Tornado Outbreak April 29-May 2, HIGH RISK AR, TN, MS

[CrazyC83]

A week later, we might be doing this all over again. Seems to be aiming for the exact same areas hit last week into last weekend.

[KWT]

Here is the day 3 forecast, which is a slight risk:


SPC AC 270729

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CDT TUE APR 27 2010

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY REGION
SSWWD INTO PARTS OF OK/N TX...

...SYNOPSIS...
LARGE UPPER LOW/TROUGH INITIALLY CENTERED OVER THE INTERMOUNTAIN
WEST WILL MAKE SLOW EWD PROGRESS THIS PERIOD...INCREASINGLY
AFFECTING THE CENTRAL CONUS.

AT THE SURFACE...AN OCCLUDED SYSTEM WILL PROGRESS ACROSS THE NRN AND
CENTRAL PLAINS. BY THE END OF THE PERIOD...THE OCCLUDED FRONT IS
EXPECTED TO ARC SEWD FROM A LOW OVER THE ND/NRN MN VICINITY ACROSS
THE UPPER MS VALLEY...AND THEN ON SWWD AS A COLD FRONT ACROSS
IA...ERN KS/WRN MO...ERN OK...AND INTO CENTRAL TX.

...MID MO VALLEY REGION SSWWD INTO PARTS OF OK/N TX...
BOUNDARY-LAYER MOISTURE WILL CONTINUE SPREADING NWD INTO THE CENTRAL
U.S. AS STRONG SLY FLOW CONTINUES...WITH DEWPOINTS AROUND 60 F
SPREADING INTO OK/KS AND INTO THE MID MO VALLEY REGION. DAYTIME
HEATING OF THE MOISTENING -- BUT CAPPED -- BOUNDARY LAYER WILL
CONTRIBUTE TO AFTERNOON DESTABILIZATION...WITH 1000 TO 1500 J/KG
MIXED-LAYER CAPE EXPECTED TO EVOLVE.

WHILE SURFACE EVOLUTION ACROSS THE CENTRAL PLAINS DIFFERS WITHIN THE
NAM AND GFS SOLUTIONS...ATTM EXPECT CAP EROSION ALONG SOME
COMBINATION OF A FRONT AND/OR DRYLINE FROM THE MID MO VALLEY INTO
CENTRAL KS/WRN OK TO EVENTUALLY RESULT IN ISOLATED STORM
DEVELOPMENT.

WHILE THE CAP SHOULD LIMIT STORM COVERAGE DURING THE
AFTERNOON...VERY STRONG/VEERING FLOW WITH HEIGHT SPREADING ACROSS
THE CENTRAL U.S. WILL YIELD SHEAR VERY FAVORABLE FOR
STRONGLY-ROTATING SUPERCELL STORMS. THUS...ANY STORM WHICH DEVELOPS
SHOULD QUICKLY BECOME SEVERE...WITH VERY LARGE HAIL EXPECTED ALONG
WITH THE POTENTIAL FOR LOCALLY-DAMAGING WINDS. WHILE DEGREE OF
LOW-LEVEL SHEAR WILL BE VERY SUPPORTIVE OF TORNADO
POTENTIAL...SOMEWHAT LIMITED LOW-LEVEL MOISTURE - AND THE FAIRLY
DEEP BOUNDARY LAYER WHICH SHOULD RESULT -- SHOULD LIMIT THE OVERALL
TORNADO THREAT.

OVERNIGHT...STORMS SHOULD BECOME MORE LINEARLY-ORGANIZED ALONG THE
ADVANCING COLD FRONT. WHILE DECREASING INSTABILITY AND CHANGE IN
STORM MODE SHOULD YIELD A SLOW DECREASE IN HAIL/TORNADO
POTENTIAL...MARGINAL HAIL/DAMAGING WIND POTENTIAL WILL LIKELY
PERSIST WELL INTO THE OVERNIGHT HOURS.

[CrazyC83]

It seems the big question mark is moisture return. The dynamics seem to be virtually a carbon copy of last week into last weekend.

[KWT]

Yeah moisture return is a fairly big question point, though I suspect its going to be increasingly less of a deal buster as it has been at times so far, so to speak!

[CrazyC83]

Yeah moisture return is a fairly big question point, though I suspect its going to be increasingly less of a deal buster as it has been at times so far, so to speak!

