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January 28th Minor Icing Event

Isopycnic

By Isopycnic,
in Southeastern States

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Isopycnic

Isopycnic

Posted
Posted

post-130-0-93590300-1359293796_thumb.png

Area forecast discussion

National Weather Service Raleigh NC

645 am EST sun Jan 27 2013

Synopsis...

cold and dry high pressure will hold over the area today. An upper

level disturbance will pass northeastward through the region tonight

through Monday morning. The surface high will move off the coast

late Monday...followed by a warm southwest flow into the region

through midweek.

&&

Near term /today and tonight/...

as of 310 am Sunday...

{CUT}

For tonight..the main concern is evolving precipitation potential. The

midlevel ridge axis is prognosticated to set up over the southeast and will

initiate warm air advection across our area that will take place above the

shallow cooler near-surface layer. Models are generally depicting the

more significant synoptic scale lift and moisture transport occurring

to our north closer to a short wave trough that will be moving across the

Midwest region. The GFS is the most generous regarding quantitative precipitation forecast across

our area overnight...while other models keep most if not all of the

quantitative precipitation forecast north of the Virginia/NC state line. If light precipitation does materialize

across our County Warning Area later tonight...still think we have a decent chance

to see some light and brief frozen/freezing precipitation at the onset

given wet bulb cooling and lingering cold near-surface temperatures. Forecast

soundings for the overnight period depict the aforementioned gradual

warm air advection and moisture increase from the middle-levels down...yet there

remains plenty of dry air between 750-900 mb which results in wet

bulb temperatures below freezing for a signif layer below 850mb. If lift

was stronger and precipitation rates heavier...I wouldn't be surprised if

we even saw a quick p-type transition from S to ice pellets to freezing rain then rain

while the column saturates and warms. For now will keep low-end probability of precipitation

across our northern zones closer to The Triad and Virginia border

beginning after 3 am. While the precipitation risk still looks low...if it

indeed evolves...there will be a chance for a few localized slick

spots Monday morning at the onset...which would mainly impact

elevated surfaces and bridges...before temperatures rise above freezing after

sunrise. While confidence in precipitation occurring is too low at this time to

warrant any sort of advisories...will continue to mention in the severe weather potential statement

the potential for light freezing rain if precipitation does indeed evolve. Expect

lows from around 30 north to lower 30s south.

Aviation /12z Sunday through Wednesday/...

as of 645 am Saturday...

Latest NAM/GFS runs have come in with perhaps a little deeper

moisture overnight as middle level warm air advection and weak lift sets up across our

area...thus increasing the concern that some light frozen/freezing

precipitation may occur after 28/05z. While amounts are still prognosticated

to be very light...areas potentially impacted would be mainly across

the northern Piedmont and northern coastal plain and affecting

kint...kgso...krdu...and to a lesser extent krwi. Temperatures are expected

to rise above freezing after sunrise Monday morning with improving

conditions. Then expect MVFR or VFR conditions the rest of the

Monday.

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NavarreDon

NavarreDon

Posted
Posted

GSP's hwo:

 

HAZARDOUS WEATHER OUTLOOKNATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC456 AM EST SUN JAN 27 2013NCZ033-035>037-048>050-053-056-057-501>506-281000-AVERY-ALEXANDER-IREDELL-DAVIE-MADISON-YANCEY-MITCHELL-BUNCOMBE-CATAWBA-ROWAN-CALDWELL MOUNTAINS-GREATER CALDWELL-BURKE MOUNTAINS-GREATER BURKE-MCDOWELL MOUNTAINS-EASTERN MCDOWELL-456 AM EST SUN JAN 27 2013THIS HAZARDOUS WEATHER OUTLOOK IS FOR PIEDMONT NORTH CAROLINA ANDWESTERN NORTH CAROLINA..DAY ONE...TODAY AND TONIGHT.BRIEF FREEZING RAIN IS POSSIBLE ALONG AND NORTH OF INTERSTATE 40FROM THE PIEDMONT TO THE CENTRAL NORTH CAROLINA MOUNTAINS MONDAYMORNING. LIGHT ICE ACCUMULATIONS COULD RESULT IN PATCHY SLICKCONDITIONS ON BRIDGES AND OVERPASSES.
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calculus1

calculus1

Posted
Posted

GSP has just issued Freezing Rain Advisory along I-40 roughly from Marion to Statesville. Also includes Mitchell, Avery and Yancey Counties. Trace to a few hundredths possible.

