MESOSCALE DISCUSSION NWS STORM PREDICTION CENTER

[CaptinCrunch]

MESOSCALE DISCUSSION 0819
NWS STORM PREDICTION CENTER NORMAN OK
0225 PM CDT WED MAY 11 2005

AREAS AFFECTED...OK/TX PANHANDLES...MUCH OF WRN TX...AND FAR WRN OK

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 111925Z - 112130Z



THUNDERSTORM DEVELOPMENT IS ANTICIPATED IN A NORTH-SOUTH LINE ACROSS
THE OK/TX PANHANDLES DURING THE MID-LATE AFTERNOON HOURS. THREAT
EXISTS FOR VERY LARGE HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES
IN THIS AREA THROUGH EVENING. A TORNADO WATCH WILL LIKELY BE
REQUIRED SOON.

AT 19Z...999MB SURFACE LOW WAS LOCATED OVER SERN CO WITH AN
INCREASINGLY WELL-DEFINED DRYLINE EXTENDING SWD THROUGH THE WRN OK
PANHANDLE...SWD TO NEAR A AMA-LBB-MAF LINE. INSOLATIONAL HEATING HAS
LEAD TO MODERATE TO STRONG INSTABILITY /MLCAPE VALUES OF 2000-3000
J/KG/ ACROSS THE DISCUSSION AREA EAST OF THE DRYLINE...AND
DECREASING CONVECTIVE INHIBITION. VISIBLE SATELLITE INDICATES AN
AXIS OF TOWERING CU ALONG THE DRYLINE AND COINCIDENT AXIS OF
CONFLUENT SURFACE WINDS.

THE 18Z RUC INDICATES THAT STRONGER DEEP-LAYER SHEAR WILL REMAIN
NORTH OF THE REGION...AS 500MB JET ROTATES NEWD FROM NERN NM INTO
ERN CO/WRN KS. HOWEVER...SFC-6KM SHEAR VALUES OF 30-35KT IN THE
PANHANDLES SHOULD STILL SUPPORT SOME SUPERCELL STRUCTURES.
ALSO...THE 17Z OBSERVED AMA SOUNDING INDICATED VERY STEEP MID-LEVEL
LAPSE RATES CONDUCIVE FOR STRONG UPDRAFTS. ANTICIPATE ISOLATED
SUPERCELLS WITH LARGE HAIL...PERHAPS IN EXCESS OF 2" IN
DIAMETER...THE PRIMARY THREAT. IF SURFACE WINDS CAN BACK SLIGHTLY
THIS EVENING AHEAD OF DEEPENING SURFACE LOW...AND WITH INCREASE IN
LOW-LEVEL JET TOWARD 12/00Z...POTENTIAL EXISTS FOR INCREASED SRH AND
AN ISOLATED TORNADO THREAT. THIS WOULD MOST LIKELY OCCUR DURING THE
EVENING HOURS.

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MESOSCALE DISCUSSION 0820
NWS STORM PREDICTION CENTER NORMAN OK
0236 PM CDT WED MAY 11 2005

AREAS AFFECTED...NW KS

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 111936Z - 112130Z



SUPERCELL DEVELOPMENT WILL BE LIKELY ACROSS NW KS ONCE INITIATION
OCCURS. TORNADOES...LARGE HAIL AND WIND DAMAGE WILL BE POSSIBLE AS
STORMS INTENSIFY LATE THIS AFTERNOON. A TORNADO WATCH SHOULD BE
NECESSARY WITHIN THE HOUR.

19Z SFC ANALYSIS CURRENTLY SHOWS A QUASI-STATIONARY FRONT POSITIONED
FROM ECNTRL CO EXTENDING EWD ACROSS NRN KS. A DRYLINE EXTENDS SWD
ALONG THE CO-KS STATE-LINE AND SEWD AND ACROSS THE WARM
SECTOR...VERY UNSTABLE AIR EXISTS WITH SBCAPE VALUES OF ABOUT 4000
J/KG. THE MOST LIKELY POINT OF INITIATION SHOULD BE NEAR THE
STATIONARY BOUNDARY AND DRYLINE TRIPLE POINT JUST TO THE NORTH OF
GOODLAND. OBJECTIVE ANALYSIS SHOWS STRONG DEEP LAYER SHEAR ACROSS
FAR NW KS...SW NEB AND ERN CO WITH 0-6 KM SHEAR VALUES IN THE 55 TO
75 KT RANGE. ALTHOUGH CUMULUS TOWERS MAY STRUGGLE WITH THE SHEAR
INITIALLY...SUPERCELL DEVELOPMENT WILL EVENTUALLY OCCUR. CELLS THAT
INITIATE ALONG THE FRONT WILL MOVE NEWD AND QUICKLY BECOME ELEVATED
NORTH OF THE FRONT WITH A POTENTIAL FOR VERY LARGE HAIL. CELLS THAT
INITIATE FARTHER SOUTH NEAR THE DRYLINE...WILL MOVE NEWD INTO THE
WARM SECTOR AND WILL HAVE A POTENTIAL FOR TORNADOES...VERY LARGE
HAIL AND ISOLATED WIND DAMAGE. OTHER CELLS WILL LIKELY INITIATE AND
STRENGTHEN ACROSS ERN CO WHERE STRONG SHEAR EXISTS WITH ENOUGH
INSTABILITY FOR AN ORGANIZED SEVERE THREAT.

[CaptinCrunch]

MESOSCALE DISCUSSION 0821
NWS STORM PREDICTION CENTER NORMAN OK
0321 PM CDT WED MAY 11 2005

AREAS AFFECTED...CENTRAL/WRN OH...CENTRAL IND...AND E-CENTRAL IL

CONCERNING...SEVERE THUNDERSTORM WATCH 246...

VALID 112021Z - 112215Z



WW 246 CONTINUES IN EFFECT ACROSS PORTIONS OF CENTRAL/WRN OH AND ERN
IND. ADDITIONAL THUNDERSTORMS ARE DEVELOPING WWD ACROSS MUCH OF
CENTRAL IND INTO E-CENTRAL IL. THESE STORMS POSE A SEVERE
THUNDERSTORM THREAT AND MAY NECESSITATE AN ADDITIONAL WATCH.

