Tornado Outbreak Possible 5/11/2014

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Tornado Outbreak Possible 5/11/2014

#1 Postby TropicalAnalystwx13 » Fri May 09, 2014 10:42 pm

The threat for a significant severe weather and/or tornado outbreak returns again this weekend as a strong shortwave trough ejects into the Plains. With a lack of significant troughing across the East the past few days, Gulf moisture has been able to begin surging northward pretty effectively; that won't be an issue for Sunday's setup. Instability is forecast to be more than sufficient, 3000-4000j/kg, and directional/shear look great. With 0-1km SRH of 150-200m2/s2 and 0-3km SRH of 250-300m2/s2 (coupled with the directional shear), several supercells will be possible along the cold front, and these cells will have the potential to put down long-tracked, significant tornadoes. Only fly in the ointment across the IA/NE/MO area is the potential for morning convection that would stabilize the atmosphere some.

I'm personally expecting a Moderate risk to be issued at the upcoming 6z Day 2 Outlook; NWS Des Moines has mentioned that they wouldn't be surprised to see this go Moderate or even High as the event progresses:

AFTER A BRIEF LULL INTO THE NIGHT ATTENTION TURNS UPSTREAM WITH
INCREASING INFLUENCE BY MATURING ROCKIES LONG WAVE TROUGH. STRONG
THETA-E ADVECTION AND ADVANCING ELEVATED INSTABILITY ALOFT WILL
LIKELY RESULT IN MO VALLEY MCS ENTERING SWRN IA PLUS/MINUS 12Z.
THIS THERMODYNAMIC FORCING CONTINUES INTO THE DAY ALONG WITH
INCREASING KINEMATIC FORCING AND DIFFLUENCE ALOFT AS AS WARM FRONT
MATURES INTO IA. NAM/GFS MLCAPES BOTH DEPICT MLCAPES OVER 3000 J/KG
DURING THIS PERIOD WITH LITTLE CINH SO THERE SHOULD BE NO PROBLEM
INITIATING CONVECTION AND HAVE BOOSTED POPS THROUGH THE LIKELIES TO
CATEGORICAL IN SPOTS. LOW LEVEL AND DEEP SHEAR ARE IMPRESSIVE...AS
WELL AS HODOGRAPHS WITH SRH WELL INTO THE HUNDREDS...SO TORNADIC
POTENTIAL IS CERTAINLY DISCONCERTING. GFS/NAM SOUNDINGS BOTH DEPICT
VERY FAVORABLE TORNADO PARAMETERS WITH ELEVATED SIG TOR VALUES AND
SUFFICIENTLY LOW LCLS. WOULD NOT BE AT ALL SURPRISED TO SEE CURRENT
DAY 3 SLIGHT RISK ELEVATED TO MODERATE OR HIGH ALONG AND SOUTH OF
WHERE EVER THE FRONT EVENTUALLY LAYS OUT. PRECIPITABLE WATER
VALUES EXCEED 2SDS IN THE WARM SECTOR AS WELL SO LOCALLY HEAVY
RAINS ARE ALSO QUITE POSSIBLE. ALTHOUGH CONDITIONS ARE NOT AS
IDEALISTIC...ANOTHER ROUND OF SEVERE PEAK HEATING CONVECTION MAY
BRIEFLY OCCUR IN ERN SECTIONS MON BEFORE ADVANCING EWD WITH THE
FRONT.


Current SPC Day 3 Outlook:

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT FRI MAY 09 2014

VALID 111200Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID-MS VALLEY TO THE
SRN PLAINS...

...SUMMARY...
A SIGNIFICANT SEVERE WEATHER EPISODE APPEARS PROBABLE BEGINNING
SUNDAY AFTERNOON FROM THE MID-MISSISSIPPI VALLEY TO THE SOUTHERN
GREAT PLAINS.


...SYNOPSIS...
A VIGOROUS SHORTWAVE IMPULSE EMBEDDED WITHIN AN AMPLIFIED
UPPER-LEVEL TROUGH WILL TRACK FROM THE SRN GREAT BASIN TO THE SRN
ROCKIES. ATTENDANT MID-LEVEL SPEED MAX WILL BECOME CENTERED FROM THE
SRN HIGH PLAINS TO THE CNTRL PLAINS EARLY MON. AT THE SURFACE...A
LEE CYCLONE WILL DIURNALLY DEEPEN OVER THE SRN HIGH PLAINS. THE
DRYLINE SHOULD MIX TOWARDS THE ERN TX PANHANDLE/WRN OK BORDER S/SWWD
ACROSS THE PERMIAN BASIN. GUIDANCE DIFFERS ON THE ACCELERATION OF A
S/SEWD-PROGRESSING COLD FRONT OVER THE CNTRL/SRN PLAINS.

