March 2-3 Disco, Part III

[CAPE]

Looking at the latest RAP the best VVs @ 700 mb sets up in VA, through DC over to SNJ, then progresses SE from there.Thats where the heaviest snowfall rates should be focused, and generally agrees with the other guidance.

[WeSuck]

Try to tackle him and make sure to wear your cup. I really expect to see you and Randy on You Tube tomorrow.

This post just made me bust out laughing. Priceless. Sorry for ot but worth it

[ers-wxman1]

The models are pumping out snowfall accumulations. One concern I have that has not been discussed much anywhere else on the net is the type of snow that could fall. Because this is more of a banding and convective structure are we fully getting the lift within the dendritic snow growth zone to enable efficient accumulations on the ground. It could very well fall in snow pellets or without presence of larger dendrites. Yes it's gonna be cold but models do not tell us the type of snow that falls.

[Deck Pic]

I'm prob weenieing out but I can't stop thinking about how heavy the rates can be with this for a couple hours. Very dynamic system with all kinds of convective stuff feeding into it. HRRR really likes 2-3" OTG by 7am. I could see some of us get 2"+/hr rates for a couple hours. Prob sometime between 6am-10am. 

 

yup

[RIC_WX]

LoCo schools get the call from Wayde.

[dailylurker]

I'm feeling about 10x more optimistic than earlier.  I like radar and the HRRRRRRRRRRR.    Temps are crashing a bit earlier, but unlike Mtich, I welcome it.

You and me both. Seems a lot of others also. Mike Misco seems to be liking DC, PG and AA county for a jackpot (ish) zone, due to radar trends. Foot likes DC also for a jackpot zone. My weenie eye likes the trend on radar also.

[WxUSAF]

So here's a question for the mets and BUFKIT junkies.  With colder, drier air working in, is it possible this prevents the good dendrites from forming and instead we see snow grains or pellets that really do not accumulate?  Not trying to incite rage, just a inquiry.

 

 

The models are pumping out snowfall accumulations. One concern I have that has not been discussed much anywhere else on the net is the type of snow that could fall. Because this is more of a banding and convective structure are we fully getting the lift within the dendritic snow growth zone to enable efficient accumulations on the ground. It could very well fall in snow pellets or without presence of larger dendrites. Yes it's gonna be cold but models do not tell us the type of snow that falls.

I haven't looked at BUFKIT, but the column is saturated up to at least 500mb (and close to saturated almost all the way to the tropopause) on the forecast soundings, so I don't think dry air is too much of a problem.  Given the big honkin inversion in the lowest 250mb because of the arctic air, temps might be a bit warm in the snow growth zone for ideal dendrites overnight tonight, but I think it will be good by later in the morning.  And as ers-wxman said, with the banding structure we're likely to see, that should produce good dendrites. 

[CAPE]

You and me both. Seems a lot of others also. Mike Misco seems to be liking DC, PG and AA county for a jackpot (ish) zone, due to radar trends. Foot likes DC also for a jackpot zone. My weenie eye likes the trend on radar also.

Dont focus so much on radar, model sim radar or precip plots. If you want to get an indication of where the heavy snow and possible thunder might occur, look at the vertical velocities, esp at 700 mb. 23z RAP and 22z HRRR both have some impressive VVs in N VA over to DC and points south and east.

[ravensrule]

Hurricane Schwartz from Philly with a good map:

 

 

[dailylurker]

Dont focus so much on radar, model sim radar or precip plots. If you want to get an indication of where the heavy snow and possible thunder might occur, look at the vertical velocities, esp at 700 mb. 23z RAP and 22z HRRR both have some impressive VVs in N VA over to DC and points south and east,

Gotcha. Thanks bud.

[Eskimo Joe]

I haven't looked at BUFKIT, but the column is saturated up to at least 500mb (and close to saturated almost all the way to the tropopause) on the forecast soundings, so I don't think dry air is too much of a problem.  Given the big honkin inversion in the lowest 250mb because of the arctic air, temps might be a bit warm in the snow growth zone for ideal dendrites overnight tonight, but I think it will be good by later in the morning.  And as ers-wxman said, with the banding structure we're likely to see, that should produce good dendrites. 

Hey thanks man, I'm in Gaithersburg in our county's OPS center and a few of the snow nuts were wondering about that.

[mitchnick]

Mark's final call:

 

http://madusweather.com/2014/03/winter-storm-threat-mar-2-3-final-call/

1st time since he posted here I'm in his top category      lol

[chris87]

Dont focus so much on radar, model sim radar or precip plots. If you want to get an indication of where the heavy snow and possible thunder might occur, look at the vertical velocities, esp at 700 mb. 23z RAP and 22z HRRR both have some impressive VVs in N VA over to DC and points south and east,

 

you do understand that these are basically just three parameters that give you the same information -- upward motion (vertical velocities) produces precipitation in the model and the simulated radar is just trying to back out precipitation from the microphysics in the model -- one of those isn't going to give you anymore more information than the other.

[ravensrule]

1st time since he posted here I'm in his top category      lol

He likes you more now that he does not have to deal with you .