One worrisome thing is that if this outbreak takes place, it would be almost exactly where the last one happened, 6-7 days later. The areas hit hardest last week (such as central MS) should get it late Friday night.

[srainhoutx]

SPC has a large area under a Slight Risk for Friday into Saturday. Even a mention of Moderate Risk...




DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0236 AM CDT WED APR 28 2010

VALID 301200Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE SRN AND
CNTRL PLAINS...LOWER THROUGH MID AND UPPER MS VALLEY AND GREAT
LAKES...

...SYNOPSIS...

UPPER PATTERN WILL BE CHARACTERIZED BY AN UPPER TROUGH OVER THE WRN
TWO THIRDS OF THE COUNTRY AND AN UPPER RIDGE OVER THE ERN U.S.
FRIDAY. A SHORTWAVE TROUGH AND ATTENDANT STRONG UPPER JET WILL EJECT
NEWD ALONG ERN PERIPHERY OF THE UPPER TROUGH THROUGH THE CNTRL
PLAINS INTO THE MID AND UPPER MS VALLEY. PRIMARY SURFACE LOW WILL
CONSOLIDATE AND DEEPEN OVER THE UPPER MS VALLEY...WHILE TRAILING
COLD FRONT ADVANCES INTO THE GREAT LAKES REGION. SWRN EXTENSION OF
THE FRONT WILL LIKELY STALL OVER THE SRN PLAINS.


...SRN PLAINS THROUGH LOWER MS VALLEY...

A MOIST WARM SECTOR WITH RICH GULF MOISTURE WILL ADVECT NWD THROUGH
THE ERN PORTIONS OF THE SRN PLAINS AND THE LOWER MS VALLEY FRIDAY
BENEATH A MODEST EML PLUME RESULTING IN MODERATE INSTABILITY. MODEL
SOLUTIONS CONTINUE TO DEVELOP CONVECTION WITHIN LOW-LEVEL THETA-E
ADVECTION REGIME IN WARM SECTOR. DETAILS OF HOW STORMS WILL INITIATE
AND EVOLVE REMAIN UNCERTAIN AT THIS POINT...BUT SEVERAL MODES OF
CONVECTION APPEAR LIKELY INCLUDING DISCRETE STORMS AND CLUSTERS.
LARGE HODOGRAPHS ALONG THE LOW LEVEL JET AXIS AND 40-50 KT DEEP
LAYER SHEAR WILL SUPPORT A THREAT OF SUPERCELLS AND TORNADOES AS
WELL AS LARGE HAIL AND DAMAGING WIND. OTHER STORMS WILL LIKELY
DEVELOP ALONG SEWD ADVANCING COLD FRONT. THIS AREA WILL CONTINUE TO
BE MONITORED FOR A POSSIBLE MODERATE RISK IN LATER OUTLOOKS.


...MID-UPPER MS VALLEY AND GREAT LAKES...

AN AXIS OF PARTIALLY MODIFIED GULF AIR WITH LOW-MID 60S DEWPOINTS
WILL RETURN NWD THROUGH THE MID-UPPER MS VALLEY AND GREAT LAKES AND
RESULT IN THE POTENTIAL FOR MODERATE INSTABILITY. A 90 KT MID LEVEL
JET ATTENDING THE EJECTING SHORTWAVE TROUGH WILL CONTRIBUTE TO
STRONG DEEP LAYER SHEAR...AND LARGE HODOGRAPHS WILL EXIST ALONG THE
LOW LEVEL JET AXIS. STORMS WILL LIKELY DEVELOP IN WARM SECTOR AND
ALONG SEWD ADVANCING COLD FRONT DURING THE AFTERNOON. ORGANIZED
STORMS INCLUDING SUPERCELLS AND BOWING SEGMENTS WILL BE LIKELY WITH
LARGE HAIL...DAMAGING WIND AND TORNADOES POSSIBLE.

..DIAL.. 04/28/2010

Day Four bears watching as well...

[KWT]

Wow that really is a large slight area it has to be said. I certainly think a moderate risk is the likely outcome for this event...

Also here is day 2 outlook:


DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT WED APR 28 2010

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE SRN AND
CNTRL PLAINS INTO THE UPPER MS VALLEY...

...SYNOPSIS...

