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The Big One - Forecast & Discussion II


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MESOSCALE DISCUSSION 0090
NWS STORM PREDICTION CENTER NORMAN OK
1013 AM CST WED FEB 12 2014

AREAS AFFECTED...NC

CONCERNING...WINTER MIXED PRECIPITATION

VALID 121613Z - 122215Z

SUMMARY...FREEZING RAIN AND SLEET ARE EXPECTED TO DEVELOP ACROSS
PARTS OF ERN NC LATE THIS MORNING. ICE ACCUMULATIONS SHOULD INCREASE
TO 0.10 TO 0.15 OF AN INCH PER HOUR IN SOME AREAS AS PRECIPITATION
SPREADS NWD THROUGH EARLY AFTERNOON. MODERATE TO HEAVY SNOW IS
FORECAST TO DEVELOP ACROSS NCNTRL AND WRN NC THIS AFTERNOON WHERE
SNOWFALL RATES SHOULD INCREASE TO 1 INCH PER HOUR WITH LOCALLY
HIGHER RATES POSSIBLE.


DISCUSSION...THE LATEST WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL
TROUGH EXTENDING SWD FROM THE ARKLATEX INTO THE WRN GULF OF MEXICO.
A LEAD SHORTWAVE TROUGH IS MOVING ENEWD ACROSS THE SRN APPALACHIAN
MTNS EXTENDING SWD INTO THE FL PANHANDLE WITH WIDESPREAD
PRECIPITATION LOCATED JUST AHEAD OF THE TROUGH. LIFT IS BEING
ENHANCED BY STRONG WARM ADVECTION ASSOCIATED WITH A 40 TO 55 KT LOW
TO MID-LEVEL JET IN ERN GA AND SC. THIS FEATURE IS FORECAST TO MOVE
NWD INTO NC EARLY THIS AFTERNOON WHICH WILL RESULT IN A NWD
EXPANSION OF MODERATE SNOW FROM THE WINSTON-SALEM EWD TO THE
VICINITY OF RALEIGH/DURHAM EARLY THIS AFTERNOON. HEAVY SNOW IS
EXPECTED BY EARLY TO MID-AFTERNOON WITH 1 INCH PER HOUR RATES WITH
LOCALLY HIGHER RATES POSSIBLE.


FURTHER TO THE EAST...SFC TEMPS ARE GENERALLY BELOW FREEZING FROM
WILMINGTON NWD TO GREENVILLE. FORECAST SOUNDINGS ALONG THIS CORRIDOR
SHOW A WARM LAYER NEAR 850 MB WHICH SHOULD KEEP PRECIPITATION IN THE
FORM OF FREEZING RAIN AND SLEET. FREEZING RAIN RATES OF 0.10 TO 0.15
OF AN INCH PER HOUR ARE EXPECTED EARLY THIS AFTERNOON. LATER THIS
AFTERNOON...SFC TEMPS NEAR THE COAST ARE EXPECTED TO RISE ABOVE
FREEZING RESULTING IN A CHANGEOVER TO RAIN.

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1124 AM EST WED FEB 12 2014

.SYNOPSIS...
A MAJOR WINTER STORM WILL DEVELOP AS A LOW MOVES FROM THE FLORIDA
PANHANDLE TODAY AND RAPIDLY STRENGTHENS UPON REACHING THE EASTERN
CAROLINAS TONIGHT. THE LOW WILL TRACK NORTHEAST TO THE NEW ENGLAND
COAST BY LATE THURSDAY NIGHT. A FEW WEAK SYSTEMS WILL AFFECT OUR
WEATHER INTO THE FIRST HALF OF NEXT WEEK WITH WARMER TEMPERATURES.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1120 AM...NE GA AND THE WESTERN CAROLINAS WILL SEE HEAVY
SNOWFALL RATES DEVELOP THIS AFTERNOON AND REMAIN THROUGH THIS EVENING.

