SPC eyeing another Illinois/Mizzou derecho Wednesday.

[Ed Mahmoud]

SWODY2 valid on Tuesday (ie, for Wednesday)

(will be edited for SWODY1 tomorrow...)


Edit to change SWODY3 link yesterday to SWODY2 link today...

[RL3AO]

EARLY IN THE PERIOD...AN MCS SHOULD BE ONGOING IN THE MID-MS VALLEY
WITH THIS CONVECTIVE CLUSTER MOVING EWD ACROSS PARTS OF THE OH
VALLEY. IN THE WAKE OF THE MCS...SFC-BASED THUNDERSTORMS SHOULD
INITIATE ALONG AND AHEAD OF A COLD FRONT WEDNESDAY AFTERNOON FROM
NCNTRL IL SWWD ACROSS MO INTO SE KS. MODEL FORECASTS REMAIN
CONSISTENT THAT THIS CONVECTION WILL ORGANIZE INTO A WELL-DEVELOPED
LINEAR MCS EWD ACROSS THE WRN PORTION OF THE OH VALLEY SWWD ACROSS
THE MID-MS VALLEY...NRN OZARKS INTO ERN OK WEDNESDAY EVENING. THE
GFS AND ECMWF ARE IN GOOD AGREEMENT WITH THE POSITION OF THE
UPPER-LEVEL TROUGH. THIS COMBINED WITH GOOD CERTAINTY CONCERNING THE
DEVELOPMENT OF NUMEROUS STORMS IN A STRONGLY SHEARED ENVIRONMENT
SUPPORTS THE ISSUANCE OF A MODERATE RISK IN IL AND MO WEDNESDAY
AFTERNOON AND EVENING. PARAMETERS ON FORECAST SOUNDINGS SUGGEST THE
ENVIRONMENT WILL BE FAVORABLE FOR A SIGNIFICANT SEVERE WEATHER EVENT
WITH A STRONGLY FORCED LINE OF INTENSE STORMS. SWWD ACROSS THE
OZARKS AND SRN PLAINS...THUNDERSTORMS SHOULD BE MORE ISOLATED DUE TO
WEAKER FORCING. A GRADUAL DROP OFF IN SEVERE REPORT COVERAGE SHOULD
OCCUR IN THE OZARKS AND SRN PLAINS FOR THIS REASON.

[Ed Mahmoud]

Little directional shear, and not even great speed shear as seen here, but very impressive instability along the front and 700 mb winds 30 to 50 knots as the line begins organizing.

[Ed Mahmoud]

Latest SWODY2 predicts possible tornadic supercells early, before storms form a line with potentially damaging winds. Yesterday's discussion seemed more focused on a forced line of storms with high winds along the front.

...MID TO UPPER MS VALLEY...
A PROGRESSIVE UPPER-LEVEL TROUGH AND WELL-DEFINED 75 TO 90 KT
MID-LEVEL JET WILL MOVE EWD ACROSS THE NRN PLAINS WEDNESDAY. AHEAD
OF THE SYSTEM...A BROAD LOW-LEVEL JET WILL BE IN PLACE WITH A LARGE
WARM SECTOR FROM THE SRN PLAINS NEWD ACROSS THE OZARKS INTO THE MID
TO UPPER MS VALLEY. A DEEPLY MOIST BOUNDARY LAYER...MODERATE
INSTABILITY...STRONG VERTICAL SHEAR AND IMPRESSIVE LOW-LEVEL SHEAR
PROFILES SHOULD RESULT A SIGNIFICANT SEVERE WEATHER EPISODE ACROSS
PARTS OF THE MID TO UPPER MS VALLEY. AN OUTBREAK OF SEVERE WEATHER
AND TORNADOES WILL BE POSSIBLE WEDNESDAY AFTERNOON AND EVENING.

