1/28 - 1/30 Storm Thread II

[BullCityWx]

The 18z gfs snowfall maps posted by Allan must not have taken ratios into account. If GSO gets .7 qpf, then there would be no doubt more then 6" of snow.

TW

10:1 maps

[thunderbolt]

Good luck I hope u guys get hammered!

[SnowGoose69]

no, 12z runs had new data as well. 00z runs tonight are the ones with the most ingested though.

18z runs will get aircraft data into them and an occasional 18z sounding that a specific NWS Office may be doing due to a severe weather event at times, sometimes ncep will request offices in a region to all do a 06 or 18z sounding before a major weather event

[Wow]

10:1 maps

 

With temps in the teens... going to be closer to 20:1.

[billypg]

Just looking at the radar, satelite, and wv over SC is that the baja Low coming on shore in SO CAL ????

Anyone please??

[DixieBlizzard]

i was wondering the same thing (btw i have yet to see the usual "its 18z throw it out" lol).  is this the first real run with actual data into the model?  if so the ones coming up at 0z could be quite interesting.  seems like the last couple of days we have been talking about the data getting in starting about this time. we can only hope and gasp. 

 

most of us were used to the nw shift (which usually took most of us out of the game) but it worked in our favor a couple of years ago.  with all these arctic blasts i assumed the storm would be shunted as well.  if the system is coming in stronger, perhaps slowing down the strong cold air push enough to bring it nw some?

 

...or, the high is not quite as strong so this thing can come north.

[wxgeek]

As mentioned earlier NWS Mobile has issued a WS Watch for this area.  What I found interesting is they said there could be

between 1/4 to 3/4 in of ice accumulations...then a transition of snow all the way to the coast with 1-3 inches of snow on top of

the ice. 

 

From the NWS Mobile  AFD:

 

SIGNIFICANT WINTER
WEATHER EVENT UNFOLDING TUESDAY INTO WEDNESDAY MORNING. A POWERFUL
COLD FRONT WILL HAVE MOVED SOUTH OF THE FORECAST AREA BY MONDAY
EVENING...BRINGING STRONG NORTHERLY WINDS AND SUBFREEZING
TEMPERATURES INTO THE AREA MONDAY NIGHT THROUGH WEDNESDAY MORNING.
WITH COLD AIR IN PLACE...MOST OF THE AREA CAN EXPECT A MIX OF
FREEZING RAIN AND SLEET THROUGHOUT THE DAY TUESDAY. WHILE THERE WILL
BE A MIX OF PRECIPITATION TYPES...THE MOST SIGNIFICANT IMPACT WILL
BE FREEZING RAIN...FOLLOWED BY A TRANSITION TO SNOW AS A SERIES OF
STRONG UPPER LEVEL DISTURBANCE MOVE FROM WEST TO EAST OVER THE AREA.
TEMPERATURE AND MOISTURE PROFILES ARE IN MUCH BETTER AGREE ACROSS
THE AREA...SO CONFIDENCE IS NOW HIGH THAT A WINTER STORM WARNING
WILL BE UPCOMING. POTENTIALLY WE COULD SEE 0.25 TO 0.75 INCH OF ICE
COATING THE ROADS...BRIDGES...POWER LINES AND TREES. THIS MIXED
PRECIPITATION TYPE IS THEN EXPECTED TO TRANSITION TO ALL SNOW NORTH
OF A LINE FROM HATTIESBURG MISSISSIPPI TO ANDALUSIA ALABAMA TUESDAY
EVENING...AND SOUTH OF THIS LINE ALL THE WAY TO THE COAST AFTER
MIDNIGHT TUESDAY NIGHT. 1 TO 3 INCHES OF SNOW COULD FALL IN ADDITION
TO THE ICE...COVERING THE ICE ALREADY IN PLACE. THE TRACK OF THE
UPPER LEVEL DISTURBANCE INDICATES THE HEAVIER PRECIPITATION AMOUNTS
WILL BE SOUTHEAST OF A LINE FROM WIGGINS MISSISSIPPI TO GREENVILLE
ALABAMA...WHERE SIGNIFICANT HAZARDOUS WINTER WEATHER ACCUMULATIONS
ARE POSSIBLE. LIFE THREATENING IMPACTS TO TRAVEL WILL LIKELY OCCUR.
IT IS HIGHLY ADVISED NOT TO TRAVEL IN THESE CONDITIONS.