...MID-MS VALLEY TO SRN PLAINS...
PERVASIVE AND STRENGTHENING SWLYS AT 700 MB WILL RESULT IN AN
EXPANDING EML PLUME AND ATTENDANT CAPPING INVERSION EARLY SUN...WITH
INCREASINGLY RICH BOUNDARY LAYER MOISTURE GIVEN STRONG POLEWARD
ADVECTION FROM THE WRN GULF. MIDDLE TO UPPER 60S SURFACE DEW POINTS
SHOULD BECOME ESTABLISHED FROM THE LOWER MO VALLEY SWD...YIELDING A
BROAD STRONGLY UNSTABLE AIR MASS WITH MLCAPE AOA 2500 J/KG AHEAD OF
THE DRYLINE/COLD FRONT. THE NRN EXTENT OF STRONG DESTABILIZATION
SHOULD BE DELIMITED BY EARLY SUN WAA-DRIVEN CONVECTION OVER PARTS OF
THE LOWER MO VALLEY. SOME OF THIS ACTIVITY MAY CONTINUE E/NEWD
THROUGH THE DAY WITH AN ISOLATED SEVERE RISK...BUT MORE PROBABLE
SURFACE-BASED DEVELOPMENT SHOULD OCCUR WITH SWRN EXTENT WHERE
GREATER INSOLATION OCCURS. STRONG CONVERGENCE ALONG THE FRONT WILL
LIKELY YIELD INCREASINGLY NUMEROUS STORMS LATE AFTERNOON INTO
EVENING FROM ERN KS INTO SRN IA. LARGE HAIL /SOME SIGNIFICANT/ AND A
FEW TORNADOES WILL BE POSSIBLE INITIALLY. THE POTENTIAL FOR
UNDERCUTTING BY THE FRONT SHOULD YIELD CLUSTER AND EVENTUAL LINEAR
MODES WITH SEVERE HAIL/WIND HAZARDS PERSISTING INTO SUN NIGHT. A
LARGE MCS MAY ULTIMATELY EVOLVE GIVEN THE STRENGTHENING LARGE-SCALE
ASCENT DOWNSTREAM OF THE UPPER TROUGH AND BROADLY UNSTABLE WARM
SECTOR.

FARTHER S...CONVERGENCE ALONG THE DRYLINE WILL STRENGTHEN
/ESPECIALLY INVOF TRIPLE-POINT/ AND INTENSE SURFACE HEATING SHOULD
REMOVE INHIBITION...WITH ISOLATED TO SCATTERED STORMS DEVELOPING
LATE AFTERNOON. ALTHOUGH HODOGRAPHS MAY NOT BE OVERLY
LARGE...CROSS-BOUNDARY DEEP-LAYER FLOW WILL BE FAVORABLE FOR
DISCRETE SUPERCELLS GIVEN THE DEGREE OF INSTABILITY. RELATIVELY
LARGE SURFACE DEW POINT DEPRESSIONS SUGGEST VERY LARGE HAIL WOULD BE
THE PRIMARY INITIAL HAZARD. THE TORNADO RISK SHOULD BE MAXIMIZED IN
EARLY EVENING AS A SLY LLJ STRENGTHENS AND SPREADS LOWER. EWD EXTENT
OF OVERNIGHT SEVERE POTENTIAL IS UNCERTAIN OWING TO MODEL
DIFFERENCES IN COLD FRONT EVOLUTION AND DEGREE OF NOCTURNAL WARM
SECTOR INHIBITION.

..GRAMS.. 05/09/2014


Image
Last edited by TropicalAnalystwx13 on Sat May 10, 2014 1:47 pm, edited 1 time in total.
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#2 Postby EF-5bigj » Fri May 09, 2014 11:13 pm

I will be watching this carefully. Long tracked significant tornadoes is never a good thing.
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#3 Postby TropicalAnalystwx13 » Sat May 10, 2014 1:14 am

No Day 2 Moderate risk, though Grams did note that he contemplated issuing one. Ultimately, questions regarding early morning convection deterred the upgrade for this outlook. Maybe 1730z. Strong tornadoes now being mentioned.

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1243 AM CDT SAT MAY 10 2014

VALID 111200Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY TO THE
SRN PLAINS...

