DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT SAT MAY 16 2015
VALID 161200Z - 171200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF SOUTHERN
NEBRASKA..WESTERN AND CENTRAL KANSAS...THE WESTERN HALF OF
OKLAHOMA...AND A SMALL PORTION OF WESTERN NORTH TEXAS... ..THERE IS AN ENH RISK OF SVR TSTMS FROM CENTRAL NEB SWD TO N TX
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN PLAINS SWD TO
CENTRAL TX...
...THERE IS A MRGL RISK OF SVR TSTMS ACROSS THE PLAINS FROM THE
U.S./CANADA BORDER TO THE RIO GRANDE...
...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SRN NY AND ROUGHLY THE
NRN HALF OF PA INTO NRN NJ...
..SUMMARY
AN OUTBREAK OF SEVERE THUNDERSTORMS IS EXPECTED ACROSS THE PLAINS
STATES SATURDAY INTO SATURDAY NIGHT...FROM PARTS OF NEBRASKA
SOUTHWARD TO TEXAS. RISKS WILL INCLUDE VERY LARGE HAIL...DAMAGING
WIND GUSTS...AND SEVERAL TORNADOES -- WITH A FEW LIKELY TO BE
SIGNIFICANT/LONG-LIVED. ..SYNOPSIS
A LARGE UPPER TROUGH CROSSING THE INTERIOR WRN U.S. AT THE START OF
THE PERIOD IS FORECAST TO SHIFT INTO THE PLAINS THROUGH THE
DAY...TAKING ON AN INCREASINGLY NEGATIVE TILT WITH TIME AS AN
EMBEDDED VORT MAX SHIFTS QUICKLY ACROSS THE SRN ROCKIES INTO THE
CENTRAL/SRN HIGH PLAINS BY EARLY AFTERNOON. DOWNSTREAM...RIDGING
WILL PREVAIL ACROSS MOST OF THE U.S. E OF THE MS RIVER.
AT THE SURFACE...LOW PRESSURE IS FORECAST TO GRADUALLY CONSOLIDATE
INVOF THE CENTRAL HIGH PLAINS...WHILE A PACIFIC COLD FRONT CROSSES
THE SRN HIGH PLAINS INTO THE AFTERNOON. BY THE END OF THE
PERIOD...A FAIRLY DEEP LOW IS FORECAST ACROSS NEB...WITH THE
TRAILING FRONT EXTENDING SWD ACROSS CENTRAL KS/CENTRAL OK AND INTO
NRN/WRN TX. THE EMERGENCE OF THIS POTENT STORM SYSTEM INTO THE
PLAINS SHOULD SUPPORT WIDESPREAD/SUBSTANTIAL SEVERE STORMS FROM
EARLY AFTERNOON INTO THE OVERNIGHT HOURS.
..CENTRAL AND SOUTHERN PLAINS
THUNDERSTORMS ARE FORECAST TO BE UNDERWAY ACROSS PORTIONS OF THE
PLAINS STATES AT THE START OF THE PERIOD...AND EVOLUTION OF THIS
CONVECTION AND ASSOCIATED CLOUD COVER THROUGH THE DAY MAY HAVE
SUBSTANTIAL INFLUENCE OVER SUBSEQUENT AFTERNOON DESTABILIZATION --
AND OVERALL DEGREE OF SEVERE RISK. WITH THAT SAID HOWEVER...THE
SYNOPTIC/KINEMATIC ENVIRONMENT ACROSS THE CENTRAL PLAINS AND SWD
ACROSS OK INTO N TX APPEARS OTHERWISE HIGHLY SUGGESTIVE OF POTENTIAL
FOR A SEVERE WEATHER OUTBREAK. THEREFORE -- DESPITE THE
UNCERTAINTIES...AN UPGRADE TO MODERATE RISK APPEARS WARRANTED AT
THIS TIME. LATEST RUNS OF BOTH THE NAM AND GFS AS WELL AS NUMEROUS HIGH-RES
CAMS SUGGEST -- TO VARYING DEGREES -- THAT THE EARLY/ONGOING
CONVECTION WILL DIMINISH SIGNIFICANTLY THROUGH THE MORNING AS IT
SPREADS EWD ACROSS NEB/KS/OK. THIS SHOULD ALLOW AT LEAST SOME
AFTERNOON HEATING OF THE MOIST BOUNDARY LAYER...PARTICULARLY OVER
WRN PORTIONS OF THE AREA -- INVOF THE ADVANCING PACIFIC
FRONT/DRYLINE AND LIKELY TO THE W OF MOST OF THE MORE RECENT
PRECIPITATION AND ASSOCIATED CLOUD COVER.