[cmichweather]

With temps in the teens... going to be closer to 20:1.

Even with cold temperatures 20:1 is very hard to do. In North Dakota when snowing around 15-20 degrees we usually averaged around 15-12:1. The DGZ needs certain conditions like very good lift and moisture and that always isn't present even if it is cold. 

[FLweather]

Well since the Ens mean matches operational that would be a worse case scenario for zr  Macon S/E Augusta S/E, Columbia S/E Fayetteville S/E

 

Both GFS GEFS should a broad ill define 850 low with those areas pretty much being the dividing line for the above freezing and below freezing 850 temp.

[HKY_WX]

The PJ s/w is in n alberta and the stj wave is just offshore s. california.

Just looking at the radar, satelite, and wv over SC is that the baja Low coming on shore in SO CAL ????

Anyone please??

[Tony Sisk]

We have come full circle first love the euro hate the gfs, then love euro ensemble and canadian hate the euro/gfs, love the nam/canadian hate the euro/gfs, and now love the GFS hate the NAM/Canaidan. LOL

Don't you just love potential winter storms! We all get excited! Thanks for sharing this thought...too funny!

[Wow]

Even with cold temperatures 20:1 is very hard to do. In North Dakota when snowing around 15-20 degrees we usually averaged around 15-12:1. The DGZ needs certain conditions like very good lift and moisture and that always isn't present even if it is cold. 

 

Good to know that now. Thanks!

[RaleighWx]

The 18z GFS I believe has the worst verification scores of all the 4 runs, I would not get too excited yet but that was an interesting run

Possibly, but it also has the most ACARS and asynoptic data often since it is a run launched in the middle of the day and lots of aircraft are aloft.

 

With that said, the fact that the 18z GFS and GFS ENS members are such an outlier compared to the other global families and mesoscale models certainly gives pause. Likely overdone, but the NAM/GGEM/ECMWF very well may be underdone, so an in-between solution may be what we arrive at.

[HKY_WX]

it's interesting loooking at that wv loop, the stj north of hawaii could perhaps act as a kicker for our stj wave. this is basically a splitflow pattern. good trends... good trends tonight.

[LithiaWx]

Macon would be an absolute mess if the 18Z GFS verified, 1.22" of liquid all with temps in the 20's.  Looks like half sleet and freezing rain with a switchover to snow....

[NEGa]

no, 12z runs had new data as well.  00z runs tonight are the ones with the most ingested though.

thanks.  i have been reluctantly paying attention and already called some family members south of athens in case i need to take a road trip tues lol.  this big change caught me off guard. hopefully its not a fluke, but a lot of times these things in the SE tend to come out of the blue (within a couple days of the event) so obviously my attention is peaked (as are a lot of others i see)

 

if we start seeing the models converge (not necessarily this scenario but close) tonight it could be a wild week in the se. 

 

edited to add:

 

 

 

18z runs will get aircraft data into them and an occasional 18z sounding that a specific NWS Office may be doing due to a severe weather event at times, sometimes ncep will request offices in a region to all do a 06 or 18z sounding before a major weather event

 

thanks for the additional info, and thanks to RaleighWX too

[griteater]

Even with cold temperatures 20:1 is very hard to do. In North Dakota when snowing around 15-20 degrees we usually averaged around 15-12:1. The DGZ needs certain conditions like very good lift and moisture and that always isn't present even if it is cold. 

I'd say you know a thing or two about snow ratios being in the Dakotas.

 

Both GFS GEFS should a broad ill define 850 low with those areas pretty much being the dividing line for the above freezing and below freezing 850 temp.

Was just looking at this on Dupage, the 850mb streamlines show the circulation running from Macon to just south of Charlotte, to just south of Raleigh.  If the 500mb wave pattern looks good, the rest will fall in line.

