• Hello, please take a minute to check out our awesome content, contributed by the wonderful members of our community. We hope you'll add your own thoughts and opinions by making a free account!

Freezing Rain, Sleet, Snow, Rain...Kitchen Sink (12/15-16)

Myfrotho704_ said:
Is this even surprising ?! View attachment 57389
Click to expand...

Lol nope, and many wonder why I've been so gung-ho, seen this happen more times than I can count during CAD/Miller B events.

Keep in mind that we still have another 3 days to go for this to keep trending colder/drier prior to onset (which often happens).
 
Last edited:
I don’t understand how the EPS is going away from a look yet the GEPS/GEFS are trending favorable for winter weather DE1D4935-1920-4BA8-9DD7-E8C876F0D9A4.gif122FD23E-D9F8-45F0-A2DD-3718EC571710.gif
 
Here was the 00z UKMET. Temps look like low to mid 30’s across western NC.
8CA52601-3EF4-4724-BD21-0CBF155BA80B.jpeg432BFEB7-5474-4D07-8C93-02D5163B5147.jpegF4728ED5-706C-41D6-96BD-35C1A53CD2BA.jpeg
Here’s two 6-hour intervals of precipitation
3A25E4FA-F623-45A5-8AAD-6EFD1B308AE8.jpegE430DEED-EECB-49EB-BD0A-7494055A0CA7.jpeg
 
Last edited:
Really cool study from Sanders & Barjenbruch (2016) wrt ice liquid ratios that's worth reading imo.

https://journals.ametsoc.org/view/journals/wefo/31/4/waf-d-15-0118_1.xml?tab_body=fulltext-display


For ice radial accumulations, which are the standard for measuring freezing rain accumulation, they found that for every inch of radial ice accrual about 3-4" of liquid equivalent is measured (via ASOS).

1607849076612.png




Thus, when you see maps like this, especially when there's a ton of QPF, it's usually a good idea to take ~25-33% of these 1:1 QPF-ice accumulations.

1607849422590.png


Pivotalweather also now has an option for those w/ a subscription where you can select for the Freezing Rain Accumulation Model (FRAM) accumulations described in the aforementioned study & these are considerably more reliable than 1:1 QPF-ice accum model output. The FRAM model uses regression on modeled precipitation rate, wet bulb temperature, and wind speed to estimate ice accrual. It's certainly better than using straight 1:1 QPF-ice output, but I would still urge caution in using a product like this.

1607849529918.png
 
06z NAM looking more like the Euro? Warmer less QPF! I think? I certainly could be wrong.


Sent from my iPhone using Tapatalk
449be786f14c5b1edbf17d2083da31e7.png
 
Myfrotho704_ said:
More confluence, and definitely a way less amped trend, which is toward the GFS rather than the euro, it’ll be interesting to see what they do later View attachment 57450
Click to expand...
I like the meso high it has over the NY/PA border should help to reinforce the cold push
87F4568E-5CC3-44A3-9978-8EAAE9C60106.jpeg
 
Myfrotho704_ said:
Just a tad bit, more so in SC however, but it does switch it over to rain
Click to expand...

I bet we see the cold models begin a warming trend today, so they can fall inline with the KING! Not a good sign, IF you want a winter storm. If it was just 12-48 hours out I would not put as much emphasis on the Euro, short range models will do better then (But that’s what they’re job is)! But I’m just a babbling Snowman what do I know? Lol I know a lot of people don’t want an ice storm, but me personally I would like to see a decent Ice storm haven’t had one in a long time.


Sent from my iPhone using Tapatalk
 
Webberweather53 said:
Really cool study from Sanders & Barjenbruch (2016) wrt ice liquid ratios that's worth reading imo.

https://journals.ametsoc.org/view/journals/wefo/31/4/waf-d-15-0118_1.xml?tab_body=fulltext-display


For ice radial accumulations, which are the standard for measuring freezing rain accumulation, they found that for every inch of radial ice accrual about 3-4" of liquid equivalent is measured (via ASOS).

View attachment 57443




Thus, when you see maps like this, especially when there's a ton of QPF, it's usually a good idea to take ~25-33% of these 1:1 QPF-ice accumulations.