...SUMMARY...
AT LEAST SCATTERED SEVERE STORMS APPEAR PROBABLE BEGINNING SUNDAY
AFTERNOON FROM IOWA TO WESTERN OKLAHOMA. SEVERE TO VERY LARGE
HAIL...DAMAGING WINDS...AND TORNADOES WILL BE POSSIBLE.

...SYNOPSIS...
A VIGOROUS SHORTWAVE IMPULSE EMBEDDED WITHIN AN AMPLIFIED
UPPER-LEVEL TROUGH WILL TRACK FROM THE SRN GREAT BASIN TO THE SRN
ROCKIES. ATTENDANT MID-LEVEL SPEED MAX WILL BECOME CENTERED FROM THE
SRN HIGH PLAINS TO THE CNTRL PLAINS EARLY MON. AT THE SURFACE...A
CYCLONE WILL DIURNALLY DEEPEN IN THE LEE OF THE SRN ROCKIES WITH A
DRYLINE MIXING TOWARDS THE ERN TX PANHANDLE/WRN OK BORDER S/SWWD
ACROSS THE PERMIAN BASIN. GUIDANCE CONTINUES TO DIFFER ON THE
ACCELERATION OF A S/SEWD-PROGRESSING COLD FRONT OVER THE CNTRL/SRN
PLAINS. MODEST CYCLOGENESIS SHOULD OCCUR ALONG A PORTION OF THIS
FRONT FROM THE CNTRL PLAINS TO UPPER MIDWEST ON SUN NIGHT.

....UPPER MS VALLEY TO CNTRL PLAINS...
CONSIDERED A MODERATE RISK FOR PORTIONS OF KS TO IA WHERE SCATTERED
TO NUMEROUS STORMS ARE EXPECTED WITHIN A STRONG COMBINATION OF
INSTABILITY/SHEAR. BUT UNCERTAINTIES WITH REGARD TO FRONTAL
PLACEMENT...DEEP-LAYER FLOW GENERALLY PARALLELING THE FRONT AND
EFFECTS OF EARLY-DAY CONVECTION PRECLUDE AN UPGRADE THIS OUTLOOK.

STRENGTHENING SWLYS AT 700 MB WILL RESULT IN AN EXPANDING EML PLUME
AND ATTENDANT CAPPING INVERSION EARLY SUN...WITH INCREASINGLY RICH
BOUNDARY LAYER MOISTURE AMIDST POLEWARD ADVECTION FROM THE WRN GULF.
MIDDLE TO UPPER 60S SURFACE DEW POINTS SHOULD BECOME ESTABLISHED
FROM AT LEAST THE LOWER MO VALLEY SWD...YIELDING A BROAD STRONGLY
UNSTABLE AIR MASS WITH MLCAPE REACHING 2500-3500 J/KG IN THE
AFTERNOON AHEAD OF THE COLD FRONT AND DRYLINE.

LOW-LEVEL WAA ON THE LEADING EDGE OF THE RICHER MOISTURE
RETURN/CAPPING INVERSION SHOULD AID IN REGENERATIVE CLUSTERS OF
ELEVATED STORMS SUN MORNING INTO AFTERNOON FROM PARTS OF THE LOWER
MO TO UPPER MS VALLEY. HOW EXACTLY THIS CONVECTION WILL PLAY OUT IS
UNCLEAR...BUT THERE IS POTENTIAL FOR AN EFFECTIVE WARM FRONT/OUTFLOW
BOUNDARY TO BECOME ESTABLISHED FROM PARTS OF IA TO IL. SHOULD THIS
OCCUR...HODOGRAPHS DURING LATE AFTERNOON AND EVENING ALONG THIS
W/E-ORIENTED BOUNDARY WOULD BECOME QUITE FAVORABLE FOR SUPERCELLS AS
THE LLJ STRENGTHENS. THIS SUGGESTS A RISK FOR STRONG TORNADOES MAY
DEVELOP IN IA.

THE ECMWF/UKMET REMAIN CONSISTENTLY SLOWER WITH COLD FRONT
PROGRESSION COMPARED TO THE NAM/GFS IN NEB/KS. EVEN SO...STRONG
CONVERGENCE ALONG THIS FRONT WILL YIELD INCREASINGLY NUMEROUS STORMS
LATE AFTERNOON INTO EVENING. LARGE HAIL /SOME SIGNIFICANT/ AND A FEW
TORNADOES WILL BE POSSIBLE INITIALLY. THE POTENTIAL FOR UNDERCUTTING
BY THE FRONT APPEARS MORE LIKELY IN KS WITH WEAK CYCLOGENESIS
EXPECTED TO OCCUR TOWARDS THE MO VALLEY. WITH MID-LEVEL WINDS
GENERALLY PARALLELING THE FRONT...CLUSTER/LINEAR MODES SHOULD BECOME
DOMINANT AS CONVECTION SHOULD TEND TO ZIPPER S/SWWD ALONG THE FRONT.
SEVERE HAIL/WIND HAZARDS SHOULD PERSIST INTO SUN NIGHT.

