One More Shot: Feb 20-21 Event

[TARHEELPROGRAMMER88]

1 minute ago, griteater said:

The GEFS mean precip ticked south, just barely...matching the GFS move...they will probably lock in together now going forward

It also cut the total snowfall a little for many places in central/eastern nc

[SnowDawg]

Looks fairly certain at this point that MBY is going to be right around the dividing line which can make for a fun now-casting event or a downright torturous one. My guess at this point is mostly rain/sleet/white rain then finally a sloppy inch or two in the grass towards the end. 

[FLweather]

48 minutes ago, GunBlade said:

Take the GFS qpf and the NAM warm nose and that’s your storm.  NAM has sniffed out more than enough warm noses in my area over the years for me to never underestimate it. I’ve also seen it ramp up QPF like crazy right up to the storm and then verify with half what was modeled. 

Granted.  Sometimes the warmnoses do come in a little warmer.

But this is not a amped system with a powerful H850 lp running through the coastal plain of GA, SC, NC, VA. With a bombing sfc low off the coast.

This warm nose exists roughly 800mb to 750mb. From a over running system transitioning to a coastal with high potential of alot of frontogenesis. 

Not exactly sure  where in Charlotte you stay. But judging by the soundings and raw data. Around Charlotte and north ward with plenty of moisture and lift a warmnose should be overcame. 

Granted you may have some pingers  mix in briefly. The warmnose is not that strong. 

Even around Raleigh and south those levels stay at or below freezing. 

 

[SnowDawg]

Lol, just flipped through the rest of the GFS and it's got a big time fantasy land storm in March. 

[FatherNature]

0z Euro showing the snowy solution for NC. 

[FatherNature]

0z12z 

 

[lilj4425]

I see the Euro is caving. Lol.

[SnowDawg]

43 minutes ago, FatherNature said:

0z12z 

 

Lol, just your average run to run change inside 48 hours.

[SnowDawg]

SREF continues to make this look more and more like a primarily NC and Virginia event... GFS and NAM look the best on the southern fringes but have been trending poorly for a while now. 2 days ago when I was begging for a northward trend I should've known this would happen lol. 

[ForsythWx]

6z NAM just snapped.. 

 

3km

[lilj4425]

How does the GFS look? 

[Tacoma]

GSP mighty conservative only saying a dusting to an inch around Asheville, with all the data I would have thought for sure 3 maybe 4 inches around these parts.

[MOD]

3 minutes ago, lilj4425 said:

How does the GFS look? 

https://www.pivotalweather.com/model.php?m=gfs&p=snku_acc&rh=2020021906&fh=60&r=us_ma&dpdt=&mc=

[lilj4425]

GSP:

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 400 AM EST Wednesday: With cold, sfc high pressure to the northwest and nearly zonal flow aloft, along with a lingering cold front well south of the area, the potential for snow across the area remains the main topic of interest for the forecast period. While guidance continues to disagree on total QPF with this event (as has been the trend the past few days), the general consensus continues for cyclogenesis along the front somewhere off the GA/FL Coast on Thursday, as the parent sfc low then moves just off the Carolina coast into Thursday afternoon. With upper dynamic support, along with moisture infiltrating in across the Gulf states and Southeast, precipitation is expected across the area Thursday, tapering off into Thursday night as the system pulls away. Expect precip to be ongoing at the beginning of the fcst period, with mainly snow across the mountains, and all rain across northeast GA and the Upstate given temperatures around daybreak in the lower 40s. Temperatures are expected to decrease throughout the rest of the day, and as this occurs, precipitation is expected to expand across the area. Per latest fcst soundings, the NAM continues to be the outlier suggesting a small window of wintry mix around midday as precipitation transitions from rain to snow. Meanwhile, both the GFS and ECMWF suggest a clean cut rain to snow transition. Thus, have kept with this trend into the early afternoon hours, though wet bulb temps suggest the transition could occur sooner, around noon, especially around the CLT Metro area. Something to keep a close eye on. Throughout the afternoon hours, the rain/snow line will shift southward into the Upstate as temperatures continue to drop. However, as this transition occurs into the evening, QPF will decrease significantly as well. Thus, with this fcst package, the Upstate and portions of northeast GA will struggle to see much in the way of snow accumulation, while across across the NW Piedmont could see a dusting to near an inch, and slightly higher amounts across the mountains, especially across the higher elevations. Expect all precipitation to dissipate overnight. Any changes in the next guidance could alter snow accumulations, and could warrant the issuance of a Winter Weather Advisory. On Friday, expect dry conditions as sfc high pressure builds in. However, given recent rain/snow, along with low temperatures Friday morning in the low to upper 20s across the Upstate and NW Piedmont, into the teens across the mountains, black ice issues will become a concern, especially given any residual water/snow on roadways and elevated surfaces. With clouds clearing out throughout the day, expect high temperatures to climb into the low to mid 40s across the Upstate and NW Piedmont, with temperatures across the mountains in the 30s, with the higher elevations struggling to reach freezing.