AT 20Z...SCATTERED NEW THUNDERSTORM DEVELOPMENT IS OCCURRING NEAR A
PRE-FRONTAL TROUGH...EXTENDING FROM 10S FWA TO 20S LAF TO 30NE MTO.
AXIS OF HIGH BOUNDARY LAYER MOISTURE EXTENDS ALONG THIS BOUNDARY
/DEWPOINTS IN THE MID 60S/...CONTRIBUTING TO MLCAPE VALUES BETWEEN
2000-2500 J/KG. WITH THE SURFACE BOUNDARY ACTING AS A FOCUS...THESE
STORMS ARE EXPECTED TO CONTINUE FOR SEVERAL HOURS WHILE TRACKING
GENERALLY EWD AT 20-25 KT. DEEP-LAYER SHEAR RANGES FROM
30-35KT...WHICH SHOULD SUPPORT SOME LONG-LIVED...ORGANIZED STORMS
WITH SUPERCELL CHARACTERISTICS. LOW-LEVEL HODOGRAPH CURVATURE AND
SRH IS LIMITED...ALONG WITH LOW MAGNITUDE OF LOW-LEVEL WINDS.
THUS...PRIMARY THREAT WITH THESE CELLS IS EXPECTED TO BE LARGE HAIL
AND ISOLATED DAMAGING WINDS ASSOCIATED WITH CONVECTIVE DOWNDRAFTS.

FURTHER EAST...ACROSS WW 246...ACTIVITY EXTENDING FROM NWRN OH INTO
E-CENTRAL IND WILL PROGRESS INTO THE WRN PORTION OF THE WATCH AREA
DURING THE NEXT 1-2 HOURS...WITH THREAT OF LARGE HAIL AND ISOLATED
DAMAGING WINDS. SEPARATE CLUSTER OF STORMS TRACKING ESEWD THROUGH
ERN OH HAVE GENERALLY REMAINED BELOW SEVERE LIMITS. LIMITED
INSTABILITY SHOULD KEEP SEVERE POTENTIAL ISOLATED ACROSS THE UPPER
OHIO RIVER VALLEY. LASTLY...NORTH WINDS FROM LAKE ERIE HAVE
EFFECTIVELY ELIMINATED SEVERE THREAT ACROSS NRN OHIO GIVEN COOL
BOUNDARY LAYER. MAIN SEVERE WEATHER POTENTIAL SHOULD BE ACROSS WRN
PORTION OF WATCH AREA NEXT 1-2 HOURS.

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MESOSCALE DISCUSSION 0822
NWS STORM PREDICTION CENTER NORMAN OK
0341 PM CDT WED MAY 11 2005

AREAS AFFECTED...NE KS...NRN MO

CONCERNING...SEVERE THUNDERSTORM WATCH 245...

VALID 112041Z - 112215Z



AN ISOLATED TORNADO THREAT WILL CONTINUE WITH SUPERCELLS ACROSS WW
245. THE STRONGER CELLS WILL ALSO HAVE A LARGE HAIL AND WIND DAMAGE
THREAT. IF STORMS CONTINUE TO DEVELOP SWD ACROSS ERN KS AND CNTRL
MO...A REPLACEMENT WW MAY BECOME NECESSARY.

A LINE OF SEVERE STORMS IS CURRENTLY ONGOING NEAR KANSAS CITY ALONG
AN EAST TO WEST INSTABILITY AXIS SOUTH OF A QUASI-STATIONARY FRONT.
SOUTH OF THE FRONT...MLCAPE VALUES IN THE 2000 TO 3000 J/KG EXIST.
IN ADDITION...MODERATE DEEP LAYER SHEAR IS PRESENT MAINLY NORTH OF
THE I-70 CORRIDOR AS SHOWN ON OBJECTIVE ANALYSIS. THIS WILL HELP
MAINTAIN A SUPERCELL THREAT AS STORMS TRACK NEWD INTO THE STRONGER
SHEAR. INITIATION WILL ALSO BE POSSIBLE FARTHER SOUTH IF AN OUTFLOW
BOUNDARY CAN BECOME ESTABLISHED ACROSS ERN KS AND CNTRL MO. VERTICAL
SHEAR IS WEAKER IN THIS AREA BUT IS STILL SUFFICIENT...COMBINED WITH
THE INSTABILITY...FOR LARGE HAIL AND WIND DAMAGE.

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MESOSCALE DISCUSSION 0823
NWS STORM PREDICTION CENTER NORMAN OK
0400 PM CDT WED MAY 11 2005

AREAS AFFECTED...W-CENTRAL AND CENTRAL NEB...AND FAR NERN CO

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 112100Z - 112300Z



THREAT EXISTS FOR SCATTERED ELEVATED SEVERE THUNDERSTORMS WITH LARGE
TO VERY LARGE HAIL ACROSS W-CENTRAL/CENTRAL NEB AND FAR NERN CO
THROUGH THIS EVENING INTO TONIGHT. SEVERE THUNDERSTORM WATCH #252
HAS RECENTLY BEEN ISSUED FOR THIS REGION.

AT 2045Z...STRONG QUASI-STATIONARY FRONT EXTENDS EAST-WEST ACROSS
SRN NEB...NEAR OR JUST SOUTH OF I-80. AIR MASS SOUTH OF THE FRONT
HAS BECOME VERY UNSTABLE WITH AFTERNOON HEATING /MLCAPES OF
2500-3500 K/KG/. STRONG LOW-LEVEL SLY FLOW ORTHOGONAL TO THE FRONT
IS ALLOWING FOR A PLUME OF ELEVATED INSTABILITY AND SEVERE
THUNDERSTORMS TO PROGRESS NWD ACROSS W-CENTRAL NEB AT THE PRESENT
TIME. THE 18Z RUC INDICATES THAT THE LOW-LEVEL JET STRENGTHENS
ACROSS THE DISCUSSION AREA THROUGH TONIGHT...WHICH SHOULD ALLOW FOR
STRONG 850-700MB WARM ADVECTION AND WIDESPREAD ELEVATED THUNDERSTORM
COVERAGE ACROSS CENTRAL NEB INTO TONIGHT. WITH MUCAPE VALUES IN
EXCESS OF 2000 J/KG AND SUFFICIENT SHEAR FOR SUPERCELLS...LARGE TO
VERY LARGE HAIL IS POSSIBLE WITH LONGER-LIVED CORES NORTH OF THE
SURFACE FRONT.

