MESOSCALE DISCUSSION NWS STORM PREDICTION CENTER

[ColdFront77]

MESOSCALE DISCUSSION 0358
NWS STORM PREDICTION CENTER NORMAN OK
0117 AM CST WED MAR 23 2005

AREAS AFFECTED...PORTIONS CENTRAL/NRN FL PENINSULA

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 230717Z - 230915Z

WIDELY SCATTERED TO SCATTERED TSTMS MAY INCREASE IN COVERAGE ACROSS
REGION...AND MOVE ONSHORE FL W COAST FROM GULF -- PRIMARILY BETWEEN
LEVY/ALACHUA/PUTNAM/ST JOHNS COUNTIES SWD TO TBW-MLB LINE.
SUPERCELLS ARE POSSIBLE ALONG WITH POTENTIAL FOR HAIL AND DAMAGING
WIND. SOME TORNADO POTENTIAL ALSO EXISTS. AREA WILL BE MONITORED
FOR POSSIBLE WW.

ALTHOUGH LOW LEVEL FORCING APPEARS TO BE WEAK AND
NEBULOUS...MODIFIED RUC SOUNDINGS INDICATE SMALL CINH...WHICH IS
CONSISTENT WITH INCREASING CONVECTIVE COVERAGE TRENDS. DIFFERENTIAL
HEATING BOUNDARY MAY BE ARRANGED ALONG S EDGE OF LARGE PRECIP PLUME
NOW EVIDENT FROM LEVY COUNTY SWWD OVER GULF...N OF WHICH SFC TEMPS
WILL REMAIN IN LOW 60S F. AIR MASS ALONG AND S OF THAT PLUME WILL
BE CHARACTERIZED BY SFC TEMPS UPPER 60S TO LOW 70S F...DEW POINTS
APCHG 70 F...AND NEARLY SFC-BASED MUCAPE OF APPROXIMATELY 1500 J/KG.
TBW VWP AND RUC HODOGRAPHS INDICATE 0-1 KM AGL SRH 200-300 J/KG FOR
SLIGHT RIGHT--MOVING STORMS AND EFFECTIVE LAYER SRH SLIGHTLY HIGHER.
AMBIENT KINEMATICS ARE FAVORABLE ALSO WITH 0-6 KM SHEARS 50-60 KT.
LOW LEVEL VORTICITY MAY BE MAXIMIZED ALONG SERN EDGE OF PRECIP PLUME
WHERE BAROCLINICITY IS STRONGEST.

..EDWARDS.. 03/23/2005


ATTN...WFO...MLB...TBW...JAX...

28548346 29358263 29918183 29978135 29458110 29068079
28728055 28478076 28158146 27848271 28008344 28418350

[CaptinCrunch]

MESOSCALE DISCUSSION 0364
NWS STORM PREDICTION CENTER NORMAN OK
0746 AM CST WED MAR 23 2005

AREAS AFFECTED...PORTIONS CENTRAL/SRN FL

CONCERNING...TORNADO WATCH 75...

VALID 231346Z - 231445Z



REMAINDER WW SHOULD BE MAINTAINED FOR TIME BEING...AND AREAS FARTHER
SE WILL BE MONITORED FOR POSSIBILITY OF ADDITIONAL OR REPLACEMENT
WW AS SFC HEATING INCREASES BUOYANCY.

PRONOUNCED WEAKENING TREND NOTED BOTH WITH CONVECTION ACROSS CENTRAL
FL...AND ACTIVITY MOVING ONSHORE SRQ REGION. WHILE VERTICAL SHEAR
AND BUOYANCY PROFILES STILL SUPPORT SUPERCELLS AND BOWS...PER BLEND
OF MLB VWP AND 12Z MFL RAOB...CONVECTIVE MODE AND ORIENTATION
APPEARS ONLY MARGINALLY FAVORABLE FOR SEVERE ATTM. ONE OFFSETTING
FACTOR WHICH MAY REKINDLE SEVERE THREAT OVER NEXT FEW
HOURS...HOWEVER...IS DIABATIC SFC HEATING THAT HAS ALREADY BEGUN IN
PRECONVECTIVE BOUNDARY LAYER OVER E-CENTRAL AND SRN FL. MODIFIED
MFL RAOB AND RUC SOUNDINGS SUGGEST CINH REMOVED WITH ONLY 2-3 DEG F
MORE SFC HEATING AND DEW POINTS 72-74 F AS PRESENTLY OBSERVED ALONG
SE COAST. THIS YIELDS MLCAPE AROUND 2000 J/KG IN ENVIRONMENT
CHARACTERIZED BY 40-50 KT 0-6 KM SHEAR...DESPITE SOME VEERING OF SFC
WINDS.

[CaptinCrunch]

MESOSCALE DISCUSSION 0365
NWS STORM PREDICTION CENTER NORMAN OK
0946 AM CST WED MAR 23 2005

AREAS AFFECTED...CENTRAL/SRN FL

CONCERNING...TORNADO WATCH 75...

VALID 231546Z - 231615Z



NEW WW NOT ANTICIPATED AT THIS TIME FOR CENTRAL INTO SRN FL.

