Severe Outbreak for May 18-19-20-21 (Watches-Warnings)

[KatDaddy]

On the way to W KS. Chasing with Reed Timmers Extreme Tornado Chase tour.

[cycloneye]

On the way to W KS. Chasing with Reed Timmers Extreme Tornado Chase tour.

Keep us informed when you can. Have a safe chasing.

[WeatherGuesser]

On the way to W KS. Chasing with Reed Timmers Extreme Tornado Chase tour.

Is there some valid reason for that? Or are you a sightseer?

[cycloneye]

Cape is up there around 7000 j/KG. CrazyC83,what do you think of the cape?

[CrazyC83]

Cape is up there around 7000 j/KG. CrazyC83,what do you think of the cape?

Explosive!!!! That should get storms high in the sky. The big downside is that shear isn't optimal, so hail is primary threat.

[cycloneye]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1127 AM CDT SAT MAY 18 2013

VALID 181630Z - 191200Z

...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
PARTS OF SOUTHWEST AND SOUTH CENTRAL NEBRASKA...WESTERN AND CENTRAL
KANSAS...AND PARTS OF WESTERN OKLAHOMA...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
AREA ACROSS MUCH OF THE PLAINS...

...SYNOPSIS...
IN ADVANCE OF THE UPPER TROUGH OVER THE INTERMOUNTAIN WEST...WARM
ELEVATED MIXED LAYER AIR HAS OVERSPREAD MOST OF THE PLAINS AND LOWER
MISSISSIPPI VALLEY. THIS IS WHERE THE BOUNDARY LAYER CONTINUES TO
MOISTEN DUE TO BOTH EVAPOTRANSPIRATION AND A RETURN FLOW OF MOISTURE
OFF GULF OF MEXICO. VEERED LOW-LEVEL FLOW /AT 850 MB/ TO A
SUBSTANTIAL WESTERLY COMPONENT APPEARS TO BE CUTTING OFF THE GULF
RETURN FLOW TO THE CENTRAL/NORTHERN PLAINS...THOUGH...AT LEAST
TEMPORARILY. BUT THIS MAY BEGIN TO CHANGE BY THIS EVENING...AS
LOW-LEVEL FLOW BACKS TO A MORE PROMINENT SOUTHERLY COMPONENT...AND
STRENGTHENS...IN ASSOCIATION WITH DEEPENING AND CONSOLIDATION OF A
SURFACE LOW OVER THE CENTRAL PLAINS...AS MID-LEVEL HEIGHT FALLS
INCREASE TO THE EAST OF THE ROCKIES.

MODEST STRENGTHENING OF CYCLONIC MID/UPPER FLOW IS EXPECTED ACROSS
THE PLAINS TODAY...AS SEVERAL SMALLER SCALE IMPULSES BEGIN TO EMERGE
FROM THE INTERMOUNTAIN WEST. STRONGEST FLOW ALOFT...HOWEVER...WILL
PERSIST IN A BELT ACROSS THE NORTH CENTRAL PACIFIC COAST INTO THE
SOUTHERN ROCKIES...BUT COULD BEGIN TO NOSE EASTWARD ACROSS THE TEXAS
PANHANDLE REGION TOWARD THE END OF THE FORECAST PERIOD.
STILL...GIVEN THE THERMODYNAMIC PROFILES EVOLVING ACROSS MUCH OF THE
PLAINS...WHICH WILL INCLUDE AREAS OF STRONG TO EXTREME CAPE...A RISK
FOR SEVERE THUNDERSTORMS WILL EXIST ACROSS A FAIRLY BROAD AREA.
ORGANIZED CLUSTERS OF STORMS APPEAR POSSIBLE...IN ADDITION TO THE
RISK FOR DISCRETE SUPERCELLS ...THE STRONGEST OF WHICH MAY BECOME
CAPABLE OF PRODUCING VERY LARGE HAIL AND A COUPLE OF TORNADOES.

ALTHOUGH SEVERE PROBABILITIES STILL SEEM A BIT LOWER THAN THE
PLAINS...OTHER STRONG/ISOLATED SEVERE STORM DEVELOPMENT MAY ALSO
OCCUR TODAY EAST OF THE LOWER MISSISSIPPI VALLEY INTO PARTS OF THE
EASTERN GULF STATES. THIS IS WHERE LOWER/MID TROPOSPHERIC WARM
ADVECTION ON THE EASTWARD ADVANCING EDGE OF WARMER ELEVATED MIXED
LAYER AIR...IN THE WAKE OF A WEAKENING UPPER IMPULSE ADVANCING
TOWARD THE SOUTH ATLANTIC COAST...MAY CONTRIBUTE TO INCREASING LIFT
AND STEEPENING MID-LEVEL LAPSE RATES.