[CaptinCrunch]

MESOSCALE DISCUSSION 0837
NWS STORM PREDICTION CENTER NORMAN OK
0934 AM CDT THU MAY 12 2005

AREAS AFFECTED...PORTIONS TX/OK PANHANDLE...NWRN OK

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 121434Z - 121630Z



WIDELY SCATTERED TSTMS POSSIBLE THROUGH LATE MORNING...WITH HAIL
POSSIBLE FROM MOST VIGOROUS/PERSISTENT CELLS. AREA WILL BE
MONITORED FOR POSSIBLE WW.

SFC MESOANALYSIS -- INCLUDING W TX MESONET AND SCHOOL DATA -- SHOWS
COLD FRONT MOVING SEWD ACROSS REGION FASTER THAN PROGGED. FRONT IS
ANALYZED AT 1415Z FRM WRN WOODS COUNTY OK SWWD ACROSS NWRN ROGER
MILLS COUNTY...THEN FROM CENTRAL WHEELER COUNTY TX WSWWD ACROSS
ARMSTRONG/SWISHER COUNTY LINE TO CENTRAL ROOSEVELT COUNTY NM. FRONT
SHOULD DECELERATE NEXT SEVERAL HOURS ACROSS EXTREME W-CENTRAL OK TO
VICINITY PVW AND S-CENTRAL ROOSEVELT COUNTY. ALTHOUGH AREA IS
BENEATH THERMAL RIDGE ANALYZED ON 500 MB CHART...ASSOCIATED MIDLEVEL
STABLE LAYER APPEARS TO BE OVERCOME IN BUOYANCY PROFILE IN MODIFIED
12Z AMA RAOB. COMBINATION OF MEAN MIDLEVEL LAPSE RATES 7-8 DEG C/KM
AND NEARLY SATURATED BASE LAYER BETWEEN 800-850 MB YIELD 2000-3000
J/KG ELEVATED MUCAPE. FORCING APPEARS WEAK WITH LOW-ANGLE
ISENTROPIC SLOPING ATOP SHALLOW FRONTAL LAYER. HOWEVER...ANY
CONVECTION WHICH DOES PERSIST MAY PRODUCE HAIL...ESPECIALLY GIVEN
35-40 KT EFFECTIVE SHEAR USING MOST-UNSTABLE LIFTED LAYER.

[CaptinCrunch]

MESOSCALE DISCUSSION 0838
NWS STORM PREDICTION CENTER NORMAN OK
1159 AM CDT THU MAY 12 2005

AREAS AFFECTED...SRN VA...NC...AND FAR NRN SC

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 121659Z - 121930Z



SCATTERED THUNDERSTORM DEVELOPMENT IS ANTICIPATED THIS AFTERNOON
ACROSS FAR SRN VA...NC...AND FAR NRN SC. STORM ORGANIZATION SHOULD
BE LIMITED BY WEAK DEEP-LAYER SHEAR. HOWEVER...A FEW SEVERE CELLS OR
MULTICELLULAR CLUSTERS WITH LOCALLY DAMAGING WINDS OR ISOLATED LARGE
HAIL ARE POSSIBLE. WW IS NOT ANTICIPATED AT THIS TIME.

MUCH OF SRN VA/NC/NRN SC CONTINUES TO HEAT STRONGLY EARLY THIS
AFTERNOON /TEMPERATURES IN THE LOW TO MID 80S/ WITH GENERALLY CLEAR
SKIES PRESENT. DISCUSSION AREA IS SITUATED ON NERN PERIPHERY OF
MID-LEVEL RIDGE ACROSS THE CENTRAL GULF STATES.
AT THE SURFACE...A WEAK WIND SHIFT/PRE-FRONTAL TROUGH EXTENDS E-W
ACROSS CENTRAL NC. THE SYNOPTIC COLD FRONT WILL CONTINUE TO MOVE SWD
FROM CENTRAL VA AND THE DELMARVA PENINSULA...IN RESPONSE TO STRONG
COLD AIR ADVECTION AND AN UNSEASONABLY STRONG SURFACE ANTICYCLONE
ACROSS ONTARIO CANADA. SURFACE DEWPOINTS INITIALLY IN THE LOW 60S
EARLY THIS AFTERNOON WILL LIKELY MIX DOWN INTO THE MID 50S ACROSS
MOST OF THE REGION AS BOUNDARY LAYER DEEPENS. THIS WILL HELP
ESTABLISH SURFACE DEWPOINT DEPRESSIONS OF 30-35F.

SEVERE THREAT TODAY WILL BE PRIMARILY DRIVEN BY INSTABILITY AND THE
POTENTIAL FOR STRONG CONVECTIVE DOWNDRAFTS WITH STRONGER CORES.
MLCAPE VALUES ARE EXPECTED TO PEAK OUT AROUND 1500 J/KG.
DEEP-LAYER SHEAR IS MARGINAL FOR ORGANIZED STORMS /SFC-6KM SHEAR IS
NWLY AT 20-30KT/. IT IS POSSIBLE THAT MESOSCALE OUTFLOW BOUNDARIES
MAY ALLOW FOR A COUPLE OF SWD OR SEWD MOVING BANDS OF STORMS DURING
THEIR EVOLUTION THROUGH LATE AFTERNOON/EARLY EVENING. THE
PRE-FRONTAL TROUGH AND APPROACHING COLD FRONT SHOULD PROVIDE A FOCUS
FOR LOW-LEVEL CONVERGENCE SUFFICIENT FOR INITIATION DURING THE NEXT
FEW HOURS. SEPARATE TOWERING CU ALONG THE EAST SLOPES OF THE
APPALACHIANS MAY ALSO RESULT IN ISOLATED THUNDERSTORMS THAT TRACK
SEWD. ENVIRONMENT SUGGESTS LOCALIZED DAMAGING WIND POTENTIAL...AS
WELL AS MARGINALLY SEVERE HAIL WITH STRONGER CELLS.

