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


wdrag
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New 15z/ WPC D4-5 qpf. As you see, slipping south on max axis.  Usually I don't like to be in max axis of qpf for winter weather, UNLESS deep layer cold. The reason: MAX axis suggests warmer higher PWAT closer to the warm front 850MBJET and rain involvement.  I like this portrayal for I84 north wintry.  This is going to be interesting ... tho to me its front end snow-ice end as drizzle then see what late 2/3 brings, IF anything. 12z NAM looks good to me to at least give us ice and possibly snow on the front side - mid lvl FGEN WELL ahead of the primary low heading into the OH Valley. 

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It's D4 but here are the 06z/28 GEFS probs for more than a T of freezing rain and more than 0.2"  The snow probs for more than 3" (10 to 1 ratio) look good just north of I90 (NNE and N NYS). Offline til 1 or 2 P.  Hopefully Global models are not depressingly warm for I84.

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The 12z GFS still looks really ugly for Jan 1st and 2nd. The might be some ice in that solution for favored northern locations, but the warm push is too strong. There does appear to be some room for a better phase for the follow up coastal system on the 3rd and 4th. This system doesn't have much cold air to work with either, but it could be enough with a slightly more wrapped up mid level low.

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The new CMC is much warmer than last night's run.  Still has some sleet or freezing rain to start, especially NW areas. But it's not nearly as interesting as yesterday. The follow up coastal is gone too. It looks like maybe the 0z was a blip. It's been so tough to get any momentum going lately.

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1 hour ago, Stormlover74 said:

Who wants to freeze unnecessarily? Bring on the warmth if it's not going to snow

Agreed, especially since I can't play pond hockey this winter anyway due to the virus.  The town where I play isn't even filling the ditch with water this year.  Unless I'm on the ice, I don't have as much tolerance for the cold as I used to.

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Patience on this coming event:  I could be wrong and I see lots of folks are on the EC warm, very little ice.  That could be right.  However, the NAEFS is arguing considerably colder than the op cycle of the GGEM. The BL temp has dropped about 4-5C near I90 for 00z/2 and now sitting nr 0C with at least 1/4 qpf by that time.  

I'll add these NAEFS images and let this be, til tomorrow morning... maybe consensus by then will convince me that I'm wrong.  I sure like the RRQ of  the Maritimes Jet and LF quad of the Ohio Valley, and while thicknesses are warm, in the top of the ridge it can snow down to a 543-546 thickness. That will need individual checks of soundings.  12Z GEFS continues the 06z several inches I84.   

12z NAEFS qpf by 00z/2,  BL temp 00z/2,  500MB pattern 00z/2. Use with caution as I know many like the north, stronger and warmer.  Until the NAEFS caves, it's just time to  wait on outcomes with I think the 12z Wednesday cycle the potentially more reliable guidance and closing in on whatever. 

As far as GFS V16: seems like I'm an outlier on it's lack of reliably improving here in the northeast, but i only look at the big events.  Coin flip for me.  Go with your colleagues on it's improvement over V15 (hopefully improved BL temps).   

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Think I figured out the GEFS snow accumulations on the first. I think it's taking sleet and converting it as a 10 to 1 ratio. Therefore, I think the GEFS is offering quite bit of sleet to I84 on the first as the 18z/28 version continues with its 2-3"snowfall there. I kind of think that is correct (sleet, but total sleet less than 0.3"). Noticed the 18z EC op has 27F in PHL 12z Friday..not precipitating yet. That's 7F colder than the GFS MOS. 

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Good Tuesday morning everyone,  Dec 29.  Have concentrated the event to primarily 1/1.  It may bleed into 1/2 morning, but for now trying to simplify. 

From the topic update; Decreased model qpf has dropped the impact level to what i think is a relatively routine 3/4" to 1.5" qpf event with sleet and glaze expected I84 corridor.  I dropped the front end concern on the 31st since it's minor, maybe a bit of snow or ice mix in the higher Poconos with the CFP. I'll begin a new topic for 1/3 late today if it's still on the EC and GFS para but prefer GGEM on board That one is very low confidence for what could be a grazing fast developing nor'easter w snow somewhere close to NYC??? Again low confidence but on recent GFS parallel and EC OP. 

Timing for renewed precipitation seems to have delayed about 6 hours from prior modeling with 6-10 hours of ice anticipated for the I84 high terrain, beginning midday the first in the Poconos-far nw NJ-se NYS and late day CT/MA portion. Treated surfaces may be just wet during the daylight hours, but if it's several hours of sleet, then a bit of a different story. Glaze, probably 1/4" or less even if .75" freezing rain occurs. This will need much more refinement as we move into mesoscale-fram analysis. So I see this as an advisory hazard NY afternoon/evening for at least parts of I84. Unsure if temps can remain at or below freezing long enough to have glaze approach 1/2" in our I84 corridor high terrain.  As of this time, would not favor that higher end impact but worthy of monitoring. Flooding rain is probably no longer a risk,due to less qpf.  However, those who had sump pumps running for the 12/24 event, may see a resumption-not that this is a big deal, provided they are operational,  but in our area of nw NJ, it's unusual for this to occur in December. No new graphics today. 537A/29

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6 minutes ago, NJwx85 said:

Watch for a 6-12 hr period of significant ice threat N&W of I-287. Highest impact area for our sub forum is Orange county.

Agreed: Maybe Pike too, and High Point SR 23 extreme northern Sussex County.  Just difficult for me to see above freezing prior 9P Friday night at High Point, points n and w, at least based on modeling through the 06z/29 cycle. 

Enclosed map shows the defined subforum coverage area. Sometimes, I'll mention interior MA for those who might be interested in New England. 

NYC Forum - American WX.png

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43 minutes ago, crossbowftw3 said:

any clue on how much icing might be possible in that window? 

Probably a glaze North of I-80 in NJ, 0.10-0.20" once you get North of the NYS Thruway in Rockland, perhaps as much as 0.25", maybe slightly more once you get close to I-84. The Port Jervis area up into Ulster County could see more than >0.25".

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Just now, NJwx85 said:

Probably a glaze North of I-80 in NJ, 0.10-0.20" once you get North of the NYS Thruway in Rockland, perhaps as much as 0.25", maybe slightly more once you get close to I-84. The Port Jervis area up into Ulster County could see more than >0.25".

That was what I pretty much figured in my post above, looks plenty messy but fairly typical. Right now my P&C has me as rain-sleet mix for most of Friday.

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2 minutes 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?

You have to account for runoff and temperatures are just below freezing so it's not as bad as it would be if it was raining with temps in the 20's.

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2 minutes ago, crossbowftw3 said:

That was what I pretty much figured in my post above, looks plenty messy but fairly typical. Right now my P&C has me as rain-sleet mix for most of Friday.

I'm interested to see what the NAM shows over the next few runs. The GFS has consistently been the coldest at the surface. The 00z EURO limited icing to the far interior sections of Ulster and Sullivan Counties.

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7 minutes ago, NJwx85 said:

I'm interested to see what the NAM shows over the next few runs. The GFS has consistently been the coldest at the surface. The 00z EURO limited icing to the far interior sections of Ulster and Sullivan Counties.

Should be interesting. In any case once we warm and flip completely to rain it should only keep warming further from there, my high Saturday is now mid-40s. An issue to probably still sort out is when the flip happens. At my lower elevation in Sullivan, my house could probably stay all rain as it did last 12/29, while areas like MSV become a mess.

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