...CENTRAL PLAINS...
AN INITIAL IMPULSE...NOW LIFTING NORTHEAST OF THE PANHANDLE REGION
INTO THE CENTRAL PLAINS...IS CONTRIBUTING TO SOME UNCERTAINTY
CONCERNING DRYLINE POSITION AND CONVECTIVE POTENTIAL LATER THIS
AFTERNOON...MAINLY SOUTH OF THE KANSAS/OKLAHOMA BORDER.
HOWEVER...THE DRYLINE IS STILL EXPECTED TO BE THE MAIN FOCUS FOR
STRONGEST DESTABILIZATION AND STORM DEVELOPMENT LATER THIS
AFTERNOON. AIDED BY FORCING ASSOCIATED WITH CONTINUING MID-LEVEL
HEIGHT FALLS...SUBSTANTIAL MID-LEVEL INHIBITION IS EXPECTED TO
WEAKEN SUFFICIENTLY FOR THE INITIATION OF DISCRETE SUPERCELLS ACROSS
SOUTHWESTERN NEBRASKA INTO WESTERN KANSAS DURING THE 21-00Z TIME
FRAME...PERHAPS SOUTHWARD ACROSS WESTERN OKLAHOMA INTO NORTHWEST
TEXAS AS WELL.

VERY LARGE HAIL MAY BE THE PRIMARY SEVERE THREAT...INITIALLY... BUT
LOW-LEVEL LAPSE RATES PROBABLY WILL BE SUFFICIENTLY STEEP TO SUPPORT
A RISK FOR TORNADOES BENEATH INCREASINGLY CYCLONIC AND DIFLUENT
HIGH-LEVEL FLOW. AS THE 850 MB JET BECOMES MORE SOUTHERLY AND
STRENGTHENS TO 40-50+ KT LATER THIS EVENING...A WINDOW OF
OPPORTUNITY WILL EXIST FOR INCREASING TORNADIC POTENTIAL...INCLUDING
THE RISK FOR ONE OR TWO STRONG TORNADOES. THIS POTENTIAL APPEARS TO
HINGE LARGELY ON HOW LONG IT TAKES FOR CONVECTION TO GROW UPSCALE
INTO ORGANIZING MESOSCALE CONVECTIVE SYSTEMS...WITH DAMAGING
STRAIGHT LINE WINDS BECOMING A MORE PROMINENT THREAT. THIS REMAINS
UNCERTAIN...BUT IT APPEARS THAT UPSCALE GROWTH COULD OCCUR FAIRLY
QUICKLY.

..KERR/DEAN.. 05/18/2013

% of possible tornadoes



Hail

[JonathanBelles]

This is going to be a classical bad day in NE, KS, OK, and N TX with hail. I wouldn't be surprised to see a few of those shaved Starbucks type pictures tonight, possibly with a few holes in the roof. Once the cap is removed early-mid evening expect hailers.

[CrazyC83]

This is going to be a classical bad day in NE, KS, OK, and N TX with hail. I wouldn't be surprised to see a few of those shaved Starbucks type pictures tonight, possibly with a few holes in the roof. Once the cap is removed early-mid evening expect hailers.

I agree, and bigger than softballs. The most intense storms could still produce tornadoes (a few strong), but the 10%-hatched seems reasonable.

[cycloneye]

Here are the latest Torcon numbers by Dr Greg Forbes.

Today:

TOR:CON -
KS southwest - 6
KS northwest - 5
KS central - 4 to 5
MN southwest - 3
MN north - 2 to 3
ND southeast, south-central - 3
NE southwest - 4
NE northwest - 3
NE central - 4
OK northwest, north-central - 5
OK southwest - 3
SD - 3 to 4
TX extreme east panhandle - 3
Other areas - less than 2


Tomorrow:

TOR:CON -
IA central - 5 to 6
IA west - 4 to 5
IA east - 3
IL northwest - 3
KS east - 7
KS central - 4
MN central, south - 2 to 3
MO southwest - 4
MO northwest - 6
ND southeast - 3
NE east - 4
OK central, northeast - 7
SD east - 3
TX north-central - 4 (concerns about whether cap will break)
WI west-central, southwest - 3
other areas - less than 2

[WeatherGuesser]

A few light echoes, but not much happening so far.

