Severe weather outbreak? February 24-25

[CrazyC83]

The SPC is already mentioning that a major tornado outbreak is possible later this week.

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 200947
SPC AC 200947

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0347 AM CST SUN FEB 20 2011

VALID 231200Z - 281200Z

...DISCUSSION...
AN ACTIVE PATTERN WILL PERSIST THROUGH THE PERIOD WITH THE POTENTIAL
FOR A SIGNIFICANT SEVERE WEATHER OUTBREAK ON THU/D5.

ON WED/D4...MODEL CONSENSUS HAS A BROAD BELT OF SWLY FLOW ALOFT FROM
NRN MEXICO ACROSS THE CNTRL AND ERN U.S...AHEAD OF AN UPPER TROUGH
AXIS THAT IS FORECAST TO BE IN THE VICINITY OF THE BAJA CA/SRN CA
COAST WED MORNING. WELL AHEAD OF THIS FEATURE...LOW LEVEL MOISTURE
WILL BEGIN TO STREAM NWD OFF THE GULF OF MEXICO AS A LARGE SURFACE
HIGH OVER THE ERN STATES GRADUALLY SHIFTS OFFSHORE.

BY THU MORNING...A SURFACE LOW IS FORECAST TO BE SOMEWHERE ACROSS
NWRN TX OR CNTRL OK WITH BOUNDARY LAYER DEWPOINTS AS HIGH AS 60F UP
TO THE LOW CENTER....AND UP TO A WARM FRONT THAT WILL EXTEND EWD
ACROSS NRN OK/AR OR PERHAPS SRN MO. A SURFACE LOW AND POTENT UPPER
LEVEL JET STREAK WILL THEN CONTINUE EWD ACROSS THE LOWER MS AND INTO
THE TN/OH VALLEYS BY 00Z.

UPPER LEVEL COOLING AND A PLUME OF STEEP DEEP LAYER LAPSE RATES WILL
OVERSPREAD THE WARM SECTOR...CREATING A VERY UNSTABLE SITUATION.
ALTHOUGH THE EXACT GEOMETRY OF THE TROUGH MAY NOT BE WELL HANDLED
THIS FAR IN ADVANCE...THE CURRENT MODEL DEPICTION WOULD INDICATE THE
POTENTIAL FOR NUMEROUS SUPERCELLS ALONG THE DRYLINE/COLD
FRONT...RATHER THAN A MORE LINEAR STORM MODE. IN THIS SCENARIO...A
SUBSTANTIAL TORNADO THREAT COULD MATERIALIZE BY AFTERNOON AND
EVENING.

BY FRI/D6...A SEVERE THREAT OF SOME FORM MAY REMAIN ALONG THE COLD
FRONT...AS IT APPROACHES THE ERN SEABOARD...BUT TIMING OF THE FRONT
AND PREDICTABILITY BECOME TOO LOW FOR ANY ADDITIONAL SEVERE AREAS.

..JEWELL.. 02/20/2011

CLICK TO GET WUUS48 PTSD48 PRODUCT

[Metalicwx220]

Thats interesting, the severe weather threat always diminishes whenever it gets toward the eastern seaboard. We always get plain rain with rumbles of thunder. I love intense thunderstorms as long as there is no damage or power outages. The best part of the storm is when the winds are strong and the rain starts to pick up with lightning in the background.I don't like boring thunderstorms. Lol

[CrazyC83]

Thats interesting, the severe weather threat always diminishes whenever it gets toward the eastern seaboard. We always get plain rain with rumbles of thunder. I love intense thunderstorms as long as there is no damage or power outages. The best part of the storm is when the winds are strong and the rain starts to pick up with lightning in the background.I don't like boring thunderstorms. Lol

This looks to be a mid-South event. I'm thinking the bullseye will run from about Shreveport to Nashville.

[WeatherGuesser]

IN THIS SCENARIO...A
SUBSTANTIAL TORNADO THREAT COULD MATERIALIZE BY AFTERNOON AND
EVENING.

Always make me nervous when they start talking like that 5 days out.

Any bets on a Moderate Risk

[charlesw]

Here is the current Day 3 outlook which is for Wednesday:



Nothing much on Wednesday but the on Thursday the real severe threat begins:



The severe threat will be major with a possible tornado outbreak. There is the potential for strong, long track tornadoes.

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0353 AM CST MON FEB 21 2011

VALID 241200Z - 011200Z

...DISCUSSION...
AN OUTBREAK OF SEVERE THUNDERSTORMS APPEARS LIKELY ON THU/D4 FROM
ERN OK/NERN TX EWD ACROSS MUCH OF AR...SRN MO...NRN MS...CNTRL AND
WRN KY AND TN...AND POSSIBLY CONTINUING INTO FRI/D5 ACROSS PORTIONS
OF THE MID ATLANTIC STATES.