REGIONAL RADARS INDICATED AT 1530Z A LINE OF THUNDERSTORMS EXTENDING
FROM SEMINOLE COUNTY SWWD TO OFF THE COAST AT CHARLOTTE COUNTY.
ADDITIONAL INTENSE CONVECTION WAS LOCATED OFFSHORE OVER THE ERN
GULF. REGIONAL RADARS AND SURFACE OBSERVATIONS ALSO SHOWED A
WEAKENING COLD POOL IN THE WAKE OF THE INLAND LINE OF STORMS. THIS
COMBINED WITH VEERING SURFACE WINDS AHEAD OF THE LINE ACROSS ERN AND
SRN FL SUGGESTS FORCING FOR DEEP CONVECTION IS MARGINAL. ALTHOUGH
INSTABILITY AND DEEP LAYER SHEAR REMAIN FAVORABLE FOR ORGANIZED
STORMS...OVERALL SEVERE THREAT ACROSS THE REST OF ERN INTO SRN FL
APPEARS TO BE LIMITED AT THIS TIME. AREA WILL...HOWEVER...REQUIRE
CONTINUED MONITORING SINCE CIN HAS BEEN WEAKENING ACROSS SRN FL
WHERE VISIBLE/RADAR IMAGERY SHOW CONVECTIVE SHOWERS HAVE ALREADY
DEVELOPED.

[CaptinCrunch]

MESOSCALE DISCUSSION 0385
NWS STORM PREDICTION CENTER NORMAN OK
0705 AM CST FRI MAR 25 2005

AREAS AFFECTED...EXTREME SERN AL...SRN GA AND NRN FL

CONCERNING...SEVERE THUNDERSTORM WATCH 79...

VALID 251305Z - 251430Z



MORNING KINEMATIC PROFILE HAS BEEN SUPPORTIVE OF SPLITTING
SUPERCELLS...FAVORING LEFT-MOVING MEMBERS...SOME OF WHICH HAVE BEEN
NOTEWORTHY LONG-LIVED CELLS. AVAILABLE 12Z RAOBS CONTINUE TO SAMPLE
VERY STEEP MID-LEVEL LAPSE RATES AND GIVEN 45-55 KTS OF
CLOUD-BEARING SHEAR...VERY LARGE HAIL HAS BEEN COMMON.

PROLONGED EVOLUTION OF SPLITTING/COLLIDING CELLS HAS FINALLY
CONTRIBUTED TO TSTMS CONGEALING INTO A MCS WITH EMBEDDED SUPERCELLS.
THIS MCS WILL PROBABLY CONTINUE MOVING EWD ACROSS SERN GA AND NRN
FL FOR A FEW MORE HOURS. CONTINUAL FEED OF UNSTABLE AIR INTO THE
SWRN FLANK OF THE MCS WILL PROBABLY PROLONG THE SEVERE THREAT ACROSS
NRN...AND PERHAPS PARTS OF CNTRL...FL INTO THE EARLY AFTERNOON. AS
THE BOUNDARY LAYER BEGINS TO HEAT... ACTIVITY MAY BECOME
SUFFICIENTLY ROOTED IN THE BOUNDARY LAYER TO POSE A DAMAGING WIND
AND TORNADO THREAT LATER THIS MORNING ALONG THE SRN EDGE OF THE WW.
IF THIS INDEED OCCURS...A NEW WW MAY BE REQUIRED FARTHER TO THE S.

[CaptinCrunch]

MESOSCALE DISCUSSION 0387
NWS STORM PREDICTION CENTER NORMAN OK
1007 AM CST FRI MAR 25 2005

AREAS AFFECTED...NORTHERN FLORIDA

CONCERNING...SEVERE THUNDERSTORM WATCH 79...

VALID 251607Z - 251800Z

CONTINUE WW.



SUBTROPICAL SHORT WAVE TROUGH WILL SHIFT OFF THE FLORIDA/GEORGIA
COAST SHORTLY...AND RISING MID-LEVEL HEIGHTS IN ITS WAKE COULD TEND
TO SUPPRESS CONVECTIVE DEVELOPMENT BY MID DAY. HOWEVER...30 KT
WESTERLY LOW-LEVEL JET IS FORECAST TO PERSIST ACROSS NORTHERN
FLORIDA AND THE NORTHERN PENINSULA AREAS INTO THE AFTERNOON.
FORCING WITH THIS FEATURE MAY HELP MAINTAIN CONVECTIVE CLUSTER NOW
DEVELOPING EAST OF THE BIG BEND.

SURFACE RIDGING OVER THE FLORIDA PENINSULA IS PROVIDING FURTHER
UNCERTAINTY WITH REGARD TO EXTENT OF CONVECTIVE THREAT...AND
POSSIBILITY OF TORNADOES...BUT SURFACE HEATING OVER INTERIOR
NORTHERN PENINSULA AREAS COULD CONTRIBUTE TO AT LEAST INCREASING
RISK OF DAMAGING WINDS AS CLUSTER MOVES BACK ONSHORE. THIS APPEARS
LIKELY TO OCCUR NEAR/NORTH OF CEDAR KEY INTO THE OCALA AREA BY THE
18-19Z TIME FRAME.

