RCNYILWX

Maybe someone more intricately involved in NWP can chime in, but my perception from my NWS career (started in Feb 09 at OKX) and my hobbyist phase going back years before that, is that modeling has grown less stable at closer in lead times on the most important details for system evolution. I think that global modeling systems are better than they've ever been at nailing the large scale pattern at long leads, but these large swings inside D5 feel more common to me than back in the 2000s and 2010s. My theory is that it's partially related to faster flow due to CC and partially related to ever increasing resolution (high resolution garbage in still = high resolution garbage out; ie. errors in those high res details, such as convective parameterizations, reach many of the members which all have the same physics and then amplify). I have no idea if I'm right on this, but I'm def interested in hearing from others better versed than me. Sent from my Pixel 9 Pro using Tapatalk

Heh, revisit my 2nd post about a 4-7"/5-8" type event for the Chicago metro going to 1-5" in 2 days. Sent from my Pixel 9 Pro using Tapatalk

We've definitely been on the cusp of something better but had too much predominantly dry NW flow in January after missing the big early January event not too far to our south. And then this past week looked good synoptically but again didn't come together for a widespread significant to major event (places in IA, NW IL, WI did do very well on Wednesday with mid-level frontogenensis and high ratios). Regarding the 98-99 winter, it's a good example of how getting a major storm or multiple to significant events (solid advisory to warning type amounts) makes a winter. This winter will end up much colder than that one, but getting almost 22" in one storm, an occurrence that's actually much more rare in our area than the northeast coast, went a huge way to ORD getting about 50" in 98-99. Even though this has been a weak La Niña winter, it reminds me somewhat of 2014-15, in that we had plenty of cold, dry NW flow (tied for coldest Feb on record that winter), but we cashed in with the Superbowl snowstorm in early Feb, with 19.3" at ORD the 5th largest snowstorm for Chicago. We're literally pennying up our snow totals out here this winter, haha. Makes it less fun to deal with the ~20 below wind chills we're getting tonight and tomorrow night. At least we do have about 5" otg in my neighborhood though, better than brutal cold with bare ground.

You're welcome! Honestly as someone who grew up in Queens with snowstorms my number one drive to getting into this field, I understand the frustration. We're somehow on track to end up with a solidly below normal temperature AND well below normal snowfall winter out here in the Chicago area lol. We just had a system back on Wednesday go from being in a winter storm watch two days out to a 1-5" event for most of the area. And then there was some potential for the current messy system hitting the northeast to become a solid storm out here and especially just east of here, and that missed as well (we did get a nice 2-4 hour burst of moderate to heavy snow Friday night). Sent from my Pixel 9 Pro using Tapatalk

While ensembles are the way to go days out from a threat, the important thing to keep in mind is that ensemble systems (some more/less than others) tend to be underdispersive, meaning that more members will in general come out in the general direction of the operational. When you look at members showing various scenarios, the probabilities are not absolute probabilities - they're called experimental probabilities. While it's fair to say that taking all systems and other op solutions into account allows you to lean a certain way in your thinking (such as there probably being a higher chance of the system missing much of the NYC with heavy snow as of this current lead time), at point X lead time, all member solutions are still equally plausible. When there's still guidance members showing the outcome snow lovers want, it's still a plausible solution and can't be ruled out yet. Definitely understand not being optimistic when the 84 hour NAM is the lifeline, (and I personally wouldn't be right now if I still lived in and forecasted for the NY area), but there really is plenty of time for changes. Past misses this winter aren't necessarily prologue, while it's 4+ days out. This post may end up meaning nothing, but I think it's some good context when tracking winter threats.

