TSG

@RodneyS Was curious if this view would reveal anything within the DC data. Only thing I've picked up so far is that this phenomenon seems to be visible on the 12th and 22nd as well, and that Jan 4th has been all over the place the last 40 years lol. Have you thought about including those two dates in your analysis?

Oh I know haha. I genuinely enjoy analysis like this. I do stuff like this fairly often for work to assess potential micro-climate effects on solar plant production. I might just turn this into a mini thesis level copypasta EDIT: I also spent 10 years working summers at the marina just south of the airport on Daingerfield Island. I know that terrain like the back of my hand. The river valley around the Potomac contributes to higher temps in the summer as well. it would often be 5ish degrees warmer at work than where I lived near FC/Annandale.

Also not quite sure how you expect the ~300ft of trees that are stuck between a small city and over 400 acres of paved parking lot and tarmac to be the primary driver of temperature there lol You do realize there are 100000000x more trees around IAD and BWI, right?

Oh ok. If there's so many stations that support your assessment how about you actually put that analysis together for us. It must be an easy job if there's so much supporting data around.

Nope. There's no defect, it's a combination of factors and this has been explained many times. Here it is again: Early in the season the Potomac is contributing significant warmth. This is obviously not a factor at this point as the river has frozen over. DCA radiates horribly due to being in a relative "bowl" within its landscape. See the images below. BWI is on a high point within its environment, basically the exact opposite of DCA, and IAD is in an open plain. Neither location has a significant portion of its upward view obstructed by urban environments. Portions of the sky or treelines at ambient temp that are visible at the BWI and Dulles measurement locations are replaced with city skyline radiating heat back towards the airport. This environment also contributes to localized downsloping effects. IAD is at ~325ft above sea level. Where I grew up in Falls Church it was basically the exact same elevation with a few hilltops closer to 400ft nearby. That's 17 miles as the crow flies with basically zero elevation change. You then lose those 300-400ft in the next ~6 miles which will net over a degree F in temperature increase. You also get an enhanced UHI effect when wind is coming in from the West/Northwest, which it often is when this "issue" comes up. That entire strip west of the GW parkway is ~250-300ft tall buildings built primarily in the 70s and 80s that have next to no insulation and constantly belch wasted heat into the environment during the winter. It's a one mile long, quarter mile wide heat exchanger that's less than a mile away from the measurement site. Nothing like that exists for either of the other locations. Although I could imagine IAD may be seeing similar effects on a North wind from the massive amount of data centers that have gone up the last 10 years, but they are much further from the sensor location. The overall UHI effect across a metro region is not anywhere close to homogenized or a standard gradient extending out from the cities. It's highly dependent on the local environment. Show up with some actual data if you legitimately think this needs to be looked at. Otherwise you're probably going to get this response from me every time you bring it up.

It wouldn't have felt like a real arctic outbreak without my heat going out one night

Fascinating for sure and fun to follow along all these years. I was still in college when this first got posted and it really caught my attention as it was maybe the strangest weather related phenomenon I had ever come across/read about at that age. I hadn't even made an account on here yet, I was just a perennial lurker in the winter months. Keep it up Rodney!

Cold smoke

Hope I'm not explaining something well understood here... thinking this might not be common knowledge in the SE. You can see sleet vs snow pretty well using the correlation coefficient or diff reflectivity products. Rough sleet line outlines below for SC/GA

Any CHS posters in here? Looks like yall are getting sleet-bombed right now based on radar

Just wanted to stop in and say it's fun watching the show from up here in the mid-atlantic. Historic stuff happening rn

19/1 Never made it above 20 today, forecast was 25. I wasn't expecting to see radar returns popping to my SW towards Roanoke . I have to imagine this is going to be virga this far West?

I can't imagine we're going to hit the 25F forecast in Cville. Barely made it to 20F before the clouds rolled in 30 mins ago

14/-2 Light NW wind has picked up after virtually dead air since 9pm time for bed

What exactly do you imagine the world was like 100 years ago? In 1925 the first TV broadcast was made, quantum physics had already been discovered/proposed, and the first patent for a field-effect transistor was filed. Arguably the most important invention in human history. We had accurate thermometers... jfc

CHO is down 7 degrees in the last 45! Slight southwest breeze here until about 7:45pm 37/32

High temps look to bust about 4 degrees lower than the NWS forecast here in Charlottesville. Made it to 45 at 3pm but it hasn't moved since. Forecast was 49

This is about the same amount of lead time before the 1/6 event that the GFS started to get a clue and hone in on the further south solution. We're obviously looking for a different trend here but good to see

The HRRR is just completely lost with this ULL stuff

Radar looks incredible

Big fluffy flakes coming out of the sky under this I66/Rt50 band. Best I've seen all storm

Correct me if I'm totally off base here, but wasn't the Euro kind of showing that 700mb band setting up across central PA back Friday night/Sat? See the Jan 4 00z run below. And then as a compounding factor, perhaps the precipitation depiction was just not as accurate up that way because of how dry the antecedent airmass was?

That's exactly the time period I'm talking about. I think some people held onto that and then the ~48hr NAM showed a similar northern track and it was all over for reasonable consideration of the more southern solutions. And yes, it didn't get every detail right, but the end result was closer than what the GFS was advertising. It def nailed the central VA forecast

Whatever makes you feel better dude. The GFS had the significant precip way too far north