View attachment 57444


Pivotalweather also now has an option for those w/ a subscription where you can select for the Freezing Rain Accumulation Model (FRAM) accumulations described in the aforementioned study & these are considerably more reliable than 1:1 QPF-ice accum model output. The FRAM model uses regression on modeled precipitation rate, wet bulb temperature, and wind speed to estimate ice accrual. It's certainly better than using straight 1:1 QPF-ice output, but I would still urge caution in using a product like this.

View attachment 57445
Click to expand...

I knew it was a lot less than 1:1, but thought it was on average roughly about 1" of radial ice to 2" of QPF. So. it is more like 1" of ice to 3-4" of qpf on average?

One thing I noticed with ATKL ice storms was that the ice tends to accrue more when both the winds were lighter (maybe because higher winds blow more of the dripping rain off the branches before it can freeze?) and the rainfall rate was lighter (maybe because heavier rain has an easier time to drip off the branches because it takes longer to freeze?). Also, I assume the colder the temp, the more it will accrue. So, there are a lot of variables including these 3 meaning it wouldn't surprise me if you really could have 1:2 accrural rate if, say, the rainfall rate is low, the winds are light, and the temps are 30 or lower instead of 31-32.
 
First Call. Up to 6 hour event of wintery weather for most then up to 8 to 10 hours Mount Airy NC northward. Starts as sleet (even snow for the northern foothills out to Winston Salem). Most see light glaze but 0.1 to 0.25 ice along and west of i77 and mostly north of i40. Snow up to an inch or more over the mtns and maybe half inch over parts of the foothills mixed with sleet. Little accumulations of sleet may sneak east out to Greensboro and Statesville line. Mostly cold rain Charlotte to Raleigh. A few counties of South Carolina and Georgia (extreme) will start as sleet or flake then go to a light glaze of ice.
 
GaWx said:
I knew it was a lot less than 1:1, but thought it was on average roughly about 1" of radial ice to 2" of QPF. So. it is more like 1" of ice to 3-4" of qpf on average?

One thing I noticed with ATKL ice storms was that the ice tends to accrue more when both the winds were lighter (maybe because higher winds blow more of the dripping rain off the branches before it can freeze?) and the rainfall rate was lighter (maybe because heavier rain has an easier time to drip off the branches because it takes longer to freeze?). Also, I assume the colder the temp, the more it will accrue. So, there are a lot of variables including these 3 meaning it wouldn't surprise me if you really could have 1:2 accrural rate if, say, the rainfall rate is low, the winds are light, and the temps are 30 or lower instead of 31-32.
Click to expand...

Yes, it's more like 1" Radial ZR:3-4" QPF according to this study. Stronger winds actually enhance ice accrual efficiency because it increases the rate of evaporative cooling, the rate of sensible heat transfer from cooler surrounding air to slightly warmer adjacent air near a freezing object that's undergoing latent heating & stronger winds increase a horizontal cross section's mass flux (of ice), all serving to increase ice accumulation efficiency at higher wind speeds. The effect is pretty small until wind speeds begin to approach exceed 10-15 knots.

"It is inferred that the increasing wind speed replaces air near the ice surface warmed by latent heat release, alters the droplet collision efficiency, increases the horizontal mass flux, and promotes evaporational cooling. Although, the data show that these processes are not as noticeable in the ILRs until wind speed reaches >15 kt, and may rely on the thermodynamic environment as well. Wind gusts had a similar influence on ILR with an increasing trend in ILR as wind gusts increased."

1607859861078.png


As for surface temperatures, your intuition is correct in that there's a strong temperature dependency, with wet bulb temperatures above -1C (~30F) experiencing significantly lower ice liquid ratios (ILRs) than those with temperatures between -4 to -1C. The relationship reverses and lower ILRs are observed for temps lower than about -4C (~25F), as the low-mid levels usually become more supportive of sleet instead of freezing rain, in environments where the surface temperatures are this cold or colder.

1607860417565.png



They also found rather unsurprisingly, that ice accumulation efficiency is dependent on precipitation rate with the largest changes in ILRs between rain equivalent rates of a few hundredths to a tenth or so per hour, with it asymptoting towards ILRs of about 1:7.5 or so in heavy precipitation.