Heaviest snow here since the second mid January event last winter (the Friday morning 2-3"/hour thump followed by 40-50 mph wind gusts). Edit: Probably 1/4 mile or less visibility

From everything I looked at today, rates should be good for during the meat of the event, the main burst from the late morning through the afternoon. Felt confident enough to go with temporary 1/2 mile visibility in the 18z TAFs (in collab with the CWSU), which is not super common for us to do near or over 24 hours out. Forecast soundings are supportive of 1"/hour rates at times, so maybe the beefier looking sim ref output from some of the CAMs are onto something. We did account for the possibility of some lake enhancement of the totals into NE IL, though soundings don't look particularly impressive to generate notably higher totals (and impacts). Feeling pretty good overall about the 3-6" range for the metro mentioned in the advisory. Sent from my Pixel 9 Pro using Tapatalk

Some hindsight involved here, but I think the average of the ensemble 10:1 mean, probability and percentile stuff told a pretty consistent story. From the NWS perspective, I haven't been directly involved in the forecast process this time, but the inter-office collab and collab with WPC aspect is way more challenging than many realize. Internally, we felt that the QPF and ratios were too aggressive but there's only so much we can do when trying to form a consistent picture across large regions. To me this looked like a advisory to perhaps low end warning event, particularly on the non-GFS/GEFS data. It's easy to get caught up in the Kuchera ratio output when assessing the snowfall forecast, that method is too simplistic though. 10:1 gets bashed, and it should in marginal temp situations and more clear cut high ratio setups, but I think it's a good first guess plenty of the time for synoptic systems. Use the 10:1 and then adjust up where you're confident better banding is going to set up, through using model diagnostics like f-gen and cross sections, and utilizing the Cobb output. Sent from my Pixel 9 Pro using Tapatalk

Good voice of reason today Sent from my Pixel 9 Pro using Tapatalk

Noise level changes on the GEFS all in all if you look at the past 4 runs. Sent from my Pixel 9 Pro using Tapatalk

Solid agreement in the 12z ensemble data overall (10:1 total and 24-hour snow swath as a proxy), particularly the EPS, GEFS, and UKMET ensembles (MOGREPS-G), which is good to see at this juncture. The CMCE is farther southeast but has enough more amped members to not be too crazy far off from the other ensemble systems. Sent from my Pixel 9 Pro using Tapatalk

Might be worth starting a thread for the Wednesday system. Giving me vibes of the Feb 2019 ice storm (surface pattern is reminiscent to the observed pattern from our event recap page for 2/11-12/19). The GFS is slowly but surely starting to come around to the ECMWF/EPS idea. Also the EPS has lost a lot of the farther north surface low track members. This is important because the surface evolution is such that the warm front will remain well south until Wednesday evening, and then the track somewhere across the southern LOT CWA could very well prevent some places across interior northern IL from ever getting above freezing. If you compare the past several Euro runs, there's been consistency on a swath of 0.25-0.5"+ estimated FRAM output within the DVN, LOT, MKX CWAs and then extending into lower Michigan. Also noted in the AFD, the 00z and 06z EPS had 60-80% probs of >0.1"+ ice accums near and north of I-80. Sent from my Pixel 9 Pro using Tapatalk

For the 10 year anniversary of the Superbowl snowstorm, I updated the event recap page with another one of our forecasters, and we also the added new graphics for that page to the 2011 GHD Blizzard event recap. https://www.weather.gov/lot/2015_02_01_WinterStorm https://www.weather.gov/lot/2011blizzard Sent from my Pixel 9 Pro using Tapatalk

Today's overperforming temps and winds are a harbinger of things to come on Monday. 21z RAP looks realistic and it might still be a bit too cool. Thinking 45-50F is plausible in the LOT CWA. Given that we had low to locally mid 40s highs today with wind gusts up to 35-40 mph, Monday has an even better setup for strong west-southwest winds, so feeling pretty confident that we'll need a Wind Advisory at least for areas near and north of I-80. Sent from my Pixel 9 Pro using Tapatalk

Certainly too early to feel confident in it given uncertainty in the MJO realm, but nice look (500 mb height anomalies and 850 mb temp anomalies) on the 12z EPS in early Feb. GEFS was decent too, but would be cool to get something like the EPS evolution to play out in the extended. Anything to shake things up from the extended CAD doldrums. At least next week will be warmer here. Should still be a decent pattern (clippers and periods of LES) for the northern Lakes though.