THE LATEST CONSENSUS OF THE MODELS WEDNESDAY MORNING MOVE A CLUSTER
OF ELEVATED THUNDERSTORMS ASSOCIATED WITH THE LOW-LEVEL JET EWD
ACROSS THE OH VALLEY WEDNESDAY MORNING. THE TRACK OF THIS STORM
CLUSTER SHOULD BE IMPORTANT WITH THE MOST SUBSTANTIAL
DESTABILIZATION OCCURRING TO THE SOUTHWEST. BY THE TIME OF
INITIATION...IT APPEARS MODERATE INSTABILITY WILL BE IN PLACE FOR A
WIDESPREAD SEVERE WEATHER EVENT FROM CNTRL MO NEWD INTO WRN AND
CNTRL IL. NAMKF FORECAST SOUNDINGS OVER THIS AREA LATE WEDNESDAY
AFTERNOON SHOW 45 TO 50 KT OF VERTICAL SHEAR WITH 0-3 KM SRH VALUES
IN THE 250 TO 350 M2/S2 RANGE. THIS COMBINED WITH LOW LCL HEIGHTS
SHOULD BE FAVORABLE FOR SUPERCELLS WITH TORNADOES.
FORECAST HODOGRAPHS SUPPORT THE POTENTIAL FOR A FEW STRONG TORNADOES WITH THE GREATEST POTENTIAL FROM CNTRL AND ERN IL SWWD ACROSS CNTRL AND ERN MO IN THE LATE AFTERNOON OR EARLY EVENING. IN ADDITION...FORECAST SOUNDINGS ACROSS THE MODERATE RISK AREA SHOW STEEP MID-LEVEL LAPSE RATES WHICH SHOULD ALSO SUPPORT A THREAT FOR LARGE HAIL. DURING THE EVENING...INCREASING LOW-LEVEL CONVERGENCE ALONG THE COLD FRONT MAY RESULT IN A TRANSITION TO A LINEAR MODE. HOW QUICKLY THIS TRANSITION OCCURS IS STILL IN QUESTION. IF A WELL-DEVELOPED LINEAR MCS OR BOWING LINE SEGMENT CAN ORGANIZE...A SUBSTANTIAL WIND DAMAGE THREAT WILL BE POSSIBLE AS WELL.

[Ed Mahmoud]

Latest SWODY2 discussion for region...

...MID TO UPPER MS VALLEY...
ELEVATED CONVECTION IS EXPECTED TO BE ONGOING AT DAYBREAK ACROSS
PORTIONS OF THE REGION IN RESPONSE TO 40-50 KT LOW LEVEL JET/WARM
ADVECTION NORTH OF THE WARM FRONT. MUCAPES AROUND 1000 J/KG AND
EFFECTIVE SHEAR AT 40 KT WILL BE SUPPORTIVE OF SEVERE HAIL DURING
THE MORNING HOURS.

AS THE WARM FRONT SHIFTS NWD...CLOUDS AND PCPN SHOULD DECREASE
SOMEWHAT...WITH DEWPOINTS JUMPING RAPIDLY INTO THE MID/UPPER 60S.
DIURNAL HEATING WILL RESULT IN MODERATE INSTABILITY ACROSS THE WARM
SECTOR. THIS INSTABILITY AND DEEP LAYER SHEAR AT 40-50 KT COMBINED
WITH INCREASING DIFFLUENCE ALOFT FAVORS WIDESPREAD SEVERE WEATHER
DEVELOPING ACROSS THE AREA. THE BEST COMBINATION OF
SHEAR/INSTABILITY/HEATING IS EXPECTED FROM CENTRAL MO NEWD INTO WRN
IL. THE STRONG FORCING AND INCREASING STRONGER MID/HIGHER LEVEL WINDS ARE SUGGESTIVE OF THE STORMS EVOLVING INTO A FAST MOVING SQUALL LINE/BOW...WITH WIND DAMAGE BECOMING THE PRIMARY THREAT.
HOWEVER...THE VERY MOIST BOUNDARY LAYER AND 1KM SRH BETWEEN 300-400 M2/S2 WOULD FAVOR TORNADOES..SOME STRONG...WITHIN BOWS AND DISCRETE STORMS.
THE SEVERE THREAT WILL EXTEND NWD INTO WI DURING THE
AFTERNOON HOURS...WHERE THE UPPER FORCING WILL BE GREATER BUT
INSTABILITY WEAKER...AND EWD INTO ERN IL/WRN IN DURING THE EVENING
HOURS AS THE SQUALL LINE ADVANCES EWD.