[CrazyC83]

SPC AC 181709

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1209 PM CDT SAT MAY 18 2013

VALID 191200Z - 201200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF KS/OK/WRN MO...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM
NCNTRL TX INTO SRN MN...

...REGIONAL SEVERE WEATHER OUTBREAK POSSIBLE ACROSS PARTS OF THE SRN
PLAINS...CNTRL PLAINS AND LOWER MO VALLEY...


...SRN PLAINS TO LOWER MO VALLEY....

LATEST MODEL GUIDANCE CONTINUES TO SUGGEST A SIGNIFICANT MID LEVEL
SPEED MAX WILL EVOLVE WITHIN THE BASE OF THE WRN U.S. TROUGH OVER
THE SRN ROCKIES LATE DAY1...THEN EJECT ACROSS THE SRN PLAINS TOWARD
WRN MO BY 20/00Z. THERE ARE MINOR DIFFERENCES AMONG THE 12Z NAM/GFS
AND 00Z ECMWF...WITH THE NAM FAVORING A BIT MORE AGGRESSIVE SPEED
MAX/HEIGHT FALLS ACROSS NERN OK INTO SWRN MO THAN THE OTHER
GUIDANCE. IT/S NOT ENTIRELY CLEAR IF THE MORE DISPLACED NAM SPEED
MAX IS CORRECT...IF SO THEN SIGNIFICANT SEVERE TSTM ACTIVITY COULD
SPREAD EAST OF DEPICTED MDT RISK.

FOR NOW WILL OPT FOR SOMEWHAT SLOWER GFS SOLUTION AS IT HAS BEEN
VERY CONSISTENT REGARDING THE FORECAST HEIGHT FIELD/WIND SPEEDS
ACROSS THE SRN PLAINS INTO WRN MO. GIVEN THIS SOLUTION...AT SUNRISE
IT APPEARS SYNOPTIC FRONT WILL EXTEND FROM A SFC LOW OVER NCNTRL
NEB...SWD ACROSS CNTRL KS INTO THE TX PANHANDLE. A DRYLINE IS
EXPECTED TO INTERSECT THE COLD FRONT OVER SWRN KS...EXTENDING SSWWD
INTO NWRN TX. EARLY MORNING CONVECTION WILL LIKELY BE CONFINED TO
WARM ADVECTION ZONE ALONG THE NOSE OF THE LLJ ACROSS THE CNTRL
PLAINS INTO THE MID MS VALLEY. SOUTH OF THIS ACTIVITY STRONG WARM
SECTOR BOUNDARY LAYER HEATING IS EXPECTED DURING THE
DAY...ESPECIALLY SOUTH OF I-70 CORRIDOR ACROSS KS/OK/TX.
COMBINATION OF STRONG HEATING AND STRENGTHENING WLY FLOW ALOFT WILL
ALLOW DRYLINE TO MIX TO A POSITION FROM CNTRL KS...SSWWD ACROSS SWRN
OK INTO NWRN TX BY 21Z. IF HOWEVER THE NAM SOLUTION IS CORRECT THEN
THE DRYLINE MAY MIX TO THE I-35 CORRIDOR BY LATE AFTERNOON.

GIVEN THE EXPECTED INTENSE HEATING ALONG THE DRYLINE THERE IS AMPLE
REASON TO BELIEVE DISCRETE SUPERCELL STRUCTURES WILL EVOLVE
INITIALLY NORTH OF THE MID LEVEL JET CORE ACROSS KS...THEN SWD INTO
OK. THIS MAY OCCUR BY 21Z OVER KS AND BY 20/00Z ACROSS OK TO NEAR
THE RED RIVER. FORECAST SHEAR PROFILES STRONGLY FAVOR LONG-LIVED
SUPERCELLS AND WHERE DEW POINTS HOLD IN THE UPPER 60S/LOWER
70S...TORNADOES CAN BE EXPECTED. GIVEN THE EXPECTED
SHEAR/INSTABILITY THERE IS SUPPORT FOR STRONG TORNADOES.
ADDITIONALLY...VERY LARGE HAIL SHOULD ACCOMPANY THIS ACTIVITY.
MATURING COMPLEX OF STORMS SHOULD PROGRESS ACROSS KS/NERN OK INTO
WRN MO WITH MORE SCATTERED ACTIVITY ACROSS CNTRL/SRN OK.

...SERN U.S...

