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stormtracker

February 19-20th Threat - STORM MODE

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Just now, HighStakes said:

My best guess for us is 3-4. Then sleet for a couple hours. Then a pretty good glazing. Would not be surprised if we flip to sleet a little soon than expected as the warm nose tends to race north in these type of events. If it holds off for a bit due to better banding then we could do well. I dont think we get above freezing until very late tomorrow evening perhaps midnight. I think our max potential is 5-6 if we can snow a little past 18z with some decent banding. I'm going with the euro. It been rock solid so far. Hopefully it holds at 12z.

Agreed, though I think we could see 4-6" with an upside if more if the cold holds on and we get under a good band.

you, sparky, losetoa6 and PSU will do a touch better than me. I'm on the low end of the range compared to you guys. 

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1 minute ago, stormtracker said:

Heh, the RGEM is sick.  Just took a peek.  I wish this was a varsity level meso model.   Take a look at it if you haven't already if you're in the DC area.

That's what the HRRR was doing at 12z.  A beatdown just as we were in danger of flipping. 

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Just now, stormtracker said:

Heh, the RGEM is sick.  Just took a peek.  I wish this was a varsity level meso model.   Take a look at it if you haven't already if you're in the DC area.

RGEM/ICON/extended HRRrR isn’t the best team but at least we’re on the field playing? Just reinforces the idea that whoever ends up under that moisture plume will jackpot. Will be somewhere between EZF and Harrisburg PA.

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Just now, MN Transplant said:

That's what the HRRR was doing at 12z.  A beatdown just as we were in danger of flipping. 

Yeah, I read your post and looked and exactly as you said, right when the sleet line could see the whites of our eyes, the heavy precip pushed it back.  

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1 minute ago, stormtracker said:

Heh, the RGEM is sick.  Just took a peek.  I wish this was a varsity level meso model.   Take a look at it if you haven't already if you're in the DC area.

Wow.  0.4"+ by 15z for DC.  I wish it was a reliable model.  Hrdrps has a little better track record (I think)...will be interested to see if it holds from its previous runs.

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Just now, WxUSAF said:

RGEM/ICON/extended HRRrR isn’t the best team but at least we’re on the field playing? Just reinforces the idea that whoever ends up under that moisture plume will jackpot. Will be somewhere between EZF and Harrisburg PA.

I agree...it's going to come down to nowcasting during go time.  I seriously doubt the models reach some amazing consensus between now and then on where the jackpot will be.  

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1 minute ago, stormtracker said:

Yeah, I read your post and looked and exactly as you said, right when the sleet line could see the whites of our eyes, the heavy precip pushed it back.  

Looks like the HDRPS did yesterday with two distinct W-E max bands. 12z CMC kinda does that as well.

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Thought I'd share something in regards to surface temperatures for tomorrow evening which will be a wild card in the extension of frozen precip. Take a look at the GFS trends in surface winds and temperatures compared to the Nam 3km.

447874927_GFSTrend.gif.b0a7f4b75b1c2b38f8b0c6479149cc86.gif

 

1196840035_NAMNestTrend.gif.e1590c0bbf8bd0f8faccf0c46b4c88f6.gif

Notice how the winds on the GFS are breezy out of the south-southeast and the Nam 3km is light out of the east with a much more defined CAD wedge. This is the reason for the GFS trending to all rain sooner compared to the higher resolution guidance. The GFS weakens the surface inversion significantly and allows a deeper mixing of warmer air into the lower profile. 3km on the other hand holds on and the shallow depth of cold air allows for a prolonged period of ZR across a good chunk of the sub-forum (Mainly west of the fall line). Climo will undoubtedly have some impacts on how the event transpires, like always, so if you know how temps behave in WAA regimes like this, you can probably guess what's going to happen. The main question right now is the initial thump for snow and the timing of the strongest low to mid level frontogenesis and the placement of best banding to help alleviate the warmer air mixing into the profile. Best snow potential will run from 9z in Central VA to as late as 18z up in the northern part of the sub-forum. Added orographic enhancements will likely occur as well, so mini jacks will be possible, but we won't know where that will occur until game time. General climo favors Parrs Ridge, Catoctins, and areas along I-81 out to Western MD and high country for WV. Likely will make some adjustments to my first call from yesterday on storm totals based on latest guidance.  

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3 minutes ago, mappy said:

Agreed, though I think we could see 4-6" with an upside if more if the cold holds on and we get under a good band.

you, sparky, losetoa6 and PSU will do a touch better than me. I'm on the low end of the range compared to you guys. 

I went conservative because I'm worried about sleet. If we stay under good banding we can hold off the pingers. On the other hand I've seen DC switch to sleet and it races up here an hour later. Nonetheless it's a fun event to track and my bar is 4. 

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7 minutes ago, mappy said:

Agreed, though I think we could see 4-6" with an upside if more if the cold holds on and we get under a good band.

you, sparky, losetoa6 and PSU will do a touch better than me. I'm on the low end of the range compared to you guys. 

Not necessarily . That warm nose at 700mb trajectory is coming SW to ne . You might hold a touch longer ..maybe...lol . I'm thinking anywhere from 3-7"

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2 minutes ago, HighStakes said:

I went conservative because I'm worried about sleet. If we stay under good banding we can hold off the pingers. On the other hand I've seen DC switch to sleet and it races up here an hour later. Nonetheless it's a fun event to track and my bar is 4. 

Cheers to that, friend! 

