Newman

The big ones get sniffed out 8-10 days ahead of time. I remember tracking 2016 for what seemed like ages. The emotional rollercoaster ride when everything shifted south, only for the NAM to score a coup on bringing it further north within the last 2-3 days. Obviously the pattern coming up Jan 6-10th or so looks unreal with the retrograding NAO block and split flow, but details are TBD if there's good timing with short waves in the flow. If we can get a solidly timed PNA spike WITHOUT a shortwave kicker screwing things up, I truly think the ceiling is some of the big uns in history. Just go back and look at the preloading patterns of the biggest storms for PHL, DCA, BWI, NYC, etc

Edit just to add: In no way am I guaranteeing a KU, but it's gotta be encouraging seeing some semblance of a pattern that can support said larger storms vs. Pac puke and zonal flow. Or cold and dry Northwest flow

7 minutes ago, penndotguy said:

That’s kinda my expectation out here in Berks, Mt Holly seems to have a pretty good handle on this one but it’s soon now casting will be interesting no doubt

Definitely time for nowcasting. The models are usually never perfect in nailing the warm nose and the timing of said warm nose. Who knows, maybe it comes in heavier and colder so areas thump for an hour or two and pick up more snow? Or maybe the warm nose is deeper and it's more freezing rain vs sleet? We'll see.

1-2" of snow/sleet looks like a good bet for most. Latest 12z HRRR is 0.4-0.5" of QPF area wide. With 3:1 sleet ratios, that'll get you the 1-2" of accumulation. 

Let's say something like the 0z FV3 comes to fruition which keeps the warm nose/WAA a bit muted, then perhaps in heavier rates you could stay snow longer for some areas and eek out an additional inch of snow. But the latest 12z FV3 came in with a lot of sleet.

7 minutes ago, anthonyweather said:

Totals


.

Really a great performance from the RRFS and HRRR which were highlighting the 6-8" strip somewhere across SE PA early yesterday morning

7.1" on the season in Fleetwood now, about 3 weeks ahead of normal

5.75" in Fleetwood

1 minute ago, ChescoWx said:

Another 1.5" has fallen since 445am now up to 7.5" of snow. Still heavy snow temp at 29.7

Wow! I just checked the radar loop and your area has been under the best banding all night. Love it.

Temp is down to 32° in Fleetwood with moderate snow according to my folk, looking forward to the pics from everyone. It will be my first ever winter not seeing snow now that I live and work in Florida so I will live vicariously through you all, enjoy this one!

I'm surprised Mount Holly didn't mention "localized 6 inches" for the WSW. I also thought they might follow what State College did with Lancaster and York counties and put Berks, Lehigh, Northampton under 2-5 inches. Would love to read their latest AFD to see if they're just playing it safe or if they don't trust some of the latest short term guidance from the HREF, HRRR, and RRFS. It's also kinda splitting hairs I know

HRRR has a band with 1"+ rates set up over Lancaster -> Lehigh from about midnight through 4am. Whoever ends up under that 850-700mb fronto band for an extended period of time will easily grab 4-6"

Close to go time I know, but 6z EPS bumped up QPF as well. Upper-levels ticking more favorably, hopefully the ticks continue right up to storm onset.

Philly EPS mean is 4" and probability of snowfall exceeding 4" is now 53%.

1am sounding for Allentown off the 3k, wow! Plenty of ascent right in the DGZ. The 10pm - 3am timeframe will probably be when the LHV gets the best rates before everything shunts southeast. Snow might be done by sunrise tomorrow morning

6z Euro is quite a bit more wet for the Lehigh Valley. Solid 2-4", many of the mesos are also bringing WWA amounts north. Should be a solid event for the area. 

12Z Euro shifted a bit back SE after the northwest bump at 6Z. It digs the TPV just a bit further south over the Great Lakes which keeps the heights a smidge more suppressed. But largely it's been super steady. 1-2" across the Lehigh Valley and 2-4" I-95 corridor sounds like a good bet.

A couple things I'm interested in:

1. As we near this event, how do the mesos trend with the upper level jet and any small ticks in TPV placement to allow greater height rises (or worsening).

2. QPF trends on guidance, especially along the northwest edge of the precip shield. Latest RGEM stays wet for the Lehigh Valley (0.2-0.3" of precip), NAM much drier.

3. Post-storm, I'm curious what the SLRs end up being. The NAMs are the most aggressive (no surprise) in some solid omega within the DGZ and also 850mb fronto, but mostly along and south of I-95 once the storm starts to get going a bit. I'm curious to compare 10:1 and Kuchera model maps to reality.

NAM in line with the Euro, obviously more amped because it's the NAM. But cut some of that QPF and it's a general 2-4" along the I-95 corridor. It's a shame this isn't coming 6-12 hours later for the Eagles game

Euro has been largely consistent in showing a general 2-4" for much of the Philly metro the past few runs with upwards of 5" in localized spots. Berks, Lehigh, Northampton probably 1-3" but this is one of those setups where you can get a strong fronto band on the NW side of the precip shield as the upper level jet shifts towards the area under the favorable right entrance region. I think the precip shield would actually expand a bit further northwest than what the Euro shows with isentropic glide along the frontal boundary as the TPV drops in from the north.

However, that same TPV is pushing everything along and out to sea so it's a fine balance between the flow buckling and getting that precip shield to expand vs everything shunted east. Will have to watch the trends with the models, have to get a bit greater height rises ahead of this one

1 hour ago, WxUSAF said:

.05” seems unreasonably low?

 

Glad you posted this as I came to check what others were getting SLR in the DMV region. Friend (who's also a met) from Leesburg sent me this a bit ago:

"So I measured a measly 0.04" of melted precipitation at 845am, and another 0.01 at 1pm. So I grand total of 1.7" from 0.05". I felt like it doesn't make sense so I measured the melted precipitation from a core sample off the deck that was around 1.25 to 1.5" and it was just above .03", so I don't know ha"

Seems like some real fluff up there today

Friend just measured 1.7" on his snowboard in Leesburg. Final band might push it to 2?

Extended pattern looks great if you're into cold and dry northwesterly flow with maybe an occasional clipper system potent enough to deliver C-2" of snow

Does anyone know of anywhere that has MJO RMM plots before 1975? The Australia BOM archived site only goes back to 1975.

14 minutes ago, LVblizzard said:

That sleet line just hit like a brick wall. Went from dead silence to loud pinging instantly.

Mix line seems to be washing out a bit on radar, could flip back to mostly snow for a time.

Still 29° in Fleetwood

Sleet line already up to southern Berks, can see it quickly racing northward on CC

23/19 in Fleetwood right now

3k actually never gets KABE above freezing at 850s (though it's close), but does sneak to 33 at 925 down to the surface. At 1-2pm tomorrow, the 3k shows rain BUT some deep lift just below the DGZ and even stretching into the DGZ. The DGZ is pretty high up in the atmosphere, but as you can see in the skew-T the sounding is marginally above freezing. If you can get some deep lift and rates to increase within a backside band as the storm departs, you could potentially finish with some heavy snow and fat dendrites if the column cools isothermally back to freezing. Of course, all of this could be for nothing and if 1.) The mesos are correctly handling temperatures and 2.) The rates aren't heavy enough to cool the column then we'll definitely see the lower end of snow totals materialize. Just wanted to point out a way that you could potentially see higher end (3-4" totals) materialize along the I-78 corridor which is currently the 90 percentile from the NWS.