REMNANT MID LEVEL SHORT-WAVE TROUGH WILL SHIFT ACROSS THE SRN
APPALACHIANS SUNDAY. THIS FEATURE MAY ONCE AGAIN SERVE TO FOCUS A
FEW STRONG THUNDERSTORMS BENEATH A WEAKENING MID LEVEL WIND FIELD.
GUSTY WINDS OR PERHAPS SOME HAIL COULD BE NOTED WITH DIURNALLY
DRIVEN CONVECTION.

..DARROW.. 05/18/2013

CLICK TO GET WUUS02 PTSDY2 PRODUCT

NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
CURRENT UTC TIME: 1717Z (1:17PM), RELOAD THIS PAGE TO UPDATE THE TIME

[JonathanBelles]

Can I recommend a separate thread for warnings and outlooks? They clutter the discussion.

[CrazyC83]

A few light echoes, but not much happening so far.

That tells us how much instability there is, since there is still a fairly strong cap.

[CrazyC83]

Can I recommend a separate thread for warnings and outlooks? They clutter the discussion.

Outlooks should always be posted IMO, as should watches and MD's.

Warnings should be limited or posted elsewhere. Some exceptions (in my mind):

1) The first warning or two of the event, the start point.
2) Once things get going, higher-end warnings (i.e. confirmed tornadoes) until they clutter.
3) At the peak of the event, only the biggest warnings (i.e. Tornado Emergencies or major populated areas).

[cycloneye]

Can I recommend a separate thread for warnings and outlooks? They clutter the discussion.

Outlooks should always be posted IMO, as should watches and MD's.

Warnings should be limited or posted elsewhere. Some exceptions (in my mind):

1) The first warning or two of the event, the start point.
2) Once things get going, higher-end warnings (i.e. confirmed tornadoes) until they clutter.
3) At the peak of the event, only the biggest warnings (i.e. Tornado Emergencies or major populated areas).

I ckecked back at the biggests outbreaks and those had comments posted with the watches and warnings. But we can break that policy in this case as I think we will have many warnings issued and discussions will be lost among the warnings. A Discussion Thread for this event is now up.

[Dave]

Thank you Jonathan for the idea on splitting the threads it's a great idea!

[cycloneye]

First warning of May 18 event this one a Severe Thunderstorm Warning for West-Central South Dakota.


SEVERE THUNDERSTORM WARNING
SDC081-093-181945-
/O.NEW.KUNR.SV.W.0023.130518T1842Z-130518T1945Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE RAPID CITY SD
1242 PM MDT SAT MAY 18 2013

THE NATIONAL WEATHER SERVICE IN RAPID CITY HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
EASTERN LAWRENCE COUNTY IN WEST CENTRAL SOUTH DAKOTA...
WEST CENTRAL MEADE COUNTY IN WEST CENTRAL SOUTH DAKOTA...

* UNTIL 145 PM MDT

* AT 1241 PM MDT...A SEVERE THUNDERSTORM WAS LOCATED 7 MILES SOUTH OF
DEADWOOD...AND MOVING NORTHEAST AT 15 MPH.

HAZARD...HALF DOLLAR SIZE HAIL.

SOURCE...RADAR INDICATED.

IMPACT...DAMAGE TO VEHICLES AND CROPS IS EXPECTED.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
DEADWOOD AROUND 105 PM MDT.
DOWNTOWN STURGIS AROUND 145 PM MDT.

OTHER LOCATIONS IN THE WARNING INCLUDE...GALENA AND WHITEWOOD.

THIS INCLUDES INTERSTATE 90 BETWEEN SOUTH DAKOTA MILE MARKERS 22 AND
41...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FOR YOUR PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
BUILDING.

&&

LAT...LON 4455 10361 4433 10333 4416 10370 4426 10387
TIME...MOT...LOC 1842Z 223DEG 11KT 4428 10372

HAIL...1.25IN
WIND...<50MPH

$$

CARSTENS

[CrazyC83]

MESOSCALE DISCUSSION 0675
NWS STORM PREDICTION CENTER NORMAN OK
0209 PM CDT SAT MAY 18 2013

AREAS AFFECTED...NWRN KS...NERN CO AND WRN NEB

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 181909Z - 182045Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...STORMS ARE EXPECTED TO INITIATE BY 20-21Z FROM NERN CO
INTO NWRN KS AND EXTREME SERN WY...THEN SUBSEQUENTLY DEVELOP NEWD
INTO WRN NEB DURING THE EVENING. PRIMARY THREATS WILL BE VERY LARGE
HAIL AND ISOLATED TORNADOES. STORMS MAY EVENTUALLY GROW UPSCALE INTO
ONE OR MORE CLUSTERS LATER IN THE EVENING WITH AN INCREASING THREAT
FOR DAMAGING WIND. A TORNADO WATCH WILL LIKELY BE NEEDED PRIOR TO
21Z.