[Wow]

Per DT on facebook:

 

[HKY_WX]

Even with cold temperatures 20:1 is very hard to do. In North Dakota when snowing around 15-20 degrees we usually averaged around 15-12:1. The DGZ needs certain conditions like very good lift and moisture and that always isn't present even if it is cold. 

i may be wrong, but it's a balance of the ice crystal growth layer being ideal, calm sfc wind, source region, and obviously anomalously cold 700mb-sfc temps.

[RaleighWx]

The 18z gfs snowfall maps posted by Allan must not have taken ratios into account.  If GSO gets .7 qpf, then there would be no doubt more then 6" of snow.

TW

My maps assume a 10:1 ratio, it is pretty difficult to program a changing snow ratio with these graphics, so I just set it to 10:1, the amount of liquid equivalent that is designated as snow is done by the model postprocessing package (NCEP) not by me.

[superjames1992]

The GEFS Mean is WETTER than the Op here. That's what I wanted to see. Maybe the 18z GFS isn't totally out to lunch.  I am trying to temper expectations and not get too excited, but it's hard...

[NCSNOW]

Even with cold temperatures 20:1 is very hard to do. In North Dakota when snowing around 15-20 degrees we usually averaged around 15-12:1. The DGZ needs certain conditions like very good lift and moisture and that always isn't present even if it is cold. 

So is there a model tool/tab that can calculate these for you. Or do you have to use old school pencil and paper with real time data to come up with the equation. Like wetbulbs and windchills,  they have a table-scale. Thanks for the info

[Wow]

If you have a model center subscription, you can see how the interaction between the polar and southern streams means to much to the forecast.

 

Here's the trend loop on the GFS model: http://www.americanwx.com/models/index.html?&model=gfs&run_time=18z&param=500mbHGHT&map=US&run_hour=60&loop=trend

[HKY_WX]

So is there a model tool/tab that can calculate these for you. Or do you have to use old school pencil and paper with real time data to come up with the equation. Like wetbulbs and windchills,  they have a table-scale. Thanks for the info

http://sanders.math.uwm.edu/cgi-bin-snowratio/sr_map_main.pl

 

this is the best site to try a calculation. i'm not sure the equation, but it's pretty interesting.

[packfan98]

The Cobb Bufkit Warehouse outputs shows the snow ratios in text form.  I don't know how accurate they might be.  They are showing ratios between 11:1 to 13:1 on for this storm in RDU.  Here's a link:

 

http://www.meteor.iastate.edu/~ckarsten/cobb/cobb.php?model=gfsm&site=krdu

[Wow]

The GEFS Mean is WETTER than the Op here. That's what I wanted to see. Maybe the 18z GFS isn't totally out to lunch.  I am trying to temper expectations and not get too excited, but it's hard...

 

Look nearly identical to me... actually less qpf for the coastal plain. Still 1"+, just not the adsurd 2-3" amts the operational had.

[BullCityWx]

incredible agreement on the individual ENS members WRT the westward shift.

[RevDodd]

http://sanders.math.uwm.edu/cgi-bin-snowratio/sr_map_main.pl

 

this is the best site to try a calculation. i'm not sure the equation, but it's pretty interesting.

Thanks! BTW, HKY, your call on the sweet spot this afternoon is still holding sway. Per the evening GFS-NAM, Macon-Florence-(insert Fayetteville)-Rock Mount.

[WeatherNC]

No surprise, 11/11 18z mems on the model center are big hits, p002 and p009 don't quite meet the criteria for historic (they probably do), the other 9 are sick nasty.  Lots of 15" amounts, p001 is pushing >20!  

[HKY_WX]

http://sanders.math.uwm.edu/cgi-bin-snowratio/sr_map_main.pl

 

this is the best site to try a calculation. i'm not sure the equation, but it's pretty interesting.

Using that site's equation for rdu, the gfs depicts a 56% chance of a greater than 15:1 ratio for most of the storm. that's with calm wind. If the wind is higher, it would be lower than that. My guess would be 12:1 - 14:1 for this storm in rdu. probably closer to 15-20:1 out in the foothills/mountains.