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February 7th Storm Threat Discussion/Obs

mappy

By mappy,
in Mid Atlantic

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MillvilleWx
MillvilleWx

Well well well, looks like we have ourselves a nice little event on the horizon. As we've seen the model corrections back to the NW have been due to backing from the extreme cold scenarios that place

Scarlet Pimpernel
Scarlet Pimpernel

For those who don't remember the Feb. 25, 2007 event I mentioned earlier, here's a photo I took (from the Capitol Hill northeast neighborhood, where I was living at the time):

MillvilleWx
MillvilleWx

Hey guys. First call map. I'll have a Disco later today with a Final Call tonight

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frd

frd

Posted
Posted
1 minute ago, CAPE said:

That one over here to my SE is a monster. Being adjacent to something like that would be frustrating as hell lol.

Subsidence  :P    Cool to look at,  but almost impossible to forecast.

Its doing a good job, but lets hope we both get under banding.

Meanwhile, I am still trying to figure out the 360 hour Euro snowfall mean.  Deciding whether to stock pile food stores. 

 

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MillvilleWx

MillvilleWx

Posted
Posted

There's a tool we can use at work that is experimental that incorporates the National Blend of Models and the Bias Corrected GFS to review multiple facets of data, including QPF, snow totals, snow QPF, ratios, etc. I can't show this because it's gov't use only and I'm not sure if they want it disseminated to the public. 

However, I will share what I'm seeing in terms of NBM QPF and snow ratios. As of the latest run this morning, the average snow ratios follow a traditional climo with perhaps a slight tick down than usual due to expected lower boundary layer warmth that will be present prior to storm arrival. 7-8:1 is the average I'm seeing on blended guidance for areas along Rt 50 up to central DE and @CAPE area. DC is a 7-8:1 in the metro proper, but you can see the improvement at times on the hourly time step when banding moves overhead with a 9-10:1 more common during those time frames. 9-10:1 is common for between Rt 50 and I-70 with 10-11:1 for areas out west of US15 and north of I-70. 12-14:1 is common out in the Mtns of the Alleghany front in WV into Western MD. QPF is pretty solid for a blend with 0.50" contour running through FDK with a direct SW to NE placement down the Blue Ridge into SoPa. 0.70" runs I-95, and 0.8+" is located on the eastern shore of MD into DE. 

Remember. this is a blend so there is a smoothed mean in the process, so banding potential will place lower/higher amounts in-between those contours outlined, but this is a general spread. Some of the QPF will be wasted to liquid in MOST spots, but I'm noticing areas north of I-70 and out west along the I-81 corridor will likely start as snow. I'll try to have an update later this afternoon, but I have the grids today, so I'll be busy later when I have to do the forecast. 

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baltosquid

baltosquid

Posted
Posted

So this is late, but seeing as the 12z should start rolling in soon, here's the 00z href snowfall mean and max to compare. I only link the max to demonstrate the dueling ideas of where the heaviest snow falls; do not think you're going to get those totals. You've got one camp rushing through Eastern Shore/DE and another going right along I-95. It'll be interesting to see how that pair of strips evolves in the 12z run. I'm also not sure what ratio this uses, but probably just 10:1, so adjust down mentally as needed.55304666_snowfall_024h_mean_ma.f04800(2).thumb.png.aa4209eb3d0708620ba728ea2e69e50f.png2045750805_snowfall_024h_max_ma.f04800(1).thumb.png.2ee2b7edb52ec0355a6e6ee06eb0e07c.png

 

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frd

frd

Posted
Posted
3 minutes ago, MillvilleWx said:

There's a tool we can use at work that is experimental that incorporates the National Blend of Models and the Bias Corrected GFS to review multiple facets of data, including QPF, snow totals, snow QPF, ratios, etc. I can't show this because it's gov't use only and I'm not sure if they want it disseminated to the public. 

Is this a new tool ?  

I recently saw it posted for the first time under the NBM reference.

Thanks for the breakdown.  

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blueberryfaygo

blueberryfaygo

Posted
Posted
3 minutes ago, MillvilleWx said:

There's a tool we can use at work that is experimental that incorporates the National Blend of Models and the Bias Corrected GFS to review multiple facets of data, including QPF, snow totals, snow QPF, ratios, etc. I can't show this because it's gov't use only and I'm not sure if they want it disseminated to the public. 

