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Dec 15-18 Arctic Front/Snow Thump/Meltdown to the Border


HoarfrostHubb

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1 minute ago, ORH_wxman said:

It's because the CAD on the 18z GFS is better in SE areas....I assume that both of you are looking at snow maps...so I bet the algorithm gave better snow output because the sfc was colder in SE areas.

Caught me ;) Tricky to look at the details of a run on mobile. I'm hoping that trend continues somewhat as models "recognize" the airmass in place - feels like we see that more often than not in these types of situations.

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Just now, SR Airglow said:

Caught me ;) Tricky to look at the details of a run on mobile. I'm hoping that trend continues somewhat as models "recognize" the airmass in place - feels like we see that more often than not in these types of situations.

I was looking at QPF and rates. Yes more diverse and less intense in most areas. These nuances play out, won't matter 6 hrs later its toast

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3 minutes ago, SR Airglow said:

Caught me ;) Tricky to look at the details of a run on mobile. I'm hoping that trend continues somewhat as models "recognize" the airmass in place - feels like we see that more often than not in these types of situations.

Yeah it was solely a function of the sfc on the 18z GFS...the 12z GFS was decently warmer SE of about TOL to ASH during the middle and latter stages of the thump.

 

I typically ignore the sfc on the GFS which is why I think we'd still prefer the 12z solution. You want the better mid-level thump over the weaker version on 18z all else equal...and given the GFS is essentially irrelevant for sfc temps, I don't make the distinction there. Regardless, there is plenty of time to hash out details.

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Should be a fun few days...a couple to few inches of snow tonight with the arctic front, then more snow showers throughout the day followed by brutal wind chills Thursday night and Friday.  Then more snow Saturday to an icy mix and a brief period of rain before going back below zero early next week.

 

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25 minutes ago, ORH_wxman said:

Yeah it was solely a function of the sfc on the 18z GFS...the 12z GFS was decently warmer SE of about TOL to ASH during the middle and latter stages of the thump.

 

I typically ignore the sfc on the GFS which is why I think we'd still prefer the 12z solution. You want the better mid-level thump over the weaker version on 18z all else equal...and given the GFS is essentially irrelevant for sfc temps, I don't make the distinction there. Regardless, there is plenty of time to hash out details.

What odds would you give pack survival south and north of 90 respectively .. assuming both fall in 3-6" range?

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Long time lurker, first time poster!  I think reading the AFD from my area and knowing what the presidential ridge line does to precip flow patterns and CAD, I'm thinking the MWV should make out of this with a net gain and some bomber snow pack to move into the christmas holiday.  We haven't got the orographic base here that the Greens have, above 3500' we're OK.  But at the valley floors we've only got a scant 12" on the ground.  I'm not seeing Saturday night as problematic.  Friday however.....I'll be in the controlled environs of an ER with walls and windows.  Hate being outside on those days.  

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Okay question.  I was just reading the wind discussion with the high wind watch down there.  Gray Maine's discussion says wind criteria up here does not warrant a high wind watch up here.  Why would the Arctic fropa winds be stronger in SNE?  Is this what the models show?  I'm just not good at figuring out wind data.  

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2 minutes ago, Damage In Tolland said:

What odds would you give pack survival south and north of 90 respectively .. assuming both fall in 3-6" range?

Depends where....south of 90 at low elevation is gonna be very difficult, though maybe some pockets N of HFD could last if things go right. I'd say like a 30-40% chance in your hood and prob 50/50 for somewhere like ORH. It would help if the thump can put a good 5-6" down of at least 10 to 1 snow...that would def increase the odds. If its like 4" of 13 to 1 then it's probably going.

 

Obviously other factors like how much CAD we get...a meso low developing would really help that. It would delay the sfc warmth by probably a good 6 hours.

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24 minutes ago, WeatherNurse said:

Long time lurker, first time poster!  I think reading the AFD from my area and knowing what the presidential ridge line does to precip flow patterns and CAD, I'm thinking the MWV should make out of this with a net gain and some bomber snow pack to move into the christmas holiday.  We haven't got the orographic base here that the Greens have, above 3500' we're OK.  But at the valley floors we've only got a scant 12" on the ground.  I'm not seeing Saturday night as problematic.  Friday however.....I'll be in the controlled environs of an ER with walls and windows.  Hate being outside on those days.  

yeeeah.... that depends.  i think older snow, that's compacted with higher water content in frozen form might do better than anything that falls on top, even up there.

there 850 temp's to nearly 6 C with 50 kts + sustain wind impinging on those 3,500 ' els later Sunday... That's going to eat some serious snow -

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Just now, Typhoon Tip said:

ha!

