Major National Winter Storm Dec 25-28

[DaculaWeather]

Nice river feed

[OUGrad05]

Near Houston on the morning of Christmas

Wow...

I'm going through the model data this morning and frankly this looks like it could be a significant severe weather event for the I-10 corridor. The SPC/NWS should consider the insertion of some moderate language in their HOU discussion and hazerdous weather outlooks. I think we may see some upgrading to SPC's forecast language.

I would be particularly concerned from the Houston area back to the east and north east including New Orleans.

edit: after finishing the thread some wording changes have already taken place from yesterday evening...

[tornadotony]

It seems that over the past several runs of the GFS/ECMWF, the cyclogenesis starts a bit earlier and ends up being a bit stronger, which ends up pulling the warm front further north. I always get a bit hestitant about that around the Gulf Coast, because there have been a lot of times in the past where the precip along and north of the warm front tends to make the retreat of the warm front slower than what was progged. What makes this case different though is the strong cyclogenesis.

Absolutely. Usually, cyclogenesis in this region is rather weak, resulting in maybe a 1004-1008 hPa sfc low that propagates along a baroclinic zone close to the coast because copious precip N of the axis of that zone prevents WAA from really getting underway in earnest. With such a powerful trough involved in this situation, this is a more classic sfc cyclogenesis situation, which will result in strong temperature advections, both WAA ahead of the low and CAA behind it.

One other thing that is going to be somewhat unique with this setup is the duration of the threat. We're talking about a threat that could potentially begin in the TX Hill Country Christmas Eve night and continue nonstop all the way through the Carolinas the day after Christmas. And because of the breadth of the warm sector and copious lift, there are many areas that may receive multiple rounds of dangerous weather, with discrete cells likely IMO to form in the warm sector and a squall line along the front, which could still have embedded supercell structures within it.

[Srain]

HPC Update for the Winter Storm Track and snow potential in the cold sector:

...PTNS OF THE SRN PLAINS INTO THE LOWER MS VLY/WRN TN VLY/LOWER

OH VLY...

THE ELONGATED SHORTWAVE AFFECTING THE W COAST ON DAY ONE...THEN

THE IM REGION/ROCKIES ON DAY 2...WILL DIG SE ACROSS THE SRN PLAINS

AND EVENTUALLY LIFT ENE ACROSS THE LOWER MS VLY AND INTO THE

TN/LWR OH VLYS BY THE END OF DAY 3. HPC'S SNOW/ICE PROBABILITIES

WERE BASED ON A BLENDED APPROACH BOTH WITH THE QPF AND THERMAL

STRUCTURES...AS PER THE PMDHMD...THE ENSEMBLE WAS INITIALLY

NON-GFS BASED GIVEN THE RELATIVE FAST SPEED OF THE GFS COMPARED TO

THE OTHER MODEL CLUSTERS. THE 06Z GFS HAS ESSENTIALLY COME IN

BETTER ACCORD WITH THE LATEST NAM IN TERMS OF THE SFC LOW TRACK

FROM NRN LA TO NRN MS...CEN TN...AND ACROSS CEN KY TOWARD THE END

OF DAY 3 (12Z 12/26). THE ECMWF AND UKMET REMAIN SLOWER WITH THE

LOW TRACK...AND ESSENTIALLY FARTHER S (CEN TN) WITH THE LOW BY 12Z

12/26 OR WED MORNING. GIVEN THE TIMING DIFFS BTWN THE NECP CAMP

AND THE ECMWF/UKMET...AGAIN FOR NOW HPC USED AN ENSEMBLE APPROACH

WITH THE SFC-700 MB LOW TRACKS AND QPF...WHICH WOULD BASED ON THAT

TRACK AND ASSCD FVRBL REGION OF MAX UPPER LEVEL DIFFLUENCE/MID

LEVEL DEFORMATION AND TROWAL...

WOULD FAVOR A POTENTIAL FOR HEAVY SNOW ACROSS PTNS OF THE LWR MS

VLY TO INCLUDE CEN AR NEWRD THROUGH SERN MO/WRN KY.