[CaptinCrunch]

MESOSCALE DISCUSSION 0839
NWS STORM PREDICTION CENTER NORMAN OK
1240 PM CDT THU MAY 12 2005

AREAS AFFECTED...PORTIONS SERN NEB...NERN KS...NWRN MO...SWRN IA

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 121740Z - 121915Z



SEVERE TSTMS -- INCLUDING POTENTIAL FOR A FEW SUPERCELLS -- ARE
POSSIBLE OVER MO VALLEY REGION FROM SERN NEB/SWRN IA ACROSS NERN
KS/NWRN MO THROUGH AFTERNOON. WW MAY BE REQUIRED.

17Z SFC MESOANALYSIS AND VIS IMAGERY INDICATE OUTFLOW BOUNDARY FROM
EARLIER CONVECTION EXTENDS FROM MKC AREA NWWD ACROSS NERN KS --
BETWEEN TOP-FNB -- TO NEAR BIE. SYNOPTIC WARM FRONT IS DIFFUSE BUT
LOCATED ROUGHLY FROM NEAR STJ WNWWD TO NEAR LNK...THEN NWWD TO SFC
LOW S ONL. COLD FRONT ARCS FROM LOW SWD BETWEEN CNK-MHK THEN SSWWD
NEAR HUT. PREFRONTAL CONFLUENCE LINE EXTENDS FROM INTERSECTION WITH
OUTFLOW BOUNDARY -- NEAR BIE -- SWD TO MHK THEN SSWWD TO NEAR END.
PRIND AREA MOST FAVORABLE FOR SFC-BASED TSTMS INITIALLY IS INVOF
OUTFLOW/CONFLUENCE INTERSECTION THEN SWD ALONG CONFLUENCE LINE AS
FRONT CATCHES UP. CLEARING OF LOW CLOUDS WILL ALLOW AIR MASS
BETWEEN SYNOPTIC FRONT AND OUTFLOW BOUNDARY OVER SERN NEB TO
HEAT/DESTABILIZE NEXT FEW HOURS...CREATING ZONE OF SFC-BASED
BUOYANCY AND ENHANCED LOW LEVEL HODOGRAPHS THAT WILL SHIFT NEWD
ACROSS MO VALLEY TOWARD SWRN IA WITH TIME. MESOLOW MAY DEVELOP
ALONG OUTFLOW BOUNDARY AS WELL...FURTHER ENHANCING LOW LEVEL SHEAR.
0-1 KM SRH 100-200 J/KG IS POSSIBLE...WITH MLCAPES 1000-2000 J/KG
ALONG OUTFLOW BOUNDARY.

SEVERE POTENTIAL OVER NARROW PREFRONTAL CORRIDOR FROM LNK AREA NWWD
TOWARD SFC LOW IS QUITE CONDITIONAL BECAUSE OF BRIEF/LIMITED
OPPORTUNITY FOR SFC DESTABILIZATION PRIOR TO FROPA. HEATING WITHIN
THIS CORRIDOR WILL BE LIMITED BY COMBINATION OF SLOW-ERODING LOW
STRATUS...AND HIGH CLOUDS OF ANVIL ORIGIN ADVECTING NEWD FROM
POSTFRONTAL/ELEVATED TSTMS OVER KS AND TX/OK PANHANDLES.

[CaptinCrunch]

MESOSCALE DISCUSSION 0840
NWS STORM PREDICTION CENTER NORMAN OK
0116 PM CDT THU MAY 12 2005

AREAS AFFECTED...PORTIONS CENTRAL/SWRN KS

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 121816Z - 121915Z



SEVERE TSTM WW MAY BE REQUIRED SOON OVER PORTIONS OF CENTRAL/SWRN
KS..NE OF WW 257.

SFC ANALYSIS AND CLOUD LINE IN VIS IMAGERY INDICATES DECELERATING
COLD FRONT WITHIN 30 NM E OF A CNK-SLN-HUT-P28 LINE. MID/UPPER FLOW
HAS STRONG COMPONENT PARALLEL TO THIS BOUNDARY. BAND OF TSTMS IS
MOVING/DEVELOPING NEWD FROM OK/TX PANHANDLE AND IS EXPECTED TO
EXPERIENCE FAVORABLE ELEVATED INSTABILITY BEHIND SFC COLD FRONT.
ALSO...SFC-BASED TSTMS MAY DEVELOP ALONG COLD FRONT AND MOVE NEWD.
TSTMS INITIATING ALONG FRONT MAY ATTAIN ORGANIZED MULTICELL
CHARACTERISTICS BEFORE CELLS/ANVILS MERGE AND ACTIVITY ATTAINS MORE
LINEAR CHARACTER WITH SMALL LEWPS/BOWS POSSIBLE. THEREFORE...MAIN
THREAT IS HAIL W OF FRONT...WIND AND HAIL ALONG FRONT. BRIEF
NON-MESOCYCLONE TORNADO IS POSSIBLE WITH SFC-BASED FRONTAL
TSTMS...BUT MAIN THREATS ARE DAMAGING WIND AND LARGE HAIL. MLCAPES
TO NEAR 2000 J/KG INDICATED ALONG/AHEAD OF FRONT...SUPPORTED BY SFC
TEMPS RISING INTO 80S F AND DEW POINTS LOW-MID 60S.

[CaptinCrunch]

MESOSCALE DISCUSSION 0841
NWS STORM PREDICTION CENTER NORMAN OK
0222 PM CDT THU MAY 12 2005

AREAS AFFECTED...PORTIONS NWRN OK...TX PANHANDLE AND SOUTH
PLAINS...SERN NM.