KTAN's been hitting the HWW for few cycles now ...

I don't really have a problem with a high wind watch anyway. But gusts 65-70 mph? I find that a stretch based on model forecasts. Even with that trop fold, and assuming we can even mix to it, trop winds were only 50 knots. So we're really talking the majority of gusts around 45 mph, with an isolated roof rattler, in my opinion.

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3 minutes ago, OceanStWx said:

I don't really have a problem with a high wind watch anyway. But gusts 65-70 mph? I find that a stretch based on model forecasts. Even with that trop fold, and assuming we can even mix to it, trop winds were only 50 knots. So we're really talking the majority of gusts around 45 mph, with an isolated roof rattler, in my opinion.

actually.. i kind of do have a little bit of concern about that being over stated, but will probably end up wrong.

it's just that i've come to find that that NAM's middle BL wind on the grid combined with lapse rate is a pretty good rule of thumb and i'm seeing about 45 tops. BUT, they seem to be talking about a deeper potential flip-over with that brutal 800 mb layer... -35 just above so not sure.. 

thing is, even if so, there tends to be a kind of residence for wind impact; namely, in that we've had a bit of a dearth of wind events in very recent climate, and that tends to 'set the area up' for more impact when/if wind finally does arrive.  so, ... perhaps it's for the better. 

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1 minute ago, Typhoon Tip said:

actually.. i kind of do have a little bit of concern about that being over stated, but will probably end up wrong.

it's just that i've come to find that that NAM's middle BL wind on the grid combined with lapse rate is a pretty good rule of thumb and i'm seeing about 45 tops. BUT, they seem to be talking about a deeper potential flip-over with that brutal 800 mb layer... -35 just above so not sure.. 

thing is, even if so, there tends to be a kind of residence for wind impact; namely, in that we've had a bit of a dearth of wind events in very recent climate, and that tends to 'set the area up' for more impact when/if wind finally does arrive.  so, ... perhaps it's for the better. 

I mean my take is that is a forecast for the absolute ideal scenario for wind gusts. You need a perfect wind max, perfect mixing, well timed isallobaric and CAA forcing, etc. Any one of those factors is off and you end up with 45 mph gusts instead.

So it's like a forecast of peak possible wind vs. actual wind gusts.

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5 minutes ago, OceanStWx said:

I mean my take is that is a forecast for the absolute ideal scenario for wind gusts. You need a perfect wind max, perfect mixing, well timed isallobaric and CAA forcing, etc. Any one of those factors is off and you end up with 45 mph gusts instead.

So it's like a forecast of peak possible wind vs. actual wind gusts.

yeah ... wind is brutal.  i can recall a big wind event or two that were poorly modeled and almost missed entirely, where offices scrambled to get warnings up. likewise, over forecast ones that ended up advisory... oh, one or two people got a tree to lay across some telegraph lines and poke a hole in a roof, ...take out the Lincoln SUV next door and they're pounding posts about how awesome of a call it was .. .but, no -

but again, if we don't get wind/"pruning" events in so many months, the region can be more affected by that 45 or outlier 52 mph whack.

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8 minutes ago, OceanStWx said:

I mean my take is that is a forecast for the absolute ideal scenario for wind gusts. You need a perfect wind max, perfect mixing, well timed isallobaric and CAA forcing, etc. Any one of those factors is off and you end up with 45 mph gusts instead.

So it's like a forecast of peak possible wind vs. actual wind gusts.

Nocera and Frank are the best of BOX.  Neither one hypes. He must feel it's legit. AFD mentions 70-80 mph 

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1 hour ago, OceanStWx said:

I don't really have a problem with a high wind watch anyway. But gusts 65-70 mph? I find that a stretch based on model forecasts. Even with that trop fold, and assuming we can even mix to it, trop winds were only 50 knots. So we're really talking the majority of gusts around 45 mph, with an isolated roof rattler, in my opinion.

Agreed, not seeing over 50 or so let alone 80

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