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Surprise Ice Event across the CAD areas of NC/SC?


BullCityWx

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The 12z NAM came in with a very icy solution across the NC and SC Foothills and Piedmont areas. 

 

Things in favor of this event: 

 

relatively light precip amounts(.10-.15) thus limiting any quick warmup as precip falls

very cold ground temps(close to freezing across most of NC west of 77)

very cold antecedent airmass

cloudcover rolled in early to potentially keep temperatures down

event occurs with the sun down

 

Things not in favor of this event: 

No parent high to reinforce cold air

Southerly Flow

Freezing Rain is a self limiting process in most cases

 

Thoughts?

 

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AS OF 645 AM...OF NOTE...THE 06Z NAM (WHICH IS INITIALIZING THE

CLOUD DECK FAIRLY WELL)...HAS COME IN MUCH WETTER AND COLDER FOR

LATER TODAY AND TONIGHT. I TWEAKED POPS UP FOR LATE

AFTN/EVENING...SINCE THE CAMPOP SUPPORTS THE NAM. AS FOR OVERNIGHT

FREEZING RAIN POTENTIAL...I/M STILL SKEPTICAL OF THE NAM...BUT THE

SITUATION BEARS WATCHING.

GSP agrees with your assessment.

http://www.erh.noaa.gov/gsp/PRODUCTS/afd.php

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Ever the eternal optimist, even though the odds of anything down my way are near zero, I can't help but notice the rather large area of clearing moving up from S Ga.  Just for kicks, I'll watch with interest to see if after a solid cloud deck all day, if a few hours of fair skies this evening rolls in and puts me in the game. 

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Not much of a surprise the NWS has been on top of it. A day or two ago they said possible freezing rain advisories in the AFD's. I think they follow the WPC guidance and they have been showing ice probs for days now. Highest in the NC foothills.

The simulated radar shows moisture going from barely GSP through Charlotte then NE . Looks like it misses most of NC foothills

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You might wonder what the big deal is with a tenth of an inch of QPF that's ice but if that verifies, there could be serious travel impacts across the region.

One thing that will make this a little more of a big deal is the cold ground. Without sunshine today, the roads will not have a chance to warm all that much. Combine that with an early am time frame and you have more of an event than the total precip numbers would indicate. Going to be interesting to watch this unfold.

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You might wonder what the big deal is with a tenth of an inch of QPF that's ice but if that verifies, there could be serious travel impacts across the region.

Have sort of been keeping an eye on tonight as this set up has been known to generate a little ice. While the lack of good qpf is keeping optimism tempered you are so right. As cold as it has been even freezing drizzle could cause driving issues. A couple of dec ago there was like maybe .05 frz drizzle not forecasted and there were more wrecks than with snow. Will be interesting to see how things play out.

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The simulated radar shows moisture going from barely GSP through Charlotte then NE . Looks like it misses most of NC foothills

 

Looking at the NAM/EURO the cutoff line will be in the mountains. GFS is being discounted too far east according to NWS Raleigh. Temp profiles also best the further west. Simulated radar probably not picking up on the upslope.

 

Revised temperatures have implications for ptype overnight. With the deck

appearing more solid than suggested by earlier models and holding

temperatures a few degrees warmer...freezing rain looks to be restricted to a

smaller area...mainly the NC foothills. Not yet having full 12z

guidance suite...I declined to make changes to quantitative precipitation forecast or ice accums at

this time. There is still the question of how much cloud cover

really survives the day and how much temperatures are affected this evening

by this...as well as by any evaporational cooling at onset of rain.

Thus I will do some more investigation before proceeding with any

advisory. 

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HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
417 AM EST SAT JAN 4 2014

NCZ007-021>024-038-039-050930-
PERSON-FORSYTH-GUILFORD-ALAMANCE-ORANGE-DAVIDSON-RANDOLPH-
417 AM EST SAT JAN 4 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

A BRIEF PERIOD OF LIGHT FREEZING RAIN OR FREEZING DRIZZLE WILL BE
POSSIBLE ACROSS PORTIONS OF THE TRIAD AND THE FAR NORTHERN
PIEDMONT DURING THE PRE-DAWN HOURS SUNDAY MORNING.

BITTERLY COLD TEMPERATURES AND STRONG WINDS LATE MONDAY INTO
TUESDAY WILL POTENTIALLY BRING LIFE THREATENING WIND CHILLS
TO THE AREA. LOWS MONDAY NIGHT ARE EXPECTED TO BOTTOM OUT BETWEEN
5 AND 10 DEGREES. HIGHS TUESDAY WILL ONLY BE IN THE LOWER 20S.
WIND CHILL VALUES BETWEEN 7 BELOW ZERO AND ZERO ARE EXPECTED
BETWEEN 200 AM AND NOON TUESDAY.