...SRN PLAINS...
INTENSE SURFACE HEATING ALONG WITH STRENGTHENING CONVERGENCE NEAR
THE LEE CYCLONE/DRYLINE INTERSECTION SHOULD YIELD ISOLATED STORMS
DEVELOPING LATE AFTERNOON. ALTHOUGH HODOGRAPHS SHOULD NOT BE OVERLY
LARGE INITIALLY...CROSS-BOUNDARY DEEP-LAYER FLOW WILL BE FAVORABLE
FOR DISCRETE SUPERCELLS GIVEN STRONG INSTABILITY. VERY LARGE HAIL
WILL LIKELY BE THE PRIMARY INITIAL HAZARD WITH CONVECTION PROBABLY
FORMING AMIDST MODERATELY LARGE SURFACE TEMPERATURE/DEW POINT
SPREADS. SPREADS WILL LOWER DURING THE EARLY EVENING AS A SLY LLJ
STRENGTHENS...LIKELY MAXIMIZING POTENTIAL FOR A COUPLE TORNADOES
DURING THIS TIME FRAME INVOF WRN OK. GREATER CONVECTIVE COVERAGE
SHOULD OCCUR SUN NIGHT AS THE FRONT IMPINGES ON THE STILL STRONGLY
BUOYANT AIR MASS...WITH ATTENDANT SEVERE HAIL/WIND HAZARDS.

..GRAMS.. 05/10/2014
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#4 Postby WeatherGuesser » Sat May 10, 2014 7:37 am

No upgrade (so far).

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1206 AM CDT SAT MAY 10 2014

VALID 101200Z - 111200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID MS VALLEY SWWD
INTO WRN OK...

...SUMMARY...
ISOLATED SEVERE THUNDERSTORMS SHOULD FORM DURING THE HEAT OF THE DAY
ACROSS THE MID MISSISSIPPI VALLEY...SOUTHWEST ACROSS EASTERN KANSAS
INTO PORTIONS OF WESTERN OKLAHOMA. LARGE HAIL IS THE PRIMARY SEVERE
THREAT WITH THIS ACTIVITY.

...MID MS VALLEY TO WRN OKLAHOMA...

30-60M 12HR MID-LEVEL HEIGHT RISES WILL DEVELOP ACROSS THE MID-MS
VALLEY SATURDAY AS SHORT-WAVE RIDGING BUILDS AHEAD OF STRONG UPPER
LOW DIGGING INTO THE GREAT BASIN. AT THE SFC...WARM FRONT IS
EXPECTED TO ADVANCE NWD ACROSS KS/MO TO A POSITION NEAR I-70 BY
11/00Z. INTENSE BOUNDARY LAYER HEATING ACROSS THE CNTRL/SRN PLAINS
SHOULD ALLOW THE DRYLINE TO INITIALLY ESTABLISH ITSELF FROM SWRN
OK...NEWD INTO NERN KS BEFORE LATE DAY PRESSURE FALLS IN THE LEE OF
THE CNTRL ROCKIES RESULTS IN FLOW BACKING ACROSS KS AND THE DRYLINE
RETREATING WWD.