[CaptinCrunch]

MESOSCALE DISCUSSION 0389
NWS STORM PREDICTION CENTER NORMAN OK
0151 PM CST FRI MAR 25 2005

AREAS AFFECTED...PARTS OF S CNTRL TX

CONCERNING...CONVECTIVE TRENDS

VALID 251951Z - 252145Z



DEVELOPING/DEEPENING CUMULUS FIELD IS EVIDENT IN LATEST VISIBLE
IMAGERY ACROSS THE TEXAS HILL COUNTY...ROUGHLY IN AREA BETWEEN SAN
ANTONIO/AUSTIN AND JUNCTION. THIS IS WHERE STRONGEST LOW-LEVEL
CONVERGENCE APPEARS TO BE FOCUSED...IN THE VICINITY OF STALLING
SURFACE FRONT.

ACTIVITY IS BASED IN THE BOUNDARY LAYER...WITH SUBSTANTIAL CAPPING
STILL PRESENT ALOFT. HOWEVER...WITH CONTINUED SURFACE HEATING AND
BOUNDARY LAYER MOISTENING...CAP WILL WEAKEN. SCATTERED CONVECTION/
ISOLATED THUNDERSTORM DEVELOPMENT IS ALREADY ONGOING ACROSS PARTS OF
WEST CENTRAL TEXAS. THIS ACTIVITY IS LIKELY BASED ABOVE CAP...AND
APPEARS TO BE IN RESPONSE TO STRENGTHENING ASCENT ASSOCIATED WITH
APPROACHING SHORT WAVE TROUGH. AS THIS MID/UPPER FORCING SPREADS
EASTWARD INTO THE HILL COUNTRY...AT LEAST ISOLATED SURFACE BASED
STORMS APPEAR POSSIBLE BY THE 25/21Z-26/00Z TIME FRAME.

SHEAR PROFILES ARE MORE THAN SUFFICIENT FOR SUPERCELLS...AND AS
MIXED LAYER CAPE INCREASES UP TO 1000 J/KG...RISK FOR LARGE HAIL/
DAMAGING WIND GUSTS...PERHAPS A TORNADO WILL INCREASE.

[CaptinCrunch]

MESOSCALE DISCUSSION 0390
NWS STORM PREDICTION CENTER NORMAN OK
0214 PM CST FRI MAR 25 2005

AREAS AFFECTED...CENTRAL FLORIDA PENINSULA

CONCERNING...SEVERE THUNDERSTORM WATCH 81...

VALID 252014Z - 252215Z



CONTINUE WW...BUT SEVERE THREAT APPEARS TO BE SLOWLY DIMINISHING...
PARTICULARLY ACROSS WEST CENTRAL PENINSULA AREAS.

WESTERLY SURFACE FLOW AND BUILDING MID-LEVEL RIDGE OVER THE FLORIDA
PENINSULA CONTINUE TO SUGGEST A DECREASE TO OVERALL SEVERE THREAT
LATE THIS AFTERNOON. MOST VIGOROUS CONVECTIVE DEVELOPMENT IN THE
SHORT TERM LIKELY WILL REMAIN NEAR EAST COAST SEA BREEZE AND NEAR
WEAKENING MESO HIGH/TRAILING CONFLUENT BAND NOW SHIFTING EAST
SOUTHEASTWARD ACROSS EAST CENTRAL FLORIDA COASTAL AREAS...NEAR/NORTH
OF MELBOURNE.

STRONG SHEAR AND LARGE MIXED LAYER CAPE TO 2000 J/KG WILL BE
SUPPORTIVE OF LARGE HAIL/DAMAGING DOWNBURSTS IN ANY LINGERING
CONVECTION.

[TexasStooge]

Code: Select all

   MESOSCALE DISCUSSION 0391
   NWS STORM PREDICTION CENTER NORMAN OK
   0802 PM CST FRI MAR 25 2005
   
   AREAS AFFECTED...PARTS OF CENTRAL AND ERN TX
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 82...
   
   VALID 260202Z - 260400Z
   
   THUNDERSTORMS CONTINUE ACROSS THE ERN HALF OFF WW...INCLUDING
   ISOLATED SEVERE STORMS.  NEW WW WILL LIKELY BE ISSUED S AND E OF
   CURRENT WW.
   
   LATEST RADAR LOOPS SHOW STRONG / SEVERE STORMS ACROSS PARTS OF
   CENTRAL TX...WITH THE MOST SIGNIFICANT STORM NOW MOVING ACROSS LLANO
   COUNTY.  THOUGH THIS SUPERCELL STORM APPEARS TO BE SLIGHTLY ELEVATED
   N OF SURFACE FRONT...ITS MOTION TO THE RIGHT OF THE MEAN WIND
   SUGGESTS THAT IT SHOULD REMAIN ONLY SLIGHTLY SURFACE-BASED -- AND
   THUS CAPABLE OF PRODUCING DAMAGING WINDS OR AN ISOLATED TORNADO
   ALONG WITH HAIL.  WITH OVERALL ENVIRONMENT SUGGESTING THAT THIS
   STORM SHOULD PERSIST -- AND MOVE ESEWD OUT OF CURRENT WW WITH
   TIME...NEW WW WILL LIKELY BE ISSUED S AND E OF CURRENT WATCH.
   