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This is a couple of hours old, but GSP has their eyes open now.

 

1215 PM UPDATE...STRATUS HAVING A HARD TIME PUSHING INTO THE  
MTNS...A FACT SUGGESTED BY SOME EARLIER GUIDANCE. HOWEVER MOIST  
LAYER SHOULD BECOME SUFFICIENTLY DEEP FOR SOME CLOUDS TO OVERRUN THE  
HIGHER TERRAIN. TEMPS HAVE GENERALLY WARMED ABOVE FREEZING IN THE  
CLEAR AREA...WITH ANOTHER HOUR OR TWO OF PARTIAL SUNSHINE LIKELY TO  
RAISE THEM FURTHER. TEMPS WILL REMAIN NEAR FREEZING UNDER THE CLOUD  
DECK THRU THE AFTN. WILL TAKE VERY CLOSE LOOK AT OVERNIGHT TEMPS AS  
WELL AS QPF FOR AFTN PACKAGE.

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Looking at the NAM/EURO the cutoff line will be in the mountains. GFS is being discounted too far east according to NWS Raleigh. Temp profiles also best the further west. Simulated radar probably not picking up on the upslope.

 

Revised temperatures have implications for ptype overnight. With the deck

appearing more solid than suggested by earlier models and holding

temperatures a few degrees warmer...freezing rain looks to be restricted to a

smaller area...mainly the NC foothills. Not yet having full 12z

guidance suite...I declined to make changes to quantitative precipitation forecast or ice accums at

this time. There is still the question of how much cloud cover

really survives the day and how much temperatures are affected this evening

by this...as well as by any evaporational cooling at onset of rain.

Thus I will do some more investigation before proceeding with any

advisory. 

Our dew point is 10 degrees. and a surface temp of 35. Current WB is roughly 26.7 degrees. Don't know if enough precip will fall to saturate the atmosphere, but if it does we will surely have freezing rain here. That is, unless dewpoints rise and the temps remain constant.

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Ever the eternal optimist, even though the odds of anything down my way are near zero, I can't help but notice the rather large area of clearing moving up from S Ga.  Just for kicks, I'll watch with interest to see if after a solid cloud deck all day, if a few hours of fair skies this evening rolls in and puts me in the game. 

You are as much "in the game" as anyone else. Temps and dewpoints are pretty much  the same everywhere and tonights temps will be fairly uniform as well. Even if you get some clear skies and the temperature dropped, as soon it clouds back over your temp would go back up.

 

In fact, even though right now it's pretty cold and dry at the surface after looking at it more closely, it's so warm aloft and close to the ground,  I'm thinking now it might not  do anything at all except for areas north of 85, the upstate, and western nc but even there 950mb temps are 4 or 5c, even in charlotte.   Normally if temps are as warm as they are so close to the surface, it will be just a cold rain even though temps/dewpoints initially support freezing rain since the cold is so shallow. But since the precip is so light, maybe it will give it a chance because if it's heavier at all, warmer temps aloft would quickly mix out or warm any subfreezing layer I would think. Will be interesting to see how it plays out.

 

 

Temp now is 35 with a dp of 18. That's up from 12 earlier. Temp has been more or less steady the last 2 hours. So I might hit 36 today with some other places, like gainesville, maybe not getting above 34...they are still 33.  FFC was forecasting 44 today last night and as late as this morning 42 so a decent size bust in temps it would appear.

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You are as much "in the game" as anyone else. Temps and dewpoints are pretty much the same everywhere and tonights temps will be fairly uniform as well. Even if you get some clear skies and the temperature dropped, as soon it clouds back over your temp would go back up.

In fact, even though right now it's pretty cold and dry at the surface after looking at it more closely, it's so warm aloft and close to the ground, I'm thinking now it might not do anything at all except for areas north of 85, the upstate, and western nc but even there 950mb temps are 4 or 5c, even in charlotte. Normally if temps are as warm as they are so close to the surface, it will be just a cold rain even though temps/dewpoints initially support freezing rain since the cold is so shallow. But since the precip is so light, maybe it will give it a chance because if it's heavier at all, warmer temps aloft would quickly mix out or warm any subfreezing layer I would think. Will be interesting to see how it plays out.

Temp now is 35 with a dp of 18. That's up from 12 earlier. Temp has been more or less steady the last 2 hours. So I might hit 36 today with some other places, like gainesville, maybe not getting above 34...they are still 33. FFC was forecasting 44 today last night and as late as this morning 42 so a decent size bust in temps it would appear.

to your point its 39 here at 2500 feet. Of course we have had sunshine all day too.

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