IN THE ABSENCE OF MEANINGFUL LARGE SCALE ASCENT IT APPEARS DIURNAL
HEATING WILL PROVE INSTRUMENTAL IN CONVECTIVE INITIATION...BOTH
ALONG THE DRYLINE AND ALONG WARM FRONT. EARLY IN THE PERIOD WEAK
SUBSIDENCE SHOULD BE NOTED IN THE WAKE OF EJECTING SHORT-WAVE
TROUGH. TSTMS MAY NOT DEVELOP UNTIL AFTER 21Z ALONG THE WARM
FRONT/DRYLINE INTERSECTION WHEN READINGS BREACH CONVECTIVE
TEMPERATURES. LOW LEVEL CONVERGENCE SHOULD BE MAXIMIZED ACROSS MO
AND THIS SHOULD PROVE MORE SUPPORTIVE OF SUSTAINING POTENTIALLY
ORGANIZED SUPERCELL DEVELOPMENT. FORECAST SOUNDINGS ACROSS THIS
REGION EXHIBIT SUBSTANTIAL DEEP LAYER SHEAR ALONG WITH SBCAPE IN
EXCESS OF 3000 J/KG. ADDITIONALLY...LOW LEVEL SHEAR WILL BE
MAXIMIZED ALONG THE WARM FRONT AND THIS COULD ENHANCE TORNADO THREAT
FROM LATE AFTERNOON THROUGH MID EVENING. OTHERWISE...VERY LARGE
HAIL CAN BE EXPECTED WITH SUPERCELLS THAT EVOLVE WITHIN WARM
ADVECTION REGIME. AS LLJ INCREASES DURING THE OVERNIGHT PERIOD
ADDITIONAL CONVECTION MAY EVOLVE WITHIN WARM ADVECTION BELT...THUS A
FEW SEVERE TSTMS MAY LINGER WELL INTO THE OVERNIGHT HOURS.

FARTHER SW...STRONG HEATING ALONG THE DRYLINE WILL ALLOW SFC
TEMPERATURES TO WARM INTO THE LOWER 90S AND ISOLATED HIGH-BASED
CONVECTION IS EXPECTED TO DEVELOP ACROSS PARTS OF KS/OK. DEEP LAYER
SHEAR SHOULD SUPPORT STORM ROTATION AND SUPERCELL STRUCTURES ARE
POSSIBLE. LARGE HAIL AND GUSTY WINDS ARE THE PRIMARY THREATS ACROSS
THIS REGION.

..DARROW/DIAL.. 05/10/2014


New outlook due before too long.
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#5 Postby WeatherGuesser » Sat May 10, 2014 8:10 am

Still Slight


DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0753 AM CDT SAT MAY 10 2014

VALID 101300Z - 111200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CNTRL
PLNS...OZARKS...AND LWR M/MID MS VLYS...

...SUMMARY...
WIDELY SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED LATE THIS
AFTERNOON INTO TONIGHT FROM PARTS OF OKLAHOMA AND KANSAS EASTWARD
INTO MUCH OF MISSOURI AND SOUTHERN IOWA. LARGE HAIL WILL BE THE
PRIMARY SEVERE THREAT...ALTHOUGH TORNADOES AND LOCALLY DAMAGING WIND
ALSO WILL BE POSSIBLE.

...SYNOPTIC SETUP...
MODERATE WLY FLOW NOW IN PLACE OVER THE CNTRL U.S. WILL GIVE WAY TO
STRENGTHENING SW FLOW BY EARLY SUN AS POTENT SHORTWAVE TROUGH OVER
ORE AMPLIFIES SE INTO THE SRN GRT BASIN. IN RESPONSE...EXPECT
DOWNSTREAM SHORTWAVE IMPULSES NOW OVER NEB AND MO TO SHEAR E/NE INTO
THE WRN GRT LKS/UPR OH VLY ...WHILE LOW AMPLITUDE CYCLONIC FLOW
PERSISTS ACROSS THE ERN GRT LKS...THE MID ATLANTIC STATES...AND NEW
ENGLAND.

AT THE SFC...ELONGATED AREA OF LOW PRESSURE IN THE LEE OF THE RCKYS
SHOULD CONSOLIDATE AND DEEPEN OVER SE CO/SW KS TNGT AND EARLY SUN.
DIFFUSE FRONT NOW EXTENDING ENE FROM OK THROUGH THE OZARKS SHOULD
BECOME BETTER-DEFINED AND REFORM NWD AS A WARM FRONT ACROSS KS/MO
TODAY...AND THE LWR MO VLY TNGT. THIS BOUNDARY SHOULD SERVE AS THE
MAIN FOCUS FOR STRONG TO SVR TSTMS THROUGH THE PERIOD.

...CNTRL PLNS INTO LWR MO/MID MS VLYS TODAY/TNGT...
ASCENT WITH NEG-TILT SHORTWAVE TROUGH NOW OVER NEB WILL GLANCE PARTS
OF ERN KS AND MUCH OF MO TODAY. UPLIFT WITH THIS FEATURE WILL BE
RELATIVELY WEAK. BUT COUPLED WITH SFC HEATING AND MOISTURE
RETURN/LOW-LVL UPLIFT ALONG DEVELOPING WARM FRONT...SETUP MAY
SUPPORT DEVELOPMENT OF SCTD LATE AFTN TSTMS FROM SE KS INTO WRN/NRN
MO...AND PERHAPS SRN IA AND NRN OK.