THE BROAD UPPER TROUGH NOW MOVING INTO THE WRN U.S. WILL CONTINUE
SLOWLY EWD THROUGH THURSDAY. AT LEAST A COUPLE OF IMPULSES
ORIGINATING WITHIN THE UPPER TROUGH WILL EJECT NEWD THROUGH THE
CNTRL PLAINS AND UPPER MS VALLEY DURING THE DAY. A STRONGER IMPULSE
IS FORECAST TO EJECT INTO THE SRN AND CNTRL PLAINS LATER THURSDAY
NIGHT. MODEL CONSENSUS IS THAT A SURFACE LOW INITIALLY OVER NEB
EARLY THURSDAY WILL LIFT NEWD INTO MN DURING THE DAY IN ASSOCIATION
WITH EJECTING SHORTWAVE TROUGH. THIS WILL FORCE A COLD FRONT SEWD
THROUGH ERN NEB AND NRN KS DURING THE AFTERNOON. FARTHER SOUTH A
DRYLINE WILL RESIDE ACROSS WRN TX...OK AND NWD INTO KS. A LEE
CYCLONE WITH TRAILING PACIFIC FRONT WILL SHIFT EWD THROUGH SRN
KS/WRN OK THURSDAY NIGHT IN ASSOCIATION WITH AN IMPULSE MOVING
THROUGH BASE OF UPPER TROUGH. THIS FRONT WILL OVERTAKE THE DRYLINE
ACROSS THE SRN/CNTRL HIGH PLAINS.

...CNTRL PLAINS THROUGH UPPER MS VALLEY AREA...

SURFACE RIDGE WILL MAINTAIN ELY-NELY TRAJECTORIES OVER THE NRN GULF
AND DELAY MORE SIGNIFICANT GULF BOUNDARY LAYER MODIFICATION UNTIL
WEDNESDAY NIGHT. THIS WILL RESULT IN ONLY PARTIALLY MODIFIED GULF
AIR WITH DEWPOINTS IN THE 50S TO AROUND 60 ADVECTING NWD INTO THE
CNTRL PLAINS AND UPPER MS VALLEY BENEATH ERN PERIPHERY OF STEEPER
LAPSE RATE PLUME. THESE PROCESSES AND DIABATIC WARMING WILL
CONTRIBUTE TO 800-1200 J/KG MLCAPE. EWD ADVECTION OF THE EML PLUME
ABOVE THE MODEST MOIST AXIS WILL LIKELY RESULT IN A CAP TO SURFACE
BASED STORMS. MOST LIKELY AREA OF INITIATION WILL BE WITHIN ZONE OF
DEEPER ASCENT ALONG COLD FRONT FROM ERN NEB AND WRN IA DURING THE
AFTERNOON...THOUGH AN ISOLATED STORM OR TWO CANNOT BE RULED OUT
ALONG THE DRYLINE ACROSS KS. ADDITIONAL STORMS MAY EVENTUALLY
BACKBUILD SWD INTO KS AS THE COLD FRONT OVERTAKES THE DRYLINE AND AS
THE SLY LOW LEVEL JET STRENGTHENS TO IN EXCESS OF 60 KT. VERTICAL
SHEAR IN EXCESS OF 60 KT WILL SUPPORT ORGANIZED STORMS INCLUDING
SUPERCELLS. HOWEVER...STORMS SHOULD EVENTUALLY GROW UPSCALE INTO
LINES ALONG THE SEWD ADVANCING COLD FRONT.


...SRN PLAINS...

THREAT IN THIS AREA IS MORE CONDITIONAL DUE TO LOWER PROBABILITY OF
THUNDERSTORM INITIATION. THE ATMOSPHERE WILL BECOME MODERATELY
UNSTABLE DURING THE AFTERNOON AS PARTIALLY MODIFIED GULF AIR ADVECTS
NWD BENEATH STEEP LAPSE RATES ASSOCIATED WITH EML PLUME. HOWEVER...A
STOUT CAPPING INVERSION WILL EXIST OVER MUCH OF THE WARM SECTOR. IN
WAKE OF IMPULSE MOVING THROUGH THE CNTRL PLAINS AND UPPER MS VALLEY
REGION...DRYLINE CONVERGENCE WILL NOT BE PARTICULARLY PRONOUNCED.
HOWEVER...HEATING AND MIXING ALONG THIS BOUNDARY MIGHT BE SUFFICIENT
TO INITIATE AN ISOLATED STORM OR TWO. IF A STORM DEVELOPS IT WOULD
RAPIDLY BECOME SUPERCELLULAR GIVEN THE STRONG VERTICAL SHEAR IN
PLACE. GREATER PROBABILITY FOR STORM INITIATION WILL OCCUR LATER
THURSDAY NIGHT WHEN THE PACIFIC FRONT ACCOMPANYING A SPEED MAX
MOVING THROUGH BASE OF UPPER TROUGH OVERTAKES THE DRYLINE.