GIVEN STRENGTH OF THE UPPER SYSTEM EMERGING INTO THE PLAINS AND
ASSOCIATED UVV FOCUSED INVOF THE FRONT/DRYLINE...IT APPEARS THAT
EARLY REDEVELOPMENT/INTENSIFICATION OF STORMS WILL OCCUR -- LIKELY
IN THE 19-20Z TIME FRAME. ALONG WITH DEVELOPMENT NEAR THE SURFACE
BOUNDARY FROM THE ERN TX PANHANDLE/WRN OK NWD INTO THE WRN KS
VICINITY...SOME OF THE REMNANT STORMS FARTHER E MAY ALSO REINTENSIFY
AS DESTABILIZATION OCCURS AROUND THE PERIPHERY ONGOING CONVECTION.
AS MENTIONED...THE BACKGROUND KINEMATIC FIELD IS EXPECTED TO BECOME
INCREASINGLY FAVORABLE FOR THE DEVELOPMENT OF INTENSE/LONG-LIVED
SUPERCELLS. THUS...STORMS DEVELOPING INVOF THE FRONT ARE LIKELY TO
RAPIDLY ORGANIZE...WITH RISK FOR VERY LARGE HAIL AND DAMAGING WINDS
EXPECTED.
AS STORMS MATURE AND THE LOW-LEVEL SHEAR INCREASES
THROUGH THE AFTERNOON AS SLY H8 FLOW INCREASES TO IN EXCESS OF 40
KT...RISK FOR SIGNIFICANT TORNADOES IS ALSO EXPECTED. SEVERE RISK WILL CONTINUE THROUGH THE EVENING AND INTO THE OVERNIGHT
HOURS...AS STORMS EVOLVE INTO AN ARCING BAND WITH TIME WHICH IS
EXPECTED TO ADVANCE EWD ACROSS NEB/KS/OK...AND THEN SEWD ACROSS TX
AS STORMS DEVELOP SWD ALONG THE PACIFIC FRONT AFTER DARK.
..NRN PLAINS/UPPER MS VALLEY AREA
A RATHER COMPLEX SCENARIO IS LIKELY TO UNFOLD ACROSS THE N CENTRAL
U.S. THIS PERIOD...WITH AN EARLY/ONGOING AREA OF CONVECTION
SPREADING NWD ACROSS THE DAKOTAS/MN. THE RESIDUAL
CLOUDS/PRECIPITATION CAST UNCERTAINTY WITH RESPECT TO DEGREE OF
AFTERNOON DESTABILIZATION -- AND THUS SEVERE POTENTIAL ACROSS THIS
REGION.
ATTM...IT APPEARS THAT POCKETS OF AMPLE DESTABILIZATION WILL DEVELOP
BY LATE AFTERNOON NEAR AND S OF THE WARM FRONT -- PROGGED TO ARC
FROM SERN MT ENEWD ACROSS NWRN SD/ND AND THEN SEWD INTO CENTRAL MN
DURING THE AFTERNOON -- SUCH THAT SCATTERED STORM REDEVELOPMENT
APPEARS LIKELY TO OCCUR. WITH STRONGEST SHEAR EXPECTED FROM THE ERN
HALF OF THE DAKOTAS INTO MN /WITH FLOW BACKING FROM SELY AT LOW
LEVELS TO SLY/SSWLY AT MID LEVELS/...RISK FOR ISOLATED
ROTATING/SEVERE STORMS EVOLVING THROUGH LATE AFTERNOON/EARLY EVENING
IS APPARENT. PRIMARY RISKS WILL BE HAIL AND LOCALLY DAMAGING
WINDS...THOUGH SOME TORNADO RISK IS ALSO APPARENT -- PARTICULARLY
NEAR AND JUST TO THE COOL SIDE OF THE NWD-MOVING WARM FRONT.
..SRN NY/NRN PA/NRN NJ VICINITY
AS OVERNIGHT CONVECTION LINGERING ACROSS THE AREA SHIFTS EWD INTO
SRN NEW ENGLAND...WEAK DIURNAL DESTABILIZATION IS EXPECTED ACROSS
THE PA/NY VICINITY. AS A WEAK VORT MAX SHIFTS EWD ACROSS SRN
ONTARIO AND THE LOWER GREAT LAKES THROUGH THE AFTERNOON...SHOWERS
AND SCATTERED THUNDERSTORMS SHOULD REDEVELOP ACROSS THE AREA.
THOUGH WEAK CAPE EXPECTED ACROSS THE AREA SHOULD LIMIT ANY SEVERE
RISK...AN ISOLATED STRONGER CELL OR TWO -- AIDED BY AMPLY STRONG
FLOW ALOFT -- COULD PRODUCE GUSTY WINDS OR MARGINAL HAIL THROUGH
EARLY EVENING.
..GOSS/GLEASON.. 05/16/2015
hopefully no one was hurt during its life cycle