   ..GOSS.. 03/26/2005
   
   
   ATTN...WFO...SHV...HGX...FWD...EWX...SJT...
   
   30070062 30450143 32419870 33169782 33459586 31399491
   30039501 30469826

[CaptinCrunch]

MESOSCALE DISCUSSION 0398
NWS STORM PREDICTION CENTER NORMAN OK
1005 AM CST SAT MAR 26 2005

AREAS AFFECTED...S CNTRL...SE TX

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 261605Z - 261800Z



SEVERE THREAT CONTINUES...NEW WW LIKELY WILL BE NEEDED EAST OF WW 85
BY EARLY AFTERNOON.

SURFACE COLD FRONT CONTINUES TO SLOWLY ADVANCE SOUTHWARD THROUGH
TEXAS...AND IS NOW SOUTH OF SHREVEPORT/LUFKIN/COLLEGE STATION/ AND
SAN ANTONIO...WITH A SHALLOWER COLD SURGE NOSING INTO UPPER TEXAS
COASTAL AREAS. HOWEVER...ABOVE FRONTAL INVERSION...WEAK SOUTHERLY
LOW-LEVEL FLOW PERSISTS IN ADVANCE OF STRONG DIGGING UPPER TROUGH
ACROSS THE SOUTHERN ROCKIES...AND THIS IS MAINTAINING VERY MOIST
POTENTIALLY UNSTABLE ENVIRONMENT.

LARGE-SCALE ASCENT ASSOCIATED WITH LOW/MID-LEVEL WARM ADVECTION
REGIME...BENEATH DIFLUENT AND DIVERGENT UPPER FLOW FIELD DOWNSTREAM
OF TROUGH...IS SUPPORTING BROAD RAIN SHIELD WITH EMBEDDED
THUNDERSTORM ACTIVITY ACROSS CENTRAL/NORTHEAST TEXAS. STRONGEST
FORCING APPEARS IN BAND APPROACHING INTERSTATE 35...NORTHWEST OF SAN
ANTONIO INTO THE WACO AREAS. THROUGH EARLY AFTERNOON...THIS WILL
GRADUALLY SHIFT ACROSS THE INTERSTATE 35 CORRIDOR...LIKELY REACHING
THE TYLER/LONGVIEW/LUFKIN AREAS SOUTHWARD THROUGH COLLEGE STATION
INTO AREAS EAST OF SAN ANTONIO BY 21Z.

MORE NOTABLE INCREASE IN SEVERE THREAT MAY OCCUR TOWARD THE 20-21Z
TIME FRAME...AS HEATED BOUNDARY LAYER AIR MASS FROM SOUTH OF FRONT
BEGINS TO FEED INTO ACTIVITY. WITH MUCH OF ACTIVITY BASED ABOVE
RELATIVELY SHARP FRONTAL INVERSION...LARGE HAIL MAY BE PRIMARY
THREAT. HOWEVER...CELLS ON SOUTHERN FLANK OF ACTIVITY LIKELY WILL
BECOME INCREASINGLY ROOTED IN BOUNDARY LAYER NEAR FRONT...IN AREA
BETWEEN SAN ANTONIO/AUSTIN/VICTORIA BY LATE AFTERNOON...WHERE/WHEN
RISK FOR TORNADOES MAY INCREASE.

[CaptinCrunch]

MESOSCALE DISCUSSION 0397
NWS STORM PREDICTION CENTER NORMAN OK
0913 AM CST SAT MAR 26 2005

AREAS AFFECTED...PARTS OF SRN MS...SRN AL...SRN GA

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 261513Z - 261715Z



RISK OF LARGE HAIL/DAMAGING WIND GUSTS APPEARS TO BE INCREASING
ACROSS INLAND AREAS OF THE EASTERN GULF STATES. TRENDS ARE STILL
BEING MONITORED FOR POSSIBILITY OF WW.

VIGOROUS CONVECTIVE DEVELOPMENT IS ONGOING ALONG RELATIVELY BROAD
LOW-LEVEL BAROCLINIC ZONE WHICH EXTENDS ROUGHLY FROM EXTREME
SOUTHEAST LOUISIANA ACROSS THE NORTHERN FLORIDA PENINSULA. MODELS
...AND LATEST SATELLITE IMAGERY...INDICATE DE-AMPLIFICATION OF SHORT
WAVE TROUGH OVER THE EASTERN GULF STATES IS UNDERWAY...WITH UPPER
RIDGE AMPLIFYING OVER THE SOUTHEASTERN STATES. AS THIS PROCESS
CONTINUES...THERMAL GRADIENT OVER THE GULF WILL WEAKEN/REDEVELOP
NORTHWARD INTO THE UPPER TENNESSEE VALLEY/SOUTHERN APPALACHIANS
REGION BY THE AFTERNOON HOURS.

