Relatively routine hazardous icing event I84 corridor mainly 1/1 and terrain above 1000 feet in particular.

[NJwx85]

The 12z GFS trended a degree or two colder and also held onto the colder air at the surface longer than the prior run. Ice threat across the interior is increasing. 

[wdrag]

1 hour ago, crossbowftw3 said:

So upon doing the math and knowing QPF isn't always 1:1 in these situations I'd assume .1-.3 with higher elevations going up to .5" of ice

 

@wdrag what would you guess in this case?

It could.   I’m just worrying about the fact that primary jets split us. North and south so that WAA QPF is less than 1 inch in that ice period.  I see 12z GFS still on track and the for some reason furnace RGEM this year does have some ice but less than USA models.  For now I’m playing the lower end of icing but it is coming from what I can tell remotely 

[snowman19]

27 minutes ago, NJwx85 said:

The 12z GFS trended a degree or two colder and also held onto the colder air at the surface longer than the prior run. Ice threat across the interior is increasing. 

The GFS is very likely too cold as usual, i.e. the last storm. The fact that it’s colder than all other guidance is a red flag. It’s bias at play again

[NJwx85]

27 minutes ago, snowman19 said:

The GFS is very likely too cold as usual, i.e. the last storm. The fact that it’s colder than all other guidance is a red flag. It’s bias at play again

The GFS usually has a warm bias.

[snowman19]

37 minutes ago, NJwx85 said:

The GFS usually has a warm bias.

The last storm it sure didn’t. It overdid the confluence/cold and suppressed the storm so severely that it had areas which got 40+ inches of snow barely getting 4 inches. One of the most epic busts of all time. It also totally missed the mid-level warm nose over the metro area

[NJwx85]

38 minutes ago, snowman19 said:

The last storm it sure didn’t. It overdid the confluence/cold and suppressed the storm so severely that it had areas which got 40+ inches of snow barely getting 4 inches. One of the most epic busts of all time. It also totally missed the mid-level warm nose over the metro area

One storm doesn't take away from dozens of recent storms where it was way too warm. 

[jm1220]

2 hours ago, snowman19 said:

The last storm it sure didn’t. It overdid the confluence/cold and suppressed the storm so severely that it had areas which got 40+ inches of snow barely getting 4 inches. One of the most epic busts of all time. It also totally missed the mid-level warm nose over the metro area

The GFS cold bias is more of a suppressed bias. It didn’t see the warm air aloft in the Dec winter storm since it also had the mid level lows tracking too far south. The warm bias is at the surface-due to its poor resolution not seeing surface cold air pooling. I would go with the Nam any day to see the low level cold air and any mid level warmth-it typically resolves those a lot better. 

[sferic]

In Liberty NY, hoping not a lot of ice accretion. Tried to but was unsuccessful in having a backup generator installed

@crossbowftw3 what do you think?

[crossbowftw3]

20 minutes ago, sferic said:

In Liberty NY, hoping not a lot of ice accretion. Tried to but was unsuccessful in having a backup generator installed

@crossbowftw3 what do you think?

If there is any ice it should be manageable, think advisory amounts of maybe .1-.3...we will flip to rain and warm into the 40s Saturday. 

[Brian5671]

6 hours ago, jm1220 said:

The GFS cold bias is more of a suppressed bias. It didn’t see the warm air aloft in the Dec winter storm since it also had the mid level lows tracking too far south. The warm bias is at the surface-due to its poor resolution not seeing surface cold air pooling. I would go with the Nam any day to see the low level cold air and any mid level warmth-it typically resolves those a lot better. 

Good post-the 12/17 storm is a perfect example of this.  Too suppressed, but in the end missed the sleet that the NAM picked up on....

[HVSnowLover]

7 hours ago, jm1220 said:

The GFS cold bias is more of a suppressed bias. It didn’t see the warm air aloft in the Dec winter storm since it also had the mid level lows tracking too far south. The warm bias is at the surface-due to its poor resolution not seeing surface cold air pooling. I would go with the Nam any day to see the low level cold air and any mid level warmth-it typically resolves those a lot better. 