CONCERNING...SEVERE THUNDERSTORM WATCH 257...

VALID 121922Z - 122015Z



SEVERE HAIL REMAINS PRIMARY THREAT ACROSS SOUTH PLAINS AND SRN
PANHANDLE PORTION WW...HOWEVER...ENVIRONMENTAL PARAMETERS FAVORING
LOCALIZED TORNADO POTENTIAL MAY BE INCREASING...AND PARTIAL WW
REPLACEMENT/UPGRADE OF WW IS BEING CONSIDERED. MEANWHILE...SEVERE
TSTM WW SHOULD BE MAINTAINED FARTHER N ACROSS NRN PANHANDLE INTO NW
OK. UP TO 3 INCH HAILSTONES REPORTED WITH STORM OVER HALE COUNTY IN
PAST HOUR...AND ADDITIONAL VERY LARGE/DAMAGING HAIL IS LIKELY.

SFC MESOANALYSIS SHOWS FRONT NEARLY QUASISTATIONARY FROM WOODS TO NW
BECKHAM COUNTY OK...SWWD ACROSS PVW AREA TO EXTREME NE HOCKLEY
COUNTY TX...SRN LAMB COUNTY...TO ROOSEVELT COUNTY NM. DRYLINE
INTERSECTS FROM NEAR TX/NM BORDER ATTM AND EXTENDS SSWWD ACROSS LEA
COUNTY NM. DRYLINE MAY RETREAT WWD ACROSS ROOSEVELT/LEA COUNTIES
LATER THIS AFTERNOON. AIR MASS IS DESTABILIZING ENOUGH TO SUSTAIN
SFC-BASED CONVECTION ALONG AND JUST W OF FRONT -- WHERE SFC FLOW
SHOULD VEER TO MORE ELY COMPONENT AND ENLARGE HODOGRAPHS. PRIND
TSTMS OVER HALE COUNTY -- AND ANY FUTURE DISCRETE DEVELOPMENT INVOF
FRONT FROM W CDS SWWD TO NEAR NM BORDER -- MAY ROTATE STRONGLY WHILE
MOVING ALONG/ACROSS FRONTAL BOUNDARY WHERE VORTICITY/LIFT ARE
MAXIMIZED. MLCAPES 2000-3000 J/KG EXPECTED IN WARM SECTOR FROM LBB
AREA SWD...THOUGH BOTH RUC SOUNDINGS AND JTN PROFILER INDICATE
RELATIVELY WEAK LOW LEVEL FLOW. ELEVATED MUCAPE 2300 J/KG EVIDENT
IN 18Z AMA RAOB...ALONG WITH 50-55 KT EFFECTIVE SHEAR ...SUPPORTING
CONTINUED LARGE HAIL POTENTIAL WITH ANY TSTMS NRN/ERN PANHANDLE AND
NWRN OK.

[CaptinCrunch]

MESOSCALE DISCUSSION 0856
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM CDT FRI MAY 13 2005

AREAS AFFECTED...NERN IL / NRN IN / SWRN MI

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 131720Z - 131845Z



THUNDERSTORMS WILL INCREASE IN INTENSITY THROUGH THE AFTERNOON. A
WW WILL LIKELY BE NEEDED SOON.

SURFACE ANALYSIS SHOWS WARM FRONT OVER NRN IL / NRN IN...WITH
MODERATE INSTABILITY TO THE SOUTH. STORMS WILL CONTINUE TO FORM
ALONG AND N OF WARM FRONT...AND WILL GRADUALLY BUILD SWD INTO WARM
SECTOR AS UPPER TROUGHING MOVES INTO THE AREA AFTER 18Z.

MEAN SFC TO 6 KM FLOW AROUND 40 KTS AND STEEP LOW LEVEL LAPSE RATES
SUGGEST DAMAGING WINDS WILL BE POSSIBLE. HAIL UP TO GOLF BALL SIZE
WILL BE POSSIBLE AS WELL. AN ISOLATED TORNADO WILL BE POSSIBLE NEAR
WARM FRONT WHERE LOW LEVEL SHEAR IS ENHANCED. STORMS WILL QUICKLY
BECOME ELEVATED ONCE THEY GET MORE THAN ABOUT 50 MILES N OF WARM
FRONT.

[CaptinCrunch]

MESOSCALE DISCUSSION 0857
NWS STORM PREDICTION CENTER NORMAN OK
1241 PM CDT FRI MAY 13 2005

AREAS AFFECTED...SRN IN INTO NRN MS

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 131741Z - 131945Z



SCATTERED SEVERE STORMS WILL OCCUR THROUGH THE AFTERNOON HOURS. THE
MAIN THREAT WILL BE HAIL...ALTHOUGH ISOLATED DAMAGING DOWNBURSTS MAY
OCCUR AS WELL. A WW IS BEING CONSIDERED.

VERY STEEP LOW LEVEL LAPSE RATES HAVE DEVELOPED...ALONG WITH
MODERATE INSTABILITY. GIVEN CONTINUATION OF STRONG
HEATING...SEVERAL SEVERE STORMS ARE EXPECTED. A FEW STORMS MAY BE
ABLE TO SUSTAIN THEMSELVES LONG ENOUGH TO PRODUCE LARGE HAIL UP TO
GOLF BALL SIZE...DESPITE WEAK SHEAR PROFILES.

[CaptinCrunch]

MESOSCALE DISCUSSION 0858
NWS STORM PREDICTION CENTER NORMAN OK
0152 PM CDT FRI MAY 13 2005

AREAS AFFECTED...PORTIONS NW TX...ERN TX PANHANDLE...SWRN OK

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 131852Z - 132015Z



TORNADO WW WILL BE ISSUED WITHIN AN HOUR. TSTM DEVELOPMENT
ANTICIPATED BY 21Z FROM CDS AREA WWD TO INVOF CAPROCK. ACTIVITY
SHOULD EVOLVE RAPIDLY INTO SUPERCELL CHARACTER WITH VERY
LARGE/DESTRUCTIVE HAIL LIKELY. DAMAGING WIND AND TORNADO POTENTIAL
ALSO EXISTS...REINFORCED LOCALLY BY STORM-SCALE AND/OR MESOBETA
SCALE BOUNDARY INTERACTIONS.