WITH MUCAPE INCREASING TO AROUND 2000 J/KG...40 KT WNW DEEP
SHEAR...AND RELATIVELY WEAK LOW-LVL FORCING...POTENTIAL WILL EXIST
FOR DISCRETE SUPERCELLS WITH LARGE HAIL AND LOCALLY DMGG WIND.
TORNADOES ALSO MAY OCCUR AS LOW-LVL WINDS REMAIN BACKED NEAR WARM
FRONT. A MORE SVR CONDITIONAL ALSO WILL EXIST ALONG DRY LINE THAT BY
EARLY EVE SHOULD EXTEND SSW FROM NEAR WICHITA INTO SW OK. FALLING
SFC PRESSURES W OF THE DRY LINE SUGGEST THAT CONVERGENCE ALONG THE
FEATURE WILL BE WEAK. NEVERTHELESS...CANNOT COMPLETELY RULE OUT AN
ISOLD SVR STORM OR TWO GIVEN INCREASING BOUNDARY LAYER MOISTURE.

THE KS/MO STORMS SHOULD CONSOLIDATE AND DEVELOP N AND NEWD OVERNIGHT
AS WARM FRONT CONTINUES TO BECOME BETTER ESTABLISHED AND LLJ
STRENGTHENS. THE ACTIVITY COULD POSE A RISK FOR SVR HAIL AND PERHAPS
LOCALLY DMGG WIND OVER PARTS OF NEB...IA...AND WRN IL EARLY SUN.

...MID-ATLANTIC LATE THIS AFTN...
SHORT LINES/SMALL CLUSTERS OF STORMS MAY FORM E OF THE MOUNTAINS
OVER THE MID-ATLANTIC STATES THIS AFTN AS SFC HEATING AND ASCENT
WITH LOW-AMPLITUDE DISTURBANCE NOW IN THE OH VLY DESTABILIZE REGION.
40 KT UNIDIRECTIONAL WSWLY LWR TROPOSPHERIC FLOW AND RELATIVELY
STEEP LOW-LVL LAPSE RATES SUGGEST A CONDITIONAL RISK FOR A FEW
STORMS WITH DMGG WIND.

..CORFIDI/SMITH.. 05/10/2014
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#6 Postby EF-5bigj » Sat May 10, 2014 9:19 am

I do not know what to think of these risks it seems bad tornadoes have happened on less then moderate risk days.
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Re:

#7 Postby WeatherGuesser » Sat May 10, 2014 11:39 am

EF-5bigj wrote:I do not know what to think of these risks it seems bad tornadoes have happened on less then moderate risk days.


Like any other forecast, they're a guide, a piece of information to be considered. Tornadoes often happen on non-risk days or in low risk areas.

As I recall, the Vilonia tornado was outside the highest risk area.
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#8 Postby EF-5bigj » Sat May 10, 2014 11:43 am

I think it did I think it was either the slight or moderate risk area for Vilonia tornado. They are a guide your right
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#9 Postby TropicalAnalystwx13 » Sat May 10, 2014 12:22 pm

WeatherGuesser, you're posting the Day 1 Outlook, which is for today (Saturday). The outbreak is tomorrow (Sunday).
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#10 Postby TropicalAnalystwx13 » Sat May 10, 2014 12:51 pm

DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
1238 PM CDT SAT MAY 10 2014

VALID 111200Z - 121200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF IA...ERN
NEB...NW MO AND KS...


...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...CNTRL PLAINS....MID-MO VALLEY AND MID TO UPPER MS VALLEY...

CORRECTED TO REMOVE SECOND HEADLINE

...SUMMARY...
SEVERE WEATHER OUTBREAK WITH MANY TORNADOES AND VERY LARGE HAIL
POSSIBLE SUNDAY AND SUNDAY NIGHT ACROSS PARTS OF THE CENTRAL PLAINS
AND MID MISSOURI VALLEY.
SEVERE STORMS WILL ALSO BE LIKELY IN THE
SOUTHERN PLAINS.