Agree it was fine with surface temps for that storm. 

[crossbowftw3]

As an aside, here’s one facet of this storm I don’t think happens every day: up to 2’ in South Texas of all places.

 

URGENT - WINTER WEATHER MESSAGE
National Weather Service Midland/Odessa TX
436 AM CST Wed Dec 30 2020

...SIGNIFICANT WINTER STORM TAKING AIM ON THE REGION...RESULTING
IN ACCUMULATING SNOW THIS AFTERNOON THROUGH THURSDAY FOR MOST OF
THE REGION...PARTICULARLY LOCATIONS ALONG AND SOUTH OF I-20...

TXZ046>048-050>053-060>063-067>070-075-082-274>282-302300-
/O.UPG.KMAF.WS.A.0005.201230T1800Z-210101T0600Z/
/O.NEW.KMAF.WS.W.0004.201230T1800Z-210101T0600Z/
Dawson-Borden-Scurry-Andrews-Martin-Howard-Mitchell-Winkler-Ector-
Midland-Glasscock-Ward-Crane-Upton-Reagan-Pecos-Terrell-
Reeves County Plains-Chinati Mountains-Marfa Plateau-
Davis Mountains-Davis Mountains Foothills-Central Brewster County-
Chisos Basin-Presidio Valley-Lower Brewster County-
Including the cities of Lamesa, Andrews, Stanton, Big Spring,
Colorado City, Kermit, Odessa, Midland, Monahans, Crane, McCamey,
Rankin, Big Lake, Fort Stockton, Dryden, Sanderson, Pecos, Marfa,
Fort Davis, Alpine, Panther Junction, Chisos Basin, Presidio,
and Castolon
436 AM CST Wed Dec 30 2020

...WINTER STORM WARNING IN EFFECT FROM NOON TODAY TO MIDNIGHT CST
THURSDAY NIGHT...

* WHAT...Heavy snow expected. Total snow accumulations of 4 to 7
  inches expected across portions of the Permian Basin, Trans
  Pecos, Culberson county, Big Bend Area, and Presidio Valley.
  Accumulations 7 to 12 inches expected across the southeastern
  Permian Basin and along I-10 to the I-10/I-20 Split, and Marfa
  Plateau. Accumulations 12 to 17 inches expected from the Davis
  Mountains east across the Stockton 

Plateau. Locally higher
  amounts will be possible.

* WHERE...Portions of southwest and western Texas.

* WHEN...From noon today to midnight CST Thursday night.

* IMPACTS...Travel will be very difficult to impossible. Some
  roads along and south of I-10 will become impassable, possibly
  including I-10 from the Split to Fort Stockton. The hazardous
  conditions will impact the morning or evening commute. 

[wdrag]

12/30 603AM from the topic update: QPF down to .4-.8" for the forum for this event, and slowed a touch from yesterday.  Otherwise my concerns have little change from yesterdays 12/29 reassessment. This event will be a problem for the Poconos, interior se NYS high terrain with less qpf and impacts for the CT River Valley, but otherwise I84 high terrain should do okay. Sleet or freezing rain develops ne PA/nw NJ (maybe even down to I78) between 2-5PM and probably changes to non freezing rain during the night all, except elevations above 1500 feet where it may be freezing rain throughout. Since temperatures will be briefly above freezing prior to the event - midday Friday, icing on treated roads, after initial treatment will probably be limited, but otherwise all untreated surfaces become icy, especially after sundown. Expect a slight glaze on untreated surfaces near I-78 (Easton PA, Warren County NJ) ranging up to about 2 tenths of inch above 1000 feet northern Sussex County NJ (northern Wantage-High Point-Vernon) and ne PA. Meanwhile, N CT and interior MA should see sleet and snow develop between 5-8PM Friday, with a possible 1-2 inches before a change to ice, and then probably non freezing rain after 2 AM Saturday. Glaze there a little less than ne PA.  CT River Valley should see less impact due to near freezing temps. Boston: a little sleet/snow Friday evening then changes to rain or freezing rain during the night with much less certainty there on details. After sunrise Saturday, melting and improved weather!  We'll start getting some short range ensemble guidance tomorrow morning that will help us detail impacts. Hopefully this is a reasonable assessment as presented above. I prefer not to comment again on this event til Thursday morning as model variations may skew me one way or the other, too soon. Have added one graphic- 00z/30 GEFS chance of 0.1" glaze. 