DISCUSSION...THIS AFTERNOON A DRYLINE EXTENDS FROM SERN WY TO A
MESOLOW NEAR THE KS/CO BORDER THEN FARTHER SWD THROUGH SWRN KS. THE
LATEST OBJECTIVE ANALYSIS INDICATES THE WARM SECTOR HAS BECOME VERY
UNSTABLE IN CORRIDOR FROM NWRN KS THROUGH EXTREME NERN CO AND WRN
NEB WHERE VERY STEEP LAPSE RATES /APPROACHING 9 C/KM/ HAVE
OVERSPREAD THE MOIST AXIS. SPECIAL 18Z RAOB FROM NORTH PLATTE NEB
INDICATES A STRONG CAPPING INVERSION IS STILL IN PLACE JUST BELOW
700 MB IN ASSOCIATION WITH WARM AIR AT BASE OF THE EML. THIS
SUGGESTS THUNDERSTORM INITIATION WILL LIKELY BE FARTHER WEST ACROSS
NERN CO AND NWRN KS. SATELLITE IMAGERY SHOWS MID-LEVEL CONVECTION
SPREADING RAPIDLY NWD ACROSS NERN CO AND NWRN KS AND APPEARS TO BE
IN ASSOCIATION WITH MID-LEVEL ASCENT ACCOMPANYING A NEWD EJECTING
SHORTWAVE TROUGH. FORCING FROM THIS FEATURE AND DEEPER MIXING OVER
THE HIGH PLAINS OF NERN CO THROUGH WRN KS WILL LIKELY SUPPORT
THUNDERSTORM INITIATION ALONG THE DRYLINE SOMETIME DURING THE NEXT
COUPLE HOURS.

VERTICAL SHEAR THROUGH A DEEP LAYER WILL REMAIN SUFFICIENT FOR
SUPERCELLS CAPABLE OF VERY LARGE HAIL GIVEN THE FAVORABLE LAPSE
RATES AND STRONG INSTABILITY. ALSO...THE THREAT FOR ISOLATED
TORNADOES IS EXPECTED TO INCREASE IN WINDOW FROM LATE AFTERNOON INTO
EARLY EVENING AS THE LLJ STRENGTHENS AND BEFORE THE BOUNDARY LAYER
DECOUPLES AND WHILE SOME STORMS MAY STILL BE DISCRETE. STORMS MAY
EVENTUALLY CONGEAL INTO ONE OR MORE CLUSTERS DURING THE
EVENING...WITH AN ATTENDANT INCREASE IN DAMAGING WIND THREAT.

..DIAL/KERR.. 05/18/2013


ATTN...WFO...GID...LBF...GLD...BOU...CYS...

LAT...LON 39030147 39950243 40740317 42060386 42720319 42270080
39630003 38840064 39030147

[CrazyC83]

MESOSCALE DISCUSSION 0676
NWS STORM PREDICTION CENTER NORMAN OK
0219 PM CDT SAT MAY 18 2013

AREAS AFFECTED...SWRN KS...WRN OK...NW TX...FAR ERN OK/TX PANHANDLES

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 181919Z - 182015Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...SCATTERED TSTM INITIATION IS EXPECTED ON THE DRYLINE BY
21-22Z. VERY LARGE HAIL...ISOLATED TORNADOES...AND DAMAGING WIND
WILL BE POSSIBLE. WATCH ISSUANCE IS EXPECTED IN THE NEXT HOUR OR SO.

DISCUSSION...LATEST SFC ANALYSIS DEPICTS THE DRYLINE EXTENDING FROM
SWRN KS INTO THE FAR ERN OK/TX PANHANDLES AND NW TX. VIS IMAGERY
SHOWS CU INCREASING IN THE WELL-MIXED AIRMASS IN THE VICINITY OF THE
DRYLINE ACROSS SW KS INTO THE TX PANHANDLE. WHILE ONE EMBEDDED VORT
MAX IS MOVING NWD OUT OF THE AREA...ANOTHER EMBEDDED VORT MAX OVER
SERN CO/NERN NM SHOULD AID IN CONVECTIVE INITIATION LATER THIS
AFTERNOON.