SFC MESOANALYSIS -- INCLUDING W TX AND OK MESONET DATA -- INDICATES
PRONOUNCED MESOLOW CENTRAL/NERN FLOYD COUNTY AT 18Z. ASSOCIATED
BOUNDARY LAYER CYCLONIC CIRCULATION ALSO IS EVIDENT IN CU PATHS ON
ANIMATED VIS IMAGERY. DRYLINE EXTENDS DUE S THROUGH BORDEN COUNTY
AND IS EXPECTED TO MIX SLIGHTLY EWD TOWARD W EDGE OF DEEPER CU FIELD
-- NOW EVIDENT FROM SRN BRISCOE/MOTLEY COUNTIES SWD THROUGH COKE
COUNTY. DIFFERENTIAL HEATING BOUNDARY -- ALONG EDGE OF SLOWLY
ERODING LOW CLOUD DECK -- CURVES FROM MAJOR COUNTY OK SWWD ACROSS
HARMON COUNTY...THEN OVER TX PANHANDLE THROUGH SRN DONLEY TO
OCHILTREE COUNTY TX. OUTFLOW BOUNDARY FROM MORNING MCS IS BECOMING
MORE DIFFUSE AND LIFTING NWD THROUGH CDS AREA..SOON TO MERGE WITH
DIFFERENTIAL HEATING BOUNDARY.

BACKED LOW LEVEL FLOW AND ENLARGED HODOGRAPHS SHOULD REMAIN MOST
PRONOUNCED FROM JUST NE-E OF MESOLOW EWD INTO EXTREME SWRN
OK...COINCIDENT WITH SFC MOIST AXIS CONTAINING MID/UPPER 60S F DEW
POINTS. THESE FACTORS COMBINE WITH DIABATICALLY DESTABILIZING
BOUNDARY LAYER AND STEEP MIDLEVEL LAPSE RATES -- EVIDENT IN 18Z AMA
RAOB AND RUC SOUNDINGS -- TO YIELD 2000-2500 J/KG MLCAPE AND RAPIDLY
WEAKENING CINH. CONVERGENCE MAX W CDS INDICATES REGION FROM CDS
TOWARD PALO DURO CANYON SWD TO MESOLOW IS MOST FAVORED AREA FOR
SOONEST INITIATION...THOUGH OTHER DEVELOPMENT MAY OCCUR EWD OR NWD
ALONG OUTFLOW/HEATING BOUNDARIES INTO SW OK AND ERN TX PANHANDLE.
DESPITE SOME MINOR WEAKNESSES EVIDENT IN LOW LEVEL FLOW...100-150
0-1 KM SRH AND 50 KT EFFECTIVE SHEAR AND FAVORABLY MOIST INFLOW
SUPPORT SUPERCELLS AND ENHANCED HAIL GENERATION.

[CaptinCrunch]

MESOSCALE DISCUSSION 0859
NWS STORM PREDICTION CENTER NORMAN OK
0213 PM CDT FRI MAY 13 2005

AREAS AFFECTED...SRN TRANS-PECOS REGION OF SW TX

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 131913Z - 132115Z



RAPID DEVELOPMENT OF CB EVIDENT ALONG SFC DRYLINE FROM IT
INTERSECTION WITH HIGHER TERRAIN OVER NERN BREWSTER COUNTY...NEWD
ACROSS ERN PECOS COUNTY. OTHER TSTM DEVELOPMENT POSSIBLE FARTHER S
THROUGH BIG BEND AREA AND NEWD ALONG DRYLINE TO W SJT. AREA WILL BE
MONITORED FOR POSSIBLE WW.

25-30 DEG F SFC DEW POINT DEPRESSIONS INDICATE ACTIVITY WILL BE HIGH
BASED -- WITH DEEPLY MIXED SUBCLOUD LAYERS SUPPORTING MAINTENANCE TO
SFC OF ANY STRONG-SEVERE HAIL/DOWNDRAFTS GENERATE ALOFT. RELATIVELY
WEAK LOW LEVEL WINDS AND SMALL HODOGRAPHS...COMBINED WITH ANOTHER
ZONE OF WEAK FLOW IN 450-250 MB LAYER -- INDICATE PREDOMINANTLY
MULTICELLULAR STORM MODE...TRENDING TOWARD OUTFLOW DOMINANCE. ANY
ACTIVITY WHICH DOES NOT GET UNDERCUT BY OUTFLOW/COLD POOLS AND
SURVIVES INTO 23-02Z TIME FRAME MAY ACCESS DEEPER/RICHER MOIST LAYER
EVIDENT ATTM FARTHER E. VIS IMAGERY AND RUC SOUNDINGS INDICATE W
EDGE OF THIS LAYER FROM NEAR JCT TO APPROXIMATELY 40 WNW DRT...NEAR
ERN SLOPES OF SERRANIAS DEL BURRO RANGE. SELY ADVECTION MAY SHIFT
THIS PLUME NWWD UP RIO GRANDE VALLEY TOWARD TERRELL COUNTY.

[CaptinCrunch]

MESOSCALE DISCUSSION 0860
NWS STORM PREDICTION CENTER NORMAN OK
0228 PM CDT FRI MAY 13 2005

AREAS AFFECTED...WRN OH / SERN MI

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 131928Z - 132030Z



WW WILL BE ISSUED SHORTLY.

SURFACE ANALYSIS SHOWS STRONG PRESSURE FALLS SERN MI INTO NWRN OH.
EXPECT STORMS TO INCREASE OVER THE NEXT FEW HOURS IN THESE AREAS
WITH DAMAGING WINDS AND HAIL. ENHANCED SHEAR ALONG WARM FRONT MAY BE
FAVORABLE FOR MESOCYCLONE FORMATION WITH THE STRONGEST
CELLS...ALTHOUGH ANY STORMS THAT MOVE TOO FAR N OF THIS BOUNDARY
WILL BECOME ELEVATED.