[jm1220]

1 hour ago, crossbowftw3 said:

As an aside, here’s one facet of this storm I don’t think happens every day: up to 2’ in South Texas of all places.

 

URGENT - WINTER WEATHER MESSAGE
National Weather Service Midland/Odessa TX
436 AM CST Wed Dec 30 2020

...SIGNIFICANT WINTER STORM TAKING AIM ON THE REGION...RESULTING
IN ACCUMULATING SNOW THIS AFTERNOON THROUGH THURSDAY FOR MOST OF
THE REGION...PARTICULARLY LOCATIONS ALONG AND SOUTH OF I-20...

TXZ046>048-050>053-060>063-067>070-075-082-274>282-302300-
/O.UPG.KMAF.WS.A.0005.201230T1800Z-210101T0600Z/
/O.NEW.KMAF.WS.W.0004.201230T1800Z-210101T0600Z/
Dawson-Borden-Scurry-Andrews-Martin-Howard-Mitchell-Winkler-Ector-
Midland-Glasscock-Ward-Crane-Upton-Reagan-Pecos-Terrell-
Reeves County Plains-Chinati Mountains-Marfa Plateau-
Davis Mountains-Davis Mountains Foothills-Central Brewster County-
Chisos Basin-Presidio Valley-Lower Brewster County-
Including the cities of Lamesa, Andrews, Stanton, Big Spring,
Colorado City, Kermit, Odessa, Midland, Monahans, Crane, McCamey,
Rankin, Big Lake, Fort Stockton, Dryden, Sanderson, Pecos, Marfa,
Fort Davis, Alpine, Panther Junction, Chisos Basin, Presidio,
and Castolon
436 AM CST Wed Dec 30 2020

...WINTER STORM WARNING IN EFFECT FROM NOON TODAY TO MIDNIGHT CST
THURSDAY NIGHT...

* WHAT...Heavy snow expected. Total snow accumulations of 4 to 7
  inches expected across portions of the Permian Basin, Trans
  Pecos, Culberson county, Big Bend Area, and Presidio Valley.
  Accumulations 7 to 12 inches expected across the southeastern
  Permian Basin and along I-10 to the I-10/I-20 Split, and Marfa
  Plateau. Accumulations 12 to 17 inches expected from the Davis
  Mountains east across the Stockton 

Plateau. Locally higher
  amounts will be possible.

* WHERE...Portions of southwest and western Texas.

* WHEN...From noon today to midnight CST Thursday night.

* IMPACTS...Travel will be very difficult to impossible. Some
  roads along and south of I-10 will become impassable, possibly
  including I-10 from the Split to Fort Stockton. The hazardous
  conditions will impact the morning or evening commute. 

Not that unusual they receive snow in the mountainous areas there but that’s a pretty sizeable event. When I lived in TX in Dec 2015, there was an 18” snowstorm in Lubbock which isn’t in the Trans Pecos mountains. Austin is getting a cold nasty rain event with mid-40s temps and some snow nearby in the Hill Country. 

[LibertyBell]

2 hours ago, jm1220 said:

Not that unusual they receive snow in the mountainous areas there but that’s a pretty sizeable event. When I lived in TX in Dec 2015, there was an 18” snowstorm in Lubbock which isn’t in the Trans Pecos mountains. Austin is getting a cold nasty rain event with mid-40s temps and some snow nearby in the Hill Country. 

Midland has gotten like 5 8"+ events since 1998

[crossbowftw3]

Looks like my guess of .1-.3 of ice for most who do see it still makes sense after some of today’s runs. It’ll be a long gone memory by the end of the day Saturday anyway. 

[wdrag]

2 hours ago, crossbowftw3 said:

Looks like my guess of .1-.3 of ice for most who do see it still makes sense after some of today’s runs. It’ll be a long gone memory by the end of the day Saturday anyway. 