MODELS ALSO INDICATE STORMS MAY DEVELOP TOWARD THE END OF THIS
PERIOD WITHIN WARM ADVECTION REGIME FROM ERN PARTS OF THE SRN PLAINS
INTO THE LOWER MS VALLEY COINCIDENT WITH SURGE OF RICHER GULF
MOISTURE.

[thetruesms]

Day Four bears watching as well...

[img]http://i228.photobucket.com/albums/ee298/srainhoutx/04282010day48prob.gif[img]

I think it's worth mentioning that in the Days 4-8 outlook, the implication certainly seemed to be that predictability due to model differences was much more the reason for not drawing further risk areas rather than any clear lack of potential.

[brunota2003]

So, if we get a greater moisture return than last weeks episode, but the same dynamics, what would that imply for the severe weather?

[Calasanjy]

So, if we get a greater moisture return than last weeks episode, but the same dynamics, what would that imply for the severe weather?

Bad situation probably, considering that the enhanced moisture return would only amplify any supercells and provide more fuel to keep them going. Remains to be seen if that in fact occurs, however, hopefully there won't be any additional destructive tornadoes, particularly not in Dixie Alley.

[CrazyC83]

So, if we get a greater moisture return than last weeks episode, but the same dynamics, what would that imply for the severe weather?

Another major tornado outbreak most likely if the moisture return is as high or higher than last week.

[KWT]

Here is todays outlook from the SPC:


SPC AC 290540

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1240 AM CDT THU APR 29 2010

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPR MS VLY TO THE
CNTRL PLAINS...

...SYNOPSIS...
LARGE UPR TROUGH WILL CONTINUE TO DEEPEN OVER THE WRN HALF OF THE
COUNTRY ON THURSDAY. EMBEDDED WITHIN THE LARGER SCALE TROUGH...A
POTENT MID-LVL WAVE WILL TRAVEL FROM THE GRT BASIN REGION EARLY
THURSDAY INTO THE NRN/CNTRL PLAINS BY NIGHTFALL.

AT THE SFC...A FRONT DECELERATING ACROSS THE DKTS...NW KS AND THE
CNTRL HIGH PLAINS WILL RESUME A ESE TRANSLATION BY THURSDAY NIGHT AS
A DOMINANT SFC LOW MIGRATES TOWARD THE UPR MS VLY. PORTIONS OF THIS
FRONT WILL BE THE FOCUS FOR SVR TSTMS THURSDAY AFTN/NIGHT ACROSS
PORTIONS OF THE UPR MS VLY TO THE CNTRL PLAINS.

...UPR MS VLY TO THE CNTRL PLAINS...
LOW-LEVEL MOISTURE OVER THE RIO GRANDE VALLEY/TX HIGH PLAINS WILL BE
RAPIDLY TRANSPORTED NWD INTO THE CNTRL PLAINS AND UPR MS VLY BENEATH
A STRONG CAP ON THURSDAY. BY LATE AFTN...MID/UPR 50S SFC DEW POINTS
WILL BE COMMON ALONG/AHEAD OF THE CDFNT WITH CAPES 1000-1500 J/KG.


AS AFOREMENTIONED PV-ANOMOLY SWINGS NEWD FROM THE CNTRL ROCKIES
EARLY THURSDAY AFTN...HIGH-BASED TSTMS WILL DEVELOP ACROSS THE CNTRL
HIGH PLAINS WITH ISOLD DMGG WIND GUSTS/HAIL. MORE ROBUST DEEP MOIST
CONVECTION WILL EVOLVE MID-LATE AFTN IN WRN IA AND ERN NEB AND
EXPAND SWD INTO AT LEAST NCNTRL/NERN KS AS THE EML MOISTENS/COOLS
VIA DEEP-LAYER ASCENT.

