Plains Tornado Outbreak 4/14-15

[Cyclenall]

SPC AC 111730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT WED APR 11 2012

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/SRN PLAINS...

...SYNOPSIS...
PROGRESSIVE UPPER-AIR PATTERN WILL FEATURE HEIGHT FALLS OVER MUCH OF
WRN CONUS...AND EWD MOVEMENT OF SYNOPTIC-SCALE RIDGE NOW ANALYZED
FROM TX BIG BEND REGION NNWWD ACROSS ERN MT. BY START OF
PERIOD...500-MB RIDGE SHOULD BE LOCATED FROM DEEP S TX ACROSS
CENTRAL OK AND DAKOTAS. EMBEDDED VORTICITY RIBBON AND SHORTWAVE
TROUGH OVER CENTRAL PORTIONS KS/OK INTO N TX...PERHAPS STRONGLY
REINFORCED BY MCV PROCESSES RELATED TO DAY-1 CONVECTION MOVING EWD
FROM SRN HIGH PLAINS...SHOULD MOVE ESEWD THEN SEWD ACROSS ARKLATEX
REGION TO MS DELTA DURING PERIOD. COMPACT MID-UPPER CYCLONE AND
ACCOMPANYING TROUGH OVER IA/WI BORDER REGION WILL MOVE SEWD RAPIDLY
TO GA COAST BY 12/12Z.

OVER WRN CONUS...BASAL SHORTWAVE TROUGH NOW OVER COASTAL SRN CA IS
FCST TO EJECT NEWD TO NRN ROCKIES BY 12/12Z...THEN MOVE NWD ACROSS
CANADIAN BORDER INTO SK/AB. SERIES OF LOWER-AMPLITUDE
PERTURBATIONS...TRAILING THAT INITIAL TROUGH...WILL BE EMBEDDED IN
STRENGTHENING CYCLONIC FLOW ALOFT...FROM CENTRAL HIGH PLAINS ACROSS
GREAT BASIN...CONTRIBUTING TO HEIGHT FALLS OVER HIGH PLAINS AND
LOW-LEVEL WAA OVER MUCH OF CENTRAL CONUS. MOISTURE CHANNEL IMAGERY
INDICATES LARGE...SE-NW ALIGNED...MID-UPPER LEVEL CYCLONE OVER NERN
PAC...WHICH IS PROGGED TO MOVE ESEWD TO JUST OFFSHORE ORE/NRN CA
COAST BY 13/12Z. NET RESULT BY THAT TIME WILL BE BROAD FETCH OF
CYCLONIC FLOW FROM OFFSHORE SRN CA ACROSS CENTRAL/SRN ROCKIES TO
CENTRAL/NRN PLAINS.

AT SFC...WAVY COLD FRONT IS ANALYZED FROM CENTRAL FL NWWD ACROSS
NERN GULF TO CENTRAL LA AND N-CENTRAL TX...BECOMING QUASISTATIONARY
OVER SWRN OK AND TX PANHANDLE. THIS BOUNDARY SHOULD MOVE FARTHER
SWWD OVER N-CENTRAL GULF AND NRN/ERN TX BY START OF PERIOD AS UPPER
MS VALLEY PERTURBATION PASSES TO ITS NE...AND LOW-LEVEL/POST-FRONTAL
ANTICYCLONE IS REINFORCED. THIS PROCESS WILL RESULT IN NARROWING OF
MOIST SECTOR THIS PERIOD. AS LEE TROUGHING DEEPENS AND SWLY FLOW
DEVELOPS TO ITS W...EXPECT DRYLINE TO MIX/ADVECT EWD ACROSS SRN HIGH
PLAINS DURING DAY. BY 12/21Z-13/00Z TIME FRAME...DRYLINE SHOULD BE
POSITIONED FROM NWRN/W-CENTRAL KS SWD ACROSS ERN TX PANHANDLE TO
W-CENTRAL TX...THEN SSWWD ACROSS RIO GRANDE OVER NWRN COAHUILA.
LITTLE SUBSEQUENT MOVEMENT OF KS/OK DRYLINE SEGMENT IS
LIKELY...WHILE SW TX PORTION RETREATS NWWD OVERNIGHT.