THE LATEST SFC ANALYSIS SHOWS A WELL DEFINED COLD AIR DAMMING ACROSS
THE WESTERN CAROLINAS AND NE GA...SOURCED FROM HIGH PRESSURE
CENTERED OVER NEW ENGLAND. SFC LOW PRESSURE WAS ANALYZED NEAR THE
PANHANDLE OF FL. INITIAL SNOW FROM MORNING JET DIVERGENCE HAS
PRODUCED 1 INCH ACROSS THE I-85 CORRIDOR TO OVER 5 INCHES AT
GREENWOOD. RECENT IR SATELLITE IMAGES INDICATE ANOTHER ROUND OF
COOLING CLOUD TOPS ACROSS NRN GA AND THE WESTERN CAROLINAS. 12Z NAM
INDICATES THAT STRONG ISENTROPIC LIFT WILL RAPIDLY SPREAD
NORTH...REACHING THE NORTHERN ZONES BY 18Z. THE LIFT WILL COMBINE
WITH A POOL OF HIGH PW...SHOWN ON THE BLENDED PW...PRODUCING A
SHIELD OF MODERATE TO HEAVY SNOW LIFTING SOUTH TO NORTH. IN
ADDITION...SEVERAL BANDS OF -EPV WILL RIPPLE ACROSS THE REGION THIS
AFTERNOON...FAVORING THE FORMATION OF MESOSCALE SNOW BANDS. A LARGE
FIELD OF MID LEVEL Q-VECTOR CONVERGENCE WILL ARRIVE THIS AFTERNOON
AND INCREASE THROUGH MOST OF TONIGHT. THE OVERLAP OF LLVL AND MID
LEVEL FORCING SHOULD RESULT IN THE GREATEST SNOWFALL THIS AFTERNOON
THROUGH THIS EVENING.


PRECIP TYPE IS COMPLICATED BY SUSPECT ABSENCE OF ICE NUCLEI THIS
AFTERNOON AND EVENING. GIVEN THE TREMENDOUS MOISTURE AND OVERALL COLD
LLVL CONDITIONS ACROSS THE WESTERN CAROLINAS...I BELIEVE THAT ICE
NUCLEI WILL BE PRESENT. HOWEVER...DOPPLER VELOCITY AND DUAL POL AGREE
WITH FORECAST SOUNDINGS WITH DEVELOPING A H85 WARM NOSE OVER THE
EASTERN PIEDMONT. THE WARMING ALONG THE EASTERN TIER WILL CONTINUE
THROUGH MIDNIGHT...YIELDING A BLEND OF SLEET AND FZRA.

THE WINTER STORM WARNING REMAINS ON TRACK. I WILL UPDATE TO ADJUST
ACCUMS TO ACCOUNT FOR THE OVERLAP OF DEEP MOISTURE...SYNOPTIC
FORCING...AND POTENTIAL BANDING.

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Burger I know you mentioned that the RAP changed AVL to FZRA around 12 hours.  The maps I have show AVL solidly within the 850 freezing line and the 925 freezing line.  What am I looking at wrong?

 

I was being loose with the AVL area and timing. Sorry about that. here is what I have for hour 15 and it expands west from there. 850's start backing off on both the HRRR and RAP by hour 12.  

NqDnwlv.png

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GSP fully onboard for moderate/heavy snow this afternoon:

 

AS OF 1120 AM...NE GA AND THE WESTERN CAROLINAS WILL SEE HEAVY
SNOWFALL RATES DEVELOP THIS AFTERNOON AND REMAIN THROUGH THIS EVENING.

THE LATEST SFC ANALYSIS SHOWS A WELL DEFINED COLD AIR DAMMING ACROSS
THE WESTERN CAROLINAS AND NE GA...SOURCED FROM HIGH PRESSURE
CENTERED OVER NEW ENGLAND. SFC LOW PRESSURE WAS ANALYZED NEAR THE
PANHANDLE OF FL. INITIAL SNOW FROM MORNING JET DIVERGENCE HAS
PRODUCED 1 INCH ACROSS THE I-85 CORRIDOR TO OVER 5 INCHES AT
GREENWOOD. RECENT IR SATELLITE IMAGES INDICATE ANOTHER ROUND OF
COOLING CLOUD TOPS ACROSS NRN GA AND THE WESTERN CAROLINAS. 12Z NAM
INDICATES THAT STRONG ISENTROPIC LIFT WILL RAPIDLY SPREAD
NORTH...REACHING THE NORTHERN ZONES BY 18Z. THE LIFT WILL COMBINE
WITH A POOL OF HIGH PW...SHOWN ON THE BLENDED PW...PRODUCING A
SHIELD OF MODERATE TO HEAVY SNOW LIFTING SOUTH TO NORTH. IN
ADDITION...SEVERAL BANDS OF -EPV WILL RIPPLE ACROSS THE REGION THIS
AFTERNOON...FAVORING THE FORMATION OF MESOSCALE SNOW BANDS. A LARGE
FIELD OF MID LEVEL Q-VECTOR CONVERGENCE WILL ARRIVE THIS AFTERNOON
AND INCREASE THROUGH MOST OF TONIGHT. THE OVERLAP OF LLVL AND MID
LEVEL FORCING SHOULD RESULT IN THE GREATEST SNOWFALL THIS AFTERNOON
THROUGH THIS EVENING.

