .2 to .4 is bad enough but if you start to see totals over .5 then it really becomes a big problem especially on trees and power lines. The good thing is we get a little milder ahead of this system plus the deep push of cold sort of undercuts this system so you can see the coldest air at the surface and higher up it may be a few degrees warmer which may help for awhile in keeping some of the ice off the trees and power lines.

NAM with CVG at surface 32 12z thursday

kywthrluvr wrote: ↑Mon Jan 31, 2022 3:34 pm Louisville NWS has WSW out for counties in KY and IN that border the river.

Hey Leslie and that was a little bit of a surprise imo. I thought maybe Tuesday afternoon we would see those come out for the Louisville area.