Severe weather outbreak - May 29-31

[CrazyC83]

SPC has 15-hatched for Day 3, which suggests significant weather possible but great uncertainty. Large areas marked for Days 4 and 5.

SPC AC 270717

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0217 AM CDT TUE MAY 27 2008

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN HIGH PLAINS ESEWD
INTO THE MIDDLE MO VALLEY...

...SYNOPSIS...
UPPER FLOW FIELD IS FORECAST TO DEAMPLIFY THIS PERIOD...AS
SHORT-WAVE TROUGH EJECTING EWD OUT OF THE ROCKIES/ATOP THE CENTRAL
U.S. RIDGE WILL LEAD TO A FLATTENING OF THE RIDGE WITH TIME.

AS THIS TROUGH MOVES OUT OF THE ROCKIES THROUGH THE FIRST HALF OF
THE PERIOD...A SURFACE LEE TROUGH/LOW WILL BE MAINTAINED OVER THE
NRN HIGH PLAINS. OVERNIGHT...AS THE UPPER TROUGH MOVES INTO THE NRN
PLAINS...A SURFACE LOW IS FORECAST TO MOVE NEWD TOWARD SRN MN...WITH
A TRAILING COLD FRONT TO BEGIN MOVING SEWD ACROSS THE NRN PLAINS.

...NRN HIGH PLAINS ESEWD INTO THE MID MO VALLEY...
LOW-LEVEL MOISTURE IS FORECAST TO SPREAD NWD ACROSS THE PLAINS
THROUGH THE PERIOD...AS SLY BOUNDARY-LAYER FLOW INCREASES AHEAD OF
DEVELOPING LOW PRESSURE OVER THE HIGH PLAINS. THIS COMBINED WITH
DAYTIME HEATING WILL ALLOW MODERATE DESTABILIZATION TO OCCUR THROUGH
THE AFTERNOON AND INTO THE EVENING...THOUGH CAPPING SHOULD HINDER
STORM DEVELOPMENT INTO THE AFTERNOON.

SCATTERED STORM DEVELOPMENT IS FORECAST TO OCCUR BY MID TO LATE
AFTERNOON AS HEATING/MIXING COMBINED WITH THE APPROACHING SHORT-WAVE
TROUGH COMBINE TO WEAKEN THE CAP. INITIAL DEVELOPMENT IS EXPECTED
TO OCCUR OVER THE HIGH PLAINS INVOF SERN MT/ERN WY/WRN SD...AND THEN
SPREAD EWD WITH TIME. WITH SELY BOUNDARY LAYER FLOW FORECAST
BENEATH 40 TO 50 KT MID-LEVEL SWLYS...SHEAR WILL FAVOR SUPERCELLS.
GIVEN STEEP LAPSE RATES/MODERATE INSTABILITY EXPECTED...LARGE HAIL
IS EXPECTED...ALONG WITH LOCALLY-DAMAGING WINDS.

LOW-LEVEL JET IS FORECAST TO INCREASE ACROSS THE PLAINS DURING THE
EVENING. ALONG WITH SUSTAINING/INCREASING ESEWD-MOVING
STORMS...RESULTING INCREASE IN LOW-LEVEL SHEAR MAY ALSO SUPPORT A
THREAT FOR ISOLATED TORNADOES AS STORMS SPREAD ESEWD OVERNIGHT.
MEANWHILE...THE THREAT FOR HAIL/WIND SHOULD CONTINUE AS STORMS MOVE
ACROSS THE MID MO VALLEY REGION THROUGH THE END OF THE PERIOD.

..GOSS.. 05/27/2008

CLICK TO GET WUUS03 PTSDY3 PRODUCT

NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1100Z
CURRENT UTC TIME: 1319Z (9:19AM), RELOAD THIS PAGE TO UPDATE THE TIME

[Ed Mahmoud]

It seems like one really drawn out outbreak, as the pattern is changing very slowly.

[CrazyC83]

It seems like one really drawn out outbreak, as the pattern is changing very slowly.

Different system in this case though, finally. Everything since Thursday has been from the same system (low connected by a slow cold front and dry line).

[Ed Mahmoud]

Joe Bastardi says Friday/Saturday for interior Northeast/Ohio Valley similar to the May 1985 tornado outbreak.


