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Chasing a Snowstorm: A Behind the Scenes Look at Forecasting the February 5th Event…

2/6/2016

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Introduction
Forecasting is hard.
I know I am stating the obvious to many, but it has to be said. We live in a big world with a dynamic atmosphere, and although we’ve put a man on the moon, cured diseases, and sent probes to the furthest reaches of our solar system—all wonderful scientific achievements, we can’t correctly predict how much snow will fall in our own backyard. 


The stock answer that people use—it’s weather—doesn’t quite describe how complicated it can be to get both the large scale (synoptic) and small scale (mesoscale) features right. That’s our job though, and we do our best. We won’t always be right, no forecaster or computer model ever is, but we do our darnedest to get every single thing right. 

Join me as I show you the ridiculous journey from potential to production to report card…

First Contact: Friday January 29, 2016—162 hours from impact
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GFS on January 29th showing the first hint of a wave forming along the cold front

From SA’s discussion on that day
Behind the storm, colder air filters back in to end the week, with temperatures going down into the mid 40s on Thursday and then back to seasonable levels to end the week into next weekend. Guidance hints at developing a wave of precipitation along the cold front after it passes us and stalls to our southeast, but considering the lead time and model inconsistency, will not elaborate further at this time and will save this potential for later updates should it remain on guidance through the weekend.

Friday: A slight chance of rain or snow, otherwise, partly sunny, with highs in the mid 30s. Chance of precipitation is 20%

At this point, usually we throw out precip chances with the caveat that a lot can change. We were about 7 days away from anything happening. Going back, I was surprised by how much we (read: SA) were on it. 

Over the next few days, we didn’t talk about it a whole lot. The guidance shifted away from an impactful event, and we knew we were far enough out to not really pay much attention, honestly. Our conversations reflected it…

SA (1/31): I wouldn't be shocked if there's some snow to talk about later in the week -- I like that anafrontal deal for an inch or two for Eastern areas​
​
​GP (2/1): Have a feeling we're going to be getting a lot of traffic starting in about 5 days, if u know what i mean'
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GFS images for Friday around 7am on February 1st (top) and February 2nd (bottom)
The Chase is On: Tuesday February 2, 2016—66 hours from impact
DB (2/2): That storm early next week [Monday February 8] is so close 

SA: Yeah
SA: I’m not writing off Friday either for an inch or two east
DB: I saw that on the GFS and groaned at work. That would not be easy to forecast
DB: After an HECS [historic east coast snowstorm] I'm almost fully recovered in terms of sleep
SA: The Friday thing? Or Monday? Agreed on both though
DB: I groaned about Friday. Next week is an eternity away to me
SA: Yeah. I'm not buying anything until under 100 hours
SA: We’ll see on Friday — I'll want to see another shift NW tonight to make something a legit threat as opposed to a longshot.
DB: Agreed
DB: With this pattern we can forget about a long lead event. We'll be playing a lot of model roulette
DB: I’m seeing real panic/jubilation among the northern crowd lol

Things Get Real: Tuesday February 2, 2016 approximately 11:30pm—60 hours from impact

SA: Oh ****
​SA:


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DB: GFS?
SA: And the cuckooing ukie now has warning snows over the entire state
SA: Zero on the gfs
SA: Le sigh
DB: We'll see what the euro says
SA: Well if I wake up and see the Euro went west I'm going to start honking.
DB: Yeah I agree with that
SA: No one in the media at all is mentioning this -- I'm almost tempted to throw something quickly up now. At the same time though I don't want to have it go away at 6 or 12z and we look stupid
SA: Thoughts?
DB: I wouldn't honk until tomorrow morning
DB: Wait for the ens [ensembles] and the euro to show their hand
DB: No one is going to be up now anyway
SA: Yeah that's the rational thing to do. It's a gamble to go for it now. Either we look great or we look like idiots…

SA: But wow. Wouldn't that be something if this came back to a warning event.

