May 16, 2015

Post date: May 16, 2015 1:41:04 PM

Saturday, May 16, 2015 @ 0730 MDT: Yesterday's chase was from Kansas into Colorado and the panhandle of Nebraska, and though we didn't see any tornadoes, we *did* see lots of activity (See photos HERE!), including several funnel clouds, lots of hail, localized flooding and lots of torrential rain and winds. There was even a significant gust front as we headed to our hotel for the night!

Today, our final day with the Tour 1 chasers, we have another good opportunity for nice storms. The area of interest is a broad one, as seen in the illustration below. Our complication is that we cannot stray too far north because we will need to get the Tour 1 folks back to OKC in time for their flights out tomorrow, and to pick up the Tour 2 chasers. That means that we will need to play around the southern area of the storms, likely drifting along the dryline and cherry-picking whichever cells catch our interest. It is likely going to be a very VERY long day, and a late arrival in Norman, OK at our home base, the Days Inn (formerly the Guest Inn). Keep your fingers crossed that we can catch some really good storms as a nice going-away present for our departing friends!

Forecast Discussion

SPC AC 160559

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 .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

Saturday, May 16, 2015 @ 1125 CDT: We have left the dreaded G-town now and are bound for Oklahoma. Nothing good ever happens there anyway. *lol*

A Public Severe Weather Outlook (PWO) has been issued for today.