[CaptinCrunch]

MESOSCALE DISCUSSION 0861
NWS STORM PREDICTION CENTER NORMAN OK
0241 PM CDT FRI MAY 13 2005

AREAS AFFECTED...I-44 CORRIDOR OF SWRN TO ERN MO...PORTIONS SWRN IL

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 131941Z - 132145Z



GRADUAL TSTM DEVELOPMENT POSSIBLE THROUGH MID/LATE AFTERNOON INVOF
QUASISTATIONARY BAROCLINIC ZONE -- ANALYZED JUST N I-44 FROM NERN OK
THROUGH JLN/STL AREAS INTO SWRN IL. STRONG-SEVERE GUSTS AND
OCCASIONAL HAIL ARE POSSIBLE. ORGANIZATION OF SEVERE THREAT APPEARS
MARGINAL BUT WILL BE MONITORED FOR POSSIBLE WW.

FRONTAL BOUNDARY EVIDENT ATTM BOTH IN SFC ANALYSIS AND LOW CLOUD
TRENDS FROM VIS IMAGERY. ALTHOUGH CONVERGENCE APPEARS WEAK...THIS
AREA HAS DEEPEST CUMULIFORM CLOUDS AND LARGEST CONVECTIVE INITIATION
PROBABILITIES NEXT FEW HOURS. MODIFIED 18Z SGF RAOB AND RUC FCST
SOUNDINGS INDICATE 1000-1500 J/KG MLCAPE DURING NEXT 2-3
HOURS...WITH CINH UNDER 50 J/KG. EFFECTIVE SHEAR 40-50 KT INDICATES
SOME SUPERCELL POTENTIAL...ALTHOUGH KINEMATICS/BOUNDARY GEOMETRY
INDICATES MORE LINEAR EVOLUTION WITH BOW/LEWP FEATURES EMBEDDED.
DEEP-LAYER FLOW FIELDS ARE NEARLY UNIDIRECTIONAL WITH MEAN FLOW
ALIGNED PARALLEL TO BAROCLINIC ZONE...BASED ON SRN MO PROFILER/VWP
DATA AND RUC WINDS.

[CaptinCrunch]

MESOSCALE DISCUSSION 0862
NWS STORM PREDICTION CENTER NORMAN OK
0350 PM CDT FRI MAY 13 2005

AREAS AFFECTED...NRN OK INTO SRN KS

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 132050Z - 132215Z



SEVERE TSTM POTENTIAL APPEARS TO BE INCREASING ACROSS PORTIONS OF
NRN OK INTO SRN KS AND CONDITIONS ARE BEING MONITORED FOR A POSSIBLE
WW ISSUANCE.

LATEST MESOANALYSIS INDICATED AN AREA OF LOW PRESSURE OVER THE FAR
ERN OK PNHDL WITH ASSOCIATED FRONTAL BOUNDARY EXTENDING SEWD FROM
THIS FEATURE TO S OF END AND THEN MORE NEWD TO N OF TUL.
CONSIDERABLE LOW CLOUDINESS HAS LIMITED DIABATIC HEATING AND
RESULTANT DESTABILIZATION ALONG THIS BOUNDARY...THOUGH RUC FIELDS
SUGGEST THAT CAP HAS BECOME RELATIVELY WEAK WITH MLCAPES OF
1000-1500 J/KG FROM VICINITY OF SURFACE LOW EWD ALONG FRONTAL ZONE
TO I-35.

LATEST RADAR TRENDS INDICATE AN INCREASE IN CONVECTION FROM WOODS
AND MAJOR COUNTIES EWD INTO GARFIELD AND NOBLE COUNTIES OF N-CNTRL
OK. CONTINUED HEATING/DESTABILIZATION COUPLED WITH INCREASED
LARGE-SCALE FORCING FOR ASCENT ASSOCIATED WITH SHORTWAVE/THERMAL
TROUGH MOVING THROUGH THE TX PNHDL INTO WRN OK SHOULD CONTRIBUTE TO
A FURTHER INCREASE IN STORM COVERAGE AND INTENSITY.

CURRENT LAMONT PROFILER INDICATES A QUITE FAVORABLE SHEAR PROFILE
FOR SUPERCELLS WITH STRONGLY VEERING WINDS WITH HEIGHT AND 50 KTS OF
DEEP-LAYER SHEAR. WHILE LARGE HAIL WILL BE PRIMARY SEVERE WEATHER
THREAT WITH ANY STORMS THAT DEVELOP...RELATIVELY STRONG OBSERVED
LOW-LEVEL SHEAR /0-1 KM SRH OF 150-200 M2/S2/ ALSO SUGGEST THE
POTENTIAL FOR ISOLATED TORNADOES.

CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED AND WW MAY BE
REQUIRED WITHIN NEXT HOUR OR SO.

[CaptinCrunch]

MESOSCALE DISCUSSION 0895
NWS STORM PREDICTION CENTER NORMAN OK
1253 PM CDT TUE MAY 17 2005

AREAS AFFECTED...ERN MT....WRN DAKOTAS

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 171753Z - 172000Z



THE CHANCE FOR SEVERE THUNDERSTORMS WILL CONTINUE TO INCREASE ACROSS
PORTIONS OF ERN MT AND THE WRN DAKOTAS EARLY THIS AFTERNOON. A
SEVERE THUNDERSTORM WATCH MAY BE NEEDED OVER PARTS OF THE REGION
WITHIN A COUPLE OF HOURS.

