ACUS01 KWNS 261956
SWODY1
SPC AC 261954
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT MON MAR 26 2012
VALID 262000Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
PARTS OF THE NRN PLAINS...
...20Z OUTLOOK UPDATE...NORTHERN PLAINS...
EVEN AS RAPID BOUNDARY LAYER WARMING OCCURS ACROSS NEBRASKA INTO
SOUTHERN NORTH DAKOTA LATE THIS AFTERNOON...MOISTURE RETURN INTO THE
VICINITY OF A DEEPENING SURFACE CYCLONE ACROSS THE NORTHERN HIGH
PLAINS IS EXPECTED TO REMAIN RELATIVELY WEAK...BENEATH A WARM
ELEVATED MIXED LAYER WHICH HAS OVERSPREAD MUCH OF THE REGION.
THUS...MID-LEVEL INHIBITION TO CONVECTIVE DEVELOPMENT IS EXPECTED TO
REMAIN SUBSTANTIAL.
HOWEVER...A WINDOW OF OPPORTUNITY STILL APPEARS TO EXIST FOR
BOUNDARY LAYER BASED OR NEAR BOUNDARY LAYER BASED STORM DEVELOPMENT
IN THE WARM SECTOR OF THE CYCLONE. THIS IS EXPECTED MAINLY ACROSS
PARTS OF CENTRAL SOUTH DAKOTA INTO NORTH CENTRAL NEBRASKA DURING THE
00-03Z TIME FRAME...SUPPORTED BY FORCING ASSOCIATED WITH THE
VIGOROUS SHORT WAVE TROUGH LIFTING NORTHEAST OF THE WYOMING
ROCKIES...AS AN EMBEDDED MID-LEVEL LOW FORMS AND DEEPENS. CAPE MAY
ONLY BECOME WEAK TO MODEST IN STRENGTH...BUT LOWER/MID TROPOSPHERIC
PROFILES CHARACTERIZED BY STRONG WIND FIELDS AND SIZABLE
TEMPERATURE/DEW POINT SPREADS WILL PROVIDE THE RISK FOR POTENTIALLY
DAMAGING CONVECTIVELY ENHANCED WIND GUSTS.
OTHERWISE...AS MID-LEVEL COOLING SPREADS EASTWARD INTO THE MID
MISSOURI VALLEY BY LATE TONIGHT...MODELS INDICATE THAT POTENTIAL
EXISTS FOR VIGOROUS NEW STORM DEVELOPMENT ALONG A NARROW CORRIDOR OF
MORE SUBSTANTIVE LOW-LEVEL MOISTURE RETURN. TOO MUCH VARIABILITY
PERSISTS AMONG THE MODEL DATA TO CONFIDENTLY ADD SLIGHT RISK
PROBABILITIES ACROSS PARTS OF EASTERN NEBRASKA INTO WESTERN
IOWA/EASTERN KANSAS AND NORTHWEST MISSOURI AT THE PRESENT TIME.
HOWEVER...5% PROBABILITIES HAVE BEEN ADDED...AND THIS MAY NEED TO BE
RE-EVALUATED IN THE 01Z OUTLOOK UPDATE.
ALSO...CONVECTIVE DEVELOPMENT IS NOW UNDERWAY NEAR THE UPPER TROUGH
ACROSS PARTS OF THE CENTRAL INTO NORTHERN ROCKIES. AS THIS ACTIVITY
DEEPENS AND SPREADS NORTHEASTWARD LATE THIS AFTERNOON...A DEEPLY
MIXED BOUNDARY LAYER ACROSS LOWER ELEVATIONS OF EASTERN WYOMING INTO
SOUTHEASTERN MONTANA PROBABLY WILL BE CONDUCIVE TO LOCALIZED STRONG
CONVECTIVE GUSTS. AND...5% PERCENT SEVERE WIND PROBABILITIES HAVE
BEEN EXPANDED ACROSS THIS REGION AS WELL.
..KERR.. 03/26/2012
.PREV DISCUSSION... /ISSUED 1130 AM CDT MON MAR 26 2012/
...NRN PLAINS...
A PROGRESSIVE UPPER TROUGH WILL CROSS THE ROCKIES AND EJECT IN
NEGATIVE TILT FASHION ACROSS THE NRN PLAINS THIS PERIOD. IN RESPONSE
TO THIS DISTURBANCE AND ITS ASSOCIATED 75-90KT FOCUSED MID LEVEL
SPEED MAX CURRENTLY CROSSING THE FOUR CORNERS REGION...DOWNSTREAM
LEE CYCLOGENESIS WAS ALREADY UNDERWAY ACROSS ERN WY/MT. AS PRIMARY
SURFACE CYCLONE CONSOLIDATES ACROSS MT AND MOVES INTO ND THROUGH
TONIGHT...SECONDARY/TRIPLE POINT LOW NEAR HIGH PLAINS DRYLINE/LEE
TROUGH AND COLD FRONT INTERSECTION WILL TRACK RAPIDLY NEWD FROM ERN
WY INTO NERN NEB AND SD THROUGH THIS EVENING.
