psuhoffman

Thanks. Sucks I slept through that lol. 2 year old wasn’t feeling well and was up late with her so needed to catch a few hours. Thought most of the good stuff would be after 7am here. Some guidance last night did have a pockets of warm up here between bands around 8 then flipped back to snow as heavier banding came through so hopefully I get to enjoy another heavy burst of snow.

Where are you?

WTH did I miss. Figured if I got up at 7:00 that would be right as it was getting good. But there was already 5.5” on the ground (great!) but it was also already mixing with sleet (what? Boo!). I really hope I didn’t miss the best part of the storm. WTH happened in the few hours I slept? Did it snow 3” an hour or something? And why am I mixing with sleet up here already at 7:30 am??? It’s a 50/50 snow sleet mix now. About 6” total.

Does it have round 1? yes...actually focuses that further NW. Bullseye of precip is Winchester northeast to Carroll County. Would be mostly snow NW of a line from about Sterling to Owings Mills. Mostly ice SE of there and looks like about 4-6" of snow with wave 1 NW of there.

UKMET has round 2 tomorrow night also...generally .2-.3 QPF across the area with that. Just about all guidance has that now.

It drops 3" of snow/sleet on DC (mostly sleet) but the warm layer is only about 1C for a lot of that...if its off by just a bit then its in line with the euro pretty well on the thermals. It's precipitation representation is pretty close also except in typical NAM fashion its wet. They are fairly close in terms of the progression of the event just off by very minor details. The ground truth ends up a big difference because DC is on the razors edge for precip type. But even then...the Euro was like 3-4" of snow with some sleet...the NAM would be some snow with 2-3" of sleet...so its not really that far apart in terms of how much "stuff" is on the ground in the end either.

If you tone down the mid level warm layer by like 1C the 12k NAM matches the Euro (as a slightly wetter version) pretty well actually.

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.