DB: I know right? This pattern...
SA: Yeah. I didn't block out very much time tomorrow night because I thought it would be a quick disco -- I might be up late as a result lol. I'm going to be at work until around 6 and then I'll head home and get to work on it.
DB (2/3,12:04am): Ok

We were all in on Wednesday afternoon. There were concerns with Litchfield County getting next to nothing and surface temperatures, but we had seen enough to start honking. It was a sneaky snow event. Folks were enjoying spring like temperatures and not even thinking of snow falling just a few days from then. After developing a game plan on our various social media platforms, Greg was all in:

Greg’s discussion title?
*A surprise snowstorm could be headed our way Friday, especially in the morning.*
​

By the evening, it was time to make a first call. Usually, trends start and stop as the guidance settles on a solution we can work with. We had no idea that we would be in a nonstop northwest trend that would bring more precipitation to the state. No idea at all. We thought our first call was good.
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Timing
3-5 AM Friday: Snow breaks out from SE to NW, potentially starting as rain in southern and eastern portions of the state before changing to snow.
5-9 AM: Snow persists in the eastern portions of the state, while in western areas, flurries and snow showers are the general theme of the morning. Some impacts to the morning commute are likely.
9 AM – 12 PM: Snow begins to taper off from west to east, with snow showers lingering into early afternoon in eastern areas. 

Impacts

A light to moderate snowfall across most of the state, with plowable amounts possible in eastern areas.

A tricky morning commute on Friday, especially along I395 and eastern parts of I95 where steadier snow will fall.


Some school delays and maybe a cancelation or two are possible.


​Should the system become more significant(Scenario 3), some downed trees and power outages would be possible due to the fact that this will be a heavy wet snow.


By later that night we saw even more trending toward a higher impact event. We were all over it. Even Greg mentioned how western Connecticut could produce a larger event. I should have listened…​

SA: Yeah it's [a proposed map that was never used] definitely bullish. I don't think this is done trending yet, but at the same time I'm not putting that out there with the GFS having nothing. I probably won't upgrade anything until the morning.
SA: It’s [the GFS] caving somewhat can already see by hour 24. Still pretty far SE though.
SA: Nice shift NW. Looks like the NAM and 18z RGEM.
GP: Yeah looks decent
GP: Maybe mention something about mostly on cold surfaces western hafl
half*
GP: Weird not having the GFS on board at all, but everything is coming west
SA: GFS came west. Check it out.
GP: ok
SA: Still meh but it's a big nod towards other globals.
GP: Yeah 
GP: GFS and NAM are still both east of everything else
DB: Yeah
DB: But the big boys are on board


GP: [You] have to figure, when u get that close in, they would have to get a clue, right?
GP: RGEM has 2" in NYC at least per the snow map i saw
SA: Yeah. Pretty gentle gradient though totals don't ramp up above 3" until you're getting close to Old Saybrook.
GP: Snow all the way to NC?
GP: Some of the mets on josh's site made an interesting point
GP: Western areas may do decently because of the positioning of the jet streak
DB: Haha can I get a west shift down here? Lol
The Trend is Your Friend: Thursday February 4, 2016, 24 Hours to Impact
​Even 24 hours out, we were vastly under doing totals in spots. Guidance showed more, at least some did, but that wasn’t enough to pull the trigger on going much higher. As a result, this was our new map. 

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You always have to be careful with maps. You never know which one is going to get the most eyeballs. If you put out a low map and that’s what everyone sees, it won’t matter if you put out a more accurate map later, you will have failed in the eyes of the public. 

We knew that we were dealing with an event that was going to have a sizable impact. By the afternoon, when the Euro came west again, we knew we crossed into high impact territory for most of Connecticut. ​

At this point in the story, as a forecaster, you begin to get this feeling. Call it a mixture of excitement and fear, as events begin to unfold faster than you can keep up. This close in, details begin to matter too. Not only are we looking at snowfall totals, we’re looking at:

Upper level temps
Boundary layer temps
Amounts of dry air in the column
Soundings that give you a sense of how good snow growth will be (among other things)
Wind profiles 
Low locations
Ridge and trough positions 


As a forecaster, missing key pieces of data could make the difference between succeeding and failing, and we had one heck of a high risk forecast on our hands. By the evening, it was time to upgrade again and make our final call. 

