Feb 15-16 Possible Mixed Event.

[nchighcountrywx]

Yes, wise to consider the guidance of WPC.  They rarely miss and monitor for any future changes over the weekend.

 

The probabilities in the NC High Country have fallen from 70% to 90% to 30% to 50%

 

[WSNC]

Yes, wise to consider the guidance of WPC

 

 

I thought those charts were completely automated using one model (SREF maybe).  Actually I believe it's a blend of a few models, but recall that it's an automated process.  

[Blue_Ridge_Escarpment]

Yes, wise to consider the guidance of WPC

The probabilities in the NC High Country have fallen from 70% to 90% to 30% to 50%

Nice. I like when WPC is on board!

[packfan98]

6z GFS Para is looking good.  Nice thump of snow in the upstate at hr 78.

 

And 6 hours later, the cold air is gone.  There was an increase in moisture when the temperatures were colder.  More frozen than the 0z I believe before the changeover.  The NAM should be better at the surface temps.  Next up 12z GFS.  Cross your fingers!

[franklin NCwx]

6z para shifted south from its amped 0z run.

[packfan98]

6z para shifted south from its amped 0z run.

[superjames1992]

I thought those charts were completely automated using one model (SREF maybe)

Looks like they use the SREF and some other models, but they are automatically generated, nevertheless.

http://www.wpc.ncep.noaa.gov/pwpf/about_pwpf_products.shtml

The probabilistic forecasts found here on the WPC PWPF page are also based on the deterministic WWD accumulation forecasts and are generated automatically using an ensemble of model forecasts along with the WWD forecasts. The automatic nature of this product generation allows an extensive set of displays of probabilities for snowfall or freezing rain exceeding a number of thresholds and accumulations of snowfall or freezing rain for various percentile levels. The percentile amounts and probabilities for 24-hour intervals are generated at six-hour increments through 72 hours. The six-hour increments are made possible by disaggregation of the 24-h human deterministic forecast based on six-hour accumulations from a blend of model guidance selected by the WWD forecaster.

The automatic processing also allows the generation of probabilistic winter precipitation forecasts for 48-h intervals based on 48-h accumulations obtained by adding two 24-h accumulations together. The same method used to compute the 24-h probabilistic products is applied to the 48-h intervals ending at 48 through 72 hours after the initial time. As with the 24-hour forecasts, the 48-h forecasts are produced at six-hour intervals. Finally, a single set of probabilistic forecasts are created for the entire 72-hour period.

A multi-model ensemble is utilized to create a distribution of values around the WPC accumulation at each grid point. The typical constituency of this ensemble is as follows:

26 NCEP Short-Range Ensemble Forecast (SREF) members

25 ECMWF ensemble members, randomly selected

1 NCEP North American Mesoscale (NAM) 12Z (day) or 00Z (night) operational run

1 NCEP Global Forecast System (GFS) 12Z (day) or 00Z (night) operational run

1 European Center for Medium-Range Weather Forecasts (ECMWF) latest operational run

1 Canadian Model (CMC) latest operational run

1 ECMWF latest ensemble mean

1 NCEP Global Ensemble Forecast System (GEFS) latest ensemble mean (6-h SLRs)

5 NCEP GEFS members, randomly selected

___

62 Total members

[franklin NCwx]

Has to be a lot of ice in that

[strongwxnc]

Yes, I would assume so. 

Has to be a lot of ice in that

[packfan98]

Has to be a lot of ice in that

Sure...it wouldn't be a clown map otherwise.  The mountains definitely held on longer than the last run.  This is mostly front end stuff before the changeover.  We'll see.

[franklin NCwx]

Yes, I would assume so.

better than a cutter. At least it won't wash away our front end thump

[Tacoma]

nice

[strongwxnc]

Much better than a cutter. Do we start to hone in on an agreeable track today.. 

 

better than a cutter. At least it won't wash away our front end thump

[UpstateSCBud]

Still not going to cut it for the upstate

[franklin NCwx]

Much better than a cutter. Do we start to hone in on an agreeable track today..

Hopefully. I would like a south of i-20 and then up 95 track. I'll take my chances with mixing on that one.

[Tacoma]

Hopefully. I would like a south of i-20 and then up 95 track. I'll take my chances with mixing on that one.

this track is not out of the question.

[beanskip]

At hour 72, 12z NAM gives GSO .25 of freezing rain ......... at 21F.

