OBS-NOWCAST: Potential damaging wind (45-60kt) threat NYC subforum mainly 6PM-midnight Saturday Dec 11, 2021

[wdrag]

Good Friday morning everyone,

A consistently modeled 970s MB low moving into southeast Canada later Saturday will develop a strong low level 55-70 knot 850MB southwest jet ahead of it and a period of 50 knot west-northwest dry cold advection 850 MB winds behind it.  A dying squall line is possible with the cold frontal passage Saturday evening. SPC has a D2 marginal risk for severe.  Much of the guidance has near 45 MPH wind gusts for a fairly large portion of our area along the front with potential for pockets of 50-65 MPH gusts accompanying the squall line (could be just heavy showers and no thunder).

This event should be a little more widespread than the previous two early December events. 

Mount Holly already has a wind advisory posted from 1PM Sat-1AM Sun.  In advance, there could be isolated gusts 45+MPH during the afternoon in rather warm southwest flow but the main show should be with and just after the cold frontal passage-gust front during the early night, beginning over the Poconos around 6PM and sweeping east of the Twin Forks by around midnight. 

At least spotty tree-powerline damage should occur.

Courtesy to the the NWS and Pivatol Weather for their graphics (SPC D2 outlook) and the (ECMWF sounding near LGA at squall line passage - a bit isothermal in the boundary layer which is a possible hindrance to transfer).

Title: added OBS-NOWCAST in front of the previous title at 636AM 12/11/21. 

 

[guinness77]

Oh, Ho-hum just our usual potential wind damaging event of the week. 
 

Nothing to see here, carry on 

 

[White Gorilla]

Really sick of these windy and squally frontal passages with risk of convection especially in early to mid Dec.  Enough already, as if we have a choice.  Nature will do what it will do alas.  

[bluewave]

Looks like the LLJ really maxes out over Long Island Saturday evening. There will probably be 50 mph + gusts from the tight gradient alone. So we’ll have to watch for convection in the evening that could mix down winds in excess of 60 mph. 
 

 

[rclab]

2 hours ago, White Gorilla said:

Really sick of these windy and squally frontal passages with risk of convection especially in early to mid Dec.  Enough already, as if we have a choice.  Nature will do what it will do alas.  

Good afternoon W G. Well said, i and my mirror agree fully. As always ….

[wdrag]

So OKX and BOX joined the wind advisory previously issued a day ago by Mt Holly.  SPC has no change from yesterday in it's outlook.  A squall -fine line of briefly heavy showers is continuing to be modeled by the HRRR as of 5AM this morning with the primary time frames for passage roughly 7-830PM ne PA, 8P-930P NJ/se NYS, 9-11P CT-NYC, 11P-1A BOS-E LI.  Modeling continues as posted yesterday... 

This is the same system that has caused all the fatalities upstream in the Ohio Valley, but in lesser severity here. Not impossible to see a TOR central NJ approaching NYC this eve, per HRRR 2-5KM helicity but probability quite low as of early this morning. There are some parameters that will need to monitored for increasing their values in future modeling for this to become a greater risk. 

I will probably be off line at times today, though I'll monitor-especially this evening to see what occurs. 

[wdrag]

I am dropping the following on the forum: Let's see what happens. This includes a  new tool I will reference in the future... Imperfect but it coalesces some of the finer high resolution guidance into a general solution for forecaster applications (Neural Networks).

1) 12z/11 3K NAM position of the squall line at 10PM.

2-3) Neural Network (NN) info

4) NN prob of severe today

5) NN prob of 50 KT gust

6) NN timing of event within 2 hours.

7) 12z HRRR 2-5K max updraft helicity. Suggests my earlier  concern for TOR was too far north.

Overall I may be an hour fast on the more ing timing.  

Nothing else to share. 

 

[wdrag]

Everyone has noticed the spotty lightning from the Catskills to NNJ since 830AM.?

[hudsonvalley21]

5 hours ago, wdrag said:

Everyone has noticed the spotty lightning from the Catskills to NNJ since 830AM.?

Had a couple of rumbles and some lightning flashes here move thru from s/w to n/e. A brief heavy  downpour too.

[WeatherFox]

http://www.meteo.psu.edu/fxg1/WXTYPE/loop25ne.html

[MJO812]

54 here 

[WeatherFox]

https://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=16

[Allsnow]

Still cool and dank here 

[Snowshack]

Some thunder and heavier downpours at the moment, 56F.   Starting to feel like Christmas.

