wdrag

That is important, chicken or the egg. LONGGGG ways to go to forecast accurately the potential for extremes just 4 weeks ahead. Just my 2c.

Agree...

I'm looking at NAEFS 8-14 day and both 00z/11 ensemble patterns. I think east of the Rockies it's going to get very cold for a few days. Am thinking between the 18th-25th, somewhere in there it will be even colder than this week. I think the extreme of Dec has flipped coasts and I can't see this flipping back prior to February. Will need to lose the AK ridge and then I think it takes at least 5 days to lose the cold. I need to see the NAEFS D8-14 (week two) start warming before I give up on the cold.

Will comment at 745AM... need time for other home stuff. I may be starting a thread for LI/CT at that time for the 14th including wind gusts past 40 knots, then we move onto the 16th-17th. One at a time. Nothing locked.

Also, not sure who on here in December or copied from elsewhere, predicted all of NAM turning cold in January but it seems we're on our way to a rather cold January, my guess colder than this morning. Too much modeling keeping the 500MB trough in the east and the ridge in the west. This is a good opportunity for us.

Here is the 18z NAM FOUS for LGA-NYC: Note the large change in stability between 12-18 hours (+9C), the noticeable BL wind shift between 12 and 18 hours, the R1 over 50% at 12 hours, and the excessively steep 12z hr T1-T5 17C lapse rate. The overnight snow showers and squalls occurrence was predictable yesterday. Basically a strong cold front with a very cold core aloft, and Great Lakes boundary layer moisture being lifted by the cold front then swept south of us. 0.1": Wantage NJ but I've heard of more elsewhere. This was a lot more than a flurry situation.

In the meantime, do not be surprised to see a a band of snow showers, a few with SW+ thru the 184-I80 corridors into NYC-LI between 10P-3A. Think it's forming on BGM radar at 01z, with excessively steep low lvl moist lapse rates, a slight wind shift to NNW behind the band with much more stable air arriving at sunrise (and with the more notably falling temps-unsure if anyone noticed the 6C drop in BL temp between 06z and 12z on the NAM FOUS). Hopefully I was up to a dusting. Some places might get 1/2-1" fluff? Will rereview Thu night-Fri, Sunday centered snow opportunities tomorrow morning.

Late 13 -14 still a concern: GEFS in particular likes this bombing storm for a LI/SNE grazer. Did not start a thread for this due to most modeling and WPC missing east but this probable big ocean storm is a concern by not allowing enough separation between systems for the necessary ridging in the northeast ahead of the next Great Lakes diving short wave - ie depressed weaker further south on the 16th. The good news for an event are ensembles (GEFS, and especially the EPS) are in favor of a weekend centered snow event and the new overnight WPC D6-7 graphics are added - use time period and the low probs legend to continue D6-7 perspective on 3" chance. The EPS in particular is developing a nice 850 Low just to our south, Will check back on the modeling this Monday evening.

454AM Wednesday Jan 12: title and tags adjusted to drop Saturday, focus late Sunday-Monday morning for what appears to be an 18 hour storm of snow-rain-snow. Heaviest snow tends to be modeled west of the I-95 corridor but ensembles still warrant continued concern for the axis of heavy snow including I95. At this point far too uncertain but where it snows for 12 hours, widespread 6+" seems likely. Also a 6 hour period of potential 50 kt inflow gusts is possible for the coasts Sunday morning and if it occurs with the dawn Monday high tide, would result in coastal flooding, magnitude unknown. This does not appear to be a long duration storm (24 hours+) but it should be intense for a few hours Sunday night or Monday morning. Again track uncertain, and sensitive to the intensity of the surface low. There still is opportunity that this will track too close to our area for much snow but there are several days to adjust the track and resultant precipitation type. It does appear there will be a general inch to 1.5 inches of qpf with this system, maybe thunder too. A big storm with large scale impacts entire east coast-Appalachians. The only reason I didn't highly stronger wording for impact, is that this will occur later Sunday and the following Martin Luther King Jr. Holiday. --- At this 6-7 day lead time 8PM Sunday Jan 9 issuance, options are fairly wide open. For now, a light or moderate event 'seems' likely but absolutely not a lock, nor is a heavy event excluded. This event still could be demolished to zero by what happens off New England on the 14th, or what follows between the 19th-22nd. However there already has been discussion the past several days for the coming weekend. Ending 12z/9 the past 6 cycles of the ECMWF op, the last 4 cycles of the CMC GGEM [LI 3 cycles, I84-4 cycles] have some sort of snow event, especially I84. Maybe the GFS via it's 18z/9 cycle is shifting snow emphasis on the 16th for our area instead of bombing off the coast on the 14th? Having reviewed ensembles: 12z/9 EPS/GEFS/NAEFS all have some sort of frozen event is coming to the northeast USA, along and north of I80 including LI. Have added the broad coverage low chance WPC D7 issued at 17z/9, the EPS 24 hour qpf ending 12z/17 and the 12z/EC 850 MB low (GEFS so far has nothing, still favoring the 14th but not as far south and west as previous). NAEFS products for 00z/17 are added including previous 24 hr qpf, 00z sfc temp in C, and the sfc pattern. There will be quite a few model changes-conflicts and this could end up having been a wasted effort... but it seems worthy of further scrutiny as our next possible significant snow or ice event for at least a portion of the NYC subforum.