1607860524833.png
 
GSP AFD


LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

AS OF 330 AM SUNDAY...AN UPPER TROUGH WILL QUICKLY TRACK
EAST FROM THE MIDWEST TO THE CENTRAL APPALACHIANS TUESDAY
NIGHT-WEDNESDAY, PROVIDING STRONG UPPER SUPPORT FOR A MILLER-B
TYPE LOW DEVELOPMENT. MEANWHILE, AN ~1035 MB SFC HIGH WILL BE
OVER SOUTHERN QUEBEC, MAKING FOR A CLASSICAL CAD WEDGE TO SET UP
OVER THE AREA BY TUESDAY NIGHT. THE MODELS ARE IN GOOD AGREEMENT
ON THIS SYSTEM CONSIDERING IT'S STILL DAY 4, SHOWING CYCLOGENESIS
JUST OFF THE CAROLINA COAST. THE PARENT MIDWEST LOW WILL TAP INTO
ENOUGH MOISTURE TO SPREAD LIGHT PRECIP ATOP THE WEDGE LATE TUESDAY
NIGHT. THIS SHOULD HELP LOCK IN SOME SUB-FREEZING TEMPS ACROSS THE
NC MOUNTAINS AND OUT ACROSS THE NC FOOTHILLS AND NW PIEDMONT BY
DAYBREAK WEDNESDAY. AREAS TO THE SOUTH ARE MORE MARGINAL, AND LOOK
TO REMAIN JUST ABOVE FREEZING. MODELS ARE ALSO IN GOOD AGREEMENT
ON THE LOW-LEVEL THICKNESSES AND PROFILES SHOWING A WARM NOSE
QUICKLY PUNCHING TOWARD THE N/NW TO THE NORTHERN MOUNTAINS BY 12Z
WED THANKS TO STRONG WAA. SO CONFIDENCE IS INCREASING ON A MIXED
BAG OF -S/PL/FRZA FOR MUCH OF THE HIGH TERRAIN AND OUT ACROSS THE
I-40 CORRIDOR EAST OF THE MOUNTAINS. HOW QUICKLY THINGS TRANSITION
TO ALL RAIN WITH POCKETS OF FRZA WEDNESDAY MORNING IS STILL UP
IN THE AIR. THE MODELS ARE LIKELY A BIT TOO FAST WARMING THE SFC
TEMPS ALONG THE ESCARPMENT DUE TO THE STRONG CAD. BUT AS THE LOW
RAPIDLY DEEPENS ALONG THE MID-ATLANTIC COAST, LOW-LEVEL FLOW WILL
TURN OUT OF THE WEST THEN NORTHWEST, AND THE CAD SHOULD ERODE. ALL
THIS TO SAY, THAT IT WILL BE A MESS P-TYPE-WISE. ONE CONCERN IS THAT
MODELS CONTINUE TO TREND UP WITH QPF, AND WE COULD SEE ENOUGH FOR
POCKETS OF 0.25" LIQUID EQUIVALENT OF WINTRY ACCUMS, WHICH COULD
RESULT IN IMPACTS APPROACHING WINTER STORM WARNING CRITERIA. STILL,
THE MOST LIKELY SCENARIO LOOKS TO BE ADVISORY-LEVEL ICE/SLEET/SNOW
ACCUMS, WITH SOME HAZARDOUS ROAD CONDITIONS WEDNESDAY MORNING,
HOPEFULLY IMPROVING BY THE AFTN. THE I-85 CORRIDOR WILL LIKELY
SEE ALL RAIN. WILL CONTINUE TO HIGHLIGHT THIS EVENT IN THE HWO.

BROAD HIGH PRES BUILDS IN QUICKLY WED NIGHT AND DOMINATES OUR
WEATHER THRU THE END OF THE WORK WEEK. TEMPS WILL BE HELD A FEW DEG
BELOW NORMAL. THE NEXT CHANCE FOR PRECIP LOOKS TO BE NEXT WEEKEND,
BUT THE MEDIUM RANGE GUIDANCE HAS BEEN TRENDING SLOWER. TOO MUCH
UNCERTAINTY ON WHETHER ANY OF THAT WILL BE WINTRY IN NATURE.
 
If you sleep in past 8am you may miss any glaze from Charlotte to Raleigh. This is largely gonna be a cold rain in bigger cities..with all the action in the north and west (Hickory, Yadkinville, Greensboro).
 
You must log in or register to reply here.
Back
Top