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Wintry December 28-29th Possible Winter Storm

Catfish said:
just got a special weather statement for possible light sleet tonight north of I20 in GA
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Yeah, it's not often I get 3 different periods of rain,zr,sleet and snow over a 7 day period on my point cast, lol. Good times, if some of it happens...sans the zr, or course. T
 
FFC: .LONG TERM /Thursday through Tuesday/...
Challenging forecast through the extended with diverging model
solutions and the potential for winter precip. The morning model
runs have continued to trend slightly drier than previous for
Thursday afternoon through Friday`s freezing rain/sleet event.
Model sounding continue to show that moisture will overrun wedge
of cold air, with a deep enough cold layer near the surface to
refreeze melting hydrometeors falling through the warm nose. For
now, have generally gone with freezing rain/sleet in the south
metro area, freezing rain/rain in middle Georgia, and all rain in
the far southern CWA. The NAM run for the beginning of the
extended period continues to be the outlier solution, and at this
point, given the new consistency between the ECMWF/GFS/Canadian,
have opted to trend away from its more gloomy forecast. At this
time the only accumulations are for freezing rain, with amounts of
0.02 inches or less, and only for portions of east central and
middle Georgia where the best moisture combines with the coldest
temperatures. Confidence in amounts is low.
 
Shawn said:
Flow sucks through here. Need the wave to be a bit stronger to cause it.
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Yep, the flow is due westerly until the very last second when it flips to WSWly over the Carolinas and boom the precipitation begins to blossom, but it's a little too late for areas well inland of the coast this run.
namconus_ref_frzn_seus_43.png
 
The 500mb vort maps from the ICON show a stronger digging wave shifting the winds from NW to SW to SSW as the low forms quite close to the coast. Look for a stronger wave, and winds becoming more West South West and it's game on.

Again, I can't see how the 9KM Euro can be so far off with it's solution. Swiss & Icon, we shall see.
 
I would believe that the Icon had no chance of verifying, but it has our New Years system much more Euro like versus say, the GFS trying to break Wintry precipitation out. So I'm not quite ready to totally throw in the towel, until the ICON model starts going drier. You'd think if the ICON had some sort of bias around here, it would be doing something big with the New Years storm like this event we are tracking.
 
GaWx said:
Yeah, A few years ago I researched the H5 maps for many SE sig qpf winter events that weren't clippers. The one thing that the vast majority of them had: WSW (at least a little S of W) or SW winds at H5 over one's location. VERY few had straight W winds and almost none had WNW winds at the locations of the sig winter event. Again, I'm not talking about light precip events or clippers.
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You actually want to focus your studies on a slightly lower level in the troposphere if you're trying to capture large-scale synoptic flow and its effects on moisture transport in the SE US, because that's where the most intense latent heating, moisture advection, & WAA is occurring, and this is typically somewhere around 700 hPa... The flow is increasingly geostrophic in the mid & upper levels around and above 500 hPa and if you direct most of your attention here you'll get results which are less conclusive wrt flow orientation and QPF amounts... This upcoming storm is a great example, note the flow is southwesterly to west-southwesterly over the Carolinas Thursday night especially over southeastern NC where most of the moisture over coastal GA & SC at that time is being advected in.


namconus_z700_vort_seus_44.png


Meanwhile, 500 hPa winds are west to west-northwesterly everywhere (even earlier in the run before the precipitation arrives) which argues for little-no precipitation and this isn't the case for coastal portions of the Carolinas and GA
namconus_z500_vort_seus_44.png
 
Shawn said:
I would believe that the Icon had no chance of verifying, but it has our New Years system much more Euro like versus say, the GFS trying to break Wintry precipitation out. So I'm not quite ready to totally throw in the towel, until the ICON model starts going drier. You'd think if the ICON had some sort of bias around here, it would be doing something big with the New Years storm like this event we are tracking.
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That's a pretty good point man
 
Robert West said:
That's a pretty good point man
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And to go with that; the energy and 500mb is much better for New Years, in theory, than what we have for this potential system. You'd think if ICON was over doing the strength and consolidation of the wave, it would be overly amplified and tilt happy with New Years's wave that is much more robust.

I am still routing for the Icon, not because I want ZR, but because I want another model I can half-way trust. The GFS has been such a letdown, I literally only look at the GEFS for a good idea now.
 
zr_acc.us_se.png
 
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