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2/19 Weekend Threat


am19psu

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I like where we sit essentially on the Mason Dixon line as I feel like this will creep a bit north as we get closer ala the storms in '10. A lot of people allude to the fact that there always seems to be nice deform banding on the far NW side of these types of storms and we'd be sitting right there. Would love to see the GFS and Euro move up though at 12z.

It's not impossible, but you would need a 150 mi jump in the 700mb low from the 12z NAM to get the deformation banding up to PHL/ILG and the 12z NAM is by far the farthest north model.

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also people have to remember this is falling during the day. You need some good rates to stick on grass and esp roads. We are coming off back to back 50 degree days. Even if we muster .25-.5 of qpf im not sure the rates would be hvy enough to even accum much

This might be that tyep of storm where 2-4 falls in philly and delco but only 1-2 that sticks.

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I think the best accumulating snows come toward the end of the day and night. We're getting into that time of year where snow at night is the best. Its still gonna be nice to see several hours of heavy snow coming down. Considering how this winter has been. At least we got a big storm to watch..

This might be that tyep of storm where 2-4 falls in philly and delco but only 1-2 that sticks.

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Trend has been for better influx of low-level dry air from N which cools when precip evaporates. BL issues are not as bad as a couple of days ago. Flip side is that precip can only come so far N..

Agree, at this point I am decreasingly concerned with the BL issues. The succession of colder solutions is clearly in response to the evolution of the SHP position, going from 1020 in Iowa to 1024 in Michigan the past day's worth of runs for 48 hours out from now. H5 confluence brings surface ridging well into NY/PA ahead of the low for a nice little bananna high. Now how that ends up eating into the precip shield will be well documented but other than perhaps some sprinkles at the beginning I think this is all snow all the way down to the coast in NJ.

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I am growing pretty confident there will indeed be accumulation (but not on roads) Sunday. It is very rare to have an important snow event up to BWI and totally miss the Philly area. That said those that live and die with the models will have just a few more ups and downs but somewhere in the 1 to 4" range across the city and burbs growing more likely. If the higher end of the range is reached NW Chester County may actually be above normal snow for the season to date....who would have thunk it in this pattern - nothing like a freak October storm to save the day

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I am growing pretty confident there will indeed be accumulation (but not on roads) Sunday. It is very rare to have an important snow event up to BWI and totally miss the Philly area. That said those that live and die with the models will have just a few more ups and downs but somewhere in the 1 to 4" range across the city and burbs growing more likely. If the higher end of the range is reached NW Chester County may actually be above normal snow for the season to date....who would have thunk it in this pattern - nothing like a freak October storm to save the day

I'm still up in the air whether anything more than .05 makes it up to PHL. There is going to be a very sharp cutoff on the northern edge of this system due to the confluence from the vortex to the north. PHL certainly COULD cash in with a 2-3 type event, but I wouldn't want to make that forecast right now. Given all of the model guidance, I would lean toward lighter amounts at this time.

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RGEM and the nam are the same through 48 Tom. will see if the other models even take a bite though.

The NAM is useless at this time range due its convective parameterizations and the character of this system. I'd start giving it more credence at tomorrow's 12z runs. The RGEM is a crappy version of the NAM. I don't know anyone that uses it seriously as a forecasting tool.

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RGEM and the nam are the same through 48 Tom. will see if the other models even take a bite though.

Not really, if anything the RGEM is more in line with the GFS. When looking at the 48 hour maps

The ridging to the west of the system is more in line with the GFS, the strength of the ULL on the back side (over Missouri at 48 hours) is a good bit deeper on the NAM then the RGEM, while the GFS is slightly weaker then the RGEM but overall a far better match. The enhanced band of precip in the warm sector is much farther North on the NAM compared to the RGEM but is in a similar location compared to the GFS. The surface low location and intensity also matches the GFS more then the NAM. Finally the precip shield is a far better match with the GFS, as many areas where the NAM already has significant precip, especially on the North and Northeast side, the GFS and RGEM have far lighter precip.

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You think the precip shield on the Euro should be larger? I think it should be larger... I still feel the track will be near the Virginia Capes. I still think significant snow could get into Philly, but obviously right now, thats a low risk. Definitely will have to monitor radar and satellite trends tonight and into tomorrow just to keep an eye on it. Definitely have to look over the 500mb maps tonight and tomorrow as well to see how things will be verifying.. But, not sure the Euro is capturing this storm in terms of the size of precip shield..Anyway, just some thoughts there..

But if you look at this run and had to make a forecast, probably be lucky to get some light snow at best. Probably lucky to get an inch.

Removing the emotion aspect from it, is pretty amazing how tightly clustered the medium range modeling solution has been the last two to three sounding runs since those dropsonde missions were implemented.

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You think the precip shield on the Euro should be larger? I think it should be larger... I still feel the track will be near the Virginia Capes. I still think significant snow could get into Philly, but obviously right now, thats a low risk. Definitely will have to monitor radar and satellite trends tonight and into tomorrow just to keep an eye on it. Definitely have to look over the 500mb maps tonight and tomorrow as well to see how things will be verifying.. But, not sure the Euro is capturing this storm in terms of the size of precip shield..

But if you look at this run and had to make a forecast, probably be lucky to get some light snow at best. Probably lucky to get an inch.

John,

I'm at home, so I'm just looking at the Euro off the wundermaps. I can't run my favorite model diags. The NAM soundings had alot of dry air with the Great Lakes high, so I can see the sharp cut off that most of the models have (except for the nam strangely enough). Precip can only get so north with the blocking 50/60 low in the way, the precip has had that squeeze a tube of toothpaste look to it for a couple of days now. It was nice seeing you and meeting Adam for the first time the other night.

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Removing the emotional aspect from it, is pretty amazing how tightly clustered the medium range modeling solution has been the last two to three sounding runs since those dropsonde missions were implemented.

agreed, i feel the models have converged pretty well in the last 36 hours, at the right time for them to be converging. Someone will say after the fact that the models have been all of the place, but I really dont think that is the case with this one.

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Well, it was a pleasure listening to you and Walt the other night. I mean two hall of famers of the NWS. Without you and the many other pros out there, I don't where I be and let alone, might have lost all of forecasting skill set weather forecasting over the years. So, no doubt, folks you and many other out there have kept me sharp.

Great points below.

John,

I'm at home, so I'm just looking at the Euro off the wundermaps. I can't run my favorite model diags. The NAM soundings had alot of dry air with the Great Lakes high, so I can see the sharp cut off that most of the models have (except for the nam strangely enough). Precip can only get so north with the blocking 50/60 low in the way, the precip has had that squeeze a tube of toothpaste look to it for a couple of days now. It was nice seeing you and meeting Adam for the first time the other night.

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It was rather interesting putting together the POP, QPF and snow grids early this morning given the challenges with this upcoming system. I adjusted my POP grids and ran the snowfall tools several times and I was still not all that confident with the forecast especially the farther north one goes. Early this morning was my last night shift so good luck to the next set of forecasters. :)

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With the GFS, UKMET and EC continuing to trend south, confidence in any precip up to TTN looks very low. The NAM keeps wobbling and the GEM did come a smidge north.

With the BL issues you probably need more than a tenth of an inch there to get an inch of snow, so the likelihood of an inch is very very low right now. Even a coating is iffy though any north nudge may bring up the odds. Still thinking less than an inch for TTN, obviously.

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