OBVIOUSLY...GIVEN THE GUIDANCE SPREAD AT THIS POINT...FCST

CONFIDENCE IS AVG AT BEST (AVG FOR A DAY 3 FCST). THROW IN THE

ANOMALOUS NATURE OF THIS EVENT (500 MB HEIGHTS ~ 2 STD DEVS BELOW

NORMAL FOR THE LOWER MS VLY)...AS WELL AS THE POTENTIAL FOR SHIFTS

IN THE STORM TRACK...DRY SLOT...AND CONVECTIVELY ENHANCED REGIONS

(OR ALL OF THE ABOVE)...HPC PROBABILITIES WHERE MOST HEAVILY

WEIGHTED TOWARD THE LOWER THRESHOLDS (I.E. >4 INCHES) AT THIS

POINT. FOR NOW...THE DAY 3 FINAL PROBS DID INCLUDE A STRIPE OF 10%

OF >8 INCHES OVER PTNS OF CEN AND NERN ARK...AGAIN TAKING THE

ENSEMBLE APPROACH WITH THE STORM TRACK (EVEN THOUGH THE

ECMWF/UKMET WERE ABOUT 6 HRS SLOWER).

THE DEEPENING NATURE OF THIS SYSTEM (700-500 MB LOWS) AS THE

TROUGH AXIS BECOMES MORE NEGATIVELY TILTED WILL ALLOW FOR MATURING

CYCLOGENESIS WITH THE GOMEX WIDE OPEN AND COMMA-HEAD STRUCTURES

(CCB...MID-LEVEL TROWAL...AND DRY SLOT) COMING INTO PLAY. ALL THE

MODELS SHOW A GOOD POTENTIAL FOR CONVECTION AS WELL...ANY OF WHICH

IN THE WARM SECTOR COULD CERTAINLY DISRUPT THE MSTR TRANSPORT N-NW

OF THE LOW. HOWEVER AT THE SAME TIME...NEG 850-500 MB THETA-E

LAPSE RATES AND ARE PROGGED TO NUDGE UP INTO CEN-NRN AR INTO FAR

SW TN...WITH WEAK STATIC STABILITY JUST TO THE NORTH. THUS THE

CONCEPTUAL MODEL WOULD SUGGEST THE POTENTIAL FOR ELEVATED

CONVECTION (WHETHER UPRIGHT OR SLANTWISE) AND THUS ENHANCED

SNOWFALL RATES. AGAIN...QUITE A FEW VARYING FACTORS TO CONSIDER

WITH THIS SYSTEM...THUS EXPECT FURTHER ALTERATIONS TO THESE

PROBABILITIES AS THE EVENT DRAWS NEAR.

[Srain]

NCEP Operational Status Message

Sun Dec 23 15:01:00 2012 GMT

NOUS42 KWNO 231500

ADMNFD

SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE

NWS NCEP CENTRAL OPERATIONS COLLEGE PARK MD

1457Z SUN DEC 23 2012

THE 12Z NAM COMPLETED ON TIME. THE GFS STARTED ON TIME

WITH 31 CANADIAN...9 MEXICAN AND 10 CARIBBEAN STATIONS AVBL

FOR INGEST.

12Z GFS RAOB RECAP...

78486/SDQ - DELETED ALL WINDS...ERRATIC.

72240/LCH - DELETED TEMPS/HEIGHTS/MOISTURE 745-735 MB...

TEMPS TOO COLD...NON-METEOROLOGICAL LAPSE

RATES...WET BULB EFFECT.

91376/MAJ - DELETED TEMPS/HEIGHTS/MOISTURE 815-705 MB...

TEMPS TOO COLD...NON-METEOROLOGICAL LAPSE

RATES...WET BULB EFFECT.

70261/FAI - 10142

72786/OTX - 10142

91413/YAP - 10142

CRITICAL WEATHER DAY STATUS...

THERE IS A POTENTIAL FOR CWD BEGINNING 12Z TUE 12/25

THROUGH 12Z FRI 12/28 AS AN AREA OF LOW PRESSURE AND

ASSOCIATED PCPN/MOISTURE MOVES ACROSS SOUTHERN AND

EASTERN REGIONS.

[Ian]

Christmas Eve and Christmas Day tornado history: http://www.ustornadoes.com/2012/12/23/christmas-eve-and-christmas-day-tornado-history/

[Srain]

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1131 AM CST SUN DEC 23 2012

VALID 241200Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF E TX AND

ADJACENT AREAS OF LA...

...SYNOPSIS...