I don't remember the May 1985 tornado outbreak, I was in the North Arabian Sea back then, but I guess it was a doozy.

[CrazyC83]

Joe Bastardi says Friday/Saturday for interior Northeast/Ohio Valley similar to the May 1985 tornado outbreak.


I don't remember the May 1985 tornado outbreak, I was in the North Arabian Sea back then, but I guess it was a doozy.

88 people died in that outbreak (76 in the US and 12 in Canada) - the deadliest of the last 34 years. It included 42 tornadoes (at least) in Ohio, Pennsylvania, New York and Ontario.

[KWT]

So a very powerful outbreak, have to admit the last 10 days of May have been very active in terms of severe weather hasn't it!

[tomboudreau]

Also, the only recorded F5 tornado hit Pennsylvania during that outbreak. Going to monitor trends and if these trends continue, will not be heading to the woods this weekend. Instead, will probably be spotting instead.

[Calasanjy]

And once again how ironic that this is forecasted for May 31 in the Northeast yet again (it is incidentally the deadliest day of the year in Pennsylvania weather history - including the fatalities from the first Johnstown flood and the 1985 tornado outbreak) as there was also a lesser outbreak across the region on May 31, 1998 triggered by a serial derecho. It was also coincidentally the only SPC High Risk day ever declared in the Northeast (I believe May 31, 1985 had a moderate risk).

Remains to be seen how this Saturday turns out, with Bastardi calling for a similar outbreak - however as we know he has a tendency to overhype severe events (how many times lately has he predicted a Super Outbreak encore?)

[CrazyC83]

And once again how ironic that this is forecasted for May 31 in the Northeast yet again (it is incidentally the deadliest day of the year in Pennsylvania weather history - including the fatalities from the first Johnstown flood and the 1985 tornado outbreak) as there was also a lesser outbreak across the region on May 31, 1998 triggered by a serial derecho. It was also coincidentally the only SPC High Risk day ever declared in the Northeast (I believe May 31, 1985 had a moderate risk).

Remains to be seen how this Saturday turns out, with Bastardi calling for a similar outbreak - however as we know he has a tendency to overhype severe events (how many times lately has he predicted a Super Outbreak encore?)

I think May 31, 1985 was a moderate risk that was later downgraded to a slight risk (and that busted big time) from what I read.

[Calasanjy]

I think May 31, 1985 was a moderate risk that was later downgraded to a slight risk (and that busted big time) from what I read.

Ah yes, now I remember reading this in the excellent book Tornado Watch 211 by James Fuller. The SPC evidently thought the threat was lessening because the squall line didn't begin to fire until 4:30 PM. Although, I would guess that not many in the public paid attention to the convective severe outlooks in the pre-Internet era.

[CrazyC83]

I think May 31, 1985 was a moderate risk that was later downgraded to a slight risk (and that busted big time) from what I read.

Ah yes, now I remember reading this in the excellent book Tornado Watch 211 by James Fuller. The SPC evidently thought the threat was lessening because the squall line didn't begin to fire until 4:30 PM. Although, I would guess that not many in the public paid attention to the convective severe outlooks in the pre-Internet era.

You're right, they probably didn't get much criticism for that. If such happened today, they would be flooded with criticism (it is one thing to be conservative at the start, but to downgrade and watch an outbreak happen?). But with today's technology, that kind of setup would surely be at least a moderate risk throughout.

[liveweatherman]

Looks like severe thunderstorms are out on Friday..possible for severe weather..

Central Plains


Midwest

[CrazyC83]

SPC AC 281719

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1219 PM CDT WED MAY 28 2008

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS THU/THU NIGHT ACROSS PARTS OF
THE CNTRL PLAINS INTO THE UPPER MISSISSIPPI VALLEY....