MODELS ARE IN GOOD AGREEMENT IN DEPICTING A POTENT UPPER SHORTWAVE
TROUGH MOVING EWD ACROSS THE SRN PLAINS DURING THE DAY THU WITH A
SURFACE LOW DEEPENING FROM ROUGHLY OK AT 12Z TO MO/AR BY 00Z. AHEAD
OF THE DEEPENING LOW...A RELATIVELY WIDE MOIST/WARM SECTOR WILL BE
IN PLACE WITH BOUNDARY LAYER DEWPOINTS IN THE 60S F. STRONG FORCING
WITH THE UPPER TROUGH...COOLING MID LEVEL TEMPERATURES AND THE
PRESENCE OF VERY STRONG WIND PROFILES SUGGEST SIGNIFICANT SEVERE
WEATHER WILL BE POSSIBLE...INCLUDING TORNADOES AND VERY STRONG WINDS
IN ADDITION TO HAIL.

THE GREATEST THREAT AREA ON THU WILL LIKELY BE NEAR AND JUST S OF
THE SURFACE LOW TRACK DURING THE LATE AFTERNOON AND EVENING HOURS.
LATEST ITERATION OF NUMERICAL GUIDANCE SUGGESTS THAT THIS WOULD
INCLUDE MUCH OF AR...SRN MO...FAR NRN MS...AND MUCH OF WRN KY AND
TN.

SOME SEVERE THREAT WILL LIKELY PERSIST OVERNIGHT AND CONTINUE INTO
FRI/D5...ALTHOUGH INSTABILITY AND MOISTURE WILL BE LESS. AS
SUCH...THE EXPECTED SEVERE THREAT FRI WILL LIKELY BE COMPRISED OF
DAMAGING WIND GUSTS ASSOCIATED WITH AN INTENSE COLD FRONT AND A
STRONGLY FORCED LINE OF STORMS...FROM THE DELMARVA SWD ACROSS VA.
THESE STORMS WOULD LIKELY HAVE LITTLE INSTABILITY TO WORK WITH...AND
WOULD BE RELATIVELY LOW TOPPED...BUT A STRONG SURFACE PRESSURE
FALL/RISE COUPLET WOULD ENHANCE WIND POTENTIAL WITH THE LINE.

AFTER THE D4 TO D5 TIME FRAME...MODEL SOLUTIONS DIVERGE RAPIDLY.

..JEWELL.. 02/21/2011

CLICK TO GET WUUS48 PTSD48 PRODUCT

[CrazyC83]

IN THIS SCENARIO...A
SUBSTANTIAL TORNADO THREAT COULD MATERIALIZE BY AFTERNOON AND
EVENING.

Always make me nervous when they start talking like that 5 days out.

Any bets on a Moderate Risk

You mean a High Risk? Certainly that is possible if it stays as bullish as they say. This looks like Super Tuesday redux.

[Metalicwx220]

IN THIS SCENARIO...A
SUBSTANTIAL TORNADO THREAT COULD MATERIALIZE BY AFTERNOON AND
EVENING.

Always make me nervous when they start talking like that 5 days out.

Any bets on a Moderate Risk

You mean a High Risk? Certainly that is possible if it stays as bullish as they say. This looks like Super Tuesday redux.

Yeah super Tuesday is what I was thinking of, but I don't think it will be as bad though.

[charlesw]

I am wondering if this will get into central TN like super tuesday did... it almost seems like central Arkansas will be the main area eastward toward Memphis

[Metalicwx220]

Here is thursday Outbreak I guess that is what this is. And then the 1974 outbreak in 8 days lol just kidding I don't know what this is if that is what severe weather looks like or that is heavy rain not sure. This is the 6z Gfs.12z gfs

[charlesw]

well that will likely be a severe weather outbreak if that model is true.

[charlesw]

Any guesses on the first outlook issuance??? Moderate anyone?

[RL3AO]

I think Day 3 will be a strongly worded slight risk.

[Metalicwx220]

This is late but look at what the 0z was showing earlier this morning in 8 days. Is this just heavy rain or a tornado outbreak picture on a model or just thunderstorms lol?

[RL3AO]

0z run valid next Monday morning.

500mb




850mb



Tough to tell right now because the afternoon is trapped between 180hrs and 192.

Could be something there but not sure how much directional shear there will be.

[CrazyC83]

Agreed, a large high-end SLGT for Thursday on Day 3 with a large 30% area.

A secondary threat could be flooding, particularly in Kentucky and Tennessee.

[charlesw]

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0224 AM CST TUE FEB 22 2011

VALID 241200Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN OK/ARKLATEX EWD ACROSS
AR...SRN MO...NRN MS/AL AND INTO THE TN AND OH VALLEYS...

