SWODY1
SPC AC 291955
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0255 PM CDT THU MAY 29 2008
VALID 292000Z - 301200Z
...THERE IS A HIGH RISK OF SVR TSTMS THIS AFTN AND TONIGHT ACROSS
PARTS OF CNTRL/ERN NEBRASKA INTO PARTS OF WRN IA....
...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK
AREA...ACROSS PARTS OF WRN/NRN KS...MUCH OF CNTRL/ERN NEB...SERN
SD...SRN MN...MUCH OF IA AND NW MO....
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...FROM THE CNTRL PLAINS INTO THE UPPER MS VLY....
AN OUTBREAK OF SEVERE THUNDERSTORMS NOW APPEARS TO BE UNDERWAY
ACROSS PARTS OF THE NORTH CENTRAL PLAINS INTO THE MID MISSOURI
VALLEY. SUPERCELLS CAPABLE OF PRODUCING STRONG TORNADOES ARE
POSSIBLE LATE THIS AFTERNOON...WITH A SEVERE MESOSCALE CONVECTIVE
SYSTEM LIKELY TO EVOLVE BY THIS EVENING...CONTINUING INTO THE
OVERNIGHT HOURS.
...CENTRAL HIGH PLAINS INTO UPPER MISSISSIPPI VALLEY...
MODELS CONTINUE TO INDICATE THAT A DEEPER...BROADER SCALE MID-LEVEL
SHORT WAVE TROUGH WILL EVOLVE LATER TODAY/TONIGHT ACROSS THE
NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY...AS A SERIES OF SMALLER
SCALE IMPULSES CONTINUE TO EMERGE FROM THE DEAMPLIFYING SOUTHERN
BRANCH TROUGH OVER THE EASTERN PACIFIC AND WESTERN STATES. ONE OF
THESE IMPULSES ALREADY APPEARS TO BE LIFTING INTO THE CREST OF THE
PLAINS SUBTROPICAL RIDGE...ACROSS THE DAKOTAS. ANOTHER...MORE
SIGNIFICANT IMPULSE APPEARS TO BE JUST NOW BEGINNING TO SHIFT
NORTHEAST OF THE WYOMING/COLORADO ROCKIES. THIS LATTER FEATURE IS
PROGGED TO BE ACCOMPANIED BY MORE SUBSTANTIAL HEIGHT FALLS ACROSS
THE NORTH CENTRAL PLAINS BETWEEN NOW AND EARLY EVENING. AND...THIS
SHOULD EFFECTIVELY CONTRIBUTE TO THE ELIMINATION OF INHIBITION WHICH
REMAINS CONSIDERABLE ON THE LEADING EDGE OF LOW-LEVEL MOISTURE
RETURN.
UPPER 60S SURFACE DEW POINTS HAVE REACHED CENTRAL NEBRASKA.
AND...ELEVATED MOISTURE RETURN IN A LINGERING ZONE OF LOWER/MID
TROPOSPHERIC WARM ADVECTION HAVE MAINTAINED CONSIDERABLE CONVECTIVE
DEVELOPMENT ACROSS THE EASTERN DAKOTAS/SOUTHERN MINNESOTA INTO THE
UPPER MISSISSIPPI VALLEY. THIS IS SLOWING DESTABILIZATION
NORTH/EAST OF THE MISSOURI RIVER. BUT...FORCING ASSOCIATED WITH A
CONSOLIDATING SURFACE FRONTAL WAVE IS EXPECTED TO CONTRIBUTE TO
INCREASING INSTABILITY LATER THIS EVENING/ OVERNIGHT.
THE INITIATION OF CONVECTIVE DEVELOPMENT IS ALREADY UNDERWAY ACROSS
THE HIGH PLAINS...FROM EASTERN WYOMING INTO EASTERN NEW MEXICO.
AND...HIGH BASED STORMS ARE EXPECTED TO GRADUALLY STRENGTHEN WHILE
SPREADING EASTWARD LATE THIS AFTERNOON. INSTABILITY AND DEEP LAYER
SHEAR...BENEATH A SEASONABLY STRONG MID/UPPER JET STREAK CURVING OUT
OF THE SOUTHERN PLATEAU/CENTRAL ROCKIES THROUGH THE MID MISSOURI
VALLEY...WILL BE SUFFICIENT FOR SUPERCELLS.
ACTIVITY WILL EVENTUALLY ENCOUNTER BETTER LOW-LEVEL MOISTURE...
ROUGHLY NORTH/EAST OF HILL CITY KS INTO NORTH CENTRAL NEBRASKA...
WHERE FURTHER INTENSIFICATION WILL OCCUR...AND NEW STORMS WILL
DEVELOP...WITH INCREASING TORNADIC POTENTIAL ALONG A 40-60 KT SOUTH
SOUTHWESTERLY LOW-LEVEL JET AXIS BY/SHORTLY AFTER 30/00Z. WITHIN
THE PRESENCE OF STRONG DEEP LAYER SHEAR....LARGE CLOCKWISE CURVED
LOW-LEVEL HODOGRAPHS...AND MIXED LAYER CAPE OF 2000-3000
J/KG...POTENTIAL EXISTS FOR A FEW STRONG TORNADOES IN LONG-LIVED
SUPERCELLS.
ALTHOUGH UPSCALE CONVECTIVE DEVELOPMENT INTO A SEVERE MESOSCALE
CONVECTIVE SYSTEM IS STILL ANTICIPATED THIS EVENING...ISOLATED
SUPERCELLS WITH TORNADOES MAY CONTINUE TO FORM AS INHIBITION WEAKENS
DOWNSTREAM...ALONG A WEAK WARM FRONTAL ZONE ACROSS PARTS OF EASTERN
NEBRASKA/SOUTHWEST IOWA. OTHERWISE...THE RISK FOR DAMAGING WINDS
PROBABLY WILL BECOME THE MORE PROMINENT THREAT ACROSS EASTERN
NEBRASKA INTO WESTERN IOWA...BEFORE STORMS BEGIN TO WEAKEN EAST OF
THE MID MISSOURI VALLEY OVERNIGHT.
..KERR.. 05/29/2008
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