 

Yep, here's the disco from the advisory:

 

.A WEAK UPPER LEVEL LOW WILL BRUSH WESTERN NORTH CAROLINA TONIGHT.THE LOW WILL SPREAD LIGHT RAIN ACROSS THE REGION...MAINLY OVER THENORTHERN MOUNTAINS AND THE FOOTHILLS AND PIEDMONT ALONG AND NORTHOF INTERSTATE 40. TEMPERATURES ARE EXPECTED TO FALL BELOW FREEZINGIN THESE AREAS DURING THE EVENING HOURS AND REMAIN A FEW DEGREESBELOW FREEZING OVERNIGHT. SLICK SPOTS ARE EXPECTED TO DEVELOPSHORTLY AFTER THE RAIN BEGINS...ESPECIALLY ON BRIDGES ANDOVERPASSES.
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calculus1

calculus1

Posted
Posted

Interesting disparity between the Blacksburg and GSP offices.  Apparently, Blacksburg sees no real threat near the NC/VA border counties, and yet GSP sees the threat for the northern tier of their forecast area.  This leaves a nice, gaping hole of counties between the two advisory areas that have no advisory at all.  Unless there is some trend in the precipitation forecast that would lead to a gap in totals, this non-advisory section seems odd.

 

I guess there could be different criteria for freezing rain advisories in different forecast areas, but I would think not.  Freezing rain generally has the same effects no matter where you live.

 

nU5X8Bm.png

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calculus1

calculus1

Posted
Posted

Now, we get the GSP afternoon disco and find out that they were working closely together with Blacksburg and Raleigh.  So, the Triad should expect the freezing rain advisory quite soon.  It looks to be a very light event, no more than 1/10 of an inch of precip.  But, that means we'll probably have some school delays in the morning.  The temps have remained quite cool today:  it's only 38 at my house currently, so we shouldn't have much problem getting below freezing once the sun goes down.

 

 