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Just now, losetoa6 said:

Not necessarily . That warm nose at 700mb trajectory is coming SW to ne . You might hold a touch longer ..maybe...lol . I'm thinking anywhere from 3-7"

don't get my hopes up! i always flip before you guys do. 

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25 minutes ago, stormtracker said:

GFS is definitely the dreaded "step back"  probably a quick snow changing over by 18z whereas before it had a heavy thump/band.   

 

23 minutes ago, stormtracker said:

I dunno..it's vastly different from everything else with timing.  Not sure how to weight it at this point.

I don't think its as drastically different as it seems looking at DCA as a specific spot.  GFS lacks the resolution to nail exact placement of banding OR correctly factor in mixing and other dynamic influences of that banding....and it sucks with surface tamps from CAD.  So you can only get a general idea from it, details are useless.  It just misses DC by a few miles with two different bands...just south early and just northwest later and so that specific spot lost snow... plus it warmed SLIGHTLY which hurt a lot in a marginal setup.  NOT saying the GFS didn't degrade a little but if you step back and look at the temps and precip over the period it wasnt some huge shift just a couple very minor shifts that bumped DC in the wrong direction in what was a marginal setup to begin with wrt heavy snow totals.  

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28 minutes ago, mappy said:

So, the GFS seems better for places north and west. by 06z Thursday is 1.6 IMBY, previous GFS was 1.3. Flip looks about the same time IMBY (18z). 

It's really hard to use the GFS in these situations because its lack of resolution really forces you to assume a lot about the details.  But the GFS blasts our area with some heavy precip between 11am and 3pm.  At 18z the column is still cold enough for snow across northern MD...barely.  By 0z its toast.  But how long it can hold on with mixing of the warm layer with those heavy rates would determine our fate.  If we can hold on an extra hour or two during that band (not a crazy idea given the typical mixing and dynamic cooling in such bands) the GFS implies a really good thump up here.  

@HighStakes

It totally depends on the banding.  Think of the similar events to this...Feb 2007 (NOT the VD storm the second one), December 2013, Feb 2015 had some similarities too... the area's that get under the heavy bands will hold the column longer.  The VV's and heavy precip will help to mix out the mid level warm layer from WAA for a time.  If we get under that banding we will get thumped.  If we don't...the mid level warmth will race north and its congrats PA.  We know the drill.  I have no idea where that banding will set up.  No one does.  We can all make educated guesses.   But the idea of a duel max is gaining some traction imo today.  Even the guidance that hits our area pretty good "sees" the banding associated with the jet streak up over PA its just not killing the STJ WAA moisture plume into our area as much and is hitting that band up there less.  Figuring out those kind of details are above my pay grade though.  

15 minutes ago, WxUSAF said:

RGEM/ICON/extended HRRrR isn’t the best team but at least we’re on the field playing? Just reinforces the idea that whoever ends up under that moisture plume will jackpot. Will be somewhere between EZF and Harrisburg PA.

So my goalposts from 2 days ago are still in the same place LOL...

Notice even the guidance that thumps us still has some enhancement up in central PA associated with the jet streak?  Its just the NAM is going nuts with that and killing the WAA/STJ moisture feed south of it.  The other guidance has more of a duel max idea hinted at between those two areas.  That is a much better result for us.  

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2 minutes ago, Fozz said:

How good are the WRF models (ARW and NMM)?

The 0z runs all show a good hit for MD.

Maybe someone can correct if I’m wrong but I think they’re usually too amped and wet. 

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Maybe someone can correct if I’m wrong but I think they’re usually too amped and wet. 


ARW has a known wet bias and NMM actually can run dry. They are used in ensemble packages and are better utilized for convective purposes.


.
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34 minutes ago, psuhoffman said:

It's really hard to use the GFS in these situations because its lack of resolution really forces you to assume a lot about the details.  But the GFS blasts our area with some heavy precip between 11am and 3pm.  At 18z the column is still cold enough for snow across northern MD...barely.  By 0z its toast.  But how long it can hold on with mixing of the warm layer with those heavy rates would determine our fate.  If we can hold on an extra hour or two during that band (not a crazy idea given the typical mixing and dynamic cooling in such bands) the GFS implies a really good thump up here.  

 

          we CAN see the in-between hours for the GFS on the mag.ncep.noaa.gov site which has the full hourly output.    You'll see that the changeover is well before 00z, but as has been noted, the GFS is well-known for being way too fast in breaking down inversions and warming the low levels

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10 minutes ago, Fozz said:

How good are the WRF models (ARW and NMM)?

The 0z runs all show a good hit for MD.

 

4 minutes ago, MillvilleWx said:

 


ARW has a known wet bias and NMM actually can run dry. They are used in ensemble packages and are better utilized for convective purposes.


.

 

Guys, I’m sure it’s been discussed but I really like the HERF as a tool. Still needs some work, but I think it’s pretty good. 

https://www.spc.noaa.gov/exper/href/index.php?model=href&product=snowfall_024h_prob04&sector=conus&rd=20190219&rt=1200

1 minute ago, Snowchaser said:

Weather channel is bullish :snowing:

6D0ADDC8-44B9-4FD1-A892-2CBB4A7BD42D.jpeg

I toss anything TWC puts out with regard to wintry precipitation.

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10 minutes ago, yoda said:

12z HRDPS is crushing DC metro at 12z WED with 8mm/hr

4mm/hr would be a crushing. 8mm/hr would be epic 

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Just now, BaltimoreWxGuy said:

LWX updated their snow maps. Doesn’t look to be much of a change. If I get 5” I’ll be very happy 

They went from 4-6 to 6-8 in my area and moved the heavier snow north 

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