INLAND DEVELOPMENT OF INCREASING MOIST BOUNDARY LAYER WILL
CONTRIBUTE TO INCREASING SURFACE BASED DESTABILIZATION. THIS MAY BE
ACCOMPANIED BY INLAND DEVELOPMENT OF STRONG THUNDERSTORM ACTIVITY
THROUGH AT LEAST MID DAY ACROSS EASTERN GULF COASTAL AREAS.
HOWEVER...LONGER TERM PROSPECTS FOR THIS ACTIVITY ARE UNCERTAIN DUE
TO POTENTIAL CAPPING INFLUENCE OF BUILD RIDGE.

[WXBUFFJIM]

MESOSCALE DISCUSSION 0400
NWS STORM PREDICTION CENTER NORMAN OK
0114 PM CST SAT MAR 26 2005

AREAS AFFECTED...CNTRL/SRN LA AND MS...SRN AL

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 261914Z - 262115Z

SEVERE THREAT WILL INCREASE SHORTLY...RISK FOR TORNADOES WILL
INCREASE DURING THE AFTERNOON INTO THE EVENING HOURS.

18Z SOUNDING FROM SLIDELL LA INDICATES SUBSTANTIAL LOW-LEVEL
MOISTENING SINCE 12Z. DEEP NEAR SATURATED LAYER WITH HIGH MOISTURE
VALUES HAS DEVELOPED IN RESPONSE TO NORTHWARD MOISTURE TRANSPORT AND
LIFT ASSOCIATED WITH LOW-LEVEL WARM ADVECTION. THIS REGIME WILL
CONTINUE TO SLOWLY WORK NORTHWARD THIS AFTERNOON INTO ENVIRONMENT
OVER INTERIOR PORTIONS OF THE CENTRAL GULF STATES WHICH HAS HEATED
INTO THE LOWER 80S. AS THIS OCCURS...AND MID-LEVEL INHIBITION
WEAKENS...INITIATION OF INTENSE CONVECTIVE ACTIVITY IS
EXPECTED...POSSIBLY BY 21Z. ACTIVITY WILL BE ENHANCED BY
INCREASINGLY CYCLONIC AND DIVERGENT MID/UPPER FLOW FIELD DOWNSTREAM
OF VIGOROUS SHORT WAVE TROUGH DIGGING INTO THE SOUTHERN PLAINS/LOWER
RIO GRANDE VALLEY.

THOUGH SOUTHERLY LOW-LEVEL FLOW AND SHEAR WILL INITIALLY BE SOMEWHAT
WEAK...MID/UPPER FLOW FIELDS ARE ALREADY STRONG AND SUPPORTIVE OF
SUPERCELLS WITH VERY LARGE HAIL AND DAMAGING WIND GUSTS AS MIXED
LAYER CAPE INCREASES TO 1000-2000 J/KG LATE THIS AFTERNOON.
ISOLATED TORNADOES WILL ALSO BE POSSIBLE. AS LOW-LEVEL JET
STRENGTHENS INTO THE EVENING HOURS ACROSS SOUTH CENTRAL LOUISIANA
INTO CENTRAL MISSISSIPPI...RISK FOR STRONG TORNADOES SHOULD
INCREASE.

..KERR.. 03/26/2005

[CaptinCrunch]

MESOSCALE DISCUSSION 0426
NWS STORM PREDICTION CENTER NORMAN OK
0656 AM CST MON MAR 28 2005

AREAS AFFECTED...ERN NC

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 281256Z - 281430Z



INTERESTING SCENARIO HAS UNFOLDED ACROSS ERN NC THIS MORNING.
TREMENDOUS LOW-LEVEL SHEAR VCNTY BAROCLINIC ZONE OVER ERN NC WAS
SAMPLED IN 12Z RAOBS WITH MORE THAN 30 KTS OF 0-1 KM SHEAR. STORMS
HAVE BEEN FORMING ALONG THE COAST MOST OF THE MORNING AND A FEW
CELLS ARE BEGINNING TO SHOW LOW-LEVEL ROTATION OVER SERN NC. THESE
STORMS WILL MOVE NEWD OVER THE WARM FRONT THROUGH 14Z AND MAY
PRODUCE AN ISOLD TORNADO...DAMAGING WINDS AND HAIL.

MEANWHILE...A SUPERCELL NEAR KCHS SPLIT EARLIER IN THE MORNING WITH
THE LEFT-MOVING MEMBER MOVING NWD AT NEAR 80 KTS THROUGH THE KRDU
AREA WITH VERY LARGE HAIL. STORM MORPHOLOGY WAS RATHER COMPLICATED
WITH BOTH ANTICYCLONIC AND CYCLONIC LOW-MIDLEVEL ROTATIONS DURING
ITS LIFE CYCLE. OTHER STORM SPLITS MAY OCCUR AND A HAIL THREAT
COULD EXTEND NWD INTO SRN VA THROUGH MID-MORNING.