.NEAR TERM /THROUGH MONDAY/...TEMPERATURES HAVE REMAINED QUITE COOL THIS AFTERNOON ACROSS THENORTHERN NORTH CAROLINA FOOTHILLS...PIEDMONT AND NORTHERN MOUNTAINS.AFTER SUNSET THESE AREAS SHOULD HAVE A FEW HOURS OF GOOD RADIATIONALCOOLING CONDITIONS BEFORE DENSER CLOUD COVER WORKS OVER THE REGION.THE NAM AND GFS SFC WET BULBS FALL TO BELOW FREEZING ACROSS THE NRNTIER TONIGHT. THIS IS IMPORTANT AS BOTH THE SREF AND GFS ARE NOWINDICATING A LITTLE MORE PCPN ACROSS THE NRN ZONES OVERNIGHT. ITAPPEARS THAT SOME OF THIS PCPN WILL FALL IN THE FORM OF FREEZINGRAIN...AND THERE IS A GOOD CHANCE THAT SOME ICING WILL DEVELOPOVERNIGHT. THE RALEIGH AND BLACKSBURG FORECAST OFFICES ARE INAGREEMENT AND WE HAVE ARE ALL PLANNING TO ISSUE FREEZING RAINADVISORIES FOR OUR RESPECTIVE NRN NORTH CAROLINA COUNTIES. THELATEST REGIONAL RADAR COMPOSITES SHOW AN AREA OF RAIN MOVING ACROSSNRN TN AND WRN KY. THIS LINES UP WELL WITH THE SREF AND GFS...THOUGHTHE PCPN IS A LITTLE AHEAD OF SCHEDULE. ATTM THE PLAN IS TO HAVE THEADVISORY RUN FROM 9 PM THIS EVENING TO 9 AM MONDAY MORNING. I/M ONLYEXPECTING A FEW HUNDREDTHS TO PERHAPS A TENTH OF AN INCH OF LIQUIDPCPN IN THE ADVISORY AREA...SO TRAVEL DIFFICULTIES WILL BE THE MAINISSUE OF CONCERN.LLVL WARM ADVECTION WILL INCREASE OVER NE GA...THE SRN NC MTNS ANDUPSTATE SOUTH CAROLINA MONDAY MORNING. PATCHES OF LIGHT RAIN AREEXPECTED TO FORM OVER THE WEAK IN SITU COLD AIR DAMMING. THE NAM HASMORE MOISTURE OVER THE FOOTHILLS AND PIEDMONT THAN THE GFS...THOUGHTHE HIGH SREF POPS INDICATE THAT MOST OF THE WRF MEMBERS DEVELOPPCPN OVER THE WEDGE ON MONDAY. THEREFORE I/D EXPECT MAX TEMPS TO RUNSEVERAL DEGREES COOLER THAN THE MAV GUIDANCE...AND A LITTLE COOLERTHAN THAT MET. ATTM I/VE CARRIED CHANCE POPS OVER THE THE SOUTHWESTPART OF THE FA...WHICH IS A BLEND OF THE WETTER SREF/NAM AND THEDRIER GFS.
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gritsnc

gritsnc

Posted
Posted

More counties just got included in the Freezing Rain Advisory...

 

URGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE RALEIGH NC307 PM EST SUN JAN 27 2013...VERY LIGHT AND PATCHY FREEZING RAIN OVER THE NORTHERN PIEDMONTTONIGHT INTO EARLY MONDAY MORNING....PATCHES OF LIGHT FREEZING RAIN IS EXPECTED TO PRODUCE SPOTTY ICYAREAS ON ROADWAYS TONIGHT AND EARLY MONDAY MORNING... PRIMARILY ONBRIDGES AND OVERPASSES.NCZ007>010-021>026-038>041-280430-/O.NEW.KRAH.ZR.Y.0001.130128T0200Z-130128T1400Z/PERSON-GRANVILLE-VANCE-WARREN-FORSYTH-GUILFORD-ALAMANCE-ORANGE-DURHAM-FRANKLIN-DAVIDSON-RANDOLPH-CHATHAM-WAKE-INCLUDING THE CITIES OF...ROXBORO...OXFORD...HENDERSON...WARRENTON...WINSTON-SALEM...GREENSBORO...HIGH POINT...BURLINGTON...CHAPEL HILL...DURHAM...LOUISBURG...LEXINGTON...ASHEBORO...PITTSBORO...RALEIGH307 PM EST SUN JAN 27 2013...FREEZING RAIN ADVISORY IN EFFECT FROM 9 PM THIS EVENING TO9 AM EST MONDAY...THE NATIONAL WEATHER SERVICE IN RALEIGH HAS ISSUED A FREEZINGRAIN ADVISORY...WHICH IS IN EFFECT FROM 9 PM THIS EVENING TO 9 AMEST MONDAY.* LOCATIONS...THE NORTHERN PIEDMONT OF CENTRAL NORTH CAROLINA...  ALONG AND NORTHWEST OF A LINE FROM HIGH ROCK LAKE TO ASHEBORO TO  NORTH RALEIGH TO WARRENTON.* HAZARD TYPES...PATCHES OF LIGHT FREEZING RAIN WILL SPREAD OVER  THE ADVISORY AREA FROM MID EVENING THROUGH TONIGHT... THEN EXIT  SOON AFTER DAYBREAK MONDAY.* ICE ACCUMULATIONS...A SPOTTY...VERY LIGHT...THIN GLAZE OF ICE IS  EXPECTED TO FORM TONIGHT... PRIMARILY ON ELEVATED SURFACES...  BRIDGES... AND OVERPASSES.* TIMING...FROM 9 PM TONIGHT UNTIL 9 AM MONDAY MORNING.* IMPACTS...SPOTTY ICING ON ROADS... MAINLY BRIDGES AND  OVERPASSES... WILL BRING SOME TRAVEL PROBLEMS OVERNIGHT THROUGH  DAYBREAK MONDAY.* TEMPERATURES...READINGS WILL DROP BACK BELOW FREEZING THIS  EVENING. TEMPERATURES WILL REBOUND ABOVE FREEZING MONDAY  MORNING... INTO THE MID 30S BY 10 AM.PRECAUTIONARY/PREPAREDNESS ACTIONS...A FREEZING RAIN ADVISORY MEANS THAT PERIODS OF FREEZING RAIN ORFREEZING DRIZZLE WILL CAUSE TRAVEL DIFFICULTIES. BE PREPARED FORSLIPPERY ROADS. SLOW DOWN AND USE CAUTION WHILE DRIVING. AVOIDSUDDEN BRAKING... ESPECIALLY ON BRIDGES AND OVERPASSES.
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jburns