...CENTRAL/SRN PLAINS...
POTENTIAL EXISTS FOR WIDELY SCATTERED TO SCATTERED TSTMS TO DEVELOP
DURING AFTERNOON ALONG/AHEAD OF DRYLINE...IN WIND PROFILES SUITABLE
FOR SUPERCELLS. MOIST-SECTOR MIXING AND LCL HEIGHTS SHOULD BE
GREATER OVER TX PORTION OF OUTLOOK THAN FARTHER N...RENDERING
GREATER TORNADO PROBABILITIES OVER KS/OK SEGMENT OF OUTLOOK AREA.
LARGE/DAMAGING HAIL IS LIKELY FROM ANY SUSTAINED SUPERCELLS.

MOIST-SECTOR DEW POINTS..AIDED BY UPSTREAM
EVAPOTRANSPIRATION...SHOULD REACH UPPER 50S OVER PORTIONS
W-CENTRAL/NWRN KS...AND LOW 60S OVER WRN OK INTO SWRN KS...BENEATH
STEEP MIDLEVEL LAPSE RATES. ONE COMPLICATING FACTOR FOR MOISTURE
AVAILABILITY MAY BE PRESENCE OF SEVERAL DAYS OF ANTECEDENT
MIXING/DRYING ACROSS CENTRAL/W-CENTRAL TX...ALTHOUGH UPSTREAM
LOW-LEVEL BOUNDARY LAYER ACROSS LOWER TX COAST APPEARS DEEPER AND
MORE MOIST THAN PREVIOUS DAYS. MORNING CONVECTION ACROSS PORTIONS
KS/OK ALSO WILL AFFECT ERN EXTENT OF FAVORABLE BOUNDARY-LAYER
THETAE. NET RESULT SHOULD BE NARROW...BUT STILL
SUPPORTIVE...CORRIDOR OF AFTERNOON DESTABILIZATION AHEAD OF DRYLINE
FROM W-CENTRAL/NWRN KS SWD ACROSS WRN OK...WITH VERY NARROW SLIVER
OF WARM SECTOR POSSIBLE NWWD ACROSS PORTIONS SWRN NEB/EXTREME NERN
CO. DURATION/STRENGTH OF DIURNAL HEATING IS UNCERTAIN...GIVEN THE
ABOVE FACTORS AND POTENTIAL FOR PLUME OF HIGH CLOUDS OVER AREA...BUT
RIBBON OF 1000-2000 J/KG LATE-AFTERNOON MLCAPE MAY DEVELOP FROM
W-CENTRAL/SWRN KS SWD.

STRENGTHENING EVENING LLJ WILL BOOST HODOGRAPH SIZE...AND PERHAPS
TORNADO POTENTIAL...FOR ANY SUSTAINED/SFC-BASED SUPERCELLS LASTING
THROUGH EARLY EVENING. ASIDE FROM THAT...COVERAGE OF SVR TSTMS
GENERALLY SHOULD DIMINISH AFTER DARK AS MLCINH STEADILY INCREASES.

...ERN NEB/IA...
STRENGTHENING LLJ AND RELATED WAA/MOISTURE TRANSPORT SHOULD SUPPORT
INCREASING COVERAGE OF TSTMS AFTER DARK...NE OF SFC WARM FRONT.
THIS CONVECTION MAY EITHER DEVELOP ELEVATED OR GROW UPSCALE FROM
EARLIER/SFC-BASED DEVELOPMENT CLOSER TO TRIPLE POINT IN CENTRAL-WRN
PORTIONS KS/NEB BORDER REGION. AS INCREASINGLY MOIST PARCELS REACH
LFC BENEATH FAVORABLE MIDLEVEL LAPSE RATES...ISOLATED SVR HAIL MAY
OCCUR. LACK OF MORE ROBUST EFFECTIVE SHEAR SHOULD LIMIT OVERALL SVR
POTENTIAL WITH THIS REGIME.

