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February 7th Storm Threat Discussion/Obs


mappy
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Bit of a catch-22 going on with the 3km, and a few reasons to take issue with using it over the 12km right now. The 3km has a tendency to overdo convection in marginally unstable profiles like this, which in this case, is feeding into a latent heat bias and thus -- and likely an overamplification of the surface low. Latent heat release from convection and surface pressure falls *can* work in tandem, but there's reason for this forecaster to believe that it's overdone here -- mainly experience with the NEST in this environment.

The signal for some elevated upright instability being trained in is strong enough that it wouldn't surprise me to see some weak convection and a few strikes (particularly to the south), but probably not to the ridiculous degree we see here. One thing I *do* believe is that the warm nose will be tenacious in this kind of setup. P-type and rates will be very dependent on each other near the max accumulation line. You're gonna have to smell the mixing to get the most accumulation on this one. Also, weak instability combined with intense f-gen means intense bands, and subsequently a lot of subsidence around those bands. Some folks are going to get skunked and some will get jackpotted. Nature of the beast.

Basically, when there's this big of a difference between the 2 resolutions of the same NAM, take note. There's some important details that can be gleaned from it.

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26 minutes ago, SnowenOutThere said:

So a couple days ago I asked if we might have some thunder snow, most people said not really but with the stronger low and better forcing (from my mediocre knowledge) on the 3km Nam I was wondering if that has changed and we might get some thunder snow. 

I hope so!  The geese have been really obnoxious these few days. ;)

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23 minutes ago, mappy said:

Prince died too. In case you missed that news as well. 

Frick... At least warn us next time. Not everyone was sitting down.

Hopefully the rain-snow line isn’t that far north. It’s always a battle with that thing. If it could come south a little bit, we’d be good down here.

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8 minutes ago, losetoa6 said:

1983 ( different  overall setup ) but it had 2-5"/ hour rates with gravity waves and lots of thunder from Baltimore northeast . I'll take a mini version of that :weenie:

I was only 10 but I remember that day very vividly. That was the longest period of sustained S+ and S++ I ever seen. Basically it was 2 feet plus in 12 hours.  Let's settle for 12 inches in 6 hours and then on to next week.

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1 hour ago, csnavywx said:
Bit of a catch-22 going on with the 3km, and a few reasons to take issue with using it over the 12km right now. The 3km has a tendency to overdo convection in marginally unstable profiles like this, which in this case, is feeding into a latent heat bias and thus -- and likely an overamplification of the surface low. Latent heat release from convection and surface pressure falls *can* work in tandem, but there's reason for this forecaster to believe that it's overdone here -- mainly experience with the NEST in this environment.
The signal for some elevated upright instability being trained in is strong enough that it wouldn't surprise me to see some weak convection and a few strikes (particularly to the south), but probably not to the ridiculous degree we see here. One thing I *do* believe is that the warm nose will be tenacious in this kind of setup. P-type and rates will be very dependent on each other near the max accumulation line. You're gonna have to smell the mixing to get the most accumulation on this one. Also, weak instability combined with intense f-gen means intense bands, and subsequently a lot of subsidence around those bands. Some folks are going to get skunked and some will get jackpotted. Nature of the beast.
Basically, when there's this big of a difference between the 2 resolutions of the same NAM, take note. There's some important details that can be gleaned from it.


Awesome post man. Agreed. I always use caution with a CAM dominant model during synoptic due to those issues you described above. I mentioned earlier that the uniformity we see from globals and even the 12km Parent are likely not going to occur with a setup like this where intense frontogenic forcing at 7H and 85H will be the drivers of banding potential and who gets maxed. I was thinking Easton area over to Kent Island up to CAPE and south of frd might be the jack, and still could, but the I-95 and NW crew up near the line could see the most of the frontogen placement and strength depicted materializes because they will also have the orographic factor to increase the local lift within the lowest confines of the boundary layer.

I just got the vaccine, so I’m sitting in a parking lot to make sure I don’t have a reaction or something. Them I’m gonna go home and look more at soundings. Hopefully you guys can get whacked with this one


.

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NAM MRB:

210207/0800Z  38  13003KT  32.1F  SNOW    9:1| 0.2|| 0.00|| 0.00|| 0.021    9:1|  0.2|| 0.00|| 0.00|| 0.02  100|  0|  0
210207/0900Z  39  12003KT  32.3F  SNOW   16:1| 1.1|| 0.00|| 0.00|| 0.072   14:1|  1.3|| 0.00|| 0.00|| 0.09  100|  0|  0
210207/1000Z  40  VRB02KT  32.3F  SNOW   15:1| 1.6|| 0.00|| 0.00|| 0.107   15:1|  3.0|| 0.00|| 0.00|| 0.20  100|  0|  0
210207/1100Z  41  05006KT  32.1F  SNOW   12:1| 0.7|| 0.00|| 0.00|| 0.058   14:1|  3.7|| 0.00|| 0.00|| 0.26  100|  0|  0
210207/1200Z  42  05004KT  32.1F  SNOW   20:1| 1.9|| 0.00|| 0.00|| 0.097   16:1|  5.6|| 0.00|| 0.00|| 0.35  100|  0|  0
----------------------------------------------+----++-----+-------------++--------------++-------------++-----------+---+---
210207/1300Z  43  01003KT  32.3F  SNOW   20:1| 3.9|| 0.00|| 0.00|| 0.200   17:1|  9.5|| 0.00|| 0.00|| 0.55  100|  0|  0
210207/1400Z  44  01004KT  32.4F  SNOW    9:1| 0.8|| 0.00|| 0.00|| 0.091   16:1| 10.4|| 0.00|| 0.00|| 0.65   90|  0| 10

:weenie::weenie::weenie:

Yes. That is 4 inches in one hour. 

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1 hour ago, osfan24 said:

Some places going to make a run at a foot, even maybe slightly more, if those snowfall rates are accurate and you end up being the lucky one that sees that ridiculous high rates for a few hours.

I like the mid Fairfax Co bullseye right over my house, but from what I’ve been reading here, we shouldn’t get those numbers based on the warmth on Saturday.  I would love to get close to a foot. 

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7 minutes ago, MD Snow said:

FWIW ICON has ticked the rain/snow line further west each of its last 4 runs. That run was mostly rain for many areas on the eastern shore. One more tick and we're talking mixing into the I95 corridor. 

You're gonna have the weenie police all over you for that post.

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10 minutes ago, MD Snow said:

FWIW ICON has ticked the rain/snow line further west each of its last 4 runs. That run was mostly rain for many areas on the eastern shore. One more tick and we're talking mixing into the I95 corridor. 

The council already banished one person from the realm. Don't make me re-convene the council. 

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6 minutes ago, MDRandy said:

You're gonna have the weenie police all over you for that post.

 

4 minutes ago, MD Snow said:

Know your climo. I live east of 95. Every once in a while we score but unfortunetely, I've seen this one play out time and time again....

:lol:

I guess I need a weenie badge?  But, come on, it's the icon.  I am not a model-basher but it's almost like we have too much information to pore over, and a lot of it isn't that reliable.

Maybe it ends up north of us, but I don't think it'll be because the icon is on to something. 

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