jburns

Posted
Posted

The latest 18Z Hi-Res NAM is not nearly as bullish on precipitation in NC as were previous runs.  The simulated radar images for overnight look like widely scattered showers/pockets of rain/drizzle.  We'll see how it all plays out...

 

http://raleighwx.americanwx.com/models/nam4km/18zNAM4kmreflectivity_SE.html

Driving wise that can be worse than widespread precip, especially with spotty freezing rain. If it's widespread everyone slows down. Lots of accidents but few injuries.  With the kind of event forecasted you can be driving along at full speed on clear roads and suddenly hit a bridge that has a thin coat of ice, or a curve in an area that was shaded in the afternoon, and all of a sudden your heading into a full speed crash.  

 

Edited to add: Chaos!

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jburns

jburns

Posted
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I'm hedging schools will have to close tomorrow. If you go on a 2 hour delay a lot of buses would have to start routes before 8:00. Never heard of 3 hour delay, even then you will have buses out before 9:00 a.m. The roads are cold. It got to 39 out here today and the creek still has ice in it.

I've heard of a 3 hour cruise.  It didn't turn out well.

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POWERSTROKE

POWERSTROKE

Posted
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I'm hedging schools will have to close tomorrow. If you go on a 2 hour delay a lot of buses would have to start routes before 8:00. Never heard of 3 hour delay, even then you will have buses out before 9:00 a.m. The roads are cold. It got to 39 out here today and the creek still has ice in it.

Winston salem has had a three hour delay before

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CLTwx

CLTwx

Posted
Posted

Im 46/27 in Midtown, Charlotte. Interesting the NAM shows showers all the way to the Southern Piedmont of NC?

 

Weather Stationhttp://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KNCCHARL48

What's yall's current temps? 39.7 DP 27 and cloudy... I'm not sure I'll even get to freezing tonight with it already cloudy? I expect a slow drop in temps!

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gritsnc

gritsnc

Posted
Posted

WSFCS has done 3 hour delays before. In fact when I was a kid, I remember going to school at noon and staying till 5pm. They did that because we had missed so many days already and that way we got there after the stuff started to melt and were out before it started to freeze up again. We also had to go 2 Saturdays that year. I wish I knew what year that was. I was in elementary school.

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POWERSTROKE

POWERSTROKE

Posted
Posted

WSFCS has done 3 hour delays before. In fact when I was a kid, I remember going to school at noon and staying till 5pm. They did that because we had missed so many days already and that way we got there after the stuff started to melt and were out before it started to freeze up again. We also had to go 2 Saturdays that year. I wish I knew what year that was. I was in elementary school.

You must have graduated in 1991. We were the first to go on saturday. I would imagine its going to be a close call in morning even though it shouldnt last long

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