DYNAMIC FORCING FOR ASCENT AND RAPID TRANSLATION/EVOLUTION OF THE
LARGE SCALE FLOW FIELDS WITH THIS SYSTEM ARE SUBSTANTIAL. AS
SUCH...PLAINS LOW LEVEL JET WILL CONTINUE TO INTENSIFY THROUGH THE
DAY AND CONTRIBUTE TO AT LEAST A MODEST INCREASE IN MOISTURE ACROSS
AREAS OF THE PLAINS THAT ARE CURRENTLY QUITE DRY /PW UNDER 0.75
INCH/. THIS INCREASE IN MOISTURE...HOWEVER...WILL TAKE PLACE AMIDST
SIGNIFICANT CONVECTIVE INHIBITION DUE TO STOUT EML PLUME SITUATED
ACROSS THE CNTRL AND NRN PLAINS. WHILE SURFACE-BASED INSTABILITY
NEAR THE TRIPLE POINT LOW AND SURGING FRONT ACROSS NE/SD LATER TODAY
MAY EXCEED 1000 J/KG...INHIBITION IN THIS REGIME WILL REMAIN QUITE
STRONG.
THUS...EXPECT POTENTIAL FOR NEAR SURFACE-BASED STORM INITIATION TO
OCCUR WHERE STRONGEST DYNAMIC AND DIABATIC INFLUENCES CAN ACT IN
CONCERT TO BREACH THE CAP. THIS MAY OCCUR LATE IN THE DAY...OR BY
EARLY EVENING...NEAR LEE LOW AND COLD FRONT/DRYLINE TRIPLE
POINT...FROM ERN WY ACROSS NEB PNHDL TO SWRN SD. EXPECT ISOLATED
HIGH BASED STORMS IN THESE AREAS TO TRACK NEWD AND POSSIBLY
CONSOLIDATE INTO A FAST-MOVING ARC OF SEVERE STORMS ACROSS SD. GIVEN
POTENT EFFECTIVE SHEAR ON THE ORDER OF 50-60KT AND RAPID COOLING
ALOFT...SEVERE THREAT WITH THIS INITIAL ACTIVITY WOULD BE THE
POTENTIAL FOR AN LP SUPERCELL OR TWO WITH LARGE HAIL. TORNADO
POTENTIAL WILL BE CONDITIONAL ON TRUE SURFACE-BASED STORM
DEVELOPMENT BUT SUFFICIENT LOW LEVEL FORCING AND SHEAR WILL BE IN
PLACE ACROSS A RELATIVELY NARROW CORRIDOR IN SPACE AND TIME TO
SUPPORT SOME TORNADO POSSIBILITY NEAR THE TRIPLE POINT LOW BETWEEN
00Z AND 03Z. IF STORMS CAN INCREASE IN COVERAGE ACROSS SD THIS
EVENING...SOME DAMAGING WIND POTENTIAL SHOULD ENSUE GIVEN FAVORABLE
ORIENTATION OF THE 75-90KT MID LEVEL JET STREAK AND POTENTIAL ARC OF
STORMS OVER THIS AREA. AS SMALL MCS RACES NEWD...EXPECT STORM
UPDRAFTS TO BECOME MORE REMOVED FROM THE BOUNDARY LAYER WITH A
SUBSEQUENT TRANSITION BACK TO MORE OF A HAIL THREAT AS ACTIVITY
MOVES ACROSS ND THROUGH LATE TONIGHT/EARLY TUESDAY.
...WEST TX...
FARTHER SOUTH...NO CHANGE FROM PRIOR OTLK...STRONG DAYTIME HEATING
WILL LEAD TO DEEP MIXING ALONG THE DRYLINE OVER WEST TX LATER TODAY.
A FEW OF THE OPERATIONAL MODEL SOLUTIONS SUGGEST THAT ISOLATED
THUNDERSTORMS WILL DEVELOP ALONG THE DRYLINE DURING THE LATE
AFTERNOON AND EARLY EVENING. EFFECTIVE SHEAR VALUES WILL BE SOMEWHAT
MARGINAL FOR ORGANIZED STORMS. RELATIVELY STEEP MID LEVEL LAPSE
RATES AND DEEPLY MIXED BOUNDARY LAYER MAY BE SUFFICIENT TO PROMOTE
HAIL AND GUSTY WINDS IN A COUPLE STRONGER STORMS.
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