However, I will share what I'm seeing in terms of NBM QPF and snow ratios. As of the latest run this morning, the average snow ratios follow a traditional climo with perhaps a slight tick down than usual due to expected lower boundary layer warmth that will be present prior to storm arrival. 7-8:1 is the average I'm seeing on blended guidance for areas along Rt 50 up to central DE and @CAPE area. DC is a 7-8:1 in the metro proper, but you can see the improvement at times on the hourly time step when banding moves overhead with a 9-10:1 more common during those time frames. 9-10:1 is common for between Rt 50 and I-70 with 10-11:1 for areas out west of US15 and north of I-70. 12-14:1 is common out in the Mtns of the Alleghany front in WV into Western MD. QPF is pretty solid for a blend with 0.50" contour running through FDK with a direct SW to NE placement down the Blue Ridge into SoPa. 0.70" runs I-95, and 0.8+" is located on the eastern shore of MD into DE. 

Remember. this is a blend so there is a smoothed mean in the process, so banding potential will place lower/higher amounts in-between those contours outlined, but this is a general spread. Some of the QPF will be wasted to liquid in MOST spots, but I'm noticing areas north of I-70 and out west along the I-81 corridor will likely start as snow. I'll try to have an update later this afternoon, but I have the grids today, so I'll be busy later when I have to do the forecast. 

Thanks!  Yeah if its not classified, PHI or covered by HIPPA than yeah it can be disseminated to the public.. but thanks for the break down.. very helpful!

 

1 minute ago, frd said:

Is this a new tool ?  

I recently saw it posted for the first time under the NBM reference.

Thanks for the breakdown.  

 

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MillvilleWx

MillvilleWx

Posted
Posted
3 minutes ago, frd said:

Is this a new tool ?  

I recently saw it posted for the first time under the NBM reference.

Thanks for the breakdown.  

It's fairly new. There's a few kinks to it however, one is the speed at which it updates while in use, but the GIS systems and overall physical appearance of data is pretty amazing. 

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CAPE

CAPE

Posted
Posted
Just now, Baltimorewx said:

NAMs are okay but not their monster runs of yesterday. We’ll see how the other 12zs come in today. Thinking this is a borderline advisory/warning event. Right on the fence I think between both. 

I am sticking with my thoughts from yesterday morning. 2-4. Get under a nice band and may see 6. Low ratios outside of elevated areas are going to be an issue.

Further NW will end up with the same or maybe more snow than places further SE due to better ratios, even with somewhat less qpf.

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Baltimorewx

Baltimorewx

Posted
Posted
3 minutes ago, CAPE said:

I am sticking with my thoughts from yesterday morning. 2-4. Get under a nice band and may see 6. Low ratios outside of elevated areas are going to be an issue.

Further NW will end up with the same or maybe more snow than places further SE due to better ratios, even with somewhat less qpf.

I agree with that. I think the over 6” calls by some are a bit aggressive with the marginal temps. We really need the rates and while maybe not a huge trend, the overall trend the last 12 hours has been to lower QPF a little bit 

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CAPE

CAPE

Posted
Posted
5 minutes ago, Baltimorewx said:

I agree with that. I think the over 6” calls by some are a bit aggressive with the marginal temps. We really need the rates and while maybe not a huge trend, the overall trend the last 12 hours has been to lower QPF a little bit 

We are in the range of the CAMs now, and there will be fgen banding so its time to focus on resolving that. This is probably not going to be a nice uniform distribution of snowfall across the region, because places that aren't getting heavy snow will struggle to accumulate efficiently.

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Baltimorewx

Baltimorewx

Posted
Posted
8 minutes ago, CAPE said:

We are in the range of the CAMs now, and there will be fgen banding so its time to focus on resolving that. This is probably not going to be a nice uniform distribution of snowfall across the region, because places that aren't getting heavy snow will struggle to accumulate efficiently.

Yeah true. I’m just overall noticing the lowering of QPF a bit. And we better hope the GFS is wrong lol

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Baltimorewx

Baltimorewx

Posted
Posted
2 minutes ago, leesburg 04 said:

Curious how did you do with the last event?

Sunday wasn’t too bad. Got 4” but only had decent rates for 90 mins or so. Otherwise it was mainly pixie dust. I only added a dusting Monday and Tuesday though. I got more rain Monday morning than any snow Monday and Tuesday. So overall, it was kind of a fail in my book. I like the potential of this one being thumpy but we need the rates with the borderline temps 

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