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Wintry 1/26-1/28 Winter Storm Potential

Just to illustrate how much models can change with key details even 120 hours out, let's look at the FV3 for the system that is moving through the Midwest currently. Here is the 6z run of the FV3 on Friday for the 5H look.
1548169375639.png

Now notice the 6z run from this morning. Notice the heights aren't pressing down NEARLY as much and our energy is a good bit more amped as well. This is why we often see the classic NW trend. Such a scenario and adjustment NW/stronger is well within the realm of possibility for the system Sunday/Monday we are tracking.
1548169417983.png
 
One last map. Notice the 5h trend with our PV and heights lifting north over the past 4 runs of the ICON? This is what almost always brings the N trend as the heights relax some as we near verification. I wouldn't write this one off yet. Plenty of time for things to shift back north.
icon_z500_mslp_us_fh78_trend.gif
 
snowlover91 said:
One last map. Notice the 5h trend with our PV and heights lifting north over the past 4 runs of the ICON? This is what almost always brings the N trend as the heights relax some as we near verification. I wouldn't write this one off yet. Plenty of time for things to shift back north.
Click to expand...

This is what is taking our cold air away too, right? Is the hope that the north shift will allow some interaction to help pull down some cold air? Or dynamics will help make up the difference?

I guess this is an example of how we're always threading the needle to get a good system down here.
 
snowlover91 said:
Just to illustrate how much models can change with key details even 120 hours out, let's look at the FV3 for the system that is moving through the Midwest currently. Here is the 6z run of the FV3 on Friday for the 5H look.
View attachment 12547

Now notice the 6z run from this morning. Notice the heights aren't pressing down NEARLY as much and our energy is a good bit more amped as well. This is why we often see the classic NW trend. Such a scenario and adjustment NW/stronger is well within the realm of possibility for the system Sunday/Monday we are tracking.
View attachment 12548
Click to expand...
snowlover91 said:
One last map. Notice the 5h trend with our PV and heights lifting north over the past 4 runs of the ICON? This is what almost always brings the N trend as the heights relax some as we near verification. I wouldn't write this one off yet. Plenty of time for things to shift back north.
View attachment 12550
Click to expand...

And just an example of how fast things can change on the models, the FV3 was showing this yesterday evening.

1548112814908.png
 
That’s a massive PV press
c6813dc9e1311321b928e7a2d2bda3ab.jpg



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Benholio said:
This is what is taking our cold air away too, right? Is the hope that the north shift will allow some interaction to help pull down some cold air? Or dynamics will help make up the difference?

I guess this is an example of how we're always threading the needle to get a good system down here.
Click to expand...

I believe so yeah on the north shift allowing for some interaction to pull down cold air. If this system trends north and is timed correctly with the northern stream, they should interact and pull down cold air. If this wave is left behind by the northern branch then based off what I'm seeing it's going to simply drift SE in the gulf...and some of the runs have been wanting to make it look tropical storm-ish later on.
 
Benholio said:
This is what is taking our cold air away too, right? Is the hope that the north shift will allow some interaction to help pull down some cold air? Or dynamics will help make up the difference?

I guess this is an example of how we're always threading the needle to get a good system down here.
Click to expand...

It's a pretty complex setup but by the time this storm moves through our airmass is slowly modifying (warming). The track of this wave, how much it amplifies and how much if any northern stream phasing there is are important to the eventual track. If the PV is pressing south it will suppress our wave and it won't amplify in time. That is what models currently show. Personally I am expecting them to back off the PV pressing south in the next few days and if that happens this could jump north but it's also possible models are correct with pressing the PV this far south, it's hard to know this far out.
 
This run of the GFS looks like it may be quite suppressed as the PV is pressing south more through 84.
 
GFS so far appears to be a step in the right direction. Initially the PV presses down more but then the PV appears to let up a bit more. Still likely a suppressed run but might be a positive first step.
 
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