[CaptinCrunch]

MESOSCALE DISCUSSION 0427
NWS STORM PREDICTION CENTER NORMAN OK
0117 PM CST MON MAR 28 2005

AREAS AFFECTED...ERN VA...MD...DE

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 281917Z - 282115Z



SEVERAL SHORT-LINES OF CONVECTION ARE INTENSIFYING ACROSS ERN VA AND
WILL LIKELY HAVE AN ISOLATED THREAT FOR TORNADOES AND/OR HAIL OVER
THE NEXT 1 TO 2 HOURS.

SFC ANALYSIS SHOWS A WARM FRONT EXTENDING EWD FROM A LOW ACROSS
SCNTRL VA. THE STORMS ARE DEVELOPING ALONG THE BOUNDARY NEAR THE LOW
WHERE STRONG LOW-LEVEL CONVERGENCE AND INSTABILITY HAS DEVELOPED.
OBJECTIVE ANALYSIS SHOWS STRONG VERTICAL SHEAR OF ABOUT 70 KT WITH
SBCAPE VALUES OF 1000 TO 1500 J/KG. THIS WILL BE FAVORABLE FOR
SFC-BASED ROTATING STORMS AS THE CONVECTION MOVES NEWD ACROSS ERN VA
INTO MD THIS AFTERNOON. VAD WIND PROFILES IN MD SHOW 0-1 KM SHEAR OF
35 TO 40 KT SUGGESTING AN ISOLATED TORNADO THREAT WILL EXIST. IN
ADDITION...THE INSTABILITY...SHEAR AND COLD AIR ALOFT WILL MAKE HAIL
LIKELY WITH THE STRONGER CELLS.

[CaptinCrunch]

MESOSCALE DISCUSSION 0429
NWS STORM PREDICTION CENTER NORMAN OK
0900 PM CST TUE MAR 29 2005

AREAS AFFECTED...CNTRL KS...NRN OK

CONCERNING...CONVECTIVE TRENDS

VALID 300300Z - 300430Z



...ISOLATED STRONG STORMS WILL CONTINUE INTO LATE EVENING ACROSS
PORTIONS OF KS AND OK...

STRONG FRONTAL ASCENT APPEARS TO BE FORCING PARCELS THROUGH CAPPING
INVERSION FROM SCNTRL PORTIONS OF KS...SWD INTO CNTRL OK. VERTICAL
SHEAR PROFILES ARE MORE THAN ADEQUATE TO SUPPORT ORGANIZED
UPDRAFTS...SO IT SEEMS REASONABLE THAT DESPITE MARGINAL INSTABILITY
ONGOING ISOLATED ACTIVITY MAY LINGER FOR THE NEXT FEW HOURS BEFORE
WEAKENING. STEEP LAPSE RATES MAY ENHANCE THE HAIL/WIND
THREAT...ESPECIALLY ACROSS SCNTRL KS WHERE ACTIVITY HAS BECOME MORE
LINEAR IN NATURE. WW IS NOT ANTICIPATED AT THIS TIME.

[CaptinCrunch]

MESOSCALE DISCUSSION 0430
NWS STORM PREDICTION CENTER NORMAN OK
0603 AM CST WED MAR 30 2005

AREAS AFFECTED...WRN/CNTRL IA AND SCNTRL MN

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 301203Z - 301400Z



TSTMS ARE LIKELY TO INCREASE THROUGH MID-MORNING ACROSS WRN/CNTRL IA
AND SCNTRL MN. THREATS FOR LARGE HAIL AND DAMAGING WINDS WILL EXIST
AND A SEVERE TSTM WATCH MAY BECOME NECESSARY.

WATER VAPOR LOOPS SHOW THAT THE STRONG UPPER LOW WAS MOVING SLOWLY
EWD THROUGH NERN KS WITH AN ENHANCED JET STREAK CURVING NEWD THROUGH
WRN MO. LARGE SCALE FORCING FOR ASCENT WAS BEGINNING TO SPREAD NEWD
ACROSS THE MO RVR AND RECENT TSTM DEVELOPMENT VCNTY KOMA MAY BE THE
START OF A MORE ORGANIZED BATCH OF STORMS.

00Z WRF AND 09Z RUC AGREE IN TSTMS DEVELOPING ALONG THE MO RVR BY
12Z...WITH STORMS THEN MOVING/DEVELOPING NWD INTO PARTS OF CNTRL/NRN
IA AND SCNTRL MN. A SMALL WARM SECTOR HAS EVOLVED OVER THIS AREA
AND GIVEN MID 50S/MID 40S TEMPERATURES/DEW POINTS... MUCAPE OF
AROUND 750 J/KG IS LIKELY IN PLACE. MAGNITUDE OF FORCING WILL BE
SUFFICIENT FOR THE INCREASING TSTM THREAT.

VERTICAL SHEAR IN THE CAPE-BEARING LAYER WILL BE MARGINALLY
SUFFICIENT FOR SUPERCELLULAR STRUCTURES AND GIVEN THE STEEPENING
MID-TROP LAPSE RATES...LARGE HAIL WILL BE A CONCERN. DAMAGING WINDS
MAY ALSO BECOME MORE OF A THREAT AS STORMS DEVELOP...CONGEAL AND
BEGIN TO ORIENT NORMAL TO THE MEAN WIND VECTORS.

