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mappy

February 7th Storm Threat Discussion/Obs

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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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4 minutes ago, MDRandy said:

Do you think there will be enough blocking to prevent further NW trends? Just curious. 

I don't know but I wouldn't get too concerned over a nam run.  The euro looks good and the gfs has been fairly steady so I am not concerned.

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7 minutes ago, DDweatherman said:

RGEM decides on a nice SE run after coming nicely in line at 12z and the CMC smacked us. Typical. Not a lot of consistency this week from it. 

But this a bit reassuring at least in that there is no across the board NW shift. 

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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, IUsedToHateCold said:

I'd like my first 6" storm of the season. In fact, I'd like at least 6" total, given that I'm at 5.5". Let's woo away any more NW jogs in this thing and keep it where its at. Those people up in PA have already had enough snow already. :D

I hope you get it!

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Icon looks iconic. 

Storm seems to last a few hours longer too. Earlier it was jetting out by noon. Now seems to linger into the afternoon hours. 

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8 minutes ago, EastCoast NPZ said:

I hope you get it!

Thanks! Honestly I'd take 2-4 out of this with no mix. Snowpack melted off today and I got just a few sad mounds of snow left. Looking forward to it being white again. Icon looks amazing and the NAM has been outperforming, so I have high hopes. 

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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:

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17 minutes ago, Eskimo Joe said:

Gonna hug the 18z NAM, Euro, and ICON. All solid hits, even better considering we all thought this was dead at HR90.

Indeed...been awhile since we've trended back INTO a threat at short range, lol

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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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CWP just called for 2-4” with very low confidence. They seem worried about p-type issues which I think is sound given climo. 

My first call is 3-6 for my little neck of the woods in NW DC. 

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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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2 minutes ago, HighStakes said:

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.

I remember too  in northeast Bmore...parachutes for hours . 

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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. 

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1 minute ago, North Balti Zen said:

Capital Weather PoPo?

CWG is the worst.  A true no guts no glory forecast everytime.

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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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8 minutes ago, DCAlexandria said:

CWG is the worst.  A true no guts no glory forecast everytime.

Science and weather especially are full of uncertainty. They just express it better than most. I'll take their range forecasts over "Joe From Channel 5 here calling for  6 inches of snow" 

But I know you know that. 

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2 minutes ago, MDRandy said:

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

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....

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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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