..EDWARDS.. 04/11/2012

I believe a new thread is warranted for obvious reasons. Today should be the kick-off to a potentially major tornado outbreak sequence going into next week. The main days will probably be Friday and Saturday, after that more uncertain. I'm surprised to see Thursday (today) only at Slight Risk but as the disco stated, a sliver of warm sector is possible. After Thursday, that's when the outbreak will really become elevated to dangerous.

[apocalypt-flyer]

I actually Friday could serve as another 'warm-up' round with the main action going on on Saturday and Sunday but we'll see. Kinda worried there'll be quite a lot of overnight scenarios this weekend. Those are always the worst.

[cycloneye]

Moderate Risk for Saturday April 14

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0234 AM CDT THU APR 12 2012

VALID 141200Z - 151200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS CENTRAL OK AND ERN KS...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
AND EXTENDING ACROSS THE SRN/CENTRAL PLAINS INTO THE UPPER MS
VALLEY...

...POTENTIAL EXISTS FOR A SIGNIFICANT OUTBREAK OF TORNADOES AND VERY
LARGE HAIL ACROSS PARTS OF OK/KS INTO SERN NEB/NWRN MO/SWRN IA...

...SYNOPSIS...
AN AMPLIFIED FLOW PATTERN WILL REMAIN ACROSS THE CONUS THROUGH
D3/SAT...WITH A LARGE TROUGH IN THE WEST AND DOWNSTREAM RIDGE ACROSS
THE ERN STATES. THIS WILL MAINTAIN A CORRIDOR OF STRONG SWLY
MIDLEVEL WIND EXTENDING FROM AZ/NM THROUGH OK/KS INTO THE UPPER MS
VALLEY TO GREAT LAKES REGION. A PACIFIC TROUGH DIGGING SEWD INTO THE
LOWER CO RIVER VALLEY DURING D2/FRI WILL MOVE THROUGH THE BASE OF
THE WRN LONGWAVE TROUGH DURING ON SAT...REACHING CO/NM BY 12Z
SUNDAY. AN ATTENDANT 100 KT MIDLEVEL JET WILL EMERGE INTO THE SRN
HIGH PLAINS TO KS SAT NIGHT...WITH 60-80 KT SWLY MIDLEVEL WINDS
EXPECTED ACROSS MUCH OF THE SLIGHT AND MODERATE RISK AREAS THROUGH
THE FORECAST PERIOD.

AT THE SURFACE...A FRONT IS EXPECTED TO ADVANCE EWD FROM THE UPPER
MIDWEST INTO THE GREAT LAKES...WHILE THE TRAILING PORTION OF THIS
BOUNDARY MOVES SLOWLY SWD ACROSS NEB. A LEE CYCLONE IS FORECAST TO
DEVELOP AND DEEPEN ACROSS ERN CO WITH A WARM FRONT EXTENDING EWD
THROUGH SRN NEB TO SRN IA. THE WARM FRONT WILL SPREAD NEWD INTO THE
UPPER MS VALLEY ON SAT. A DRY LINE WILL MOVE EWD SOME BY SAT
AFTERNOON AND SHOULD EXTEND FROM FAR ERN NEB SSWWD THROUGH CENTRAL
KS TO FAR WRN OK TO THE TX BIG BEND REGION BY LATE SAT AFTERNOON.