TSTMS MAY TEND TO DEVELOP FARTHER SWD LATER THIS MORNING INTO SCNTRL
IA AS THE BOUNDARY LAYER BEGINS TO WARM AND THE LARGE SCALE FORCING
SPREADS FARTHER TO THE EAST.

[CaptinCrunch]

MESOSCALE DISCUSSION 0431
NWS STORM PREDICTION CENTER NORMAN OK
1046 AM CST WED MAR 30 2005

AREAS AFFECTED...NERN MO...ERN IA...NWRN IL AND SWRN WI

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 301646Z - 301845Z



A WW WILL ISSUED SOON FOR THE AREA.

MODIFIED RUC FORECAST SOUNDINGS FOR 16Z OBS OVER THE REGION INDICATE
LITTLE CONVECTIVE INHIBITION REMAINING. CONVECTION OVER NERN MO
CONTINUES TO INTENSIFY AND WILL DEVELOP SEWD ALONG THIS LINE WITH
TIME AS IT MOVES NEWD THROUGH THE REGION DURING THE AFTERNOON HOURS.
ADDITIONAL POTENTIAL WILL EXIST FOR ISOLATED STORMS AHEAD OF THE
MAIN CONVECTIVE LINE ALONG THE WARM FRONT. STEEP LOW LEVEL LAPSE
RATES AND ALREADY WELL DEFINED LINEAR ORGANIZATION OF CONVECTION
MOVING ACROSS NERN MO SUGGESTS THAT DAMAGING WINDS WILL BE THE
GREATEST THREAT...WITH LARGE HAIL AND TORNADOES AS WELL.

[CaptinCrunch]

MESOSCALE DISCUSSION 0432
NWS STORM PREDICTION CENTER NORMAN OK
1050 AM CST WED MAR 30 2005

AREAS AFFECTED...IA/SRN MN

CONCERNING...SEVERE THUNDERSTORM WATCH 103...

VALID 301650Z - 301815Z



THUNDERSTORMS ARE CONTINUING TO EXPAND IN COVERAGE ACROSS SRN IA.
THE STRONGER CELLS WILL HAVE A POTENTIAL FOR WIND DAMAGE AND LARGE
HAIL OVER THE NEXT FEW HOURS.

SFC ANALYSIS SHOWS A LOW MOVING QUICKLY NEWD INTO SRN IA WITH STRONG
LOW-LEVEL CONVERGENCE AHEAD OF THE LOW. THE MOIST AXIS EXTENDS FROM
WRN IL ACROSS SRN IA WITH SFC DEWPOINTS IN THE LOWER 50S F. WITH SFC
TEMPS WARMING...SBCAPE VALUES HAVE RISEN TO AROUND 1200 J/KG ALONG
THE MOIST AXIS WHERE MODERATE VERTICAL SHEAR IS PRESENT. AS
DESTABILIZATION CONTINUES THIS AFTERNOON...THE ENVIRONMENT WILL
BECOME INCREASINGLY ADEQUATE FOR SFC-BASED SUPERCELLS. OBJECTIVE
ANALYSIS CURRENTLY SHOWS STEEP 0-2 KM LAPSE RATES AROUND 9.0 C/KM
FROM NRN MO TO NCNTRL IA AND 850 MB FLOW AROUND 30 KT WHICH SHOULD
BE FAVORABLE FOR WIND DAMAGE. IN ADDITION...STEEP MID-LEVEL LAPSE
RATES...INCREASING INSTABILITY AND THE MODERATE VERTICAL SHEAR WILL
BE FAVORABLE FOR LARGE HAIL WITH THE STRONGER CELLS.

[CaptinCrunch]

MESOSCALE DISCUSSION 0433
NWS STORM PREDICTION CENTER NORMAN OK
1208 PM CST WED MAR 30 2005

AREAS AFFECTED...IL

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 301808Z - 302015Z



THE TORNADO THREAT WILL INCREASE THIS AFTERNOON AS CELLS INITIATE
ACROSS WRN IL AND TRACK NEWD ACROSS THE CNTRL AND ERN PART OF THE
STATE LATE THIS AFTERNOON. A TORNADO WATCH WILL LIKELY BE ISSUED
WITH AN HOUR.