AS A WEAK SHORT-WAVE TROUGH CROSSES THE ERN U.S. AND EVENTUALLY

MOVES INTO THE ERN ATLANTIC...A SECOND TROUGH INITIALLY OVER THE PAC

NW/GREAT BASIN IS FORECAST TO DIG/AMPLIFY SEWD ACROSS THE ROCKIES

AND EMERGE INTO THE SRN PLAINS LATE IN THE PERIOD.

AS THIS FEATURE DIGS SEWD...SURFACE CYCLOGENESIS IS ANTICIPATED --

INITIALLY OVER THE SERN CO VICINITY. THROUGH LATTER STAGES OF THE

PERIOD...THIS LOW IS FORECAST TO SHIFT SEWD...REACHING N TX BY THE

END OF THE PERIOD AS COLD AIR DIVES SEWD ACROSS THE HIGH PLAINS.

ALONG WITH POTENTIAL FOR SOME CHRISTMAS DAY WINTRY WEATHER OVER

PARTS OF THE CENTRAL AND SRN PLAINS REGION...THUNDERSTORMS -- AND

SOME SEVERE POTENTIAL -- WILL BE POSSIBLE ACROSS PARTS OF E TX AND

POSSIBLY ADJACENT AREAS OF LA.

...E TX INTO LA...

WHILE SHOWERS AND POSSIBLY A FEW THUNDERSTORMS WILL SPREAD ACROSS

THE CENTRAL GULF COAST STATES AND TN VALLEY AREA DURING THE FIRST

HALF OF THE PERIOD IN CONJUNCTION WITH THE INITIAL SHORT-WAVE TROUGH

MENTIONED ABOVE...MORE SUBSTANTIAL CONVECTIVE THREAT WILL EVOLVE

AFTER DARK...AND FARTHER TO THE W.

AS THE UPPER TROUGH APPROACHES...COOLING ALOFT/STEEPENING LAPSE

RATES COMBINED WITH SLY LOW-LEVEL FLOW ADVECTING GULF MOISTURE NWD

WILL RESULT IN A DESTABILIZING ENVIRONMENT. AS WARM ADVECTION/QG

ASCENT INCREASES...STORMS SHOULD INCREASE IN COVERAGE THROUGH THE

EVENING...WITH A FEW POSSIBLY BECOMING SEVERE AS VEERING WINDS/SHEAR

INCREASES TO BECOME SUPPORTIVE OF ROTATION. THE PRIMARY THREAT

APPEARS TO BE HAIL...THOUGH ISOLATED STRONG GUSTS WILL BE

POSSIBLE...AND A TORNADO OR TWO CANNOT BE RULED OUT AS LOW-LEVEL

SHEAR INCREASES WITH THE APPROACH OF THE SURFACE LOW LATE. WHILE

SOME SEVERE THREAT SHOULD SPREAD E OF THE SABINE RIVER LATE...THE

GREATEST THREAT APPEARS TO EXIST OVER E TX FROM MID EVENING ONWARD.

..GOSS.. 12/23/2012

[Brick Tamland]

Not sure I ever remember crazy weather like this where we are talking about snow around Christmas and a chance of a tornado outbreak.

[SquatchinNY]

I remember a few years ago there was a major outbreak around New Years.

[Srain]

HPC:

...SHRTWV ENERGY AMPLIFYING THROUGH THE INTERMOUNTAIN WEST ON

MON...REACHING THE CNTRL/SRN PLAINS TUE AND LIFTING TWD THE OH VLY

WED...

PREFERENCE: 12Z GFS / 12Z ECMWF

CONFIDENCE: AVERAGE

THE NAM AND 09Z SREF ARE ON THE NWRN SIDE OF THE SPREAD TUE AND

WED REGARDING THE FCST CLOSED LOW AND SFC LOW MOVING NEWD INTO THE

OHIO VALLEY...BUT ARE BY NO MEANS OUTLIER SOLUTIONS. THE GFS HAS

TRENDED SLOWER AND A BIT WEST WITH THE TRACK OF THE UPPER SYSTEM /

SFC LOW. THE LATEST 12Z RUN OF THE ECMWF HAS SHIFTED A LITTLE

NORTH FROM ITS PREVIOUS 2 RUNS...AND IS CLOSER TO ITS 00Z ENSEMBLE

MEAN...HOWEVER THE EC IS STILL A LITTLE SOUTH OF THE 12Z GEFS /

09Z SREF MEAN CLUSTER ON WED.