...SRN AND CENTRAL PLAINS...
WEAK HEIGHT FALLS ARE EXPECTED ACROSS THE SRN/CENTRAL PLAINS THROUGH
SAT AFTERNOON...WITH STRONGER FALLS FORECAST FOR SAT
EVENING/OVERNIGHT AS THE PACIFIC TROUGH MOVES TOWARD THE SRN AND
CENTRAL HIGH PLAINS. STRONG SLY LOW LEVEL WINDS WILL MAINTAIN
MOISTURE ADVECTION E OF THE DRY LINE ON SAT WITH SURFACE DEWPOINTS
IN THE MID 60S EXPECTED ACROSS MUCH OF OK AND REACHING CENTRAL/ERN
KS BY SAT EVENING. THIS MOISTURE RETURN COUPLED WITH STEEP MIDLEVEL
LAPSE RATES AND STRONG SURFACE HEATING /ESPECIALLY NEAR THE DRY
LINE/ WILL RESULT IN MODERATE TO STRONG INSTABILITY /MLCAPE
2000-2500 J PER KG/ ACROSS THE MODERATE RISK AREA BY LATE AFTERNOON
AND THE SURROUNDING SLIGHT RISK. STRENGTHENING DEEP LAYER WIND
FIELDS...VEERING WITH HEIGHT...WILL RESULT IN STRONG EFFECTIVE BULK
SHEAR /EXCEEDING 50 KT/ AND ORIENTED ACROSS THE DRY LINE. THIS
COMBINED WITH INCREASING LOW LEVEL HODOGRAPH CURVATURE WILL SUPPORT
TORNADIC SUPERCELLS AND THE POTENTIAL FOR VERY LARGE HAIL AND
DAMAGING WINDS. THESE FACTORS COMBINED WITH FAST STORM MOTIONS
SUGGEST THE POTENTIAL FOR LONG-TRACKED...STRONG TORNADOES OCCURRING
FROM THE AFTERNOON THROUGH THE EVENING /INCLUDING AFTER DARK/.

...ERN NEB/IA/NRN MO/NWRN IL/SWRN-SRN WI...
STRENGTHENING SWLY MIDLEVEL WINDS ACROSS THIS REGION THROUGH D3
COMBINED WITH MOISTURE/DESTABILIZATION OCCURRING AS A WARM FRONT
ADVANCES NNEWD SUGGESTS THE ENVIRONMENT WILL BECOME INCREASINGLY
FAVORABLE FOR STRONG TO SEVERE STORMS. MODELS SUGGEST SHORTWAVE
RIDGING ACROSS THIS REGION. HOWEVER..A FEW WEAK IMPULSES EMBEDDED
IN THE STRONGER FLOW ALOFT AND FORCING FOR ASCENT ALONG THE SWD
MOVING FRONT AND INVOF OF THE WARM FRONT SHOULD SUPPORT DEEP MOIST
CONVECTION/TSTMS. MODERATE INSTABILITY AND EFFECTIVE BULK SHEAR OF
40-50 KT WILL FAVOR ORGANIZED STORMS WITH ALL FACETS OF SEVERE
WEATHER POSSIBLE. GREATEST TORNADO THREAT SHOULD BE CONFINED TO THE
WARM FRONT AND ALSO WWD NEAR THE INTERSECTION OF THE DRY LINE WARM
FRONT...WHERE LOW LEVEL SHEAR WILL BE ENHANCED.

..PETERS.. 04/12/2012

[Texas Snowman]

Yeah, saw that Day 3 Moderate Risk. Saturday could be a day of grinding ground scrubbers.

"THESE FACTORS COMBINED WITH FAST STORM MOTIONS
SUGGEST THE POTENTIAL FOR LONG-TRACKED...STRONG TORNADOES OCCURRING
FROM THE AFTERNOON THROUGH THE EVENING /INCLUDING AFTER DARK/."

[somethingfunny]

"Fast moving long tracked strong tornadoes after dark."

[CrazyC83]

Today doesn't look too bad. Tomorrow might see some, but Saturday looks scary. Be ready folks in the area! Last Day 3 MDT? April 27, 2011 - and we ALL know what happened that day.

[Bunkertor]

History 2011 Tusca

[Bunkertor]

History 2011

[EF-5bigj]

Ahhh 2011 the day that got me into weather however knowing a EF-5 tornado was a couple of miles away was scary

[RL3AO]

11th day 3 MDT since 2000.

