Terpeast

You’re looking at ptype in the Op at D+10 right?

Wow, you’ve changed.

60 here in Ashburn. Walked outside with my wife. Loved it.

55 here. Think I’ll go for a sunny Jebwalk.

Ha ha, point taken. Guess I'm still tracking, but at an arm's length. Not gonna let myself get burned again like I did by that cutter

Haven't looked at the 12z gfs, but remember that the gfs held onto its own offshore solution until 5 days before the big cutter... and then it caved. Waiting to see agreement between gfs, euro, and cmc, then I'll start tracking.

28 for the low

I used to live there during college. It was always extremely muddy throughout the year.

Low of 23. Think it was colder than forecast

Stats from Ocean City MD or coastal delaware would also be interesting to see. They’ve done a lot better lately.

Maybe we should have a separate thread for DCA stats. Oh wait, we already have one. Either way, this conversation is getting kinda boring.

Maybe this will be backloaded. Maybe we’ll get nothing. Nobody knows. If we get a 3-4 incher at the end of February, I’ll take the W and then get ready for spring weather. And if we really do get nothing… well… see you next year, I guess.

Yeah its crap, at least how it’s modeled for now. It did tick up around an inch though. Best we can hope for in that period is a post frontal wave that pops up within 3-4 days. Otherwise we’re looking into the second half of the month.

Thanks. I’m hoping we get a backloaded winter this time. My monthly temp forecasts are tracking well so far, but my -1 January call may already be in trouble even before it starts. We’re going to have a lot of ground to make up after the second week.

At this point I'd be ecstatic with one warning snow and one minor advisory event. Hell, I'll take a 3-4 incher and call it a winter.

Well there we go. This immediately makes the entire graph suspect. If we really want to get scientific about this, we should cut out anything before 1941. Or pull snowfall records from other stations in/around DC and do a regression against the DCA data, then extrapolate the slope backwards to 1884. Like Bob Chill said, I’m willing to bet the result will have us just needing one prozac instead of two.

20 for the low. Thick frost. Ashburn

Like clockwork huh?

The way I read this graph is that 100 years ago, we averaged 10 more inches of snow a year than we do now. Or put another way, average snow decreased by 45% over 100 years. To be fair, the downtrend started way early - around the 1910s to 1920s. By the 40s and 50s, we were getting similar amounts as now. Then the 60s went bonkers, then back down to around 13-15” a year. I wonder though, is there a discontinuity in this graph when they changed the measuring station to DCA? And what year was that?

Well then, lets bring on the salt!

That’s why I’m a lot more hopeful for Jan-Feb. I also heard the same for the 2013-15 winters

All ens models show the PNA flipping from - to + around the 7th, and it looks to have some staying power. Atlantic not quite where we want it to be, though.

Thank you. And did you use ChatGPT by any chance?

Remember that the wind controls the flow and track of a storm system. To understand blocking, let’s think of the opposite scenario: Cold airmass (low geopotential height) over Greenland and a warm airmass (high geopotential height) over the west Atlantic. This is a +NAO. The temp gradient in between the two air masses are going to be pretty damn steep. So we should expect very strong winds going between the two air masses. An incoming storm is going to follow the wind and traverse between the two air masses. Since the wind is moving fast, the storm will race through there. Now, lets flip the air masses around and get a -NAO. 50/50 low in the western atlantic with a greenland high. Now the temp gradient will be much flatter. Wind will be moving very slowly, and may even reverse. An incoming storm approaches, and then because of weaker winds, it has nowhere to go. It gets “blocked”, hence the term. Sometimes it goes under the block, which means further south bringing more cold air south, which means snow for our location.

Couple of things. First, for the models to work well, they use pressure as a vertical coordinate system instead of height. Instead of 2,000 feet 4,000 ft 10,000 ft and so on, you have 900mb 800mb 700mb all the way up to 10 mb. It’ll be too complicated for the models/equations otherwise. Second, geopotential height patterns tells you where the warm air masses and cold air masses are. The higher the geopotential height at the 500mb pressure surface (think coordinate system), the warmer the airmass. The lower the geopotential height is, the colder the air mass. Now, when you have a cold and warm airmass butting up against each other, there is wind… and the stronger the temperature gradient between the air masses, the stronger the wind is. And it is that wind that controls the flow and track of storm systems. Took me three paragraphs to explain it. Maybe someone else can do it in one.