...SYNOPSIS...
A POTENT SHORTWAVE TROUGH WITH 80-100 KT MID LEVEL SPEED MAX WILL
TRAVEL EWD FROM THE SRN HIGH PLAINS INTO THE LOWER TO MIDDLE MS
VALLEY BY EARLY EVENING. AT THE SURFACE...LOW PRESSURE WILL DEEPEN
AS IT MOVES FROM OK THU MORNING EWD ACROSS SRN MO AND NRN AR BY LATE
AFTERNOON. A DRYLINE WILL SHARPEN AS THE SYSTEM PROGRESSES
EWD...EXTENDING ROUGHLY FROM SWRN MO SWD ALONG THE OK/AR BORDER AND
INTO SERN TX AROUND 00Z.

AHEAD OF THE LOW...INCREASING SLY FLOW WILL BRING LOW TO MID 60 F
BOUNDARY LAYER DEWPOINTS NWD ACROSS THE WARM SECTOR...WHICH WILL BE
BOUNDED ON THE N END BY A WARM FRONT. THIS FRONT WILL STRETCH
ROUGHLY FROM NRN AR EWD INTO TN...LIFTING SLOWLY NWD WITH TIME INTO
SRN MO...SRN IL...AND WRN KY.

AFTER 00Z...THE SURFACE LOW SHOULD CONTINUE TO TRACK NEWD ACROSS THE
OHIO VALLEY...WITH CONTINUED STRONG FORCING AND VERY STRONG WIND
FIELDS.

...ERN OK/ARKLATEX EWD INTO THE TN AND OH VALLEY...
A COMPLEX...AND RAPIDLY CHANGING SCENARIO WILL UNFOLD ON THU. WHILE
SOME SIGNIFICANT MODEL DIFFERENCES STILL EXIST...A SIGNIFICANT
SEVERE THREAT APPEARS LIKELY REGARDLESS OF FINER SCALE DETAILS WHICH
WILL BECOME CLEARER IN LATER OUTLOOKS.

STRONG TO SEVERE STORMS...WITH MAINLY A HAIL THREAT...MAY BE ONGOING
ACROSS PORTIONS OF OK THU MORNING. THESE STORMS WILL LIKELY BE
ELEVATED. ADDITIONAL STORMS WILL BE ONGOING FROM SERN KS ACROSS MO
AND INTO NRN AR AND THE LOWER OH RIVER VALLEY ALONG AND N OF A WARM
FRONT...BUT THESE ARE NOT EXPECTED TO BE SEVERE.

THE PRIMARY SEVERE THREAT SHOULD DEVELOP DURING THE AFTERNOON ALONG
THE OK/AR BORDER FROM THE ARKLATEX INTO SWRN MO AS COOLING ALOFT
OVERSPREADS A TIGHTENING DRYLINE SURGE BENEATH SUBSTANTIAL DCVA
ALOFT. WHILE PROGGED INSTABILITY FIELDS ARE NOT STRONG...THEY WILL
BE SUFFICIENT GIVEN A MOIST BOUNDARY LAYER AND VERY STRONG FORCING
FOR ASCENT. SHEAR PROFILES WILL FAVOR SUPERCELLS AND BOWING
STRUCTURES. ENVIRONMENTAL SHEAR WILL BE MORE THAN SUFFICIENT FOR
TORNADOES...AS WELL AS DAMAGING WIND GUSTS. ALTHOUGH THE LOCATION IS
NOT PRECISELY KNOWN AT THIS TIME...AN ENHANCED TORNADO THREAT MAY
EXIST ALONG THE JUST S OF THE SURFACE LOW TRACK EWD ALONG THE WARM
FRONT...WHERE LOW LEVEL SHEAR WILL BE MAXIMIZED.

A SEVERE THREAT IS LIKELY TO PERSIST THROUGH THE LATE EVENING/EARLY
MORNING HOURS AS FAR E AS SRN INDIANA AND CNTRL KY AS THE LOW
CONTINUES TO DEEPEN.

..JEWELL.. 02/22/2011

[WeatherGuesser]

Question is, will they go Moderate Wednesday, or wait until Thursday morning?

[charlesw]

I think that they will go moderate for the 2nd outlook on Wednesday

[CrazyC83]

I personally think the SPC might have it too far north, it might be farther south than that, such as in central Louisiana and central/southern Mississippi as well instead of the Ozarks and Tennessee Valley (I think flooding could be a bigger threat north of I-40)

[CrazyC83]

After looking through all the models, I have a feeling this may not be the big outbreak to start the year that I first thought. Instability will be not too high, so there may not be a huge window to develop tornadoes.

The second storm - early next week - could be the real deal. (That is for a separate thread as it gets closer)