[Random Chaos]

Here's HRRR's take on thundersnow, at about 10 am tomorrow:

http://rapidrefresh.noaa.gov/HRRR/displayMapLocalDiskDateDomainZip.cgi?keys=hrrr_jet:&runtime=2014030222&plot_type=ltg3_t3sfc&fcst=15&time_inc=60&num_times=16&model=hrrr&ptitle=HRRR%20Model%20Fields%20-%20Experimental&maxFcstLen=15&fcstStrLen=-1&domain=t3&adtfn=1

[ers-wxman1]

Thanks WxUSAF

[CAPE]

you do understand that these are basically just three parameters that give you the same information -- upward motion (vertical velocities) produces precipitation in the model and the simulated radar is just trying to back out precipitation from the microphysics in the model -- one of those isn't going to give you anymore more information than the other.

Yup, but some tend to look at modeled total precip, and actual upstream radar. Seen plenty of times where total accum precip on a model is misleading. Sometimes there are dry punches of air. I prefer to look at the 700 RH and VVs.

[nj2va]

Here's HRRR's take on thundersnow, at about 10 am tomorrow:

http://rapidrefresh.noaa.gov/HRRR/displayMapLocalDiskDateDomainZip.cgi?keys=hrrr_jet:&runtime=2014030222&plot_type=ltg3_t3sfc&fcst=15&time_inc=60&num_times=16&model=hrrr&ptitle=HRRR%20Model%20Fields%20-%20Experimental&maxFcstLen=15&fcstStrLen=-1&domain=t3&adtfn=1

 

Interesting, I've never seen that product.  So basically its saying the whole sub forum has a chance at thundersnow?

[ravensrule]

The 23Z Rap is sweet for DC. 8" on the ground by 12 noon tomorrow.

[Bob Chill]

The 23Z Rap is sweet for DC. 8" on the ground by 12 noon tomorrow.

HRRR supports it. 4" by 9am and dumping.

[chris87]

Yup, but some tend to look at modeled total precip, and actual upstream radar. Seen plenty of times where total accum precip on a model is misleading. Sometimes there are dry punches of air. I prefer to look at the 700 RH and VVs.

 

i think you're missing the point and that's fine -- modeled precip and the vertical motion field are directly related -- you don't have one without the other -- not trying to be smug but your interpretation of the modeled uvv/rh fields aren't going to be better than the microphysics parameterization in the model -- you haven't found a "silver bullet", you're just interpreting the model incorrectly. 

[snowfan]

The 23Z Rap is sweet for DC. 8" on the ground by 12 noon tomorrow.

looks to be closer to 6 on wxbell.

[mdhokie]

The 23Z Rap is sweet for DC. 8" on the ground by 12 noon tomorrow.

 

Where do you get the latest run? The noaa site doesnt have any of the 23z gfx up yet. 

[ravensrule]

looks to be closer to 6 on wxbell.

Meh this looks like 8" but who the hell knows:

 

[ravensrule]

Where do you get the latest run? The noaa site doesnt have any of the 23z gfx up yet. 

instantweathermaps has it.

[mitchnick]

Meh this looks like 8" but who the hell knows:

 

and that says it's using 1:10 ratios

[ravensrule]

and that says it's using 1:10 ratios

I hope not 1:10   , but that is why i was saying sweet 8" without any ratios built in .

[CAPE]

i think you're missing the point and that's fine -- modeled precip and the vertical motion field are directly related -- you don't have one without the other -- not trying to be smug but your interpretation of the modeled uvv/rh fields aren't going to be better than the microphysics parameterization in the model -- you haven't found a "silver bullet", you're just interpreting the model incorrectly. 

Dude I get what you are saying. But explain then how you can look at modeled precip, and have it look the same for area A and area B, but in area A there ends up being heavier snow, which aligned with the modeled VVs that were stronger in area A. There must be some flaw or maybe a resolution issue, but I have seen this plenty of times. It does not always align.

 

Part of my point in the op was how to get an idea of where thunder might occur. Not sure how you would get an indication of that by looking at modeled qpf or sim radar.

[psuhoffman]

You all rail on NWS and local network mets down there a lot but let me assure you it is not just a localized phenomenon.  Up here it has been obvious to me that I am a good 20 miles north of where any accumulating snow will fall for at least 24 hours now, and yet NWS still has an advisory for 2-4 that they only just now lowered from 4-6, and local networks keep putting out maps that have my area in 2-4 or even 3-6".  I don't even know what they are looking at, my county is north of the sharp cutoff on all the models.  Sometimes I get the feeling because its an unpopulated area they don't even bother to put any effort into this area.  There have been times this winter where NWS still had an advisory up even after the storm had passed and nothing had fallen, and the one decent snowfall I did get they never placed even an advisory out even when I already had 6" on the ground.  Never seen anything like it honestly the forecasting in this area is just awful. 

[yoda]

FWIW, 21z SREFs has 0c 850 line moving though DCA at 1am... 2mT 0c line is already through and down by EZF

DCA is in upper teens by 12z (7am)