 
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Phil..the time you are giving us on this storm is awesome. Karma will swing back.

 

GSP fully onboard for moderate/heavy snow this afternoon:

 

AS OF 1120 AM...NE GA AND THE WESTERN CAROLINAS WILL SEE HEAVY

SNOWFALL RATES DEVELOP THIS AFTERNOON AND REMAIN THROUGH THIS EVENING.

THE LATEST SFC ANALYSIS SHOWS A WELL DEFINED COLD AIR DAMMING ACROSS

THE WESTERN CAROLINAS AND NE GA...SOURCED FROM HIGH PRESSURE

CENTERED OVER NEW ENGLAND. SFC LOW PRESSURE WAS ANALYZED NEAR THE

PANHANDLE OF FL. INITIAL SNOW FROM MORNING JET DIVERGENCE HAS

PRODUCED 1 INCH ACROSS THE I-85 CORRIDOR TO OVER 5 INCHES AT

GREENWOOD. RECENT IR SATELLITE IMAGES INDICATE ANOTHER ROUND OF

COOLING CLOUD TOPS ACROSS NRN GA AND THE WESTERN CAROLINAS. 12Z NAM

INDICATES THAT STRONG ISENTROPIC LIFT WILL RAPIDLY SPREAD

NORTH...REACHING THE NORTHERN ZONES BY 18Z. THE LIFT WILL COMBINE

WITH A POOL OF HIGH PW...SHOWN ON THE BLENDED PW...PRODUCING A

SHIELD OF MODERATE TO HEAVY SNOW LIFTING SOUTH TO NORTH. IN

ADDITION...SEVERAL BANDS OF -EPV WILL RIPPLE ACROSS THE REGION THIS

AFTERNOON...FAVORING THE FORMATION OF MESOSCALE SNOW BANDS. A LARGE

FIELD OF MID LEVEL Q-VECTOR CONVERGENCE WILL ARRIVE THIS AFTERNOON

AND INCREASE THROUGH MOST OF TONIGHT. THE OVERLAP OF LLVL AND MID

LEVEL FORCING SHOULD RESULT IN THE GREATEST SNOWFALL THIS AFTERNOON

THROUGH THIS EVENING.

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FFC not too worried about the gap, but may reduce amounts later:

 

 

 

NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1117 AM EST WED FEB 12 2014

...MAJOR WINTER STORM WITH CRIPPLING EFFECTS STILL EXPECTED TO
CONTINUE...

.UPDATE...
EARLY MORNING SURGE OF MOISTURE AND DIABATIC EFFECTS FIGHTING THE
CAA FROM THE REINFORCED CAD WEDGE RESULTED IN 0.1-0.25 INCHES OF
FREEZING RAIN ACCUMULATION PRIMARILY ACROSS NORTHERN AND EASTERN
PORTIONS OF CENTRAL GA AND SEVERAL INCHES OF SNOW IN THE NORTHERN
TIER WITH SOME SLEET OBSERVED BETWEEN. TRENDS HAVE BEEN ON THE
LOWER QPF SIDE LIKELY DUE TO AN ENHANCED SLUG OF UPSTREAM MOISTURE
IN THE SOUTH GA AND NORTH FL...ALLOWING FOR A MOMENTARY LULL WITH
ONLY LIGHT PRECIP OCCURRING ASIDE FROM THE SOUTHERN TIER OF
COUNTIES WHICH HAVE HAD PRIMARILY RAIN. HRRR GUIDANCE HAS
CONSISTENTLY INDICATED PRECIP FILLING BACK IN AND A DECENT BAND OF
DEVELOPMENT STARTING BACK BY 21-00Z...AND HAS VERIFIED WELL WITH
BREAKS IN THE ACTION SO NOT WANTING TO ADJUST TOTALS TOO MUCH AT
THE MOMENT. STILL FREEZING TEMPS EXPECTED OVERNIGHT AND CURRENTLY
DEALING WITH WIDESPREAD POWER OUTAGES MAINLY IN A NW TO SE SWATH
FROM NEAR CARROLLTON...THROUGH ATLANTA...THEN WITHIN THE I-20 TO
I-16 CORRIDOR. STILL STRONG ISENTROPIC FORCING FORECAST AGAINST
THE WEDGE COUPLED WITH STRONG UPPER DYNAMIC FORCING. WILL STAY THE
COURSE WITH THE MAIN FORECAST BUT COULD END UP ADJUSTING TOTALS A
BIT WITH FRESH GUIDANCE CONSENSUS THIS AFTERNOON. PREVIOUS
DISCUSSION FOLLOWS...
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It seems the nam continues to give cae 2.14" of zr.  I've got .50 of that now ;)