[guinness77]

Already getting whipping winds around my parts. Had to put some outdoor stuff away because, you know, it’s mid-December. 
 

If it’s already kicking like this at noon, I’m sure things are gonna be interesting after sundown. 

[dWave]

2 hours ago, wdrag said:

Everyone has noticed the spotty lightning from the Catskills to NNJ since 830AM.?

Had some flashes of lightning late morning with a brief downpour.

[crossbowftw3]

Right at 50 here at quarter past in the Catskills with little wind to speak of yet. Clearing skies are on their way to our friends in WNY—they’re gonna get whacked. 

2 hours ago, wdrag said:

Everyone has noticed the spotty lightning from the Catskills to NNJ since 830AM.?

I did not but certainly had downpours here.

[qg_omega]

Where is the warmth 

[guinness77]

Just now, qg_omega said:

Where is the warmth 

South Shore of LI. Muggy and warm. 

[Rjay]

2 minutes ago, qg_omega said:

Where is the warmth 

Mid to upper 50s isn't warm for December?

[NorthShoreWx]

A little out of our area, but impressive:

Lakeshore Hazard Message
National Weather Service Buffalo NY
921 AM EST Sat Dec 11 2021

NYZ001-010-019-085-112300-
/O.CON.KBUF.LS.W.0004.211211T1800Z-211212T0600Z/
Niagara-Northern Erie-Chautauqua-Southern Erie-
921 AM EST Sat Dec 11 2021

...LAKESHORE FLOOD WARNING REMAINS IN EFFECT FROM 1 PM THIS
AFTERNOON TO 1 AM EST SUNDAY...

* WHAT...Significant lakeshore flooding expected. The lake level
  at Buffalo may reach 11 feet above low water datum, which is 3
  feet above flood stage.

* WHERE...Lake Erie shore and Upper Niagara River shore of
  Niagara, Erie, and Chautauqua counties.

* WHEN...From 1 PM Saturday to 1 AM EST Sunday.

* IMPACTS...The rapid rise in water levels will result in
  lakeshore flooding along the Lake Erie and Upper Niagara River
  shores. Along the Lake Erie shore, flooding is likely along
  Route 5 and Hoover Beach in Hamburg, Buffalo Harbor and
  Canalside, Dunkirk Harbor, and other flood prone locations.
  Along the Upper Niagara River, flooding is likely to affect
  Grand Island, Cayuga Island, and beneath the North Grand
  Island Bridge at the Lasalle Expressway ramps. Very high wave
  action will also result in significant shoreline erosion.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Lakeshore Flood Warning means lakeshore flooding is occurring,
is imminent, or is expected to occur. For your safety, stay off
breakwaters, piers, rock outcroppings and beaches! Waves are
often larger than they appear and can easily wash you away.
Expect significant beach erosion and debris, local road closures
and extremely dangerous boating conditions.

[qg_omega]

7 minutes ago, Rjay said:

Mid to upper 50s isn't warm for December?

It’s 52, forecast is 66

[IrishRob17]

4 minutes ago, qg_omega said:

It’s 52, forecast is 66

Oh, so you thought high temps today would be right now, noted. 

[Allsnow]

Record breaking warmth fail 

[SnoSki14]

7 minutes ago, qg_omega said:

It’s 52, forecast is 66

I'm already at 60F, the warm temps are coming

[Rjay]

2 minutes ago, Allsnow said:

Record breaking warmth fail 

The temps are supposed to spike later this afternoon and into the evening.  At least according the models I've looked at.  

[rclab]

1 minute ago, Rjay said:

The temps are supposed to spike later this afternoon and into the evening.  At least according the models I've looked at.  

Good afternoon Rjay. Is it the approaching airmass itself that containes the warmth, albeit modified to us, and not the sun creating it in our area? As always ….

[Allsnow]

3 minutes ago, Rjay said:

The temps are supposed to spike later this afternoon and into the evening.  At least according the models I've looked at.  

Yeah, we have to 9pm. 

[Rjay]

1 minute ago, rclab said:

Good afternoon Rjay. Is it the approaching airmass itself that containes the warmth, albeit modified to us, and not the sun creating it in our area? As always ….

Yeah, I don't expect to see much sun today if at all.  

[MJO812]

Getting alot windier  here in Brooklyn