You're probably right.  Yet, this may be getting tricky. 12z EPS starting to favor low pressure development along the SNE coast, with 1 L nr LI by 12z/2...and certainly baggy suggestion of a warm frontal wave going s of LI.  Fortunately qpf should be less than 0.8" but the 12z V16 and 18z NAM look a little reluctant to warm up and I can see that due to very little sfc wind  over I84 due to 850MB  jet splitting N and S.  18z/31 NAM doesn't get temps out of the 30s prior 18z Sat...  will have to presume that's wrong and too cool, but interesting. Even the 850MB wind near 06z/2 is lightening up and bending to s late at night., favoring a little better chance of CAD, already seen in the swwd ridged isobars across I84,  Tomorrow's HPC HREF may  be of interest for this probable light weight hazardous interior icing event. Blocking seems to be helping. Not a big deal, except for the unprepared stepping outside.  Later, Walt

[crossbowftw3]

1 hour ago, wdrag said:

You're probably right.  Yet, this may be getting tricky. 12z EPS starting to favor low pressure development along the SNE coast, with 1 L nr LI by 12z/2...and certainly baggy suggestion of a warm frontal wave going s of LI.  Fortunately qpf should be less than 0.8" but the 12z V16 and 18z NAM look a little reluctant to warm up and I can see that due to very little sfc wind  over I84 due to 850MB  jet splitting N and S.  18z/31 NAM doesn't get temps out of the 30s prior 18z Sat...  will have to presume that's wrong and too cool, but interesting. Even the 850MB wind near 06z/2 is lightening up and bending to s late at night., favoring a little better chance of CAD, already seen in the swwd ridged isobars across I84,  Tomorrow's HPC HREF may  be of interest for this probable light weight hazardous interior icing event. Blocking seems to be helping. Not a big deal, except for the unprepared stepping outside.  Later, Walt

The trends on the NAM are a bit surprising but again we can be thankful this doesn’t have much staying power and/or much precipitation to go with it...otherwise problems would certainly begin to arise. I’ll definitely be on the lookout for HREFs tomorrow but figure I’ll stay right where I am with .1-.3 with maybe a high end of .5 in typical elevations where the cold takes longest to clear out. Pretty typical messy little system and to me it never changed from being that. 

[sferic]

1 hour ago, crossbowftw3 said:

The trends on the NAM are a bit surprising but again we can be thankful this doesn’t have much staying power and/or much precipitation to go with it...otherwise problems would certainly begin to arise. I’ll definitely be on the lookout for HREFs tomorrow but figure I’ll stay right where I am with .1-.3 with maybe a high end of .5 in typical elevations where the cold takes longest to clear out. Pretty typical messy little system and to me it never changed from being that. 

Agreed

[wdrag]

12/31 5AM Update: Little change from 12/30 603AM. Timing the start probably closer to the end of the ranges listed below, and emphasis for event beyond 3 hours is for the  terrain above 1000 feet. Snow, if any,  is less than 1" far northern edge of the forum, but sleet a possibility at the start in many areas. Probably worth tracking wet bulbs for this mainly at night event... think it suggests longer duration than meets the eye but the model dew point forecast may be too low. mPING will be of value.  Valleys, below 700 feet should have mainly wet roads after initial treatment and possibly the same higher up.  Worthy of caution and best we can do for marginal thermal profiles.  It should be noted that the NAM3K is trying to hold onto icing into the Saturday morning daylight hours highest elevations northern fringe of the NYC subforum - that may be an outlier but not impossible. 

[HVSnowLover]

Looks like mild icing event for I84 corridor and points north. We know the models can overestimate how fast CAD will scoot out even in the valleys in these scenarios. As others have said not much previously and also temps being near 32 helps a lot compared to when it’s in the 20s in terms of avoiding significant icing. 

[crossbowftw3]

16 minutes ago, HVSnowLover said:

Looks like mild icing event for I84 corridor and points north. We know the models can overestimate how fast CAD will scoot out even in the valleys in these scenarios. As others have said not much previously and also temps being near 32 helps a lot compared to when it’s in the 20s in terms of avoiding significant icing. 