[franklin NCwx]

Nan brings it it fast. I like to see that, it's usually too slow

[Blue_Ridge_Escarpment]

At hour 72, 12z NAM gives GSO .25 of freezing rain ......... at 21F.

 Oooof

[superjames1992]

At hour 72, 12z NAM gives GSO .25 of freezing rain ......... at 21F.

Regardless of what the models show verbatim, if we start out at 21F and keep precip falling, it would take quite awhile to make it above freezing. In-situ CAD can be hard to budge here.

[SN_Lover]

12z has the low in Mexico 

[wncsnow]

GFS with a solid front end thump for WNC foothills and mountains

[FLO]

Someone wake Shawn up please up so us SC folks can get an update.

[UpStateCAD]

_{Edit.....I was just looking at precip maps.......SC did much better in later frames.}

 

_{looks like the 12z GFS has NC in the game with a nice wedge (HP looks a lot better) and nice precip, but moisture is too far north for anyone in SC....at least through mid day Monday.  VA and WV doing very good.  Cutter.}

[SN_Lover]

WOW night and day on the GFS!! 

[Lookout]

It looks like there is a pretty good consensus that the high is either out or on its way out before the bulk of the system moves in.  There is not a great consensus on the track of the storm or the timing of when the precip moves in.  The magnitude of this air mass in terms of it being cold and dry is impressive -- not your ordinary weak wedge.  Therefore, we have a greater than normal opportunity for a good hit of front end snow and ice before any changeover occurs, IF we can see precip fall quickly enough.

 

So what we are left with here, since the high is going to be gone, is needing the precip to get in here as early as possible and lock in the wedge.  IF that happens, then we would most likely see the track and/or the redevelopment of the system occur farther south and east than shown.  That's what you want to see, if you are wanting a higher impact winter storm.  If we don't see the precip move in before the high moves well offshore, well, then outside of a few spots, it'll be just another ho hum advisory (maybe) to rain thing.

 

The magnitude of this air mass makes this scenario possible.  That's the only reason this is even worth talking about outside of the mountains.

In some ways this system reminds me of the january 22-23rd ice storm of 2000...except conditions with that one were not ideal either. The departing high was much weaker, worse position and  progressive...The 2000 high was only around 1025 to 1030mb and already was moving/ had moved off shore the mid atlantic by the time precip arrived. (so winds were pretty light at the surface out of the NE),  850mb temps started similar to this one with 0c moving from ga to the nc/va border by the time it was over while warming to 6 to 8c over north ga by 12z of the 23rd,  925 mb temps went from 0c in ne ga  when the precip started to several degrees above freezing overnight,  and the precip didn't start until early to mid afternoon here in georgia. After morning lows around 29 to 31, the late arrival of precip allowed temps to warm into the mid to upper 30s...and dewpoints has risen into the teens after being in single digits earlier. But Despite what is less than ideal conditions there still was  major ice accumulations across north ga, causing hundreds of thousands of power outages, and a lot of egg on a lot of local mets faces.

 

With this system, **assuming we don't see a gfs like track and timing** we have a much stronger high initially, better arrival time of precip, if it starts as early as the canadian, nam, french, and jma, we will have colder surface temps/wetbulbs at the start of it, and just like the 2000 storm precip will cool down the interior carolinas at the same time as north ga..thus helping to maintain easterly flow and causing the cold pool to be even more stubborn to dislodge or warm up. Again though if things played out with timing and surface low track like the 06z gfs, cooling/damming will be much less.

 

One other thing to note is the gfs dewpoints. For whatever reason, the gfs warms dewpoints into the 20s over north ga/upstate by 12z despite no precip or response in dry air temperature.  No other model is showing such a big rise in dewpoints without precip already starting.  So  that is something those should keep in mind when looking at the gfs as this obviously would mean much less evap cooling potential and would greatly reduce the cooling potential.

[franklin NCwx]

Gfs is like the ukie, but with that far south of a track There is no way it warms the mtns and foothills up that quick

[Blue_Ridge_Escarpment]

What's 200 miles among friends?

[calculus1]

Someone wake Shawn up please up so us SC folks can get an update.

 

You don't need to rely on Shawn.  Do your own research.  Take a look at the GFS right here.  It's just a click away...

 

http://www.tropicaltidbits.com/analysis/models/

[franklin NCwx]

Ninja by lookout