...MID-MO VALLEY/CNTRL PLAINS...
AN UPPER-LEVEL TROUGH WILL MOVE ACROSS THE FOUR CORNERS REGION
SUNDAY AS DIFFLUENT SOUTHWEST MID-LEVEL FLOW REMAINS IN PLACE ACROSS
THE CNTRL STATES. AT THE SFC...A COLD FRONT WILL ADVANCE SEWD ACROSS
THE CNTRL PLAINS AS A WARM FRONT MOVES NWD ACROSS THE MID MO VALLEY.
A CLUSTER OF THUNDERSTORMS MAY BE ONGOING IN THE MID MO VALLEY
SUNDAY MORNING ON THE NOSE OF THE LOW-LEVEL JET. HOWEVER...MOST OF
THE WARM SECTOR SHOULD REMAIN UNDISTURBED THROUGH EARLY SUNDAY
AFTERNOON AS MODERATE TO STRONG INSTABILITY DEVELOPS. BY LATE
AFTERNOON...NUMEROUS THUNDERSTORMS SHOULD INITIATE ALONG THE WARM
FRONT FROM IA EXTENDING SWWD ALONG THE COLD FRONT INTO SE NEB AND
CNTRL KS. DUE TO THE VERY UNSTABLE AIRMASS...STRONG DEEP LAYER SHEAR
AND IMPRESSIVE LOW-LEVEL SHEAR...AN OUTBREAK OF SEVERE STORMS WITH
MANY TORNADOES WILL BE POSSIBLE ACROSS THE REGION SUNDAY AND SUNDAY
NIGHT.

FORECAST SOUNDINGS FOR 00Z/MON ACROSS THE MODERATE RISK AREA FROM
DES MOINES IA SWWD TO TOPEKA KS SHOW IMPRESSIVE SHEAR PROFILES
COUPLED WITH STRONG INSTABILITY. THE NAM IS FORECASTING MLCAPE IN
THE 2000 TO 3000 J/KG RANGE WITH 0-6 KM SHEAR OF 40 TO 50 KT. IN
ADDITION...LONG LOOPED HODOGRAPHS RESULT IN 0-3 KM STORM RELATIVE
HELICITIES OF 350 TO 500 M2/S2 SUGGESTING THE ENVIRONMENT WILL BE
FAVORABLE FOR SUPERCELLS AND TORNADOES. SEVERAL STRONG OR LONG-TRACK
TORNADOES APPEAR POSSIBLE ACROSS THE REGION AS THE LOW-LEVEL JET
RAPIDLY BECOMES FOCUSED LATE SUNDAY AFTERNOON INTO SUNDAY EVENING.

SUPERCELLS SHOULD BE ACCOMPANIED WITH LARGE HAIL AND WIND DAMAGE.
HAILSTONES GREATER THAN 2 INCHES IN DIAMETER WILL BE POSSIBLE WITH
THE MORE DOMINANT SUPERCELLS.

UNCERTAINTIES STILL EXIST CONCERNING HOW THE EVENT WILL UNFOLD
SUNDAY AND SUNDAY NIGHT WITH THE MAIN CONCERN BEING STORM MODE. THE
IMPRESSIVE SHEAR ENVIRONMENT SHOULD PROMOTE STRONG ROTATION WITH
SUPERCELLS BUT THE STORMS IN THE CNTRL PLAINS MAY EVENTUALLY MERGE
INTO LINES ALONG THE COLD FRONT WHERE LOW-LEVEL LINEAR FORCING WILL
BE MAXIMIZED. FURTHER TO THE NORTHEAST ALONG THE WARM FRONT IN
IA...SUPERCELLS SHOULD HAVE AN EASIER TIME REMAINING DISCRETE. THE
NAM FORECAST SOUNDINGS SHOW THE MOST FAVORABLE HODOGRAPH FOR STRONG
TORNADOES AT DES MOINES IA AT 00Z/MON SUGGESTING THE WARM FRONT MAY
HAVE THE GREATEST TORNADO POTENTIAL.
AS THE LOW-LEVEL JET
CONSOLIDATES DURING THE EARLY TO MID EVENING...THE GREATEST TORNADO
THREAT MAY DEVELOP SWWD AS THE LOW-LEVEL JET CONSOLIDATES.

