December 26th and 27th Winter Storm Update

First off we want to wish everyone a Merry Christmas for those who do celebrate the holiday. It has been 10 years since ABE has had a white christmas and with last nights snowfall followed by freezing drizzle, which left 1.5 inches we can officially say that we had a white christmas for 2012.

For snow lovers that will NOT be the end of it .. There is another storm system that is developing over the south central states.

This system is responsible for severe thunderstorms today and the potential for some strong tornado's which we discussed on our Facebook page.
Lets look at what the guidance does with this system and we are going to start with the GFS because the GFS by far is the warmest model that is out there...

The GFS would start as a period of frozen in places like East Central PA etc but then it would end up turning over to ice and then to plain rain. The only other model that is probably as warm as the GFS is the NAM, which will not be showed here because it is still beyond the 24 hr window.

Lets look at the rest of the guidance and what you are going to notice is that the rest of the guidance is actually colder then the GFS..

 European computer model is actually colder at the approach of the storm then last nights run but would still imply a change over to ice and probably rain..

 The GGEM above is actually colder then the GFS and now this should be considered a red flag to the GFS because generally speaking the GGEM is a rather warm biased model and the very fact that it is now colder and also more southeast raises questions to the track and the air mass in place.

The NOGAPS which not that many people look at outside of us and the HPC..has actually trended more south and east and this is actually colder then its run last night. Last night was virtually showing nothing but rain but this would indicate snow/frozen to rain back to snow/frozen.

Last but not least is the UKMET which is above which also is showing a colder system. While we do not have the in between hours we can pretty much figure that it would be similar to the other guidance above and this to would indicate a longer front end duration of snow and ice before a changeover to rain.
Now lets turn to a little nowcasting for this storm system to lay the final pieces in place...

This is the current pressure fall maps and we have put an " L" where the area of low pressure is by the deepest pressure falls. This is further east then what the GFS had indicated it would be at 18 z. So what this tells us is that it had not made the NE turn as soon as what the GFS was indicating and has allowed it to make it a little further to the east. This should start to make its NE turn but remember because of being slightly further east ..this means its going to end up being slightly more south and east as it makes that turn to the Northeast. Which means as it moves up towards the region it should be more south and east then what the GFS anticipated which also means it would be slightly colder then what the GFS is anticipating.
So at the top of the page we have come out with a scenario map which basically shows where all snow should occur and where rain would occur and the battle zone in the middle which may be dealing with snow to sleet/zr to rain.
The all snow zone should be on the order of upwards of 8+ inches of snow..perhaps some sleet mixing in..
The next zone we feel should be on the order of 4 to about 8 inches of snow /sleet followed by what could be a longer duration of freezing rain because CAD (cold air Damming) likes to hold on longer....
And then the other zone is the rain zone where we could see about 1-2 inches of rain occur.

We would not be surprised to see a slightly more south and east shift tonight on the 00z model guidance because of the observation discussed above.