50+KT SLY H92/85 FLOW VEERING TO 75+KT SWLY H5 WINDS WILL BOOST
EFFECTIVE SHEAR TO OVER 65 KTS AND WILL SUPPORT SUPERCELLS
INITIALLY. 0-1KM SRH WILL INCREASE DURING THE LATE AFTN/EARLY EVE
OWING TO NOCTURNAL ACCELERATION OF THE LLJ. SFC TEMP/DEW-POINT
SPREADS WILL BE SOMEWHAT HIGH AT INITIATION...BUT WILL LOWER
COINCIDENT WITH INCREASE IN LOW-LEVEL SHEAR. THUS...ISOLD TORNADOES
WILL BE POSSIBLE...PRIMARILY WITH LONGER-LIVED DISCRETE STORMS.
OTHERWISE...MAGNITUDE OF LAPSE RATES/SHEAR WILL SUPPORT VERY LARGE
HAIL AND SPORADIC DMGG WIND GUSTS.

ACTIVITY WILL EVOLVE INTO A LOOSELY-ORGANIZED LINEAR MCS LATER
THURSDAY EVENING AND ADVANCE E TOWARD THE UPR MS VLY AND THE LWR MO
VLY WITH AT LEAST ISOLD HAIL/GUSTY WINDS. MORE INTENSE ACTIVITY
WILL FAVOR SRN END OF THE LINE AMIDST STRONGER INSTABILITY.

[KWT]

Day 2 is still fairly bullish, I'd imagine by tomorrow this will have been upgraded to a moderate...also covers a HUGE area as well!


SPC AC 290559

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT THU APR 29 2010

VALID 301200Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE SRN PLAINS
THROUGH THE MS VALLEY AND GREAT LAKES...

...SYNOPSIS...

A BROAD UPPER TROUGH WILL CHARACTERIZE THE UPPER PATTERN OVER THE
WRN TWO THIRDS OF THE COUNTRY FRIDAY WITH AN UPPER RIDGE OVER THE
ERN STATES. SHORTWAVE TROUGH AND ATTENDANT STRONG UPPER JET WILL
EJECT NEWD ALONG ERN PERIPHERY OF THE UPPER TROUGH THROUGH THE CNTRL
PLAINS INTO THE MID-UPPER MS VALLEYS. MAIN SURFACE LOW WILL
CONSOLIDATE AND DEEPEN OVER THE UPPER MS VALLEY...WHILE TRAILING
COLD FRONT ADVANCES THROUGH THE UPPER MS VALLEY AND GREAT LAKES.
SWRN EXTENSION OF THE FRONT WILL STALL OVER THE SRN PLAINS. WARM
FRONT WILL LIFT NWD THROUGH THE LOWER MS VALLEY REGION.

...SRN PLAINS THROUGH LOWER MS VALLEY...

RICH GULF MOISTURE WILL SURGE NWD ALONG STRONG SLY LOW-LEVEL JET
THROUGH ERN PORTIONS OF SRN PLAINS AND LOWER MS VALLEY BENEATH A
MODEST EML PLUME. THIS WILL RESULT IN THE POTENTIAL FOR MODERATE
INSTABILITY. FORECAST SOUNDINGS IN THIS REGION VALID 12Z FRIDAY
INDICATE THE ATMOSPHERE WILL INITIALLY BE CAPPED WITH RESPECT TO
SURFACE BASED PARCELS DUE TO THE PRESENCE OF THE EML.
HOWEVER...MODELS CONTINUE TO SUGGEST EARLY CONVECTION MAY DEVELOP
WITHIN THE PRE-FRONTAL THETA-E ADVECTION REGIME...AND THIS ALONG
WITH LIKELIHOOD OF LOW CLOUDS MAY LIMIT DIABATIC HEATING IN PORTIONS
OF WARM SECTOR. DETAILS REGARDING THE EVOLUTION OF EARLY CONVECTION
REMAIN UNCERTAIN...BUT INFLUX OF RICH LOW-LEVEL MOISTURE AND
POTENTIAL FOR DEEPER ASCENT WITHIN EXIT REGION OF SUBTROPICAL JET
ROUNDING BASE OF UPPER TROUGH MAY EVENTUALLY SUPPORT THE DEVELOPMENT
OF SURFACE BASED STORMS. LARGE HODOGRAPHS ALONG THE LOW LEVEL JET
AXIS AND 40-50 KT DEEP LAYER SHEAR WILL SUPPORT A THREAT OF
SUPERCELLS AND TORNADOES AS WELL AS LARGE HAIL AND DAMAGING WIND.
OTHER STORMS WILL LIKELY DEVELOP OVERNIGHT ACROSS CNTRL/ERN TX AND
OK ALONG SEWD ADVANCING COLD FRONT WITH A THREAT FOR MAINLY ISOLATED
DAMAGING WIND AND HAIL.

