Dec 16-17 Snow/Ice potential storm

Winter Weather Advisory from MON 1:00 PM EST until TUE 7:00 AM EST
1 of 2
Action Recommended
Execute a pre-planned activity identified in the instructions
Issued By
Philadelphia - PA, US, National Weather Service
Affected Area
Portions of central, northern and northwest New Jersey and east central and southeast Pennsylvania
Description
...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM 1 PM MONDAY TO 7 AM EST TUESDAY...

WHAT...Mixed precipitation expected. Total snow accumulations of up to one inch and ice accumulations of up to two tenths of an inch.

WHERE...Portions of central, northern and northwest New Jersey and east central and southeast Pennsylvania.

WHEN...From 1 PM Monday to 7 AM EST Tuesday.

IMPACTS...Plan on slippery road conditions. The hazardous conditions could impact the Monday evening commute.

ADDITIONAL DETAILS...Snow begins Monday morning and then will mix with sleet and freezing rain Monday afternoon. Precipitation then changes to plain rain Monday night. Rain then continues through Tuesday before tapering off Tuesday night.

They are riding the GFS and may bust hard Irish.
If people follow this they and these maps like the Euro and NAM come to fruition there will be many unhappy peeps.

What are we looking at in terms of start times for the initial possible thump of snow? And will it be constant precipitation or more intermittent until any possible ice comes in?

Gotcha mugs, certainly have no expectations with this one. Just figured I'd post the advisory since it went up. Happy to see activity this early in the season.

This has potential for being less ice and more snow as per HRRR and new HRRR para runs.

What a frustrating storm to track anyway good news all the short-range guidance hrrr, nam, and rgem all show a burst of heavy snow between 10 p.m. and 2 a.m. tomorrow morning for New York City metro 2 to 4 in on the snow Maps. Most of the short-range models have sleet and freezing rain for the nearby suburbs through 7 a.m. tomorrow morning going to be a nightmare commute. Obviously the further north and west you go could stay frozen through the entire storm following the storm bitter cold air this is going to be a wintry week in the New York metro area

Al, SR models are taking this till about 7pm Tuesday from what I can see, not just 7am.  Anyways yes we look to be back to 2-5 inches of snow (except 3km nam which has snow confined to northern areas) and then ice ice babay! Yikes! Snow encased in ice be ready to lose some power if these numbers are correct, trees are going to be sagging like crazy. There is now a HWO for the coastal areas saying WWA will likely be needed, with the ice shown we may need ice storm warnings too, it will be interesting to see if freezing rain really persists that long, hoping we do see at least some snow.

All the SR models have this insanely heavy frz for a hour or two preeceeded and post from about 5am till 8am though continues lighter most of the day. Tomorrow mornings commute is a no go, stay off the raods please, you cannot control a car on ice.  Going to be a lot of closures IMO, I dont think it;ll be just delays for schools.

That SR puts me in more snow than ice but I don't see how .6 inch plus of ice can fall with temps so close to freezing or a little above in the immediate NYC area.The cold to follow makes for a mess as the slop will freeze solid.Hoping that warm nose obliterates the ice scenario.Storms like this as projected make me want to pack up and move to Florida.Absolutely hate slop storms!

Euro is also back to having 2-4 snow and a lot of frz pretty much all models are in line now. Now please stay that way!! LOL, I mean the ice isnt good but please this model mayhem less than 24 hrs out is just nuts.

jmanley32 wrote:Al, SR models are taking this till about 7pm Tuesday from what I can see, not just 7am.  Anyways yes we look to be back to 2-5 inches of snow (except 3km nam which has snow confined to northern areas) and then ice ice babay! Yikes! Snow encased in ice be ready to lose some power if these numbers are correct, trees are going to be sagging like crazy. There is now a HWO for the coastal areas saying WWA will likely be needed, with the ice shown we may need ice storm warnings too, it will be interesting to see if freezing rain really persists that long, hoping we do see at least some snow.

Ths hrdps is out to lunch and i wouldn't regard it as reliable in terms of ice.  Check out the disparity of surface temps from what was progged to reality.  Those that are at and above the baroclinic zone (area separating warm/cold mid level temps) can can 2"+ of snow out of this.  I would say above route 80 best shot at that.  I would also say those are the areas which should be most concerned about the ice.

See CAD signature at the lower levels now.  This is 925mb temps. A warm nose is already coming into Pittsburgh. This is a storm which is further south, otherwise the warm nose would be well into PA. How far south it stays determines the baroclinic zone. Interesting stuff.

The current temps tell the story of where the rain/snow/ice line will set-up later tonight thru tomorrow.



Outside of North-Central and NW NJ, majority are already above freezing. Short range models such as the NAM show a secondary low developing off the coast that tries to drag colder air to the coast. Global models do not recognize this secondary low, thus keeping many of us above freezing duration of the event.

My forecast remains unchanged of a C-1" of snow for NYC Metro, including NE NJ, LI, and parts of eastern/central NJ. Those N&W of I-95 into NW NJ and upper most NNJ into SNY and NEPA can expect 1-3" with pockets of 4" amounts. This also includes Morristown, NJ and areas west of there. This is more of a 3-6" snow event once you get into the Albany region.

Snow is not the difficult forecast here. That is fairly set in stone. It is the freezing rain forecast that is challenging.



In my opinion the GFS has the best handle of the storm and where the greatest ice threat is. Again, temps are above freezing already for many and I am not a believer in the secondary low off the coast. And even if it does come to fruition, I dont think it will pull the cold air to the coast as extreme as models show. Therefore, N&W areas can expect 1-3/2-4" type of snow with possibility of 0.10" to 0.40" of freezing rain, aka ice. That is NOT good and calls for dangerous conditions.