SFC ANALYSIS CURRENTLY SHOWS MOISTURE RAPIDLY RETURNING NWD INTO IL
WITH UPPER 50S F TO NEAR 60 F DEWPOINTS IN SRN IL. AS THE MOISTURE
SPREADS NWD ACROSS THE STATE...MODERATE INSTABILITY SHOULD DEVELOP
AS A COLD FRONT APPROACHES FROM THE WEST. IN ADDITION...OBJECTIVE
ANALYSIS SHOWS AN 80 KT MID-LEVEL JET APPROACHING FROM THE SOUTHWEST
AND THIS WILL QUICKLY INCREASE VERTICAL SHEAR FROM ABOUT 40 KT TO 65
KT OVER THE NEXT FEW HOURS. AS A RESULT...AS CELLS INITIATE
ESPECIALLY ACROSS CNTRL AND SRN IL...RAPID SUPERCELL FORMATION
SHOULD OCCUR. STRONG LOW-LEVEL SHEAR IS PRESENT DUE TO A 50 KT
LOW-LEVEL JET ACROSS THE REGION AND THIS WILL MAKE TORNADOES
POSSIBLE WITH SUPERCELLS. LARGE HAIL AND WIND DAMAGE WILL ALSO BE
LIKELY WITH THE STRONGER STORMS DUE TO THE AMOUNT OF
INSTABILITY...STRONG VERTICAL SHEAR AND STEEP LAPSE RATES ACROSS THE
REGION.

[CaptinCrunch]

MESOSCALE DISCUSSION 0434
NWS STORM PREDICTION CENTER NORMAN OK
0114 PM CST WED MAR 30 2005

AREAS AFFECTED...CENTRAL/NERN IA...SCENTRAL MN

CONCERNING...SEVERE THUNDERSTORM WATCH 103...

VALID 301914Z - 302015Z



SEVERE THUNDERSTORM THREAT WILL CONTINUE FOR THE REMAINDER OF THE WW
TIME /20Z/ WITH THE GREATEST POTENTIAL EXISTING OVER NCENTRAL/NERN
IA AND FAR SCENTRAL MN...AHEAD OF SFC/UPPER LOW TRACK.

18Z SFC ANALYSIS SHOWS AREA OF MODERATE PRESSURE FALLS OVER
NCENTRAL/NERN IA AHEAD OF 990 SFC LOW LOCATED JUST WEST OF DSM. SFC
COLD FRONT EXTENDED NE FROM THE LOW ACROSS NCENTRAL IA INTO SCENTRAL
MN. WEST OF THIS FRONT...DEEPENING COLD AIR WILL PRECLUDE ANY
ADDITIONAL SVR THREAT.

LOW LEVEL SHEAR WILL REMAIN MAXIMIZED TO THE NE OF THE SFC LOW AS IT
TRACKS INTO NERN IA BY 21Z. DEGREE OF SHEAR ALONG THE COLD FRONT
COMBINED WITH LOWER LCL HEIGHTS DUE TO RAIN COOLED AIR WILL FAVOR
ISOLATED WEAK TORNADOES. THERE MAY BE A FEW COUNTIES IN THE NERN
PORTION OF WW 103 WHERE A SVR THREAT WILL EXIST BEYOND 20Z FOR AN
HOUR OR TWO. GIVEN THE SMALL SPATIAL AND TEMPORAL THREAT...AND TOR
WW 104 JUST EAST OF THIS AREA...WW 103 MAY BE EXTENDED LOCALLY IN
IA. FARTHER NORTH IN SERN MN...A NEW WW MAY BE NEEDED THAT WOULD
ALSO INCLUDE PARTS OF WCENTRAL WI.

[CaptinCrunch]

MESOSCALE DISCUSSION 0435
NWS STORM PREDICTION CENTER NORMAN OK
0123 PM CST WED MAR 30 2005

AREAS AFFECTED...ERN IA...SRN WI...NW IL AND FAR NE MO

CONCERNING...SEVERE THUNDERSTORM WATCH 104...

VALID 301923Z - 302100Z



SCATTERED SUPERCELLS ARE MOVING NEWD ACROSS WW 104. THE STORMS WILL
HAVE A POTENTIAL FOR LARGE HAIL...WIND DAMAGE AND A FEW TORNADOES.

OBJECTIVE ANALYSIS CURRENTLY SHOWS INSTABILITY AND VERTICAL SHEAR
CONTINUING TO INCREASE ACROSS WW 104 DUE TO SFC HEATING AND AN
APPROACHING 85 KT MID-LEVEL JET. AS A RESULT...THE ENVIRONMENT WILL
CONTINUE TO BE FAVORABLE FOR SUPERCELLS OVER THE NEXT FEW HOURS WITH
THE POSSIBILITY OF A FEW TORNADOES. THE BEST TORNADO THREAT SHOULD
BE NORTH OF I-80 IN ERN IA AND NORTH OF I-74 ACROSS NRN IL DUE TO
SMALLER SFC TEMP-DEWPOINT SPREADS. IN ADDITION...THE MODERATE
INSTABILITY AND VERTICAL SHEAR COMBINED WITH COLD AIR ALOFT AND
STEEP MID-LEVEL WINDS SUGGESTS VERY LARGE HAIL WILL BE POSSIBLE WITH
THE STRONGEST SUPERCELLS. STEEP LOW-LEVEL LAPSE RATES...0-2 KM LAPSE
RATES NEAR 9.0 C/KM...WILL ALSO HELP TRANSFER STRONG LOW-LEVEL WINDS
TO THE SFC...CREATING A WIND DAMAGE POTENTIAL ESPECIALLY WITH THE
FASTER MOVING LINE SEGMENTS.