...MID-UPPER MS VALLEY AND GREAT LAKES...

PARTIALLY MODIFIED GULF AIR WITH LOW 60S DEWPOINTS WILL ADVECT NWD
THROUGH PRE-FRONTAL WARM SECTOR...BUT WIDESPREAD CLOUDS WILL LIKELY
LIMIT DESTABILIZATION POTENTIAL WITH MLCAPE GENERALLY AOB 1000 J/KG.
A 90 KT MID LEVEL JET ATTENDING THE EJECTING SHORTWAVE TROUGH WILL
CONTRIBUTE TO STRONG DEEP LAYER SHEAR...AND LARGE HODOGRAPHS WILL
EXIST ALONG THE LOW LEVEL JET AXIS. STORMS WILL LIKELY DEVELOP IN
WARM SECTOR AND ALONG SEWD ADVANCING COLD FRONT DURING THE
AFTERNOON. ORGANIZED STORMS INCLUDING SUPERCELLS AND BOWING SEGMENTS
WILL BE POSSIBLE WITH A THREAT FOR DAMAGING WIND...LARGE HAIL AND
ISOLATED TORNADOES.

[KWT]

Finally here is the day 3 outlook:


SPC AC 290730

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT THU APR 29 2010

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE LOWER MS
VALLEY...TN AND OH VALLEYS...

...SYNOPSIS...

UPPER PATTERN WILL REMAIN CHARACTERIZED BY A BROAD DOUBLE VORTEX
POSITIVE TILT UPPER TROUGH SATURDAY. A SIGNIFICANT IMPULSE WILL LIFT
NEWD THROUGH THE GREAT LAKES EARLY SATURDAY. ANOTHER SHORTWAVE
TROUGH INITIALLY OVER NRN MEXICO SATURDAY MORNING WILL EJECT NEWD
REACHING THE MID MS VALLEY OVERNIGHT. FRONTAL BOUNDARY WILL LIKELY
BECOME QUASI-STATIONARY FROM THE GREAT LAKES SWWD THROUGH ERN TX. A
SURFACE WAVE IS FORECAST TO DEVELOP AND LIFT NEWD ALONG THE FRONT
THROUGH THE LOWER AND MID MS VALLEYS IN ASSOCIATION WITH EJECTING
SRN BRANCH JET STREAK. THIS WILL ACCELERATE EWD SRN PORTIONS OF THE
FRONT INTO THE LOWER MS VALLEY OVERNIGHT.


...LOWER MS...TN AND OH VALLEYS...

BOUNDARY LAYER WINDS WILL TEMPORARILY WEAKEN DURING THE DAY AS
INITIAL LOW LEVEL JET LIFTS NWD INTO SRN ONTARIO IN ASSOCIATION WITH
LEAD SHORTWAVE TROUGH. HOWEVER...MODERATE SLY FLOW WILL PERSIST OVER
THE LOWER MS VALLEY MAINTAINING INFLUX OF RICH GULF MOISTURE.
WIDESPREAD CLOUDS AND ONGOING CONVECTION WILL LIMIT DIABATIC WARMING
OF THE BOUNDARY LAYER WITH MLCAPE GENERALLY BELOW 1000 J/KG EXCEPT
OVER THE LOWER MS VALLEY REGION WHERE RICHER GULF MOISTURE WILL
PERSIST. AT THIS POINT...UNCERTAINTY EXISTS REGARDING EVOLUTION OF
ONGOING CONVECTION. HOWEVER...DEEP LAYER FLOW/VERTICAL SHEAR WILL
REMAIN SUFFICIENT THROUGHOUT THE DAY FOR A THREAT OF ORGANIZED
SEVERE STORMS. THE SEVERE THREAT MAY INCREASE FROM LATE AFTERNOON
INTO THE OVERNIGHT INITIALLY OVER THE LOWER MS VALLEY AS THE LOW
LEVEL JET STRENGTHENS IN RESPONSE TO EJECTING IMPULSE. STORMS WILL
LIKELY REDEVELOP AHEAD OF EWD ADVANCING COLD FRONT. DEEP LAYER SHEAR
AND HODOGRAPHS WILL BECOME SUPPORTIVE OF ORGANIZED STORMS WITH A
THREAT OF DAMAGING WIND AND ISOLATED TORNADOES CONDITIONAL UPON
SUFFICIENT SURFACE BASED INSTABILITY. THREAT WILL EXPAND NEWD ALONG
MIGRATORY LOW-LEVEL JET TOWARD THE OH VALLEY OVERNIGHT.