...SYNOPSIS...
MODEL GUIDANCE IS SUGGESTIVE THAT THE AMPLIFIED UPPER PATTERN WILL
BECOME A BIT MORE ZONAL ACROSS THE U.S. DURING THIS FORECAST PERIOD.
THE DEEP NORTHERN STREAM TROUGH IS PROGGED TO SHIFT EAST OF THE
CANADIAN MARITIMES/NORTH ATLANTIC COAST REGION. AND...THE
SUBTROPICAL RIDGE AXIS OVER THE NORTH CENTRAL STATES IS PROGGED TO
FLATTEN...WHILE RIDGING REMAINS STRONG ACROSS THE NORTHERN MEXICAN
PLATEAU INTO THE GULF STATES. THIS IS FORECAST TO OCCUR AS A STRONG
MID/UPPER JET STREAK CONTINUES TO EMERGE FROM THE BASE OF THE BROAD
SOUTHERN BRANCH TROUGH OVER THE EASTERN PACIFIC/WESTERN U.S....AND
NOSE THROUGH THE CREST OF THE DOWNSTREAM RIDGE.

WITHIN THIS REGIME...ONE SIGNIFICANT SHORT WAVE IMPULSE APPEARS
LIKELY TO ALREADY BE PROGRESSING THROUGH BROADER SCALE ANTICYCLONIC
FLOW ACROSS THE NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY BY 12Z
THURSDAY. THIS FEATURE IS EXPECTED TO BE TRAILED BY A MORE
PROMINENT IMPULSE...LIFTING THROUGH THE GREAT BASIN... BEFORE
CONTINUING THROUGH THE NORTH CENTRAL ROCKIES AND NORTHERN PLAINS
LATER THURSDAY/THURSDAY NIGHT.

...CENTRAL PLAINS INTO THE UPPER MISSISSIPPI VALLEY...
DESTABILIZATION ASSOCIATED WITH ELEVATED MOISTURE RETURN AND
LOWER/MID TROPOSPHERIC WARM ADVECTION IS EXPECTED TO BE ONGOING
NEAR/NORTHEAST OF THE MIDDLE MISSOURI VALLEY AT 12Z THURSDAY...IN
ASSOCIATION WITH THE LEAD IMPULSE. INSTABILITY MAY BE SUFFICIENT
FOR SOME MARGINALLY SEVERE HAIL IN STRONGER CELLS. THIS ACTIVITY
LIKELY WILL WEAKEN AS IT SPREADS EASTWARD THROUGH THE UPPER
MISSISSIPPI VALLEY...BUT MODELS ARE SUGGESTIVE THAT LIFT AND
STRONGER CONVECTION ASSOCIATED WITH WARM ADVECTION WILL REMAIN
FOCUSED NEAR THE MID MISSOURI VALLEY THROUGH MUCH OF THE DAY. CLOUD
COVER/PRECIPITATION WILL LIKELY MAINTAIN COOL/STABLE BOUNDARY LAYER
CONDITIONS ACROSS MUCH OF MINNESOTA AND IOWA...AS STRONG HEATING AND
BOUNDARY LAYER MOISTURE RETURN CONTRIBUTE TO STRONG DESTABILIZATION
FROM PARTS OF SOUTHERN SOUTH DAKOTA/NEBRASKA SOUTHWARD THROUGH THE
SOUTH CENTRAL HIGH PLAINS.

INHIBITION ACROSS THE WARM SECTOR OF A DEVELOPING SURFACE LOW TO THE
LEE OF THE NORTH CENTRAL ROCKIES IS EXPECTED TO SUPPRESS CONVECTIVE
DEVELOPMENT UNTIL LATE THURSDAY AFTERNOON...WHEN CONVECTIVE
TEMPERATURES SHOULD BE APPROACHED AND FORCING INCREASES AHEAD OF THE
NEXT IMPULSE. STORMS MAY INITIATE NEAR THE LEE SURFACE TROUGH
ACROSS THE CENTRAL HIGH PLAINS FIRST...BEFORE THIS ACTIVITY SPREADS
EASTWARD...WITH ADDITIONAL DEVELOPMENT ALONG A WARM FRONT EAST OF
THE SURFACE LOW. THIS SEEMS MOST PROBABLE ACROSS NORTHERN/EASTERN
NEBRASKA...BEFORE ACTIVITY CONSOLIDATES WITH INCREASINGLY FOCUSED
LARGE-SCALE ASCENT ACROSS THE MID MISSOURI VALLEY DURING THE
EVENING.