ONE INTENSE SUPERCELL WAS ALREADY TRACKING NWD THROUGH PHILLIPS
COUNTY MT WITHIN LEFT-FRONT QUADRANT OF STRONGLY DIFFLUENT MID LEVEL
WIND MAX. ADDITIONAL STORMS ARE EXPECTED TO DEVELOP ACROSS THE
REGION THROUGH THIS AFTERNOON AS STRONG MID/UPPER LEVEL TROUGH LIFTS
NEWD FROM NRN/CNTRL WY. ALTHOUGH INSTABILITY IS EXPECTED TO REMAIN
LIMITED... STRONG DYNAMIC FORCING FOR ASCENT WILL CONTINUE TO ACT ON
WARMING AND MOISTENING LOW LEVEL AIR MASS NEAR SURFACE LOW AND
ASSOCIATED FRONTAL BOUNDARIES. RESULTING CONVECTION WILL BE SITUATED
IN A STRONGLY SHEARED ENVIRONMENT WITH LOW LEVEL SELY UPSLOPE FLOW
TOPPED BY 50-60KT SLY FLOW AT MID LEVELS. INITIAL STORMS MAY EXHIBIT
SUPERCELL CHARACTERISTIC WITH HAIL AND HIGH WINDS POSSIBLE. ACTIVITY
MAY ALSO ORGANIZE INTO SHORT LINE SEGMENTS ALONG THE ADVANCING COLD
FRONT LATER TODAY WITH A CHANCE FOR DAMAGING WINDS.

[CaptinCrunch]

MESOSCALE DISCUSSION 0896
NWS STORM PREDICTION CENTER NORMAN OK
0129 PM CDT TUE MAY 17 2005

AREAS AFFECTED...SRN SD AND WRN NEB

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 171829Z - 172030Z



A SEVERE TSTM WATCH MAY BE NEEDED ACROSS PARTS OF NEB AND SRN SD
WITHIN 1-2 HOURS.

DESPITE LIMITED LOW LEVEL MOISTURE AND STRONG CAP ACROSS THE CNTRL
PLAINS THIS AFTERNOON...SFC HEATING AND STRONG DYNAMIC FORCING ARE
EXPECTED TO PROMOTE SCATTERED STORM INITIATION ALONG ADVANCING COLD
FRONT/DRYLINE FROM SCNTRL SD TO WRN NEB IN THE NEXT FEW HOURS.
LATEST LBF SOUNDING SUGGESTS STRONG CAP IS HOLDING ACROSS THIS
REGION. HOWEVER...LATEST SFC OBSERVATIONS DEPICT RAPID WARMING
OCCURRING AHEAD OF THE DRYLINE/COLD FRONT FROM NWRN KS ACROSS WRN
NEB. WHEN THE LBF SOUNDINGS IS ADJUSTED WITH THIS WARM SECTOR AIR
MASS IT APPEARS THAT REMAINING INHIBITION COULD BE ELIMINATED
THROUGH STRONG FRONTAL FORCING. THIS SCENARIO IS FURTHER SUPPORTED
BY LATEST SHORT TERM MODEL QPF FROM THE RUC/NAM AND EXPERIMENTAL
WRF. THESE MODELS SUGGEST THAT STORMS WILL DEVELOP NEAR THE FRONT
AND BUILD FROM NNW TO SSE ACROSS SWRN SD INTO NEB IN THE 20-22Z TIME
FRAME.

STORMS MAY EVENTUALLY EVOLVE INTO A SQUALL LINE GIVEN LINEAR FORCING
ON THE FRONT AND DEEP LAYER MERIDIONAL FLOW. DEEP LAYER SHEAR
APPROACHING 30KT WILL SUPPORT CELL/UPDRAFT PERSISTENCE AND SOME
CHANCE FOR BOWING SEGMENTS WITH WIND DAMAGE AS WELL AS HAIL.

[CaptinCrunch]

MESOSCALE DISCUSSION 0902
NWS STORM PREDICTION CENTER NORMAN OK
1222 PM CDT WED MAY 18 2005

AREAS AFFECTED...ERN ND/SD...SWRN MN...NRN IA

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 181722Z - 181945Z



TSTMS ARE EXPECTED TO DEVELOP ACROSS ERN PARTS OF ND AND SD...AS
WELL AS SRN MN...AND PERHAPS NRN IA...OVER THE NEXT FEW HOURS. SOME
OF THIS ACTIVITY COULD BECOME SEVERE WITH THE PRIMARY THREAT BEING
HAIL. THIS REGION WILL CONTINUE TO BE MONITORED FOR A POSSIBLE
WATCH.

HEIGHT FALLS AND DIFFLUENT MID LEVEL FLOW ASSOCIATED WITH UPPER
TROUGH CENTERED OVER THE WRN DAKOTAS WILL CONTINUE TO OVERSPREAD
WARMING AND MOISTENING BOUNDARY LAYER FROM NWRN IA INTO WRN MN. LOW
LEVEL CONVERGENCE WAS CURRENTLY MAXIMIZED WITHIN A NARROW WARM
SECTOR EXTENDING FROM THE WRN MN BORDER NWD TO THE RED RIVER VLY.
LIFT WITHIN THIS ZONE...AND PERSISTENT WARM AIR ADVECTION INTO SRN
MN SHOULD SUPPORT CONVECTIVE INITIATION OVER THE NEXT 1-3 HOURS.
HIGH-BASED/POST FRONTAL CONVECTION MAY ALSO INCREASE ACROSS ERN
SD/SERN ND AS MID LEVEL COLD POOL SPREADS EAST ACROSS THIS REGION.

MARGINAL INSTABILITY WITHIN A STRONGLY SHEARED ENVIRONMENT WOULD
SUGGEST SOME LIMITATIONS TO OVERALL STORM ORGANIZATION AND SEVERE
POTENTIAL. HOWEVER...POCKETS OF GREATER SFC-BASED INSTABILITY
ASSOCIATED WITH THE NARROW WARM SECTOR FROM SERN ND INTO SWRN MN
COULD PROMOTE MORE INTENSE CELLS. GIVEN SHEAR AND FORCING ACROSS THE
REGION...SOME OF THESE STORMS MAY POSE A GREATER THREAT OF HAIL/WIND
AND A SMALL WATCH MAY BE NEEDED OVER THE REGION LATER THIS
AFTERNOON.