GIVEN OVERALL RECENT TRENDS...THE RECOMMENDATION WILL NOW INCLUDE

THE 12Z ECMWF ALONG WITH THE 12Z GFS...FAIRLY CLOSE TO THE 00Z EC

MEAN. DO NOT FEEL COMFORTABLE GOING QUITE AS FAR NW AS THE

NAM/SREF...BUT ONE MUST GIVE RESPECT TO THE NRN ENSEMBLE MEANS IN

CONTRAST TO THE SRN UKMET/CMC SOLUTIONS. THE 12Z CMC HAS COME

INTO BETTER AGREEMENT WITH THE CONSENSUS COMPARED TO ITS 00Z

RUN...BUT THE CMC CONTINUES TO BE A BIT SOUTH OF THE PREFERENCE

WITH THE UPPER LOW.

[blizzard1024]

The 12Z euro is EPIC for snow in inland NY/ PA and nrn/wrn New England...two back to back snowstorms and then very cold. wow. haven't seen something like this in a while. Hope it

comes close to verifying!!!

[CUmet]

The 4km NAM reflectivity, relatively meager precip shown on the ECMWF, and the mid level dry punch showing up on the RH fields hint at the development of discrete cells as opposed to the messy, rain-contaminated warm sector that we often see in the cool season in the Deep South. The biggest threat area, and the most likely area to see a moderate risk issued, looks to be from central/southern MS eastward into central and southern AL. This includes cities such as Jackson, Hattiesburg, and Meridian, MS, and Tuscaloosa, Birmingham, and Montgomery, AL.

Synoptically, the broad base of the trough and the way it swings from neutral to negatively tilted (as others have noted) on the day of the outbreak reminds me somewhat of the 4/27/11 trough, but displaced a bit further south this time, and obviously with much, much less instability. Still, given that most of the tornadoes will occur after dark Tuesday, this poses a substantial threat to life and property, and I hope people down there are paying attention to this threat.

[SquatchinNY]

The 4km NAM reflectivity, relatively meager precip shown on the ECMWF, and the mid level dry punch showing up on the RH fields hint at the development of discrete cells as opposed to the messy, rain-contaminated warm sector that we often see in the cool season in the Deep South. The biggest threat area, and the most likely area to see a moderate risk issued, looks to be from central/southern MS eastward into central and southern AL. This includes cities such as Jackson, Hattiesburg, and Meridian, MS, and Tuscaloosa, Birmingham, and Montgomery, AL.

Synoptically, the broad base of the trough and the way it swings from neutral to negatively tilted (as others have noted) on the day of the outbreak reminds me somewhat of the 4/27/11 trough, but displaced a bit further south this time, and obviously with much, much less instability. Still, given that most of the tornadoes will occur after dark Tuesday, this poses a substantial threat to life and property, and I hope people down there are paying attention to this threat.

The date that gave me my inspiration. Anyway, do you see a 10% or 15% TOR threat?

Another added danger is that with all the family suppers, I doubt anyone will have tornadoes on the brain.

EDIT: Where do you get the 4km NAM, my source is messed up.

[andyhb]

The date that gave me my inspiration. Anyway, do you see a 10% or 15% TOR threat?

Another added danger is that with all the family suppers, I doubt anyone will have tornadoes on the brain.

EDIT: Where do you get the 4km NAM, my source is messed up.

 

Too early to really call that, but I do think that many signs point to a moderate risk with one of the two tornadic probabilistic risks you mentioned.

[Srain]

URGENT - WINTER WEATHER MESSAGE

NATIONAL WEATHER SERVICE NORMAN OK

233 PM CST SUN DEC 23 2012

OKZ004>031-033>038-241100-

/O.NEW.KOUN.WS.A.0001.121225T0600Z-121226T0600Z/

HARPER-WOODS-ALFALFA-GRANT-KAY-ELLIS-WOODWARD-MAJOR-GARFIELD-

NOBLE-ROGER MILLS-DEWEY-CUSTER-BLAINE-KINGFISHER-LOGAN-PAYNE-

BECKHAM-WA****A-CADDO-CANADIAN-OKLAHOMA-LINCOLN-GRADY-MCCLAIN-

CLEVELAND-POTTAWATOMIE-SEMINOLE-HARMON-GREER-KIOWA-JACKSON-

TILLMAN-COMANCHE-

INCLUDING THE CITIES OF...BUFFALO...ALVA...CHEROKEE...MEDFORD...

