If you believed the global models from 36 hours ago... ECM, UK, GFS, ICON, CMC - all of them - you would think it should be all-snow throughout the NYC area right now. The NAM is just really good at sniffing these out.
The NAM was the first model to bring sleet to our area and eventually most of NNJ and southern Westchester. Eventually all other guidance followed suit. It was the earliest to mix today and it was RIGHT. All other guidance was WRONG. PIVOTAL CLOWN MAPS DO NOT EQUAL THE NAM FORECAST SNOW ACCUMULATION. People seem to be clueless about interpreting model output. UK, GFS, Euro were way too late and south with the mix line.
Hats off to the NAM model on the sleet timing. It won again. If it was a little light on the QPF before the mix, most guidance was. Now let's cool the mid-levels and flip back to all snow. Radar looks amazing for the Hudson Valley region!
I was out on a ski tour for several hours. The snow is much denser than I would have expected. It was fluffy before 9am and then increasingly dense. I don't think ratios have been great since this morning. After 12pm I began noticing melted flakes foretelling mid-level warming. It's been going back and forth between various combinations of snow and sleet since 1:45.
Sleet began mixing here at 1:45 - right on time. Sleeted for about 30 minutes with >2mi vis then parachute flakes fought back and now moderate snow with low vis. again! 10" new and 12.6F
I'm seeing 18"+ for parts of the mid-HV across to CT on the latest guidance... maybe down to Orange & Putnam... especially if measuring with a snowboard every 6 hours.
The ECMWF-AIFS Ens not withstanding, it looks like we're back to an all-northern stream "pattern." It's a shame we can't get another southern stream wave to turn the corner. Looks cold and dry.
Really a shame all the HEAVY sleet obs from VA and MD. Such a waste of surface cold and QPF. There's going to be some places that see 0.75"+ QPF as sleet.
The mid-level warm surge is setting up through SEPA progged to head towards north central NJ. NYC east should be a little cooler or later to warm. The latest few HRRR runs are really trying to push the sleet line back south after 22z or so. Looks really close for Passaic Co. to southern Westchester.
The GFS clearly performed terribly. If shifted significantly northward for 8 cycles in a row to catch up to the rest of guidance. DCA is not getting 18" of snow. They already flipped.
The NAM has had about 0.5" QPF as snow for Staten Island for several cycles. I'm not sure how much melted liquid has fallen there. It might not end up so far off when the mix begins. With good ratios to begin that could easily end up as 8" of snow.
Let's do it! Bronx would seem to have a better shot. I figure we have at least 3 more hours of clean snow and then several more with possible snow/sleet mix. I feel slightly more confident about double digits. Ratios are decreasing unfortunately.
The latest HRRR does sink the mix line down a little this afternoon! That could really help NNJ and northern Westchester pick up an extra inch or two this evening and flush the sleet vibe. It continues to look sick for Orange and Putnam on north!!
I think the NAM has been great - just like with Dec. 26. Thank god we have the NAM model. Otherwise people would have been thinking for days that we were getting 18"+ (i.e., Apple Weather App). People think the Pivotal clown maps are the NAM model. They're not. The NAM forecasts QPF and temperature. How other people (pivotal, TT, even Bufkit) calculate snowfall based on that is separate from the model itself. This morning we've had a slight overperformance in terms of QPF and really good ratios. But the NAM has clearly been the best with the mix line.
We saw heavy rates overcome a shallow layer in Little Rock yesterday morning. But that sounding didn't punch through with +3C like this afternoon's forecast sounding looks to.