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Weekend Snowfest/Rainfest/Mixed Mess?


showmethesnow

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4 minutes ago, psuhoffman said:

Looks like a big step down in qpf from earlier runs unless I'm missing something. Last run was about 13-15mm across the area. This looks like 8-12mm  

It's that jump in between hr 48 and 60 that's messing me up... We'll see what the meteogram says... you'd think that we would have green over us at 54

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1 minute ago, yoda said:

It's that jump in between hr 48 and 60 that's messing me up... We'll see what the meteogram says...

Yea but the 60 hour plot says it's 12 hour precip not 6 hr like the others so it should encompass everything. The jump northeast is the coastal taking over and maybe robbing some energy from us. Not sure the maps suck honestly. 

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It's tricky to predict snowfall totals for this one because there's so much uncertainty in ratios.  We often use Kuchera ratios as an estimate, and I belive these are based on the maximum column temperature.  Looking at some soundings and temp maps, it appears that in a lot of places (my backyard included) the surface will be the warmest layer during the heaviest snow.  I suspect snow depth maps are heavily dependent on the surface temp as well.  The problem is that surface temps are the most difficult temps to predict (the Superbowl ice storm comes to mind).  So there is a lot of uncertainty in the estimates of snow depth / liquid ratios due to uncertainty in surface temps.  The uncertainty becomes more important when temps are near melting, as relative ratios (and snow depths) become highly sensitive to temperatures. 

So I wouldn't be surprised to see some suprises on Saturday night / Sunday morning (good or bad) even if qpf predictions are accurate.

 

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Looks like a narrow stripe of the best rates, column temps and timing....what looked to be a far NW jackpot could end up being the hills of Howard up through N balt co.  If the nams are right...a very narrow stripe of asteroids that will look like mashed taters sunday morning will set up somewhere in the area.   

Maybe a case where Westminster records the same amount as Columbia but for dif reasons.  I'll be in WV up in the hills at a cabin with the better half...Looks like a 2-4/3-6 out there.  Will be the first snow while we are there since the Feb '15 arctic front.  Sat on the deck during the blitz and the snow filled our wine glasses faster than we could drink! 

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2 minutes ago, cae said:

Even though the RGEM got better, the RGEM ensemble cut back from 12z.  There are still some good hits in there, but also some nearly complete misses.

GevA4Dn.png

Yea... gefs increased the number of total whiffs also. The nams love this but there is still more spread then I want. I'll feel better if the euro has another qpf bomb solution. 

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2 hours ago, psuhoffman said:

Yea... gefs increased the number of total whiffs also. The nams love this but there is still more spread then I want. I'll feel better if the euro has another qpf bomb solution. 

Permission granted for you to feel better. Apparently the Euro delay plus Jebman's positive energy are paying off.....

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12 minutes ago, Ralph Wiggum said:

I posted over in Philly that the spread among guidance at this short of lead time is nothing short of silly quite honestly. Everything from complete misses (quite a few on the ens members) vs big ticket SECS/MECS (quite a few of those as well). Major bust potential on either side with this one.

March 25, 2013 redux? This one could be a lot of fun if it turns out to be a positive bust during nowcasting with LWX scrambling to increase WWA/WSWs mid-event.

What's the current tally right now: Euro/NAMs, maybe RGEM (end of range still going) v GFS/CMC/UKIE/ICON....ens spreads all over the map RGEM/EPS/GEFS? 

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10 minutes ago, Ralph Wiggum said:

I posted over in Philly that the spread among guidance at this short of lead time is nothing short of silly quite honestly. Everything from complete misses (quite a few on the ens members) vs big ticket SECS/MECS (quite a few of those as well). Major bust potential on either side with this one.

Just shows how marginal the setup is with temps. A degree here or there makes or breaks this. One positive is, though we are not dealing super cold air we are dealing with fresh cold. If this was stale and degrading I would probably be siding with the less snow out comes. But it's not, so I'm not.

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10 minutes ago, Ralph Wiggum said:

I posted over in Philly that the spread among guidance at this short of lead time is nothing short of silly quite honestly. Everything from complete misses (quite a few on the ens members) vs big ticket SECS/MECS (quite a few of those as well). Major bust potential on either side with this one.

I know the models have not been great this winter but it seems ever since the SSW began the atmosphere has really been in a state of flux and very volatile which I guess is to be expected. The one thing I like seeing is that the weather has become much more active with storm systems regardless if they are liquid or frozen and I think that will continue.

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We have see an improvement once again for the most part with the temps at all levels (700, 850, 925, surface). Below we have the 850's from the 12Z run for the beginning of the storm.

12Z54hr.gif.3b6f65a956e4c8d6a7f1ad83d3a2d696.gif

Now compare the temps from the overnight run. 

00Z48hr.gif.b6abf14d33e33dd8ef1820ed4c370cec.gif

 

Below are the temps for the second half of the storm from the 12Z run.

12Z60hr.gif.11361f07d316f9e6c2781b32a4ae8ccc.gif

Now compare the latest run. We see a significant shift southward of the zero line just north of DC through central MD. 

00Z54hr.gif.72e5375b60082412de16f3c8827aab65.gif

700's stay fine throughout with the zero line confined to the southern tip of MD running e/w. 925 is the one level that is the biggest question mark. Saw improvements to the the NE of our region and a degradation to the southwest. Zero line withdraws up to the PA/MD line for the second half of the storm. Temps though are only a degree or two above through central MD which can be manageable. Surface temps saw an improvement as well. Temps hover between -1 and +1 through central Md for the duration.

Really think this is going to come down to 3 things. How deep is the warming we are seeing at 925 mb and what kind of rates will we have to overcome that warmth by drawing cold air down. Dewpoints from the surface up through this warm layer will play a part as well. With the cold being essentially fresh we should see good dews leading into this.

 

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9 minutes ago, WxUSAF said:

When the euro’s been consistent for 6 or 8 runs in a row and the gfs is lurching around like a drunken sailor, it’s pretty easy to pick one.

Yeah, decided yesterday I was going to pull a DT and hug the Euro for all it's worth and go down with the ship if I have to. Hard to argue with that kind of consistency. Of course if the Euro fails we are going to get the typical 'GFS won this one' from some. And I will have to laugh because that will be nothing more then by virtue of on it's swings back and forth a run or two actually hit on the right solution.

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