PONCA CITY...ARNETT...WOODWARD...FAIRVIEW...ENID...PERRY...

CHEYENNE...TALOGA...WEATHERFORD...CLINTON...WATONGA...

KINGFISHER...GUTHRIE...STILLWATER...ELK CITY...SAYRE...CORDELL...

ANADARKO...YUKON...EL RENO...MUSTANG...OKLAHOMA CITY...CHANDLER...

CHICKASHA...PURCELL...NORMAN...MOORE...SHAWNEE...SEMINOLE...

HOLLIS...MANGUM...HOBART...ALTUS...FREDERICK...LAWTON

233 PM CST SUN DEC 23 2012

...WINTER STORM WATCH IN EFFECT FROM LATE MONDAY NIGHT THROUGH

TUESDAY EVENING...

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A WINTER STORM

WATCH...WHICH IS IN EFFECT FROM LATE MONDAY NIGHT THROUGH TUESDAY

EVENING.

* TIMING: SNOW WILL DEVELOP BETWEEN MIDNIGHT AND 9 AM CST ON

TUESDAY AND BE HEAVIEST DURING THE DAYTIME HOURS BEFORE TAPERING

OFF TO FLURRIES TUESDAY EVENING. BLOWING AND DRIFTING SNOW WILL

OCCUR AS WELL DURING TUESDAY AFTERNOON AND EVENING DUE TO

STRONG NORTH WINDS.

* MAIN IMPACT: SNOW ACCUMULATIONS...BLOWING AND DRIFTING SNOW WILL

BE THE MAIN IMPACTS. TOTAL SNOW ACCUMULATIONS WILL BE GENERALLY

2 TO 6 INCHES WITH LOCALLY HEAVIER AMOUNTS.

URGENT - WINTER WEATHER MESSAGE

NATIONAL WEATHER SERVICE TULSA OK

302 PM CST SUN DEC 23 2012

ARZ002-010-011-019-020-029-OKZ049-053-065-066-068>076-241100-

/O.NEW.KTSA.WS.A.0001.121225T1800Z-121226T0600Z/

CARROLL-WASHINGTON AR-MADISON-CRAWFORD-FRANKLIN-SEBASTIAN-PUSHMATAHA-

CHOCTAW-OKFUSKEE-OKMULGEE-CHEROKEE-ADAIR-MUSKOGEE-MCINTOSH-SEQUOYAH-

PITTSBURG-HASKELL-LATIMER-LE FLORE-

302 PM CST SUN DEC 23 2012

...WINTER STORM WATCH IN EFFECT FROM TUESDAY AFTERNOON THROUGH

TUESDAY EVENING...

THE NATIONAL WEATHER SERVICE IN TULSA HAS ISSUED A WINTER STORM

WATCH FOR SNOW...WHICH IS IN EFFECT FROM TUESDAY AFTERNOON THROUGH

TUESDAY EVENING...

FOR THE FOLLOWING COUNTIES...

* IN OKLAHOMA...MUSKOGEE...MCINTOSH...CHOCTAW...CHEROKEE...

ADAIR...OKFUSKEE...PITTSBURG...SEQUOYAH...OKMULGEE...

PUSHMATAHA...LE FLORE...LATIMER AND HASKELL. IN ARKANSAS...

WASHINGTON...SEBASTIAN...CARROLL...MADISON... FRANKLIN AND

CRAWFORD.

HAZARDOUS WEATHER...

* A POWERFUL UPPER LEVEL STORM SYSTEM IS EXPECTED TO MOVE INTO

THE SOUTHERN PLAINS ON CHRISTMAS DAY. A BAND OF HEAVY SNOW IS

EXPECTED TO SET UP FROM SOUTHEAST OK ON INTO WEST CENTRAL AND

NORTHWEST ARKANSAS DURING THE AFTERNOON AND CONTINUE INTO THE

EVENING HOURS. THE SNOW WILL TAPER OFF AFTER MIDNIGHT TUESDAY

NIGHT.

* UP TO 7 INCHES OF SNOW ACCUMULATION IS POSSIBLE FROM TUESDAY

AFTERNOON THROUGH TUESDAY EVENING.