[Dave]

PUBLIC SEVERE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0702 AM CDT WED MAY 13 2009

...SEVERE THUNDERSTORMS EXPECTED FROM THE CENTRAL/SOUTHERN PLAINS TO
THE MID MISSISSIPPI VALLEY LATER TODAY AND TONIGHT...

THE NWS STORM PREDICTION CENTER IN NORMAN OK IS FORECASTING THE
DEVELOPMENT OF TORNADOES...LARGE HAIL AND DAMAGING WINDS FROM THE
CENTRAL/SOUTHERN PLAINS TO THE MID MISSISSIPPI VALLEY LATER TODAY
AND TONIGHT.

THE AREAS MOST LIKELY TO EXPERIENCE THIS ACTIVITY INCLUDE

NORTHWEST ARKANSAS
ILLINOIS
SOUTHEAST KANSAS
MISSOURI
OKLAHOMA

ELSEWHERE...SEVERE STORMS ARE ALSO POSSIBLE FROM NORTH TEXAS TO THE
GREAT LAKES.

SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP LATER TODAY ALONG A
SHARP COLD FRONT THAT WILL SURGE SOUTHEASTWARD ACROSS THE CENTRAL
PLAINS INTO THE MID MISSISSIPPI VALLEY. THUNDERSTORMS ARE EXPECTED
TO INTENSIFY DURING THE HEAT OF THE DAY AS A VERY MOIST LOW LEVEL
AIRMASS SURGES INTO AN INCREASINGLY CONVERGENT FRONTAL
ZONE...INITIALLY ACROSS PARTS OF SOUTHEAST IA AND WEST CENTRAL
ILLINOIS...THEN DEVELOPING SOUTHWESTWARD ACROSS MISSOURI INTO KANSAS
BY LATE AFTERNOON. THIS ACTIVITY WILL SPREAD SOUTHWARD INTO
OKLAHOMA AND ARKANSAS LATER THIS EVENING. VERY LARGE HAIL AND
DAMAGING WINDS ARE LIKELY WITH MANY STORMS...ALONG WITH A FEW
TORNADOES.

ADDITIONALLY...A MID LEVEL CIRCULATION LOCATED JUST NORTHWEST OF
FORT SMITH ARKANSAS WILL LIFT NORTHEASTWARD INTO SOUTHERN MISSOURI
THIS AFTERNOON. THIS FEATURE WILL LIKELY ENHANCE SEVERE POTENTIAL
DOWNSTREAM ACROSS PARTS OF EASTERN/SOUTHERN MISSOURI INTO SOUTHERN
ILLINOIS. WIND/MOISTURE PROFILES WITH THIS CIRCULATION SUGGEST A
FEW STRONG TORNADOES MAY BE NOTED WITH SUPERCELLS THAT EVOLVE ACROSS
THIS REGION. IN ADDITION...LARGE HAIL AND DAMAGING WINDS SHOULD ALSO
BE ANTICIPATED WITH THESE STORMS.

STATE AND LOCAL EMERGENCY MANAGERS ARE MONITORING THIS DEVELOPING
SITUATION. THOSE IN THE THREATENED AREA ARE URGED TO REVIEW SEVERE
WEATHER SAFETY RULES AND TO LISTEN TO RADIO...TELEVISION...AND NOAA
WEATHER RADIO FOR POSSIBLE WATCHES...WARNINGS...AND STATEMENTS LATER
TODAY.

..DARROW.. 05/13/2009

[Dave]

HWO Indianapolis IN issued this morning at 0854 hrs..multimedia link:

http://www.crh.noaa.gov/ind/?n=briefing

HWO Text:
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
854 AM EDT WED MAY 13 2009

INZ021-030-031-036>042-045>049-054>057-062>065-069-070-072-141300-
CARROLL-CLINTON-HOWARD-MONTGOMERY-BOONE-TIPTON-HAMILTON-MADISON-
DELAWARE-RANDOLPH-PUTNAM-HENDRICKS-MARION-HANCOCK-HENRY-MORGAN-
JOHNSON-SHELBY-RUSH-MONROE-BROWN-BARTHOLOMEW-DECATUR-MARTIN-
LAWRENCE-JENNINGS-
854 AM EDT WED MAY 13 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL INDIANA.