[lilj4425]

RAH: 

SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 500 AM Wednesday... ...Rain is expected to change to snow Thursday night before tapering off pre-dawn Friday... What has changed: Reduced snowfall amounts a bit across the southeastern zones and focused the peak accumulation amounts (1-2") a bit further north and west to better coincide with latest model trends. Our forecast remains much lower than most raw forecast guidance due to numerous limiting factors, including; (1) Warm surface temperatures, (2) Self-limiting CAA processes, and (3) Low rain to snow liquid ratios. Impacts should remain rather minimal, however, a few slick spots may form on area roadways during the overnight hours Thursday into early Friday morning, primarily along and east of US-1. If the forecast holds true, a Winter Storm Advisory issuance may be needed in future forecast packages (Our criteria is areas that are expecting to see 1" of snow or greater in a 12 hour period). Full Discussion: The surface front will settle in a nearly west to east orientation in vicinity of the SC/GA border, with ongoing surface CAA processes occurring north of the boundary. The front is progged to buckle back north as a series of weak disturbances begin to develop during the day Thursday, with strong coastal cyclogenesis beginning to initialize off the SC coast as early as Thursday evening. Around the same time, strong Canadian surface high pressure will continue to settle southeast through the central Corn Belt states, extending east through the Great Lakes and northeastern US states before beginning to south along the lee side of the Appalachians. Location and strength of the developing coastal low/trough will be key to the forecast going forward, as a stronger and closer to shore area of low pressure (NAM) will help to promote more rapid cold air entrainment from the north. Forecast models continue to trend increasingly wetter during the daytime hours Thursday, primarily as a result of strong convergence in the 850mb level where steepening temperature gradients and FGEN banding sets up in vicinity of the US- 64 corridor. Around this same time, a 925mb weakly defined cold front (marking the leading edge of the cold nose) will extend south into the area. This will aid, at least initially, in the ability for wet bulb/evaporative cooling processes to promote a light rain to snow changeover to occur in vicinity of the VA/NC border mid to late afternoon. From there, a gradual changeover to a rain/snow mix to eventually all snow will occur. At first, accumulations will remain little to none with more of a "white rain" type scenario unfolding. Eventually, especially areas east of US-1 where rain rates will remain higher for longer, the wet-bulb effect will help to cool surface temperatures below freezing, helping to promote accumulations primarily on grassy and elevated surfaces. Best timing for this will be between 02z/9pm Thursday through 10z/5am Friday morning. Snow amounts continue to remain highly uncertain in this event, however, thinking that raw model output remains way too high in this scenario. Several limiting factors remain at work, including: (1.) Persistent above freezing surface temperatures that will help temper/melt the majority of the snowfall. The exception to the rule may be areas closer to the VA/NC border, however, these are the areas that will likely see far less QPF throughout the event (2.) 10:1 snow to liquid ratios are not likely in an event like this, expect closer to 3:1 at precipitation changeover onset, 5:1 toward the middle of the event, and perhaps ending in vicinity of 10:1 if we are lucky. (3.) While the CAA process will be key in the original changeover, it will also become the ultimate limiting factor through the frozen ptype portion of the event. Gradual drying is expected to persistently take place in the lower-third of the boundary layer as the cold air slides south into the region. This will work to greatly reduce QPF from northwest to southeast in general. Higher amounts of QPF in the southeast will remain, however, dewpoints in the middle 30s will keep widespread snowfall accumulations from occurring. With these limiting factor in mind, have shifted the geographic location of accumulations a bit further north and west. Amounts are down a bit also with this run, topping out in the 1 - 2" range in northeastern Coastal Plain. From there, if you follow the US-64 further west, expect accumulations in vicinity of an inch with lesser amounts as you progress west of US-1 and south of US-64. Alterations and fine tuning to the accumulation forecast is highly likely to continue with sequential model runs and forecast packages, but still finding it highly doubtful that significant snowfall amounts will occur across central NC. For the snow lovers out there, the canary in the mine that could indicate the potential for higher amounts lies in surface dewpoints Thursday afternoon. If dewpoints become significantly cooler, a possibility advertised by the recently cold-initialized NAM, wet-bulb cooling processes may promote an earlier changeover and perhaps higher amounts somewhere across central NC assuming the moisture is available. Precipitation should clear out of central NC rapidly pre-dawn Friday leaving sub-freezing temperatures and a light northerly breeze in its wake until sunrise. With sustained northerly winds in the 6 to 10mph range, thinking that drying processes in the coldest areas should limit the black ice/flash freeze potential to only patchy areas during the overnight hours. Sunshine and a breeze will help to clear and dry any leftover frozen surface moisture rather quickly Friday morning.