WITH MOISTURE NOT YET RETURNING TO THE REGION...UNCERTAINTIES
CONCERNING THE MAGNITUDE OF INSTABILITY EXIST. BUT...WITH THE
EVOLUTION OF STEEP LAPSE RATES LIKELY...A RETURN OF MID/UPPER 60S
SURFACE DEW POINTS PROBABLY WILL CONTRIBUTE TO AFTERNOON MIXED LAYER
CAPE OF 2000-3000+ J/KG. IN THE PRESENCE OF STRONG DEEP LAYER
SHEAR...AND SIZABLE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS... A FEW
SUPERCELLS WITH THE RISK FOR TORNADOES WILL CERTAINLY BE POSSIBLE
EARLY...BEFORE UPSCALE GROWTH INTO AN INCREASINGLY ORGANIZED
MESOSCALE CONVECTIVE SYSTEM OCCURS THURSDAY EVENING. MODELS SUGGEST
THAT THIS WILL OCCUR NEARLY COINCIDENT WITH THE INTENSIFICATION OF
AN 850 MB JET IN A BROAD WEST SOUTHWEST BELT ACROSS THE CENTRAL
PLAINS INTO THE UPPER MISSISSIPPI VALLEY. AND ...AT LEAST SOME
POTENTIAL APPEARS TO EXISTS FOR A DERECHO TYPE DAMAGING WIND EVENT
ACROSS THE MID MISSOURI VALLEY TOWARD THE UPPER GREAT LAKES REGION
THURSDAY NIGHT. BUT...UNCERTAINTY IS STILL LARGE DUE TO UNCERTAIN
STABILIZING INFLUENCE OF EARLY PERIOD CONVECTION.

..KERR.. 05/28/2008

CLICK TO GET WUUS02 PTSDY2 PRODUCT

NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
CURRENT UTC TIME: 1826Z (2:26PM), RELOAD THIS PAGE TO UPDATE THE TIME

[HarlequinBoy]

The SPC doesn't really seem to be predicting a major outbreak. Maybe hinting at it over Illinois and Indiana.

[Ed Mahmoud]

NMC021-037-047-290300-
/O.CON.KABQ.TO.W.0012.000000T0000Z-080529T0300Z/
HARDING-QUAY-SAN MIGUEL-
825 PM MDT WED MAY 28 2008

...TORNADO WARNING REMAINS IN EFFECT FOR EXTREME SOUTHEASTERN SAN
MIGUEL...CENTRAL QUAY AND SOUTHEASTERN HARDING COUNTIES UNTIL 900 PM
MDT...

AT 821 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A LINE OF STORMS CAPABLE OF PRODUCING A TORNADO. THESE
STORMS WERE LOCATED ALONG A LINE EXTENDING FROM 12 MILES NORTH OF
LOGAN TO 8 MILES SOUTHWEST OF TUCUMCARI...OR ALONG A LINE EXTENDING
FROM 24 MILES WEST OF NARA VISA TO 8 MILES SOUTHWEST OF TUCUMCARI...
MOVING EAST AT 24 MPH. IN ADDITION...THESE STORMS WILL PRODUCE
BASEBALL SIZED HAIL AND 70 MPH WINDS...ESPECIALLY IN TUCUMUCARI.

* TORNADO PRODUCING STORMS WILL BE NEAR...
TUCUMCARI AROUND 830 PM MDT...
LOGAN AROUND 845 PM MDT...

THIS IS A VERY DANGEROUS STORM...SEEK SHELTER IMMEDIATELY.

A TORNADO WATCH REMAINS IN EFFECT UNTIL 900 PM MDT WEDNESDAY EVENING
FOR EASTERN NEW MEXICO.

LAT...LON 3555 10303 3535 10303 3529 10308 3529 10309

[KWT]

They are going for a moderate risk today so may need to be watched, the 30th sees the threat moving off to the east:

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT THU MAY 29 2008

VALID 291200Z - 301200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS MOST OF CNTRL/ERN NEB AND
SMALL PART OF NCNTRL KS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE CNTRL/NRN
PLAINS...