Advisories will probably get issued later on today, and maybe some WSWs for CTP? (Only really because their threshold for WSWs is .25 of ice). Either way Sunday-Monday is of more interest at this point

[HVSnowLover]

1 minute ago, crossbowftw3 said:

Advisories will probably get issued later on today, and maybe some WSWs for CTP? (Only really because their threshold for WSWs is .25 of ice). Either way Sunday-Monday is of more interest at this point

Yea if you combined surface temps for this with upper air temps on Sunday it’d be a real nice storm for the interior lol

[snywx]

16 minutes ago, NEG NAO said:

which counties does I84 pass through ? 

 

Orange, dutchess, Putnam 

[gravitylover]

1 hour ago, snywx said:

Orange, Dutchess, Putnam 

The highest elevations reached on 84 are in Putnam County between the Taconic Pkwy and Carmel where it reaches 1k feet. There are actually gates they use to close the road in snow or icy weather like the big mtn passes out west. When the weather gets bad in that stretch it's "inspiring" to watch.

 

[hudsonvalley21]

2 minutes ago, gravitylover said:

The highest elevations reached on 84 are in Putnam County between the Taconic Pkwy and Carmel where it reaches 1k feet. There are actually gates they use to close the road in snow or icy weather like the big mtn passes out west. When the weather gets bad in that stretch it's "inspiring" to watch.

 

Just to the south and west is Storm King mtn. There too it goes up over 1k in spots. Could have issues there also.

[wdrag]

A couple of graphics: SPC HREF icing potential... probably overdone.. but as fwiw worst case.  and the WPC ensembles for .01 icing. That latter I like. Please use legend for pops.  

I won't comment again on this til tomorrow morning at which time I'll set up the wintry elements OBS page for our W and N suburbs folk. Happy New Year!

 

[crossbowftw3]

27 minutes ago, wdrag said:

A couple of graphics: SPC HREF icing potential... probably overdone.. but as fwiw worst case.  and the WPC ensembles for .01 icing. That latter I like. Please use legend for pops.  

I won't comment again on this til tomorrow morning at which time I'll set up the wintry elements OBS page for our W and N suburbs folk. Happy New Year!

 

The SPC map does show the elevations well- but probably overdone anyway as you say. But I still wouldn’t be shocked if some instances of accretions .3-.4 happen above 1500’. 

[crossbowftw3]

And sure enough...
 

URGENT - WINTER WEATHER MESSAGE
National Weather Service Binghamton NY
226 PM EST Thu Dec 31 2020

NYZ062-PAZ040-048-072-011930-
/O.NEW.KBGM.WW.Y.0023.210101T2000Z-210102T1200Z/
Sullivan-Northern Wayne-Pike-Southern Wayne-
Including the cities of Monticello, Damascus, Equinunk, Milford,
and Honesdale
226 PM EST Thu Dec 31 2020

...WINTER WEATHER ADVISORY IN EFFECT FROM 3 PM FRIDAY TO 7 AM EST
SATURDAY...

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

* WHERE...In Pennsylvania, Northern Wayne, Pike and Southern
  Wayne counties. In New York, Sullivan county.

* WHEN...A mix of snow and sleet will develop by early evening New
  Year`s Day. The precipitation will change to freezing rain in
  the evening and last into the overnight and early morning of
  Saturday. The freezing rain will taper off to a few rain showers
  by sunrise Saturday as temperatures rise above freezing.

* IMPACTS...Travel could be nearly impossible. The hazardous
  conditions could impact the evening commute New Year`s Day.

[snywx]

2 hours ago, gravitylover said:

The highest elevations reached on 84 are in Putnam County between the Taconic Pkwy and Carmel where it reaches 1k feet. There are actually gates they use to close the road in snow or icy weather like the big mtn passes out west. When the weather gets bad in that stretch it's "inspiring" to watch.

 

Greenville Mtn in western orange is slightly higher. Up near the mountain rd exit its around 1400'