[QC_Halo]

7 hours ago, Tar Heel Snow said:

Literally every zone this guy forecast is basically exactly the same “a few or a couple or several inches” ...why is the UNCC Grad student held in such high regard by some here, but real, actual meteorologists are not.

[David Johnson]

Literally every zone this guy forecast is basically exactly the same “a few or a couple or several inches” ...why is the UNCC Grad student held in such high regard by some here, but real, actual meteorologists are not.

He explains his thinking in his next tweet

.

[David Johnson]

He explains his thinking in his next tweet





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Then later posted a more in depth prediction

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[PackGrad05]

Interesting that their "bullseye" is in the northeast NC region.  Probably due to temperatures and less of limiting factors.

[CaryWx]

Looks to me like the NWS laid out their reasoning why what we have been seeing modeled (and discussing these last few days) is not all that accurate in TRUE forecasting on this event for the following reasons:

(1.) Persistent above freezing surface temperatures that will help temper/melt the majority of the snowfall. The exception to the rule may be areas closer to the VA/NC border, however, these are the areas that will likely see far less QPF throughout the event

(2.) 10:1 snow to liquid ratios are not likely in an event like this, expect closer to 3:1 at precipitation changeover onset, 5:1 toward the middle of the event, and perhaps ending in vicinity of 10:1

(3.) While the CAA process will be key in the original changeover, it will also become the ultimate limiting factor through the frozen ptype portion of the event. This will work to greatly reduce QPF from northwest to southeast in general. 

Oh yeah, they also mention a "cold initialized NAM"

 

[PackGrad05]

In true NC fashion, we go from southern favored areas to more of a northern favored area.  Southern Wake better watch out!  I've seen this play out multiple times where it takes us too long to transition and never completely get a good snow falling.

[sarcean]

GSP is being quite conservative 

 

 

 

 

[calculus1]

Then later posted a more in depth prediction





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Webber with the snow shadow forecast in the lee of the Apps. A wide shadow, too. Ugh! I'm hoping I'm just far enough east to avoid most of the downsloping. The more the precipitation feed is oriented SW to NE, the better, IMO.

Sent from my moto e5 supra using Tapatalk

[Avid6eek]

Don't be a weenie grasping for straws.  Being in the bulls eye will make any of us excited, but the model depiction of the bulls eye and the actual bulls eye are always in two different places.  In my experience from most of my life being in upstate NY, the heaviest snow totals are almost always to the NW of what is modeled.  In this case, they are probably more to the N/NE because this far south, and at this point in the year, whether the precipitation falls during daylight hours makes a huge difference.

If I had to be anywhere during this event, far NE North Carolina would be my choice.  Elizabeth City FTW.

 

 

[Dunkman]

With snow our WFOs seem to decide how they feel about an event a few days in advance and try to stick with it, at least until the night before. It makes sense you don't want the forecast bouncing around with every model run. I'm fine with the expected forecasts, we've certainly had white rain events in the past. That said, the 1 in 10 forecasts and probability of x" of snow products aren't great.

[ILMRoss]

Literally every zone this guy forecast is basically exactly the same “a few or a couple or several inches” ...why is the UNCC Grad student held in such high regard by some here, but real, actual meteorologists are not.

A quick note on Webb; he graduated with a degree in meteorology from NC State, which in my view makes him a meteorologist. I was in a class or two with him and can personally vouch the dude is pretty brilliant. Forecast against him at your own risk.

[wake4est]

Allan's 1st call map is out.

 

[QC_Halo]

1 minute ago, ILMRoss said:

A quick note on Webb; he graduated with a degree in meteorology from NC State, which in my view makes him a meteorologist. I was in a class or two with him and can personally vouch the dude is pretty brilliant. Forecast against him at your own risk.

Ok. Point taken. But you have to admit that first map was pretty bad. The follow ups made more sense, and I’m not talking about forecast amounts people.

[sarcean]

3 minutes ago, wake4est said:

Allan's 1st call map is out.

 

Hard to put faith into a map that doesn’t even include a B on it 

[Wow]

3 minutes ago, wake4est said:

Allan's 1st call map is out.

 

Good to see he made me the nexus of all zones.