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February 25th-26th Plains Blizzard


andyhb

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Now that the NAM is off the crazy train, there's definitely a consensus track for the H5 low center along or just N of the Red. I'd say all available guidance now (18z American/12z foreign) is within a 50-75 mi. window, at least during the period in which much of W/C OK is affected. For C OK (not necessarily farther E into MO/AR), this track is reminiscent of both the 2009 storm I mentioned and also 29-30 Nov 2006.

 

Based on pattern recognition and climatology, the gradient will likely be substantially sharper than the current NWS forecast maps indicate. I completely agree with the products and maps sent out by OUN and DDC this afternoon, since they have to account for uncertainty implicitly without probabilistic accumulation forecasts, but I doubt we really see > 4" amounts in a swath wide enough to cover from Lawton all the way to Hays and Garden City. In both of the storms I just mentioned, the gradient predictably set up over or relatively near the OKC metro area, and I envision something similar here. We'll be hard-pressed to see impressive totals in Norman unless the entire guidance envelope sinks back S tonight and tomorrow by a decent margin. While that's certainly possible given the seasonal trend, the currently-modeled track that strongly favors N OK seems to have a lot of climatological precedent.

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18z GFS shifted things a bit back SE this run, at least up here. I noticed 850 MB temps cooled a bit from the 12z run in SE KS and W MO. Looks like the "jackpot" area is near KC. The 18z GFS did increase cold sector precip and developed a more prolific (QPF-wise) trowel-like feature across S KS and N OK that it lifts north. 

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Models continue to become more robust in regards to CAPE on Monday as the warm front slowly lifts northward across Louisiana, Mississippi, Alabama:
 

GFS_3_2013022318_F48_CAPE_SURFACE.png

 

Contrary to what has been the case for nearly all of this winter, strong low-level wind shear will not be present. Or, at least, that's what the GFS is saying:

 

GFS_3_2013022318_F48_WSPD_850_MB.png

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This is looking like a tricky forecast for the northern and southern end of this system as there has been quite a bit of shifting in the models. Regardless, central Kansas looks to be in for it again. Much of the same area as the last storm but perhaps extending further east and northeast. 

 

There is considerable lift too for thundersnow via the 700mb vertical velocity...

NAM_221_2013022318_F51_VVELD_700_MB.png

 

This could contribute to thundersnow and localized heavy banding with 1-3" per hour rates in the brighter shaded areas on that map. 

 

Here is my first guess on snow accumulations:

snow-accumulations.jpg

 

Some areas in Kansas could see 12-18". Obviously this will likely change as there is still quite a bit of uncertainty and we are far out.

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Greatest depth for Wichita: 17.0 inches January 19, 1962

 

Instantwxmaps - the GFS output has MCI at 24-27"! That's crazy.

 

post-2499-0-64226100-1361657598_thumb.pn

 

Greatest depth for Wichita: 17.0 inches January 19, 1962

Is this shaping up for Topeka to have a repeat performance of Thursday?

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Now that the NAM is off the crazy train, there's definitely a consensus track for the H5 low center along or just N of the Red. I'd say all available guidance now (18z American/12z foreign) is within a 50-75 mi. window, at least during the period in which much of W/C OK is affected. For C OK (not necessarily farther E into MO/AR), this track is reminiscent of both the 2009 storm I mentioned and also 29-30 Nov 2006.

 

Based on pattern recognition and climatology, the gradient will likely be substantially sharper than the current NWS forecast maps indicate. I completely agree with the products and maps sent out by OUN and DDC this afternoon, since they have to account for uncertainty implicitly without probabilistic accumulation forecasts, but I doubt we really see > 4" amounts in a swath wide enough to cover from Lawton all the way to Hays and Garden City. In both of the storms I just mentioned, the gradient predictably set up over or relatively near the OKC metro area, and I envision something similar here. We'll be hard-pressed to see impressive totals in Norman unless the entire guidance envelope sinks back S tonight and tomorrow by a decent margin. While that's certainly possible given the seasonal trend, the currently-modeled track that strongly favors N OK seems to have a lot of climatological precedent.

 

I think that is a pretty reasonable and realistic assessment. This will need to take a notable dive S or SE, especially given the moisture feed this storm eventually does develop as it tracks eastward...which is going to tend to displace the deform band farther NW.

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:santa:  :thumbsup:

 

i honestly thought the were gonna pull the gun on it around 4pm today, but they kept to winter storm watch

This is going to be impressive, and after saying that we just had the best leeside low with the last event, this is going to make that event look somewhat unimpressive in comparison. Portions of central KS into western MO are going to be slaughtered once the moisture feed really kicks in...with a line of moist convection likely feeding the deformation band near the PV anomaly/triple point. 

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While I am not even going to try and pretend this setup is remotely similar to April 14th, 2011 epic blizzard/outbreak event, it does bear some similarities to that event in that it was a deep upper level anomaly cutting off from the northern stream with a sufficiently moist warm sector to allow for surface based/near surface based DMC along the occlusion. The way the WCB wraps favorably ahead of the upper low tends to result in a much slower progression than the models sometime indicate....with a moisture feed  (typically thunderstorms) feeding into the deform band. Very similar setup here...of course we don't have 2000+ j/kg of warm sector cape...nor is the warm sector nearly as large/wide as that event, but it gives some indication of what we will be seeing as this event unfolds.

 The potential exists for someone under the pivot axis of the deformation zone to see epic snow totals in excess of 2 feet.

post-999-0-68180400-1361676296_thumb.png

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^^ This low is still digging...and the models (at least NCEP models...and apparently the UKMET) are still catching up. You can see the anomaly across southern NV diving straight S on WV. Rapid Refresh, every run, adjusts to how far S this trough is digging.

 

Also note the lead anomaly across eastern UT...that is what the 12z NAM this morning was trying to suggest would become the dominant upper level feature. What an awful model.

post-999-0-81059300-1361682372_thumb.jpg

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^^ This low is still digging...and the models (at least NCEP models...and apparently the UKMET) are still catching up. You can see the anomaly across southern NV diving straight S on WV. Rapid Refresh, every run, adjusts to how far S this trough is digging.

 

Also note the lead anomaly across eastern UT...that is what the 12z NAM this morning was trying to suggest would become the dominant upper level feature. What an awful model.

 

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