Game Time: Thursday Evening February 4th—Midday Friday February 5th
We were grounded, we were locked in, and we were prepared for anything. Our plan was being executed. Tim, our expert forecaster and map maker was hard at work putting together our final map. I was the forecaster on call, and although we all worked on the forecast, I was the guy communicating to the public. There were so many things to say…
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At this point, both the National Weather Service in Boston and New York City were underplaying the potential of this event (in our opinion). This was going to be a high impact event for most, and we needed to let everyone know it. 

My gut said that we were watching something special unfold, with a sneaky snow event turning into a bonafide snowstorm—the first of its kind for Connecticut this winter. This was a “big money” forecast. The state was watching, it was a high impact call, and there was no room for error…

Timing 
Our timing remains essentially the same. 

Now-1AM Friday: Rain showers will continue to overspread the state from SE to NW, becoming a steadier rain for most.

1-5 AM Friday: Rain transitions to snow, beginning in NW CT and working its way south and east.

5-9 AM: Snow becomes steadier and heavier as temperatures aloft and at the surface continue to drop near and below freezing. Expect periods of moderate to heavier snow with breezy conditions, especially in coastal areas. 

​9 AM – 12 PM: Snow begins to taper off from west to east, with lighter snow/snow showers lingering into early afternoon in eastern areas especially in the later hours. Conditions should improve over the course of the day but as temperatures drop during the evening hours ice will be an issue.

Impacts
Scattered power outages are possible in areas (think eastern CT) where snow is heavier and wet and the winds are breezy

Widespread commuting problems in much of the state with snow coinciding with rush hour

Widespread delays and cancellations

In the end, I was particularly happy that I mentioned scattered and not isolated power outages occurring. With over 50,000 losing power during the event, having a heads up was important. The things I was worried about never came to fruition. In fact, we busted low in many spots, especially in western CT.

By 7:40am Friday we were upgrading again, and still ended up short in spots. 

Due to the heavier snow making it farther west than we had anticipated, we are upgrading snow totals in western CT to 2-4" in our previous 1-3" zone and 3-6" in our previous 2-5" zone. Some locally higher amounts are possible, especially in the eastern portion of the new 3-6" zone where I would not be surprised to see some amounts of close to 8".
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Using spotter reports. Note how much variance there is from town to town, and how much of a SW CT winter it is--I think I will just add 3 inches to any snowfall forecast for that area the rest of the winter. 

The Report Card
Overall, I think this was our best forecast of the year. For us, it has to be more than snow totals—though those do matter. I think our followers were the most prepared out of any other group in the state. I think we did an excellent job of communicating the hazards, answering your questions quickly, and making adjustments when they needed to be made. We could have gone more bullish with snowfall, but we were probably already on the edge of the bullish forecasters. We were strong in communicating our thoughts (I think) and although it is very easy to point the finger, I don’t think we were as caught off guard as some other outlets, which is a testament to our internal communication structure and…honestly, luck. 


A band setup over central and just west of the Connecticut river threw our totals off in my mind. That’s how these things go sometimes. 

Initial recognition: Going back, I was actually surprised by how much lead time we gave on a Friday snow. We had a forecast last week that introduced a chance of snow, and we were on this threat sooner than most this week. That matters a lot in getting you prepared for a high impact event. A+

Midrange: We weren’t bullish enough. There wasn’t a whole lot of time to assess trends, but we did ok in the scheme of what the guidance was showing. B

Preliminary forecasts: Too low. Way too low. C+

Final forecast: This doesn’t just include final snow totals, which we did ok with especially in eastern areas. The timing of the changeover, the timing of the heaviest snow, and the ending time were all on point. It is what you dream of as a forecaster. Yes, we missed that death band over central Connecticut, but so did everyone else. The talk of heavy wet snow and power outages is what I care about most personally, and we got that right. I grade our snowfall forecast based on the final map we issued. A-

Rapid fire updates/communication: I think my lack of sleep speaks for itself. I did my best to read every comment and answer every question. The guys were all over it too, even if you didn’t see their name next to your response. Not quite 100%, but darn good nonetheless. A+

Overall Grade A-

Thank you for reading, sharing, and spreading awareness of the event. From the bottom of my heart, I appreciate each and every one of you. Hopefully you have more insight into what we do here. ​

-DB
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