..SYNOPSIS

THE AMPLIFIED UPR FLOW REGIME IS EXPECTED TO FLATTEN INTO A MORE
ZONAL PATTERN ON THURSDAY. THIS TRANSITION WILL OCCUR AS THE
IMPULSE OVER THE GRT BASIN TRANSLATES EWD ACROSS THE CNTRL/NRN
PLAINS AND FLATTENS THE MEXICAN SUBTROPICAL RIDGE. IN THE LWR
LVLS...A WAVY FRONT OVER THE SRN PLAINS WILL REDEVELOP NWD THROUGH
THE PLAINS. A LEE TROUGH/DRYLINE WILL BECOME BETTER DEFINED BY
AFTERNOON OVER THE HIGH PLAINS FROM SWRN NEB SWD INTO FAR WRN KS/ERN
CO. MEANWHILE...A COLD FRONT/SFC TROUGH ASSOCD WITH THE UPR TROUGH
WILL MOVE SEWD INTO THE ERN DAKS AND THE NEB PNHDL BY EVENING WITH A
TRIPLE POINT DEVELOPING OVER SWRN NEB WHERE IT INTERSECTS WITH THE
DRYLINE.

..CNTRL/NRN PLAINS EWD INTO THE UPR MS VLY

ELEVATED BANDS OF TSTMS WITH PSBL HAIL WILL LIKELY BE ONGOING AT 12Z
THURSDAY OVER PARTS OF THE MID-MO VLY/CORN BELT WITHIN A ZONE OF
WARM/MOIST ADVECTION. THIS ACTIVITY WILL MOVE NEWD AND WEAKEN
DURING THE MORNING OVER THE UPR MS VLY.

ATTENTION WILL THEN FOCUS TO THE WEST DURING THE AFTN. RESERVOIR OF
MID-UPR 60S BOUNDARY LAYER DEW POINTS NOW OVER THE SRN PLAINS IS
EXPECTED TO ADVECT AS FAR N AS THE MO VLY/SD TO THE E OF THE
DRYLINE/LEE-TROUGH AND SEWD OF THE APCHG COLD FRONT. H7-H5 LAPSE
RATES IN EXCESS OF 8 DEG C/KM ATOP THIS RETURNING MOISTURE AND
SUBSTANTIAL HEATING IN WAKE OF MORNING ACTIVITY WILL CONTRIBUTE TO
MLCAPES OF 2000-3000 J/KG OVER PORTIONS OF SCNTRL/SERN SD...
CNTRL/ERN NEB AND MUCH OF NRN/WRN KS BY MID-AFTN.

STRONGER FORCING FOR ASCENT TIED TO THE APCHG TROUGH IS EXPECTED TO
BE TIMED FAVORABLY TO PEAK HEATING. AS A RESULT...TSTMS WILL LIKELY
DEVELOP ALONG THE DRYLINE/LEE TROUGH OVER SWRN NEB AND NWRN KS BY
21Z. BULK SHEAR OF 45-50 KTS AND THE MAGNITUDE OF LAPSE RATES WILL
BE MORE THAN ENOUGH FOR SUPERCELLS. INITIAL CELLS WILL LIKELY BE
HIGHER BASED...BUT AS THEY MOVE OFF THE DRYLINE AND INTO THE
STRONGLY UNSTABLE BOUNDARY LAYER...VERY LARGE HAIL WILL BE LIKELY.
ADDITIONALLY...MODELS INDICATE THAT LOW-LEVEL WINDS WILL REMAIN
BACKED JUST TO THE EAST OF THE TRIPLE POINT OVER SCNTRL/ERN NEB AND
EXTREME NCNTRL KS DURING THE EVENING AS LCLS LOWER. 0-1KM SRH WILL
LIKELY BE AOA 200 M2/S2 BY EVENING ACROSS THE MDT RISK AREA...AND
STORM MODE SHOULD REMAIN DISCRETE. AS A RESULT... POTENTIAL EXISTS
FOR STRONG TORNADOES DURING THE EVENING. THEREAFTER...AN INCREASING
RISK FOR DMGG WIND GUSTS SHOULD EVOLVE AS ACTIVITY GROWS UPSCALE
INTO AN MCS ACROSS THE MID-MO VLY EWD INTO THE CORN BELT/UPR MS VLY
REGIONS.

