Extreme Cold, Snow & Sleet: SECS 1/25 - 1/26

[Stormlover74]

1 minute ago, eduggs said:

No noteworthy changes between the 18z and 12z HRRR through 41 hours outside typical noise. 850mb heights look a tiny bit flatter. 

Looks great. Snowing nicely at 18z and the mix line still several hours away

[eduggs]

The HRRR is noticably south of the 12z NAM in terms of mix line from KY to the mid-Atl. It looks about as good as I figured it could at the end of its run.

[SACRUS]

 

[eduggs]

The 18z HRRR is actually not that far off from the 12z GFS in terms of northern extent of precip. shield and snow - mix line. It appears to be flattening the height field a little bit more like the GFS although not quite as much. It's definitely south of the 12z RGEM positions.

[wthrmn654]

⚠️

The forecast for Sunday's winter storm has been updated. Snowfall amounts have trended down slightly, but ice amounts have trended up slightly for some areas. Regardless of exactly  The forecast for Sunday's winter storm has been updated. Snowfall amounts have trended down slightly, but ice amounts have trended up slightly for some areas. Regardless of exactly how much snow falls, our message is the same: Significant impacts are expected for our entire area!

 

Snow will begin after midnight late Saturday night into early Sunday morning. The peak of the storm and heaviest precip will occur during the daytime Sunday into Sunday evening, then wind down into Monday morning. A Winter Storm Warning is now in effect for our entire region. Very cold conditions expected through next weekend.

 

Updated briefing here: https://www.weather.gov/media/phi/current_briefing.pdf

[CPcantmeasuresnow]

1 hour ago, wilton_wx said:

I think that 8-12" line gets pulled south, theres very little consensus right now that the sleet makes it that far north into CT. Coastal areas, yes. But that 300' elevation change from Coastline to more inland will be very telling

Elevation has no bearing on mid level temps and changes to sleet. 

[SACRUS]

 

 

[SACRUS]

 

 

 

 

[eduggs]

If you cycle the past 6 runs or so of the NAM you can see the phase getting slightly sloppier over time. The northern stream is little by little shearing off the top of the trof instead of phasing back into the southern stream. It's still a good phase of energy and moisture, just not as extreme as a day or two ago. That trend is really helping keep the primary SLP and the bulk of precipitation south of the NY-Canada border... I'm really hoping it helps just enough to stave off too much sleet and reduce the severity of the dryslot. On the flip side, it might lead to a reduction in total QPF.

[MANDA]

12 minutes ago, wthrmn654 said:

⚠️

The forecast for Sunday's winter storm has been updated. Snowfall amounts have trended down slightly, but ice amounts have trended up slightly for some areas. Regardless of exactly  The forecast for Sunday's winter storm has been updated. Snowfall amounts have trended down slightly, but ice amounts have trended up slightly for some areas. Regardless of exactly how much snow falls, our message is the same: Significant impacts are expected for our entire area!

 

Snow will begin after midnight late Saturday night into early Sunday morning. The peak of the storm and heaviest precip will occur during the daytime Sunday into Sunday evening, then wind down into Monday morning. A Winter Storm Warning is now in effect for our entire region. Very cold conditions expected through next weekend.

 

Updated briefing here: https://www.weather.gov/media/phi/current_briefing.pdf

Nice that a good part of this event will be taking place during the day !  

[Nibor]

Why does the NAM take so long? Is it running on a windows 95 computer?

[mikeysed]

Nam Kuchera is gonna blow minds 

[SACRUS]

 

 

[RedSky]

2 minutes ago, Nibor said:

Why does the NAM take so long? Is it running on a windows 95 computer?

A dozen monkeys using abacus

 

[donsutherland1]

2 minutes ago, Nibor said:

Why does the NAM take so long? Is it running on a windows 95 computer?

Yes. And because Microsoft no longer supports Windows 95, each frame needs to be scanned independently for viruses. And then it has to be double authenticated.

[Stormlover74]

Looks like a quicker flip to sleet Ala 6z but we'll see if it slows again 

[SACRUS]

[eduggs]

The southern stream wave in TX sharpened up a bit again this run 

[danstorm]

Just now, eduggs said:

The southern stream wave in TX sharpened up a bit again this run 

yes but coastal reflection is a bit more pronounced and a bit further south - I think it'll be a wash

[eduggs]

Just now, danstorm said:

yes but coastal reflection is a bit more pronounced and a bit further south - I think it'll be a wash

Me too. Was still hoping for clear improvement and more breathing room.

[SACRUS]

[SACRUS]

[winterwx21]

Much lower amounts by 21z on this NAM run. It doesn't have as strong of a thump before the change to sleet. 

[wxman]

Yikes, not what we wanted to see, but it's the NAM. It giveth and taketh away every cycle.

[Stormlover74]

Just now, winterwx21 said:

Much lower amounts by 21z on this NAM run. It doesn't have as strong of a thump before the change to sleet. 

Drier and warmer. 6 runs to go

[wxman]

The coastal never gets cranking and we are flooded with warm air.  Is it right?  Who knows.

[Stormlover74]

Just now, CentralNJSnowman said:

Looks like timing of progression of the sleet line in NJ is nearly identical on 18z NAM and 12z NAM

Its about 30 miles further north which is a huge difference since that encompasses most of the metro

[SACRUS]

[CentralNJSnowman]

Just now, Stormlover74 said:

Its about 30 miles further north which is a huge difference since that encompasses most of the metro

Yeah, I actually deleted my post.  It WAS progressing identically through about 18z Sunday or slightly later, and then was substantially worse after that.

[psv88]

Jesus NAM! God awful...