.DAY ONE...TODAY AND TONIGHT.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL
INDIANA ALONG AND WEST OF A LINE FROM MUNCIE TO SEYMOUR. THE
GREATEST THREAT OF SEVERE WEATHER WILL BE IN WEST CENTRAL INDIANA
IN THE WABASH VALLEY.

THERE WILL BE THUNDERSTORMS ONGOING ACROSS THE AREA THIS MORNING.
THESE STORMS ARE NOT EXPECTED TO BE SEVERE...WITH CLOUD TO GROUND
LIGHTNING THE MAIN HAZARD.

LATER THIS AFTERNOON AND INTO THE EVENING...SCATTERED
THUNDERSTORMS WILL DEVELOP ACROSS CENTRAL INDIANA AFTER 4 PM.
STORMS WILL BE MOST LIKELY IN WESTERN PORTIONS OF CENTRAL INDIANA. ISOLATED
SEVERE THUNDERSTORMS ARE POSSIBLE WITH LARGE HAIL...DAMAGING
WINDS...AND ISOLATED TORNADOES AS THREATS.

AFTER MIDNIGHT...AN APPROACHING STRONG COLD FRONT WILL ALLOW FOR
THE POSSIBLE DEVELOPMENT OF ORGANIZED SEVERE WEATHER ACROSS
CENTRAL INDIANA. DAMAGING WINDS...LARGE HAIL...FREQUENT CLOUD TO
GROUND LIGHTNING...AND HEAVY RAIN WILL BE THE PRIMARY THREATS.
ISOLATED TORNADOES ARE ALSO POSSIBLE. THE SEVERE THREAT WILL
DIMINISH TOWARDS DAYBREAK THURSDAY.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

THUNDERSTORMS WILL CONTINUE TO BE ONGOING THURSDAY MORNING BUT ARE
EXPECTED TO DIMINISH BEFORE NOON. SEVERE WEATHER IS NOT EXPECTED
THURSDAY MORNING.

ADDITIONAL THUNDERSTORMS ARE POSSIBLE FRIDAY THROUGH SATURDAY
NIGHT. AT THIS TIME THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS
FOR CENTRAL INDIANA ON FRIDAY. LIGHTNING IS A THREAT WITH ANY
THUNDERSTORM.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE THIS AFTERNOON AND TONIGHT.

&&

[Dave]

From the Lincoln IL NWS Office...



Significant Severe Weather Likely Today and Tonight
There is the potential for significant severe weather across most of central and southeast Illinois through tonight. Here are some details we know now:

WHAT: MODERATE RISK of severe weather - which means that widespread severe storms are anticipated.



WHEN: This afternoon and evening - roughly between 3 PM and 11 PM.

POTENTIAL THREATS:


TORNADOES (Some may produce EF2 Damage or greater - wind higher than 110 mph)

DAMAGING WIND GUSTS (60 mph or greater)

VERY LARGE HAIL ( 1" in diameter or larger)
WHERE: MOST of central and southeast Illinois. In the map below, shaded areas are in the MODERATE risk as determined by the Storm Prediction Center. Areas outside of this line are in a SLIGHT RISK - which includes eastern and southeast Illinois.

--------------
608 AM CDT WED MAY 13 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
ILLINOIS.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS WILL DEVELOP AHEAD OF AN APPROACHING COLD FRONT
ACROSS THE ILLINOIS RIVER VALLEY THIS AFTERNOON...THEN WILL
SPREAD EASTWARD TO THE I-55 CORRIDOR BY THIS EVENING. ATMOSPHERIC
CONDITIONS WILL BE FAVORABLE TO SUPPORT ROTATING UPDRAFTS WITH THE
STORMS...ENHANCING THE THREAT FOR LARGE HAIL IN EXCESS OF QUARTER-
SIZED...WINDS GREATER THAN 60 MPH...AND A FEW TORNADOES. THE
STORMS WILL PUSH INTO EAST-CENTRAL ILLINOIS BY LATER THIS EVENING.