THE 18Z DDC SOUNDING SHOWS VERY STEEP LAPSE RATES IN EXCESS OF 9.5
C/KM IN THE 750-500 MB LAYER...WHICH WILL SUPPORT VERY HIGH TO
EXTREME MLCAPE OF 3000-4000 J/KG IN AREAS AHEAD OF THE DRYLINE THIS
AFTERNOON AND EARLY EVENING. WHILE FLOW IS RELATIVELY
MODEST...INCREASING SWLY MIDLEVEL FLOW IS SUPPORTING EFFECTIVE SHEAR
OF 35-45 KTS AHEAD OF THE DRYLINE...WHICH WILL BE MORE THAN
SUFFICIENT FOR SUPERCELL DEVELOPMENT UPON STORM INITIATION.

DISCRETE SUPERCELL ACTIVITY IS EXPECTED WITHIN THE FIRST 2-3 HOURS
OF INITIATION...WITH VERY LARGE HAIL IN EXCESS OF BASEBALL SIZE THE
PRIMARY THREAT. LARGE T/TD SPREADS AND RELATIVELY WEAK LOW-LEVEL
SHEAR WILL LIMIT THE TORNADO THREAT INITIALLY...BUT A MARKED
INCREASE IN THE LOW-LEVEL JET WILL INCREASE THE TORNADO THREAT
TOWARD EVENING ACROSS MAINLY NWRN OK INTO SWRN KS...WITH ISOLATED
STRONG TORNADOES POSSIBLE WITH ANY STORMS THAT CAN REMAIN DISCRETE
AFTER 00Z. HOWEVER...STORM CONSOLIDATION IN A WELL-MIXED ENVIRONMENT
MAY RESULT IN UPSCALE GROWTH AND A TRANSITION TO MORE OF A SEVERE
WIND THREAT THIS EVENING...POSSIBLY LIMITING THE WINDOW OF
OPPORTUNITY FOR A MORE ROBUST TORNADO THREAT.

..DEAN/KERR.. 05/18/2013


ATTN...WFO...ICT...FWD...OUN...DDC...SJT...GLD...LUB...AMA...

LAT...LON 37290112 37880150 38500134 38920033 38829937 38509866
38129815 37669781 36889765 35559772 34699766 33459786
32919805 32419816 32199830 31989879 31989936 32069993
32170043 32790063 33780057 35300063 36140066 37290112

[CrazyC83]

SPC AC 181938

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0238 PM CDT SAT MAY 18 2013

VALID 182000Z - 191200Z

...THERE IS A MDT RISK OF SVR TSTMS FROM NWRN OK INTO SWRN NEB...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM
WEST TX INTO SERN ND/WRN MN...

EARLIER THOUGHTS REGARDING CONVECTIVE EVOLUTION REMAIN. AS A
RESULT...ONLY MINOR MODIFICATIONS HAVE BEEN MADE TO 1630Z SEVERE
THREAT ALONG THE DRYLINE.

STRONG HEATING ACROSS THE HIGH PLAINS FROM THE TX PANHANDLE INTO
SWRN KS HAVE FORCED SFC TEMPERATURES TO NEAR/ABOVE 100F. AS A
RESULT...CAP HAS BEEN REMOVED AND BOUNDARY LAYER CU ARE DEEPENING
MARKEDLY ALONG LEADING EDGE OF STEEP LAPSE RATE PLUME ACROSS SWRN
KS. IT APPEARS TSTMS WILL EVOLVE OVER THE NEXT FEW HOURS ACROSS
THIS REGION.

HAVE OPTED TO EXTEND THE MDT RISK A BIT NORTH ACROSS NEB TO ACCOUNT
FOR SCT-NUMEROUS TSTMS THAT SHOULD EVOLVE ALONG WRN FRINGE OF HIGHER
MOISTURE/INSTABILITY. WEAK CONVERGENCE AXIS EXTENDS FROM JUST EAST
OF GLD INTO CHERRY COUNTY NEB AND THIS SHOULD FOCUS SEVERE TSTMS BY
MID-LATE AFTERNOON.

HAVE MADE A SWD ADJUSTMENT TO CATEGORICAL SLGT RISK ALONG THE
DRYLINE OVER SWRN TX TO ACCOUNT FOR EXPECTED SEVERE DEVELOPMENT AT
THIS LATITUDE. ALTHOUGH ACTIVITY SHOULD BE ISOLATED...IT APPEARS
SUFFICIENT FLOW ALOFT WILL SUPPORT DEEP ROTATING UPDRAFTS.

..DARROW.. 05/18/2013