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February 7th Storm Threat Discussion/Obs


mappy
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I wouldn't take the precip maps (QPF) to verbatim because there will be some pretty good bands and pockets of where others will see a lot more precip and others will suffer. Nature of the beast in the meso sense. Still a good moisture advection signal, but the uniformity of 1+" QPF is very unlikely in this setup. 0.6-0.8 uniformity back to perhaps US15 is possible with 1+" jacks in between a certainty with whoever can get sustained banding. Also, take into consideration some orographic enhancement over Parrs Ridge and the Blue Ridge out west. Should be some decent snow totals out of this. 3-6" with local to 10" is still my call for the area I just outlined. If NAM amplification is to be taken verbatim, might have to push my heaviest westward extent to I-81. Jury still out, but some snow will fall back that way, imo no matter what. 

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26 minutes ago, WxUSAF said:

This is definitely true. Look at temps, snow growth, etc. 

But despite all our talk, we rarely get snow ratios outside a 8-12:1 range. With the look of the soundings we’ve seen on the NAM and even GFS, I don’t see this storm being different. So unless a storm probably has substantial sleet (not the case Sunday) then the 10:1 snow maps are probably decent. 

If surface temperatures were a couple degrees below freezing, I would feel more confident that ratios would be > 10:1. But while the antecedent air mass is fairly cold, there isn't a much of a surface high or mid-level confluence to our northeast promoting a low-level flow of cold air. Surface melting during the precipitation will definitely reduce ratios.

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Just now, MillvilleWx said:

Man, you might need a cigarette if that verified. It's going to be a gorgeous morning down that way on Sunday. I've been honking the mid-level fronto for a few days. It's been hefty on guidance. 

I agree. Very dynamic system with an intense band showing along the periphery of this system on other guidance as well. Where does it set up? Dunno yet, but someone will hit the lotto.

 I didn't post the two frames before these, but it pivots over the 81 corridor down here for several hours. :pepsi:

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18 minutes ago, adelphi_sky said:

On Channel 5 News this morning they were saying 1 - 2 inches with a mix ending as rain this Sunday. I'm confused. They didn't even indicate that totals could be higher. 

Because there is still a question of how Far East the storm forms etc. models keep trending better though

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5 minutes ago, IronTy said:

I was watching WJLA 7 during my workout this morning and the weather lady said there was no chance for significant snow and don't even expect any to accumulate on surfaces other than grass.  :thumbsdown:

If this storm does give an area wide 6-10 inches of snow like the NAM model overnight the news will be in some deep mistrust because it is a day before the event and they were forecasting nothing. Would be a little funny seeing everyone wake up on Sunday with heavy snow falling and 5 inches on the ground thinking they were getting nothing.

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1 hour ago, MillvilleWx said:

I'm thinking 8-10:1 given the mid-level frontogen involved with the wave. The s/w is still fairly prolific on guidance right now and there's going to be significant large scale ascent from the 25H jet amplifying to the north. I think one of the things the globals are not going to pick up on is that meso banding is all but a given with the current 7H progs. The 7H fronto AND 85H fronto will actually work in your favor, so you'll have deeper boundary layer lift compared to areas north and west. They have the mid-level fronto, but eastern shore will likely cash on both, which is why I like your spot, Easton, Kent Island, down to Cambridge as the local jack with central DE as another good spot pending the northern latitude push of the surface low along the coast. I'm rooting for you!

 

48 minutes ago, high risk said:

       I have been one of the loudest proponents for looking at the snow depth maps, but that is because most events have a big area of sleet or mixed precip, and the 10:1 maps are horribly inflated since sleet gets tallied with snow into the snow water equivalent.     This is a setup in which I would NOT advocate the snow maps for 2 reasons     1)   this is mostly a rain or snow event with probably only a small band of sleet somewhere to our south, so 10:1 (maybe mentally lower it by 10-15% or so) map should be ok     2)  snow depth maps are underdone in events with marginal temperatures and with warm temperatures the day before which warm the top soil layer.    The land-surface model sees 33 degrees and warm soil and says "well, this is going to struggle to accumulate", not accounting for the fact that big rates can overcome those negatives.

Do either of you know whether the Kucera ratio is applied at the NCEP level or if it is something that is derived by each of the individual map providers?  I know that College of Dupage has added a map of the Kucera ratio.  For this storm, it is ~7:1.

1012390742_Screenshot2021-02-05100713.thumb.jpg.bbb63b5c9d1fc0f823d5281838328b13.jpg

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