[bsuwx]

12Z NAM Energy Helicity Index EHI (CAPE x Helicity)

http://weather.unisys.com/nam/misc/nam_ehi_4panel.html

focusing on STL/S IL and OK

wondering if we should be skeptical of the northern extent of the moderate risk. radar is sloppy in all of N IL.
peoria 61f cloudy dewp 59

http://www.weather.com/outlook/travel/b ... v_business

i think the heat is on south of the warm front

[bsuwx]

ST. LOUIS INTL PTSUNNY 70 61 73 S15G24 29.76F
thats whassup

CARBONDALE CLOUDY 68 64 87 S20G30 29.89F
maybe

EFFINGHAM* CLOUDY 63 61 94 S17 29.85F THUNDER FOG <<<
wth?!?

[Ed Mahmoud]

ST. LOUIS INTL PTSUNNY 70 61 73 S15G24 29.76F
thats whassup

CARBONDALE CLOUDY 68 64 87 S20G30 29.89F
maybe

EFFINGHAM* CLOUDY 63 61 94 S17 29.85F THUNDER FOG <<<
wth?!?

Automated recording. I saw an ASOS station report snow during a tropical storm landfall in North Carolina a few years back. I wish I remembered year/storm/station.

[Ed Mahmoud]

Just a look at Utah U 3 hour rainfall/winds/CAPE map, Oklahoma's lower tornado prospects seem somewhat justified as rain seems mostly on/behind the front, but Southwest to Central Missouri seems to have rain in the warm sector, and decent instability. IE, best chance of surface based storms, and tornadoes.

7 pm forecast NAM sounding for Springfield...

[bsuwx]

ah yes, the brilliance of the technology we rely on!

storm chaser micheal phelps weighs in from twitter twitter.com/michealgphelps
@JimCantore I'm really starting to like the south-central/southeast KS and north-central/northeast OK area. I'm stuck in the ATL!


wondering where the VORTEX II project is going to head. should know shortly. twitter.com/tornadohunt

for now i agree with you, ed: (in focusing on C, SW MO)

[Dave]

MESOSCALE DISCUSSION 0810
NWS STORM PREDICTION CENTER NORMAN OK
0927 AM CDT WED MAY 13 2009

AREAS AFFECTED...PARTS OF WRN/CENTRAL AND SRN IL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 131427Z - 131530Z

THERE IS EXPECTED TO BE AN INCREASING POTENTIAL FOR ELEVATED STORMS
TO PRODUCE HAIL...SOME SEVERE...FROM NRN MO INTO WRN/CENTRAL
IL...AND POSSIBLY PARTS OF SRN IL TO ADJACENT WRN/SWRN IND THIS
MORNING INTO THE AFTERNOON. WW MAY BE REQUIRED FOR PARTS OF THIS
REGION.

MID MORNING SURFACE ANALYSIS SHOWED AN AREA OF LOW PRESSURE IN
CENTRAL KS WITH A WARM FRONT EXTENDING EWD INTO NRN MO AND THEN SEWD
ALONG THE MID MS AND LOWER TN VALLEYS. REGIONAL RADAR IMAGERY
INDICATED AN ONGOING MCS ACROSS ERN IL/WRN IND...WITH A SECOND MCS
PROGRESSING EWD ACROSS IA/NRN MO. NEW TSTM DEVELOPMENT HAS BEEN
OBSERVED ACROSS FAR SERN IA/WEST CENTRAL IL ALONG LEADING EDGE OF
IA/MO MCS...WITH SUSTAINED DEVELOPMENT ALONG WRN PERIPHERY OF IL/IND
MCS AND SRN PERIPHERY OF MO/IA MCS.