The timing of the ice storm would be between 10-11pm this evening to 10-11am tomorrow morning. Some areas will still see precip falling beyond 11am tomorrow. Please be careful if you live in one of these areas that is in deep purple on the map above.

heehaw453 wrote:See CAD signature at the lower levels now.  This is 925mb temps.  A warm nose is already coming into Pittsburgh.  This is a storm which is further south, otherwise the warm nose would be well into PA.  How far south it stays determines the baroclinic zone.  Interesting stuff.

Nice post, and yes very interesting, however the low pressure has yet to develop over the TN valley. Once it does, with the help of the High Pressure (SE Ridge) off the coast, temps will gradually warm up the coast.

Frank_Wx wrote:

heehaw453 wrote:See CAD signature at the lower levels now.  This is 925mb temps.  A warm nose is already coming into Pittsburgh.  This is a storm which is further south, otherwise the warm nose would be well into PA.  How far south it stays determines the baroclinic zone.  Interesting stuff.

Nice post, and yes very interesting, however the low pressure has yet to develop over the TN valley. Once it does, with the help of the High Pressure (SE Ridge) off the coast, temps will gradually warm up the coast.

Will have to see how the surface temps behave when precip makes it into the area though.  While there are several locations just above freezing check out dew points region wide.  In the high teens to low to mid twenties.  Even with a warm mid level one would think if the dew points remain below freezing the surface temps will likely drop a few degrees initially before giving way to the warm air pushing back.  

12z NAM trended a bit to the GFS with showing now little snowfall for NYC Metro.

Frank_Wx wrote:12z NAM trended a bit to the GFS with showing now little snowfall for NYC Metro.

Thanks Frank for the updates...I think that for us here below the Driscoll Bridge..we should not have much to worry about with this one... current temperature 35

To Frank's and Sroc's point.  This is the current wet bulb freezing temp line.  Anything above the purple means surface temp is 32 or lower when air is saturated.  That means the surface does cool to below 32 when precip occurs.  Air is drier now though due to HP overhead.  Once that moves out air will moisten up.  

Even though storm hasn't formed I feel the position of these 925's is telling me that cold air will hang tough due to more southerly trajectory of developing storm.  Seen this setup before.  We'll see.



This is an ice signal for EPA, NNJ and LHV.

What does nam show in terms of icing? I still think it'll come closer to the coast than modeled along with snow. Just going by what you guts are saying about the cold at 850 vs surface.

I'm 75 miles north of NYC and the forecast is for snow tonight changing to sleet and a little ZR around daybreak and then changing back to snow tomorrow afternoon before ending. Total snow 2-5 inches with sleet and .10 of ice. This is going to be a very bad ice storm for a lot of people although I think 1 inch of ice is a little overdone. That would be devastating with power outages and then some very cold air coming into region.

hi res guidance insists on a colder soln. HRRR cont to drop the snow line further and further south. It would not surprise me for the north shore of LI through the northern boroughs of Manhattan get an inch or 2

weatherwatchermom wrote:

Frank_Wx wrote:12z NAM trended a bit to the GFS with showing now little snowfall for NYC Metro.

Thanks Frank for the updates...I think that for us here below the Driscoll Bridge..we should not have much to worry about with this one... current temperature 35

You're welcome! Yea the shore is spared for this one.

jmanley32 wrote:What does nam show in terms of icing? I still think it'll come closer to the coast than modeled along with snow. Just going by what you guts are saying about the cold at 850 vs surface.

The 12z NAM cut back on snow an ice accumulations for NYC Metro.

hyde345 wrote:I'm 75 miles north of NYC and the forecast is for snow tonight changing to sleet and a little ZR around daybreak and then changing back to snow tomorrow afternoon before ending. Total snow 2-5 inches with sleet and .10 of ice. This is going to be a very bad ice storm for a lot of people although I think 1 inch of ice is a little overdone. That would be devastating with power outages and then some very cold air coming into region.

Yes, I am not sure how far north the ice risk extends but 0.10" for your area sounds reasonable. Be careful!

Frank what about yonkers and then 20 miles north white plains? In terms of ice and snow? So you guts aren't buying the ice amounts? Or did they go down at 12z I don't have time to look.

jmanley32 wrote:Frank what about yonkers and then 20 miles north white plains? In terms of ice and snow? So you guts aren't buying the ice amounts? Or did they go down at 12z I don't have time to look.

I posted my thoughts earlier this morning in this thread. Give it a read and if you still have questions let me know!

The CMC, or Canadian model, is persistent and agrees with the short range models like the NAM that the ice threat will extend toward the coast. Again, I am not a believer in this scenario but would like to digest additional model runs later today and see if this holds any merit

Frank_Wx wrote:The CMC, or Canadian model, is persistent and agrees with the short range models like the NAM that the ice threat will extend toward the coast. Again, I am not a believer in this scenario but would like to digest additional model runs later today and see if this holds any merit

sorry Frank missed ur earlier post. I think it's go be a fine line wether I see more than city. Mog that's horrid most over half a inch plus!! If that comes true nj and most of Westchester to lhv are go be without power.

Surface temps are at or above freezing for most folks now.  That is good.

Wet bulb temps still below freezing for most.  

What the HRDPS is showing would be like a once in 20 year ice storm. 3/4" - 1" range. I think more like .25" - .5" is possible 40 miles NW of 95.