Wantage-Branchville NJ (the Distillery). Icing has started again since 6PM.... minor icing at worst. 31.8F. Road were being salted up here near the Appalachian Trail.

31.1F in this part of Wantage NJ and struggling up now but most solar exposed surfaces melting at Noon.

So the 12z/9 GGEM is consistent, certainly I84 corridor for a wintry event. Will check 12z/EC and ensembles and if EC continues on with wintry LI north, and 18z GFS backs off the Thu-FRI closeness and heads more toward late Sat-Sun night...then I'll start the thread at 9PM. No insight. Walt 1204P/9

Wantage NJ 740' MSL going ups degree an hour and 28.8 at 939AM. Ice even on shoulders of treated roads.

Freezing rain sprinkles have occurred Wantage. 27 at 714A. Manageable where treated, except a more careful approach I84 corridor. Not like Wednesday morning for NYC, I95.

No thread from myself on Sunday the 16th potential event. I don't think the 00z/9 EC op very close to the coast is the most probable outcome but respecting that this might yet be only I84, holding off. GGEM continues steady for a snow event. Will reevaluate for a thread at 8PM today or 6AM Monday. Looks like a nice winter pattern for the rest of January to possibly hold onto snow cover wherever its more than 3 inches deep this morning.

Likely my last post for the evening. Watch IPW-ZRW- showers, sometimes it ends up south of modeled. We'll know more in the morning. 21/12 at the house in Wantage at 751PM with a light southwest wind. Often 23F at the surface or 23F somewhere in the sounding below the above freezing layer means sleet instead of zr.

No thread from myself this eve. will revisit either Thu or Sunday events in the morning. First up: Ice, at least I95 west.

4 consec cycles of op EC producing spotty or greater coverage of 2" snowfall on LI. 2 consecutive GGEM runs of a winter storm for the northeast. I'm close to a thread centered on the 16th but need time to review ensembles. So either start it at 9P tonight or 730A Sunday, if the 00z cycle continues. Very broad ballpark wording (kitchen sink) that will permit honing in more likely solution with a solution from ice/rain to a snow event of varying unknown magnitude. That's a D8 risk so keeping this in mind. My feeling is we've already had a fair amount of speculation and I don't see it ebbing, yet. Later, Walt

Will probably convert this thread at 9PM to OBS-Nowcast with same headline.

Thanks for the feedback... I'm un sure of NOHRSC practices but am sure they use filters and the longer we wait after the event ends, the more complete the data set. We in the NWS could produce these types of maps back in 2018, but it's a bit time consuming ensuring the data is correct. Staffing and other priorities may preclude?

Wont be posting 345-630PM. What a mess coming tomorrow. Added the 12z/8 SPC HREF freezing rain, and the HRRRX freezing rain. There probably will be a relative dry slot tomorrow morning, where only T or .01. and some of these modeled amounts may end up sleet. Still, pretty impressive. Also i checked the HRRRX PTYPE at 18z (1PM) Sunday... still freezing rain much of the interior 20-30 miles nw of I95, presuming it's precipitating.

and now the most bullish model from the 12z cycle: the HRRR... Pretty interesting and there are now model hints that icing lasts into mid afternoon parts of the distant nw suburbs. Also, keeping in mind the HRRR tends to be a warmer model of the suite, certainly warmer than the RGEM and NAM.

SD is reported in whole inches... 4.7 rounds up to 5.

This ended up small northwest, moderate I95 corridor to a heavy but not extensive major event (1 foot) for the eastern edge, particularly LI CT. Occurring basically in 7 hours, the rate of fall was intense. Snow water ratio's added beyond the typical 9-11 to 1. CoCoRaHS sampler two day amounts as of 915A, the NOHRSC assessment, the NAO and PNA values during the event. Lead time by the models good, thread was underplayed LI.

Here is the wrap up...CoCoRaHs and NOHRSC analysis. Hopefully this is acceptable. NAO and PNA indicies at the time. Click for details.