ALTHOUGH THE STRONG SRN PLAINS TO MID MS VALLEY SWLY LLJ HAS
WEAKENED SOME THIS MORNING...ITS SPEED REMAINS AT 50-60 KT INTO THE
MID MS VALLEY REGION. VERY STRONG LOW LEVEL WAA ALONG LLJ...
ESPECIALLY FROM ERN KS TO IL...AND BENEATH UPPER LEVEL DIFFLUENT
FLOW REGIME ACROSS THE MID MS VALLEY WILL SUPPORT ADDITIONAL MAINLY
ELEVATED TSTM DEVELOPMENT ALONG W/SW EXTENT OF IL/IND MCS AND ALONG
LEADING EXTENT THROUGH SRN PERIPHERY OF IA/MO MCS. THIS LLJ WILL
MAINTAIN AN INFLOW OF RICH MOISTURE/MODERATE ELEVATED INSTABILITY
INTO THE ONGOING MCS/S...WITH MUCH OF THIS ACTIVITY LOCATED N AND E
OF THE WARM FRONT. ALTHOUGH BULK SHEAR HAS WEAKENED SOME THIS
MORNING DUE TO THE GRADUAL WEAKENING TREND OF THE SWLY LLJ...
INCREASING WSWLY MID LEVEL FLOW INTO THIS REGION AS STRONG UPPER
TROUGH MOVES ACROSS THE NRN PLAINS SHOULD MAINTAIN 30-40 KT OF
EFFECTIVE BULK SHEAR AND LIKELIHOOD FOR ORGANIZED STORMS. HAIL WILL
BE THE MAIN THREAT WITH THIS ELEVATED ACTIVITY.

..PETERS.. 05/13/2009

[bsuwx]

the VORTEX II chase project will be heading to western oklahoma
http://twitter.com/tornadohunt

[Dave]

MESOSCALE DISCUSSION 0811
NWS STORM PREDICTION CENTER NORMAN OK
0115 PM CDT WED MAY 13 2009

AREAS AFFECTED...PARTS OF SRN INTO ERN MO AND ADJACENT SWRN IL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 131815Z - 131845Z

TORNADO WATCH MAY BE NEEDED FOR PARTS OF ERN MO/WRN IL.

TSTMS ASSOCIATED WITH A COMPACT NEWD MOVING MCV ACROSS SRN MO WILL
CONTINUE TO POSE A THREAT FOR ISOLATED SEVERE HAIL...UNTIL SURFACE
BASED CINH WEAKENS ENOUGH FOR STORMS TO ROOT TO THE SURFACE AND
SUPPORT AN INCREASED POTENTIAL FOR ISOLATED TORNADOES/DAMAGING
WINDS. LATEST OBJECTIVE ANALYSES SUGGEST SURFACE BASED CINH IS
WEAKENING DOWNSTREAM OF THE MCV.

AT 1730Z...SATELLITE/REGIONAL RADAR IMAGERY INDICATED AN MCV
CENTERED OVER WRIGHT COUNTY MO...WITH A COMPACT AREA OF TSTMS
ATTENDANT TO THIS FEATURE. DESPITE A MODERATELY UNSTABLE AIR MASS
/MUCAPE 2000-3000 J/KG/ ACROSS MO/AR INTO WRN/SRN IL...THIS REGION
REMAINS CAPPED PER 16Z ACARS STL SOUNDING/18Z SGF SPECIAL SOUNDING.
FORCING FOR ASCENT WITH THE MCV COMBINED WITH THE MODERATE
INSTABILITY/STEEP MID LEVEL LAPSE RATES /EXCEEDING 8C/KM/ WILL
CONTINUE TO SUPPORT A THREAT FOR ISOLATED HAIL WITH THE STRONGER
SUSTAINED ELEVATED UPDRAFTS.

MODIFIED RUC FORECAST SOUNDINGS WITH SURFACE TEMPERATURES IN THE
LOWER 80S AND DEWPOINTS IN THE MID 60S SUGGEST THE CAP SHOULD WEAKEN
ENOUGH BY MID AFTERNOON FOR STORMS TO BECOME SURFACE BASED ACROSS
EAST CENTRAL MO. STL WSR-88D VAD CURRENTLY SHOWS LOW LEVEL WINDS
VEERING WITH HEIGHT/HODOGRAPH CURVATURE AND SURFACE-1 KM SHEAR
AROUND 20 KT. AS SURFACE BASED CINH WEAKENS FURTHER...THERE WILL BE
A GREATER POTENTIAL FOR STORMS TO BECOME SURFACE BASED WITH AN
ATTENDANT INCREASE IN TSTM COVERAGE/INTENSITY LIKELY GIVEN THE
AVAILABLE INSTABILITY. EFFECTIVE BULK SHEAR IS ALSO INCREASING FROM
N-S ACROSS NERN/ERN MO INTO CENTRAL/SRN IL AS SWLY MID LEVEL FLOW
STRENGTHENS ACROSS THE MID MS VALLEY. THESE FACTORS WILL FAVOR AN
ATTENDANT THREAT FOR TORNADOES...IN ADDITION TO HAIL...ONCE STORMS
BECOME SURFACE BASED.

