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Jan 22-23 East Coast Storm Discussion


Wow

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Winds could be a big issue and I haven't seen it talked about much. Places that get significant ice buildup or a heavy wet snow could be in real trouble once the winds start cranking.

I'm reading that wind gust in Asheville will be around 25 to 40 with heavy snow, sounds almost like blizzard conditions for all the mtns.  deformation zone also pivots around to include n.ga, nw upstate and wnc and points east of there

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GSP new snowfall maps has KAVL at 11-12 inches but most models say 12-18, either way, WOW! unbelievable. :snowing:     In GSP discussion they do throw out in the WSW that anywhere from 8-18 inches of snow, I guess if we get in on the deformation zone it could be the 18 inches

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From WRAL:

SE of Raleigh expect some wintry mix early but rain for the afternoon. We could see 1-2" of RAIN by Saturday

 

Welcome to my world

 

Friday Night
Rain, mainly before 4am. The rain could be heavy at times. Low around 37. Northeast wind 10 to 16 mph becoming north after midnight. Chance of precipitation is 100%. New precipitation amounts between 1 and 2 inches possible.
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From WRAL:

SE of Raleigh expect some wintry mix early but rain for the afternoon. We could see 1-2" of RAIN by Saturday

There will most likely be a sharp transition zone across the Triangle. NW half will most likely stay below freezing while areas in the SE transition over to rain. As with any winter storm, things can change some; a little warmer air could get pushed in and even the NW sections go over to rain; or a little colder air stays locked in and most stay below freezing. Again the models will be big today for these small details.

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Has everybody seen the huge differences between the GFS and NAM. The GFS give RDU north and west > 12" and the NAM barely gives anybody outside the mountains 3". I would assume the GFS is showing all wintery types and the NAM actual snow; but man the NAM is low:

 

http://www.twisterdata.com/index.php?prog=forecast&model=NAM&grid=221&model_yyyy=2016&model_mm=01&model_dd=21&model_init_hh=06&fhour=48&parameter=SNOWIN&level=SURFACE&unit=none&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false

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Has everybody seen the huge differences between the GFS and NAM. The GFS give RDU north and west > 12" and the NAM barely gives anybody outside the mountains 3". I would assume the GFS is showing all wintery types and the NAM actual snow; but man the NAM is low:

 

http://www.twisterdata.com/index.php?prog=forecast&model=NAM&grid=221&model_yyyy=2016&model_mm=01&model_dd=21&model_init_hh=06&fhour=48&parameter=SNOWIN&level=SURFACE&unit=none&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false

 

 

There is a very BIG difference in precip types on the 06Z GFS and 06Z NAM.  According to the meteogram generator, Hickory gets 13 inches of snow and virtually no ice on the GFS versus 3 inches of snow and 1.2 inches QPF of sleet.  But, I'm leaning toward the GFS since the CMC and ECMWF show similar snowfall totals.  The NAM seems to be alone on this.  It could, of course, still be right, but I'd not be willing to bet on that.

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and a big south trend with the 6z GFS. ULL cuts off more and shifts everything south.  Wow.

 

My only worry is what are the global models seeing the NAM isn't? We're starting to get into the NAM's wheel house especially come 00z. The NAM is usually better at handling the cold profiles...hopefully it makes a shift. 

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Real Time Nomogram Plots and Partial Thickness Data

 

CVJWgzM.png

 

TREND’s 6 hourly predominant p-type categories include:

  • All snow
  • All snow or snow/sleet mix
  • Icing – measurable sleet with freezing rain
  • Icing – freezing rain mixed with trace frozen
  • Freezing rain or rain
  • Rain
  • Measurable snow with rain
  • Wintry mixtures

Changes to or mixing with other p-types are in part determined by noting which predominant p-type category the thickness values are trending toward. When the partial thickness values are located near an adjacent p-type category and are trending toward that adjacent category, forecasters should reflect this trend in their 6 hourly forecast of p-type. 

 

 

Reference material and current observed are here:

 

http://www.weather.gov/rah/nomogram

 

Specific GFS Nomogram Forecasts are here:

 

Use top tabs for common geographical boundary cities.

 

http://www.weather.gov/rah/gfsnomogram

 

Specific NAM Nomogram Forecasts are here:

 

http://www.weather.gov/rah/namnomogram

 

Specific Canadian GEM RUC Forecasts are here:

 

http://www.weather.gov/rah/canadiangemnomogram

 

Specific WRF-ARM Nomogram forecasts are ehre:

 

http://www.weather.gov/rah/wrfarwnomogram

 

Specific RUC Nomogram Forecasts are here:

 

http://www.weather.gov/rah/rucnomogram

 

Data is not available for the ECMWF.

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Two trends for central NC that are disconcerting for winter weather fans: the initial precip is getting delayed, especially in the NAM. Secondly, there is an increase in precip rates early Friday night just as surface temps rise to or above freezing. With that said, the 6Z GFS was colder overall for RDU and points north and west, indicating the potential for several inches of snow/sleet before transitioning to freezing rain.

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My only worry is what are the global models seeing the NAM isn't? We're starting to get into the NAM's wheel house especially come 00z. The NAM is usually better at handling the cold profiles...hopefully it makes a shift. 

yeah that's quite a warm nose the NAM moves in. That's why I'd like to see the primary die off as quickly as possible.

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Two trends for central NC that are disconcerting for winter weather fans: the initial precip is getting delayed, especially in the NAM. Secondly, there is an increase in precip rates early Friday night just as surface temps rise to or above freezing. With that said, the 6Z GFS was colder overall for RDU and points north and west, indicating the potential for several inches of snow/sleet before transitioning to freezing rain.

It will come down to the strength of the CAD and the position of the low off our coast. Even with us only 24 hours from the start of the storm, the next models runs are very crucial.

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My only worry is what are the global models seeing the NAM isn't? We're starting to get into the NAM's wheel house especially come 00z. The NAM is usually better at handling the cold profiles...hopefully it makes a shift. 

There was a physics problem in the NAM and GEM for some reason. HRRR stayed course and is actually digging much further than the NAM right now. You will hopefully see the NAM trend more south. I do, however, think the warm nose will be stout. 

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