[srainhoutx]

Going to be another interesting weekend. It appears that things will progress a bit slower that progged (slower moving system) as this has been the trend the past few days. I would keep an eye on Saturday in areas near the Mid South (Memphis, TN Region). Also of interest is the stalling of the boundary near E TX and the deep surge of tropical moisture heading N from the GOM through the weekend. Stay Safe and heads up!

[iHeart]

Hello, I'm from the South Eastern Ohio region, and I was wondering the risks of this storm system.

We have been fairly untouched during past outbreaks, but this appears to be hitting us dead on with the current forecasts.

I monitor the weather quite frequently, possibly due to my phobia of thunderstorms, but I still have learned quite a bit yet I can't point out the trajectory of this system, possibly due to the numerous variables, so could anyone help me out?

[johnmarkthom]

New Day 2 outlook is out, showing greatest threat in IA MO and AR. Curious about the chances the SPC upgrading from slight to moderate in any of these areas in future outlooks since they are showing a hatched area.

[snoopj]

New Day 2 outlook is out, showing greatest threat in IA MO and AR. Curious about the chances the SPC upgrading from slight to moderate in any of these areas in future outlooks since they are showing a hatched area.

I think that's depending upon how everything goes earlier in the day. They mention that models are still all over the place regarding what happens in the morning. We've seen the morning activity snuff out the potential outbreak before. Pretty sure that's why they are hesitant. If we see a MDT upgrade, I'd expect it to be on a Day 1.

[KWT]

Going to be another interesting weekend. It appears that things will progress a bit slower that progged (slower moving system) as this has been the trend the past few days. I would keep an eye on Saturday in areas near the Mid South (Memphis, TN Region). Also of interest is the stalling of the boundary near E TX and the deep surge of tropical moisture heading N from the GOM through the weekend. Stay Safe and heads up!

Yep, this is going to be quite a drawn out set-up and will probably take a good 3-4 days to eject eastwards, I suspect Friday will end up being a modertate day, there has been plenty of hints from the SPC that this will be the case.

[srainhoutx]

And so it begins...



URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 108
NWS STORM PREDICTION CENTER NORMAN OK
440 PM CDT THU APR 29 2010

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

EXTREME SOUTHWEST IOWA
NORTH CENTRAL AND NORTHEAST KANSAS
EXTREME NORTHWEST MISSOURI
SOUTHEAST NEBRASKA

EFFECTIVE THIS THURSDAY AFTERNOON FROM 440 PM UNTIL MIDNIGHT CDT.

TORNADOES...HAIL TO 2.5 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 65 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 30 MILES EAST OF OMAHA
NEBRASKA TO 5 MILES NORTH OF RUSSELL KANSAS. FOR A COMPLETE
DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
(WOUS64 KWNS WOU8).

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 DEVELOPING ALONG THE SLOWLY
RETREATING DRYLINE...ON THE NOSE OF THE HOT SURFACE TEMPERATURES AND
DEEP MIXED LAYER EXTENDING NEWD INTO CENTRAL KS. INITIALLY...THE
ENVIRONMENT WILL FAVOR SUPERCELLS WITH THE THREAT FOR LARGE HAIL.
LATER THIS EVENING AS THE LOW-LEVEL JET STRENGTHENS AND LOW-LEVEL
MOISTURE INCREASES GRADUALLY...THERE WILL BE SOME THREAT FOR A
COUPLE OF TORNADOES WITH STORMS MOVING NEWD ALONG THE
MOISTURE/INSTABILITY GRADIENT.