Big bust here so far.  I'm sorry it's bad for you.  I've had 1.75 in rain for both events, and maybe an eighth of an inch build up in zr.  Along with 30 pellets of sleet about 8.  Since 8:30 I've been in the usual big no precip hole for my yard, but I'm not complaining.  I'd just as soon bust on the zr.  Right now it's just a mild nuisance, with the power out  for 4 hours.  Good luck up there.  The wind is really strong down here, so I'm very lucky to have very little accumulation.  Hope to get hit with sleet and snow, if I ever get out of this precip hole, but if it's to be zr, I just stay in it, thank you very much :)  Tony

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Sperry-Piltz Ice Accumulation Index

 

For areas that are experiencing Ice Accumulations from Freezing Rain, this is of value.

 

http://www.spia-index.com/index.php

 

http://www.spia-index.com/seIce.php

 

The Sperry–Piltz Ice Accumulation Index, or SPIA Index, is a forward-looking, ice accumulation and ice damage prediction index that uses an algorithm of researched parameters that, when combined with National Weather Service forecast data, predicts the projected footprint, total ice accumulation, and resulting potential damage from approaching ice storms. It is a tool to be used for risk management and/or winter weather preparedness.

 

The SPIA Index is to ice storms what the Enhanced Fujita Scale is to tornadoes, and what the Saffir–Simpson Scale is to hurricanes. Previous to this hazard scale development, no such ‘forward-looking’ ice accumulation and ice damage index had ever been utilized to predict – days in advance – the potential damage to overhead utility systems, along with outage duration possibilities, from freezing rain and/or ice storm events.

 

Current Index as of now for this storm:

 

ANRwLmD.png

 

QAGHPTg.jpg

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Big bust here so far.  I'm sorry it's bad for you.  I've had 1.75 in rain for both events, and maybe an eighth of an inch build up in zr.  Along with 30 pellets of sleet about 8.  Since 8:30 I've been in the usual big no precip hole for my yard, but I'm not complaining.  I'd just as soon bust on the zr.  Right now it's just a mild nuisance, with the power out  for 4 hours.  Good luck up there.  The wind is really strong down here, so I'm very lucky to have very little accumulation.  Hope to get hit with sleet and snow, if I ever get out of this precip hole, but if it's to be zr, I just stay in it, thank you very much :)  Tony

I'm glad you are busting on the zr.......for now  :hug: I have a lot of friends in the area without power and the trees are sagging. This wind isn't helping much either  :( 

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RAP is showing mixing happening in 6 hours across a wide section from CLT to the foothills right as the heaviest returns move in. I really, really hope not. 

 

RAP seems quick to erode cold wedges way too quickly, then it trends colder with each run.  The 850 low looks to track well south of I-85 but wants to develop a secondary low over the mtns that creates some serious feedback issues and pulls the warm nose wayyy west.

 

@1 am

NmLUknA.gif

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RAP is showing mixing happening in 6 hours across a wide section from CLT to the foothills right as the heaviest returns move in. I really, really hope not. 

 

There is no way that happens. If the SLP tracks off the coast the upper air features will follow it too right along the 95 corridor.

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RAP seems quick to erode cold wedges way too quickly, then it trends colder with each run.  The 850 low looks to track well south of I-85 but wants to develop a secondary low over the mtns that creates some serious feedback issues and pulls the warm nose wayyy west.

 

@1 am

 

 

What do you mean by feedback issues?

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