[EF-5bigj]

So these storms will fasting moving and they will be violent and produce destructive tornadoes. So my question is what factor causes the more violent tornadoes the jet stream feeding into the system or the instability at ground level.

[RL3AO]

So my question is what factor causes the more violent tornadoes the jet stream feeding into the system or the instability at ground level.

You need both for large outbreaks. The jet stream pushes the air in the upper atmosphere away which causes air from underneath to rise up to replace it. This causes the lift you need.

[EF-5bigj]

Well the jet stream does look to be doing that and we got a strong jet stream to boot with this and that instability from the texas gulf.

[Ntxw]

Parameters still look scary for a widespread tornado outbreak this weekend north of the Red River. We might be capped for awhile until a linear line comes through late Sat or Sunday here down south. Storm motions will be fast so areas that get tornadoes won't have a lot of time to take action. If all holds true I think we could be getting an ef5 out of this outbreak. Two main areas of concern, warm front in the central plains and dry line in the southern plains.

[MGC]

Lets pray this event is nothing compared to last year. I was on a road trip to see my sons and grandkids in Virginia on the day the EF-4 hit Tuscaloosa. We were outside Montgomery as the warning started coming in. The radio station we were listening to was carrying live coverage. The tornadoes chased us all the way to Virginia but we were one step ahead of them. One the return trip we noticed extensive damage just north of Williamburg Va and in North Carolina.......MGC

[EF-5bigj]

Well I worry about the larger cities in KS and Ok because they are in the line of fire for these storms. Plus the chance of large,violent,destructive tornadoes seems to be going up and up that jet coming in on fri/sat will make the storms rotate violently plus the instability and moisture from the texas gulf.

[WeatherGuesser]

11th day 3 MDT since 2000.

I was just wondering about that. I know there's only been one Day 2 High so far.

[cycloneye]

Here are the probabilities that TWC Severe Weather Expert Dr Greg Forbes gives for the upcomming severe events.

Thursday April 12
KS west - 6
CO northeast - 5
NE southwest - 5
OK west - 5
TX east panhandle - 5
TX west - 3
Other areas less than 2

Friday April 13
IA west - 4
KS east - 4
MO west - 4
NE east - 4
SD extreme southeast - 4
OK southwest, central, northeast - 4
TX northwest near Childress and Wichita Falls -4

Saturday April 14
OK northwest - 7
KS south-central - 7
KS north-central - 5
NE southeast - 5
IA northwest - 4
MN southwest - 4

[EF-5bigj]

I get the feeling the torcon will get higher

[cycloneye]

Tornado Watch issued

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 157
NWS STORM PREDICTION CENTER NORMAN OK
1250 PM MDT THU APR 12 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

EASTERN COLORADO
WESTERN KANSAS
SOUTHWEST NEBRASKA

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 1250 PM UNTIL
800 PM MDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE
MILES EAST AND WEST OF A LINE FROM 50 MILES NORTHWEST OF IMPERIAL
NEBRASKA TO 45 MILES EAST SOUTHEAST OF LAMAR COLORADO. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU7).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

DISCUSSION...THUNDERSTORMS ARE EXPECTED TO INTENSIFY THIS AFTERNOON
OVER EASTERN CO AND TRACK EASTWARD INTO WESTERN KS/SOUTHWEST NEB.
THIS REGION IS WITHIN A CORRIDOR OF MODERATE CAPE AND STEEP LAPSE
RATES...ALONG WITH FAVORABLE LOW LEVEL AND DEEP LAYER SHEAR. STORMS
ARE FORECAST TO QUICKLY BECOME SUPERCELLULAR WITH A RISK OF VERY
LARGE HAIL AND A FEW TORNADOES. INCREASING WIND FIELDS THROUGH THE
LATE AFTERNOON AND EVENING WOULD SUPPORT A RISK OF STRONG TORNADOES.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 27030.


...HART