...SRN PLAINS...
AN UPPER-LEVEL TROUGH WILL MOVE ACROSS THE FOUR CORNERS REGION
SUNDAY AS A COLD FRONT ADVANCES SWD ACROSS THE CNTRL HIGH PLAINS.
SSELY FLOW ACROSS THE SRN PLAINS WILL RESULT IN A VERY MOIST WARM
SECTOR EXTENDING EWD FROM A DRYLINE IN FAR WRN OK AND NW TX. AS
LOW-LEVEL CONVERGENCE ALONG THE DRYLINE INCREASE LATE SUNDAY
AFTERNOON...ISOLATED TO SCATTERED THUNDERSTORMS SHOULD INITIATE.
FORECAST SOUNDINGS FROM CLINTON OK SWWD TO WICHITA FALLS TX SHOW AN
IMPRESSIVE THERMODYNAMIC ENVIRONMENT WITH MLCAPE IN THE 3000 TO 3500
J/KG RANGE. IN ADDITION...0-6 KM SHEAR SHOULD BE AROUND 35 KT WITH
850 TO 500 MB LAPSE RATES NEAR 8.5 C/KM. THIS SHOULD BE VERY
FAVORABLE FOR SUPERCELLS WITH LARGE HAIL.
HAILSTONES OF GREAT THAN 2
INCHES WILL BE POSSIBLE WITH CELLS THAT CAN BECOME DOMINANT IN SPITE
OF THE WEAK LARGE-SCALE FORCING. A FEW TORNADOES AND WIND DAMAGE
WILL ALSO BE POSSIBLE.

...MID TO UPPER MS VALLEY...
AN UPPER-LEVEL RIDGE WILL BE LOCATED ACROSS THE UPPER MS VALLEY AND
WRN GREAT LAKES REGION SUNDAY. AT THE SFC...BACKED SELY FLOW WILL
RESULT IN A BROAD MOIST SECTOR FROM SRN MN SEWD INTO IL AND WRN IND
WHERE SFC DEWPOINTS SHOULD BE IN THE LOWER TO MID 60S F. SCATTERED
THUNDERSTORMS MAY INITIATE DURING THE AFTERNOON ALONG THIS CORRIDOR
AS THE NOSE OF THE LOW-LEVEL JET ENTERS THE REGION FROM THE
SOUTHWEST. ALTHOUGH THE ACTIVITY MAY REMAIN ELEVATED...INSTABILITY
AND SHEAR PROFILES SHOULD BE FAVORABLE FOR A SEVERE THREAT. LARGE
HAIL WILL BE POSSIBLE WITH THE STRONGER CELLS BUT ISOLATED WIND
DAMAGE MAY ALSO OCCUR.

..BROYLES.. 05/10/2014


Image
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#11 Postby EF-5bigj » Sat May 10, 2014 12:59 pm

That's a pretty strong moderate risk.
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#12 Postby TropicalAnalystwx13 » Sat May 10, 2014 1:49 pm

The 12z 4km NAM is pretty ridiculous across southern Iowa. Effective bulk shear up to 60 knots, CAPE over 3500j/kg, 0-3km SRH of 600-800m2/s2, a supercell composite of 48-52, and a maxed out 0-3km EHI of 12.

Depending on how tomorrow morning's convection plays out, a high risk looks very possible.
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#13 Postby EF-5bigj » Sat May 10, 2014 1:53 pm

Are we talking PDS type situation? With large hail and destructive, long tracked tornadoes.
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Re:

#14 Postby WeatherGuesser » Sat May 10, 2014 1:57 pm

TropicalAnalystwx13 wrote:WeatherGuesser, you're posting the Day 1 Outlook, which is for today (Saturday). The outbreak is tomorrow (Sunday).


There was nothing for then either. Only a Slight. And one for Monday too.
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#15 Postby EF-5bigj » Sat May 10, 2014 2:02 pm

I just looked on the SPC convective outlooks Sunday is a moderate risk with a 45% hatched area.
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#16 Postby TropicalAnalystwx13 » Sat May 10, 2014 2:04 pm

EF-5bigj wrote:Are we talking PDS type situation? With large hail and destructive, long tracked tornadoes.

Probably.

WeatherGuesser wrote:
TropicalAnalystwx13 wrote:WeatherGuesser, you're posting the Day 1 Outlook, which is for today (Saturday). The outbreak is tomorrow (Sunday).


There was nothing for then either. Only a Slight. And one for Monday too.

Right, it was just upgraded to a Moderate risk a while ago.
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#17 Postby EF-5bigj » Sat May 10, 2014 2:08 pm

Well I'm going to tell my friends in KS to keep their eyes on the sky and be weather aware.
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#18 Postby Alyono » Sun May 11, 2014 8:07 am

seems as if there may be issues with the LCLs today. May prevent a widespread outbreak
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#19 Postby RL3AO » Sun May 11, 2014 8:30 am

To be clear, the MDT is for hail and not tornadoes.
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#20 Postby Alyono » Sun May 11, 2014 8:47 am

may need to change the thread title then... since a significant tornado outbreak appears far less likely
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