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Revenge of the Weekend Warrior Storm: 2/15-2/16


PhineasC

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Let's not derail too much. It's a perception issue. If I was a met and I read these threads I would think they were too optimistic but there are distinct diffs between hobbyists and mets. Mets are more serious and scientific and weenies are more like fans rooting their favorite team. Fans root until any chance at winning is over. Winning this one is an inch or 2. Game is not over.

12z is gonna smoke us anyway

Not 0z?

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I think we can all agree Weatherguy701 needs to be booted out of the forum (again).

 

 

You are the most predictable poster in forum history. Never, ever broke character in nearly a decade.

Can always trust Phineas for valuable input to the discussion

 

To me, this one still has the C-2" look. Probably C-1" really.

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Can always trust Phineas for valuable input to the discussion

 

To me, this one still has the C-2" look. Probably C-1" really.

The temp profile is still better than yesterday so it may turn out better than we think....I had a car topper so a solid inch would be exciting for me...sad but true

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From where I sit, based on the models, overall pattern, trends, etc., I am looking at 2-4 inches DC area wide in two waves:

 

First wave = 1+ inch Friday night into Saturday morning

Second wave = 1-3 inches Saturday afternoon into Sunday morning

 

This 2nd wave is the much hyped coastal low from earlier in the week that I said would reappear on the models as we got closer. Both the 18z NAM and GFS have brought this closer and closer over the last 12-18 hours.

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SREF plumes are out.  Mean DCA snowfall for:

 

NMM members: 2.5"

NMB members: 0.6"

ARW members:  15.5", including two 30"+ storms

I was going to post if anyone has looked at the individual SREF plumes.  my goodness. those ARW members bomb a storm right off HAT/ORF and aren't quick to move it out.

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Friends, please enjoy your inch and hope for more. HPC snow probabilities are usually quite accurate.

 

prb_24hsnow_ge01_2013021500f048_sm.gif

 

 

Guys, check the description on those products:

 

http://www.hpc.ncep.noaa.gov/pwpf/about_pwpf_products.shtml

 

They aren't the final probabilities; they are a 28 member "auto ensemble" that includes all 21 sref members, 7 of the latest operational runs (in this case the ECMWF is the prior run), along with the HPC WWD's deterministic snowfall forecast that is sent internally to the WFOs for guidance. The reason why HPC doesn't go public with their deterministic snow/ice accum graphics is because the WFOs (and thus NDFD) have final say on accums and we don't want to add confusion or conflict within NWS products. So, the WFOs (and RFCs) can see that deterministic output from HPC via an internal webpage, usually by 0630 and 1830Z so they can have enough time to use those grids as guidance if they choose to.

The deterministic accumulations (which is prism or elevation adjusted) serve as a baseline guidance for the field offices, while also serving as a member along with the 28 member autoensemble probabilistic forecast. Ah, but it is an important lone member in that it serves as the "mode" for those probabilistic calculations that you see linked from the HPC website. The forecaster-adjusted "final" probabilities are manually edited for the 4, 8, 12 inch 10, 40, 70 percent probabilities. They come out between 8-9 and 20-21Z.

 

One other thing about those autoensemble probabilities: 21 of 28 members are the SREF components, i.e. 7 WRF members, 7 NMM members, and 7 NMMB members.  In other words: very SREF heavy.  So, if the SREF is out to lunch...guess what...so will the autoensemble.  These adjustments should show up in the HPC final 4/8/12" probabilities, though we don't edit the 1, 2, or 6" inch probs.

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The key to look for on 0Z runs is the mean trof axis staying parallel to Lake Michigan as much as possible and that will allow the vort diving into the plains to cut under it and ride close to the coast vs pushing OTS.  We usually don't do well in these thread the needle events, however.

 

This is a SNE event for sure... can you imagine waking up there tomorrow morning and "Surprise!" 

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Guys, check the description on those products:

http://www.hpc.ncep.noaa.gov/pwpf/about_pwpf_products.shtml

They aren't the final probabilities; they are a 28 member "auto ensemble" that includes all 21 sref members, 7 of the latest operational runs (in this case the ECMWF is the prior run), along with the HPC WWD's deterministic snowfall forecast that is sent internally to the WFOs for guidance. The reason why HPC doesn't go public with their deterministic snow/ice accum graphics is because the WFOs (and thus NDFD) have final say on accums and we don't want to add confusion or conflict within NWS products. So, the WFOs (and RFCs) can see that deterministic output from HPC via an internal webpage, usually by 0630 and 1830Z so they can have enough time to use those grids as guidance if they choose to.

The deterministic accumulations (which is prism or elevation adjusted) serve as a baseline guidance for the field offices, while also serving as a member along with the 28 member autoensemble probabilistic forecast. Ah, but it is an important lone member in that it serves as the "mode" for those probabilistic calculations that you see linked from the HPC website. The forecaster-adjusted "final" probabilities are manually edited for the 4, 8, 12 inch 10, 40, 70 percent probabilities. They come out between 8-9 and 20-21Z.

One other thing about those autoensemble probabilities: 21 of 28 members are the SREF components, i.e. 7 WRF members, 7 NMM members, and 7 NMMB members. In other words: very SREF heavy. So, if the SREF is out to lunch...guess what...so will the autoensemble. These adjustments should show up in the HPC final 4/8/12" probabilities, though we don't edit the 1, 2, or 6" inch probs.

Unfortunately, you could post this over and over and folks still wouldn't get the message. Oh, wait...

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