psuhoffman

the primary track is trending south across all guidance right now...and that could very well activate the lingering boundary through our area Thursday evening/night. I doubt we get anything heavy but could tack on some additional accumulations if the precip is heavy enough to mix out the warm layers left over.

True...but from the sounding the extreme dry layer coincides with the warm layer. There is a really warm but dry layer around h8. But my point was if the NAM had that layer at 0C at 60% humidity and in reality it was +1.5C with 40% humidity...in the end the wet bulb temp (which is what really matters) is about the same so the error seems insignificant imo compared to the press its getting.

alternate version for the lazy...but I like the metric version better.

The NAM was too warm...but it also wasn't dry enough...so wouldn't those 2 kind of offset in the end?

I adjusted some of the totals a little...this is my current thinking. I think during the heaviest precip it will mix out the warm layer just enough to do better then the doomsday scenario on some of the high res guidance. Ratios will be low but it will be puking precipitation so even if its a 50/50 snow/sleet mix it will accumulate a decent amount. I also think these gulf systems with true cold air in place tend to run on the wet side of guidance.

I like to see the mix line taking on more a SW to NE v W t E trajectory. That’s more a winning scenario for along and west of 95

I know someone else...

It’s annoying but you can use the other guidance wrt how far north of the h85 and h7 they get the warm layers to make an educated guess. You will get close enough that whatever minor error the model isn’t likely to be that accurate anyways.

22/7 with a few inches of solid ice on everything. I think there is a chance the surface might be cold enough

Wtf is that BS? That better be a 1 hour snowfall map!

I’m holding them to that 8-12 up here. There will be consequences...might have to wag my finger even!

We have no idea how they clown map is generated. If for example, it counts ice as snow like TT does then it’s pretty much in line with everything else.

The key is getting that initial band in hot and heavy. But that’s a typical MO got juiced up gulf systems with cold on top so you get WAA way out ahead. If that gets in early and starts thumping...dynamic cooling takes over and DC can pile up a respectable total quick before they lose the column.

Fwiw I have a feeling this could be a rare positive bust in DC.

That’s my suspicion. If everything is 1-2 degrees warmer a warm layer that was right at freezing is now just above.

My 2 cents and that’s more then it’s probably worth...it does a good job showing what the structure of the storm will be. Banding features. Temperatures. Warm layers. But its too ambitious and can’t get the exact placement of those features correct. So if you understand not to rely on exactly where it puts meso scale features but use it as a clue to the structure of the system it’s useful.

It is but it can sometimes be too aggressive. This was about the range it was showing that crazy 15” solution for the super bowl storm that blasted the 850 warm layer all the way to SE DC. In the end boundary temps sucked but it was way too aggressive with the mid levels.

Like my post above said this is 100% but I think I’m coming at this from a different angle. Imo these flaws are good reasons why this isn’t a MECS or HECS. This doesn’t have 8”+ potential in DC. But it’s not a good reason Imo it’s not a regular old 3-6” SECS. Those (at least most of the ones I studied when I looked at all the warming events at BWI) were flawed in some way. Some way more flawed then this setup. It seems like “good but flawed” setups don’t break our way as much anymore and 3-6” becomes 1-2” way too often.

I see the “flaws”. It’s not perfect. It’s not a hecs setup. But we’ve had snowstorms in this kind of setup before where a cold airmass in front and a perfect track offset that kind of trough axis. I remember one in 2004 actually that was a 4-8” event across the area that did eventually go to ice but only after the WAA banding ended and we dryslotted. I guess my point is we keep making excuses for why these little imperfections were the reason it didn’t snow but imo it shouldn’t be this difficult. We shouldn’t need EVERYTHING to be 100% absolutely perfect to get a simple 4-8” snowstorm. I’m taking the 10,000 foot view that it seems pretty good but not perfect setups that used to break our way a decent (not all) amount of the time seem to break bad a lot more recently.

It’s mid levels yes but there is usually a mid level warm layer when we have a storm. I’m going to simplify this but I feel it’s an accurate summary. There almost has to be a warm layer because it’s WAA as the wave approaches that is the primary impetus for precip. The warm air is lifted over the denser cold and that lift creates the precip. But warm is relative to normally very cold air at those levels. Rising air cools and condenses so it’s cooling as it rises. So long as that mid level “warm” layer stays just below freezing it’s ok. But what happens if EVERYTHING is say 2 degrees warmer then it used to be? Then a “warm” layer that was -1 is now +1 and the mix line just jumped 50 miles north!

I just used the icon but it’s the same idea across guidance. There shouldn’t be mixing problems in DC (at least not significant ones) with that track in mid February with an Arctic high over Montreal at the start.

I should have said this up front. My post was not meant to be an autopsy or storm cancel. It could still work out. But damnit it’s a lot more difficult then it should be with that setup. Just wanted to point out how good the track is here because we often get stuck looking at the pretty colors but I look at the temps and precip panels last. And that really makes it stick out how out of whack they are and have been multiple times in recent years!

*This is NOT a storm cancel or autopsy. It could break our way. Just wanted to highlight something larger scale going on* I wanted to illustrate something. look at 6z. This is generally the same across guidance. The primary dies in eastern TN. The coastal takes over and tracks from outer banks to east of Delmarva. Look at where the banding of precip is. That blue area is where it SHOULD be snow. But it’s not. It’s mixed with sleet and freezing rain all the way to the PA line. Guidance isn’t trending north. It’s trending warmer. And I don’t know why. What are we even rooting for there? That track is absolutely PERFECT in every way! We have an Arctic high in place. Cant use the “no cold air” excuse. This keeps happening a lot lately. Tracks that should produce snow in DC find a way not too or produce way less then they SHOULD. It’s frustrating and troubling.

It’s not even trending north. It’s trending warmer. It’s still a perfect track with an Arctic high in place. Dunno what to say.

EPS