..PETERS.. 05/13/2009

[Ed Mahmoud]

MESOSCALE DISCUSSION 0812
NWS STORM PREDICTION CENTER NORMAN OK
0152 PM CDT WED MAY 13 2009

AREAS AFFECTED...MUCH OF NRN AND CENTRAL MO/FAR SRN IA AND WRN IL

CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY

VALID 131852Z - 131915Z

TORNADO WATCH WILL BE NEEDED SOON FOR MUCH OF NRN/CENTRAL MO...FAR
SRN IA AND WRN IL.

TSTMS ARE EXPECTED TO DEVELOP ACROSS FAR SRN IA INTO NRN/CENTRAL MO
BY MID AFTERNOON ALONG THE COLD FRONT AS IT CONTINUES TO ADVANCE
E/SEWD THROUGH IA...NRN MO...AND ERN KS. ADDITIONAL DEVELOPMENT
WILL BE POSSIBLE ALONG AN OUTFLOW ENHANCED WARM FRONT WHICH EXTENDS
FROM SOUTH CENTRAL IA SEWD INTO EAST CENTRAL MO TO SRN IL.

AT 18Z...OBJECTIVE ANALYSES INDICATED VERY LITTLE CAP WAS LEFT NEAR
THE COLD FRONT/WARM FRONT INTERSECTION IN FAR SOUTH CENTRAL IA AND
SEWD ALONG THE WARM FRONT. LOW LEVEL CONVERGENCE WAS BEING
MAXIMIZED ALONG THE WARM FRONT GIVEN A 50-60 KT SWLY LLJ EXTENDING
INTO CENTRAL MO. WARM SECTOR AIR MASS IS VERY UNSTABLE WITH MLCAPE
RANGING FROM 2500-3000 J/KG. EFFECTIVE BULK SHEAR WILL CONTINUE TO
INCREASE THROUGH THE AFTERNOON AS SWLY MID LEVEL WINDS STRENGTHEN
AHEAD OF STRONG SHORT WAVE TROUGH MOVING EWD THROUGH THE NRN PLAINS.
THESE WIND FIELDS COMBINED WITH THE VERY UNSTABLE AIR MASS SUGGEST
STORMS SHOULD BECOME SEVERE FAIRLY QUICKLY ONCE THEY DEVELOP ALONG
AND AHEAD OF THE COLD FRONT. TORNADOES...LARGE HAIL AND DAMAGING
WINDS WILL BE POSSIBLE WITH THE STORMS INTO THE EVENING. AREA WIND
PROFILERS/WSR-88D VADS INDICATE STRONG LOW LEVEL SHEAR WITH
SURFACE-1 KM SHEAR AROUND 30 KT...ENHANCING THE TORNADO THREAT.

..PETERS.. 05/13/2009


ATTN...WFO...ILX...LSX...DVN...SGF...DMX...EAX...TOP...ICT...

[Ed Mahmoud]

Tornado Watch 293- much of Iowa, Missouri and Illinois

[Dave]

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 294
NWS STORM PREDICTION CENTER NORMAN OK
300 PM CDT WED MAY 13 2009

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

PARTS OF SOUTHERN ILLINOIS
SMALL PART OF SOUTHWEST INDIANA
PARTS OF EASTERN MISSOURI

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 300 PM UNTIL
1000 PM CDT.

TORNADOES...HAIL TO 2 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 60 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 15 MILES SOUTHWEST OF
FARMINGTON MISSOURI TO 45 MILES SOUTH SOUTHEAST OF TERRE HAUTE
INDIANA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).

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.

OTHER WATCH INFORMATION...CONTINUE...WW 293...