[Hoosier]

Winter storm watches already issued as far north/east as Indiana. This one is going to have a large impact on travel.

[OUGrad05]

I am a little concerned that they don't have the track nailed down on this thing yet and it could catch some people off guard. I've already talked to three people here in Tulsa basically saying "Oh it'll all be way south of us, nothing to worry about". Well the system only has to track another 80 to 100 miles north for Tulsa to get some pretty heavy wintery precip.

It definitely looks to be mainly south of I40 here in OK, I just don't like people making assumptions regarding a weather system two days out.

I do agree tomorrow we'll see some upgraded wording from SPC and that 10 or 15% tornadic area seems like a real possibility once we have another model run or two under our belts with this system.

Christmas is shaping up to be an active weather day.

[SquatchinNY]

Tornadoes anyone?

[OUGrad05]

Tornadoes anyone?

Yeah, that aint good. I just hope people are paying attention, whether it's severe weather or winter weather. This time of year we all tend to get pre-occupied, those of us on here have an affinity for weather.

This system si going to create a travel mess and then potentially more along the gulf coast.

[ICEHOCEY77]

Don't see that very often in December.

[Hoosier]

Don't see that very often in December.

Just a note for more casual/infrequent severe weather watchers, a couple of the ingredients on those maps were relaxed which makes it easier than it used to be to attain higher probabilities.

[ICEHOCEY77]

0z NAM is out. First time I've seen an EHI of 3 for the storm.

[andyhb]

Probability of the supercell composite exceeding 6, 21z Tuesday.

[Disc]

Probability of the supercell composite exceeding 6, 21z Tuesday.

Someone isn't going to have a "Merry Christmas." This isn't trending in favor of the folks living in the Gulf States for sure.

[andyhb]

Someone isn't going to have a "Merry Christmas." This isn't trending in favor of the folks living in the Gulf States for sure.

Boxing Day isn't looking too pretty either over the Carolinas/Eastern GA.

Hodograph from the 00z NAM just east of Charlotte (there's instability around the area too)

[weunice]

Quick question ... the prob sigtor numbers. Are they supposed to be analogous to something like the probabilities they publish (like probability of a tornado within 25 miles of a point) or is this number simply a calculation and thus we all know from past experience that a number over X means that the result of a tornado is pretty high in a given area?

[Disc]

Boxing Day isn't looking too pretty either over the Carolinas/Eastern GA.

Hodograph from the 00z NAM just east of Charlotte (there's instability around the area too)

That's nasty looking as well. I posted some about the Carolina threat over in the SE severe thread. These hodos are something I'd expect to see in the the spring, but not the end of December.

[Ensō]

Quick question ... the prob sigtor numbers. Are they supposed to be analogous to something like the probabilities they publish (like probability of a tornado within 25 miles of a point) or is this number simply a calculation and thus we all know from past experience that a number over X means that the result of a tornado is pretty high in a given area?

They're calculations based on various parameters (helicity, bulk shear, CAPE, etc). They aren't tied to the SPC's probabilities when they issue forecasts. They're just equations that have been found to be useful in diagnosing the potential likelihood of tornadoes.

If you go to the SPC's mesoanalysis page and click the little question mark icon next to each parameter (they're under "Composite Indices") it'll explain in more detail exactly what goes into each one.

[andyhb]

Quick question ... the prob sigtor numbers. Are they supposed to be analogous to something like the probabilities they publish (like probability of a tornado within 25 miles of a point) or is this number simply a calculation and thus we all know from past experience that a number over X means that the result of a tornado is pretty high in a given area?

It is a calculation using various probabilities of key severe parameters getting to a certain level, which has been found to support significant tornado development in many cases. The probability cut-off was adjusted for a couple of the parameters earlier this year and thus has made it easier than it used to in terms of getting large numbers (like 40-50) on the STI indicator. Before this change, values in the 40s and 50s usually indicated a potential high-impact event, such as 4/27/11, 4/24/10 (Yazoo City), 4/15/11 and 3/2 this year.

[Amped]

4/27/11 Produce plenty of tornadoes from midnight to 10AM. you don't need much daytime heating with that setup.

Also it is amazing how many large events have occurred between the 26-39th of the month in the last several years. Looks like a coincidence, but why can't the other 90% of the month get some action?