TO THE S...ISOLD TSTMS WILL BE PSBL SWD ALONG THE DRYLINE INTO THE
TX/OK PNHDLS. HERE...LARGE SCALE FORCING WILL BE MUCH WEAKER...BUT
SUFFICIENT WHEN COMBINED WITH STRONG HEATING TO INITIATE STORMS.
ROUGHLY 35-40 KTS OF WLY DEEP LAYER SHEAR WILL BE CONDUCIVE FOR
SUPERCELLS WITH LARGE HAIL AND PERHAPS A BRIEF TORNADO.

FINALLY...ISOLD SVR STORMS WITH HAIL/GUSTY WINDS WILL BE PSBL ACROSS
THE WRN DAKS WWD INTO THE NRN ROCKIES BENEATH A POCKET OF MINUS
MID-TEENS H5 TEMPERATURES. WEAK BULK SHEAR SHOULD KEEP THESE STORMS
MORE PULSEY WITH WIDESPREAD SVR STORMS NOT LIKELY.

..RACY/JEWELL.. 05/29/2008

[tornado92]

15% chance of tornadoes in Nebraska today

[liveweatherman]

Nebraska, South Dakota, Iowa, and Kansas possible to be hit with Severe Weather today..

An in-depth analysis for this potential severe weather
by Mike Defino

Nocturnal LLJ will continue to bring in the elevated moisture to the elevated convection in Nebraska. As this activity pushes eastward it should exit Nebraska in the late morning hrs not taking away too much from the threat later in the day.

The trigger for this severe weather will be a cold front with mid level s/w moving thru enhancing the converage and intensity of the threat. S/w moving thru with will increase the storng forcing along with the very strong convergence along the cold front. This will limit the tornadic threat as storms will quickly become linear, but they will initially form and take on super cell characteristics with the strong directional and deep layer shear profiles. BL-6km shear will support supercell threat with values ranging from 40-60kts. Storms forming along the cold front will quickly become linear. As the nocturnal LLJ strengthens throughout the day it will allow MCS to progress eastward through the nighttime preventing the PBL from stabilizing downstream.

Nebraska and Kansas- Isolated tornado threat early then a damaging wind threat. read more

[tornado92]

Thats probably why there's a 15% chance of Tornadoes in the Midwest...

[snoopj]

Surprised this wasn't posted yet:

Mesoscale Discussion 1078

MESOSCALE DISCUSSION 1078
NWS STORM PREDICTION CENTER NORMAN OK
0532 AM CDT THU MAY 29 2008

AREAS AFFECTED...ERN NEB...WRN IA...EXTREME SERN SD

CONCERNING...OUTLOOK UPGRADE

VALID 291032Z - 291230Z

MUCH OF ERN NEB...WRN IA...AND EXTREME SERN SD WILL BE UPGRADED TO A
HIGH RISK AT 13Z TODAY.

...PUBLIC SEVERE WEATHER OUTLOOK...

A STRONG UPPER TROUGH IS CURRENTLY MOVING ACROSS PARTS OF
UTAH/ARIZONA...AND WILL TRACK INTO THE CENTRAL PLAINS BY LATE THIS
AFTERNOON. AHEAD OF THIS SYSTEM...STRONG SOUTHERLY LOW LEVEL WINDS
ARE DRAWING A VERY MOIST AND UNSTABLE AIRMASS NORTHWARD INTO THE
CENTRAL PLAINS. THUNDERSTORMS ARE EXPECTED TO DEVELOP AND RAPIDLY
BECOME SEVERE OVER PARTS OF CENTRAL NEBRASKA...NORTH CENTRAL
KANSAS...AND SOUTH CENTRAL SOUTH DAKOTA BY MID/LATE AFTERNOON.
THESE STORMS WILL LIKELY BE SUPERCELLS CAPABLE OF VERY LARGE
HAIL...DAMAGING WINDS...AND TORNADOES. ACTIVITY WILL INCREASE IN
COVERAGE AND INTENSITY THROUGH THE EVENING AS THUNDERSTORMS SPREAD
INTO PARTS OF WESTERN IOWA AND SOUTHWEST MINNESOTA. THE COMBINATION
OF A VERY UNSTABLE AIRMASS AND STRONG VEERING/INCREASING WINDS WITH
HEIGHT INDICATE A RISK OF STRONG TORNADOES OVER THE REGION THIS
AFTERNOON AND EVENING.

..JEWELL/HART.. 05/29/2008

http://www.spc.noaa.gov/products/md/md1078.html