DISCUSSION...MCV ACROSS SERN MO IS NOW MOVING INTO AN AREA OF MDT
INSTABILITY AND LITTLE REMAINING CINH. WITH STRONG VEERING SHEAR
PROFILES IN LOW LEVELS NOTED ON PAH AND EVV 88/D VADS...SUPERCELLS
CAN BE EXPECTED AS SYSTEM MOVES EWD. IN ADDITION E/W BOUNDARY WILL
ENHANCE SHEAR AND TORNADO POTENTIAL EWD INTO SWRN IND.

[Dave]

MESOSCALE DISCUSSION 0814
NWS STORM PREDICTION CENTER NORMAN OK
0321 PM CDT WED MAY 13 2009

AREAS AFFECTED...SRN/SERN KS AND NERN INTO CENTRAL/WRN OK

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 132021Z - 132145Z

THUNDERSTORM INITIATION IS POSSIBLE BY 21-23Z OVER PORTIONS OF
SRN/SERN KS AND NRN INTO CENTRAL/WRN OK. AREA IS BEING MONITORED FOR
A WW.

WATER VAPOR IMAGERY REVEALS A S/W TROUGH PROGRESSING ENE ACROSS THE
CENTRAL/NRN PLAINS...ACCOMPANIED BY A 70+ KT MID LEVEL JET SAMPLED
BY NLG PROFILER. MEANWHILE AT THE SURFACE...A COLD FRONT POSITIONED
FROM ROUGHLY STJ TO ICT TO GAG AT 19Z IS FORECAST TO CONTINUE
SAGGING SWD ACROSS SERN KS INTO NRN AND WRN OK THROUGH THE EVENING.
STRONG SLY SURFACE WINDS OVER MUCH OF OK VEER TO SWLY ALONG THE
FRONT...AND THEN NLY IN ITS WAKE...RESULTING IN STRONG LOW LEVEL
CONVERGENCE. TEMPERATURES AHEAD OF THE COLD FRONT HAVE WARMED INTO
THE MID 80S TO AROUND 90 DURING THE AFTERNOON...AND SURFACE
DEWPOINTS RESIDE IN THE MID TO UPPER 60S. MODIFIED 18Z OUN SOUNDING
FOR A TEMPERATURE OF 90 AND DEWPOINT IN THE UPPER 60S YIELDS OVER
3500 J/KG OF MLCAPE. HOWEVER...A WARM CAPPING INVERSION STILL
RESIDES NEAR 700 MB...EVIDENT BY STABLE CUMULUS FIELD IN VISIBLE
SATELLITE IMAGERY. SHORT TERM DETERMINISTIC AND ENSEMBLE FORECAST
GUIDANCE INDICATES THAT COMBINATION OF LARGE SCALE ASCENT WITH UPPER
WAVE PASSING TO THE NORTH ALONG WITH FRONTAL CONVERGENCE WILL
ERODE/LIFT THE CAPPING INVERSION BY 23Z...RESULTING IN INCREASING
PROBABILITY OF THUNDERSTORM INITIATION FROM SERN/SRN KS INTO NRN/WRN
OK.

CONVECTIVE MODE ALONG FRONTAL BOUNDARY FROM MO INTO SERN/SRN KS AND
NRN OK IS EXPECTED TO TRANSITION TOWARD LINEAR RATHER QUICKLY
THROUGH THE EVENING...WHILE THE POTENTIAL FOR SLIGHTLY MORE DISCRETE
ACTIVITY MAY EXIST OVER WRN OK. THE COMBINATION OF VERY STEEP MID
LEVEL LAPSE RATES/LARGE CAPE AND EFFECTIVE BULK SHEAR AROUND 30-40
KT INVOF THE FRONT MAY FAVOR SUPERCELL STORM STRUCTURES
INITIALLY...POSING A THREAT OF LARGE-VERY LARGE HAIL ALONG WITH
ISOLATED TORNADOES. HOWEVER...STRONG FRONTAL FORCING WILL FAVOR
STORM TYPE TRANSITION TOWARD BOWS AND LEWPS WITHIN A FEW HRS AFTER
INITIATION...RESULTING IN AN INCREASING THREAT FOR DAMAGING WIND
GUSTS.

..GARNER.. 05/13/2009