Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 252004
SWODY1
SPC AC 252002

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0302 PM CDT THU AUG 25 2016

VALID 252000Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN MO ACROSS CENTRAL
PARTS OF IL AND INDIANA...

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE LOWER GREAT LAKES FROM
EXTREME SERN LOWER MI ACROSS PARTS OF NRN OH INTO WRN PA...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE TX PANHANDLE INTO
WRN/NORTH CENTRAL OK AND EXTREME SRN KS...

...THERE IS A MRGL RISK OF SVR TSTMS IN A CORRIDOR FROM THE SRN HIGH
PLAINS INTO THE LOWER GREAT LAKES REGION...

...SUMMARY...
STRONG TO SEVERE THUNDERSTORMS CAPABLE OF PRIMARILY DAMAGING WIND
GUSTS AND ISOLATED LARGE HAIL WILL BE POSSIBLE FROM THE SOUTHERN
HIGH PLAINS ACROSS THE LOWER MISSOURI AND MIDDLE MISSISSIPPI VALLEYS
INTO THE LOWER GREAT LAKES REGION.

NO SIGNIFICANT CHANGES HAVE BEEN MADE TO THE PREVIOUS OUTLOOK.
SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND
EVENING IN THE VICINITY OF A FRONTAL ZONE FROM PORTIONS OF THE LOWER
GREAT LAKES SOUTHWEST INTO THE CENTRAL/SOUTHERN PLAINS.  THE PRIMARY
AREAS OF FOCUS  REMAIN ACROSS THE LOWER GREAT LAKES IN ASSOCIATION
WITH A WEAK MID-LEVEL IMPULSE...FROM EASTERN MO INTO CENTRAL INDIANA
WHERE A REMNANT MCV CONTINUES TO LIFT NORTHEAST...AND FROM PORTIONS
OF KS/OK WEST INTO THE TX PANHANDLE.  RECENTLY ISSUED MESOSCALE
CONVECTIVE DISCUSSION NUMBER 1590 CONTAINS THE LATEST SHORT-TERM
THINKING REGARDING CONVECTIVE TRENDS IN THE TX-OK REGION.  A
FORTHCOMING MCD WILL ADDRESS ANTICIPATED CONVECTIVE TRENDS ACROSS
EASTERN MO EAST INTO MUCH OF CENTRAL IL.

..BUNTING.. 08/25/2016

.PREV DISCUSSION... /ISSUED 1122 AM CDT THU AUG 25 2016/

...DISCUSSION...
THE LARGE SCALE UPPER AIR PATTERN WILL UNDERGO MINOR CHANGES DURING
THE PERIOD AS AN UPPER TROUGH REMAINS OVER THE NRN/CENTRAL ROCKIES
AND A DOWNSTREAM LOW AMPLITUDE SHORT WAVE TROUGH MOVES ACROSS
ONTARIO INTO QUEBEC.  TO THE SOUTH...AN UPPER RIDGE WILL REMAIN OVER
THE SERN STATES AS A SERIES OF WEAK PERTURBATIONS ON THE SRN EDGE OF
STRONGER SWLY WINDS ALOFT TRANSLATE NEWD/ENEWD FROM THE SRN HIGH
PLAINS ACROSS THE MIDDLE MS VALLEY AND THE LOWER GREAT LAKES REGION.
 IN ADDITION...AN MCV EVIDENT IN RADAR IMAGERY OVER NWRN MO IS
EXPECTED TO PROGRESS ENEWD INTO CENTRAL IL BY LATER THIS AFTERNOON
AND EVENING.

THE LEADING EDGE OF CLOUDS ASSOCIATED WITH A FRONTAL BOUNDARY FROM
LOWER MI ACROSS NRN MO AND SWWD INTO WRN TX IS EXPECTED TO ENHANCE
DIFFERENTIAL HEATING THIS AFTERNOON...WITH STRONGER DIABATIC HEATING
OCCURRING SOUTH/SOUTHEAST OF THE BOUNDARY.  ALTHOUGH LAPSE RATES
HAVE GENERALLY BECOME LESS STEEP OWING TO AIR MASS MODIFICATION BY
PREVIOUS CONVECTIVE STORMS...SURFACE DEW POINTS GENERALLY IN THE
UPPER 60S TO LOWER 70S IN THE WARM SECTOR REMAIN AND ARE EXPECTED TO
CONTRIBUTE TO DIURNALLY INCREASED INSTABILITY WITH MLCAPE OF
1500-2500 J/KG THIS AFTERNOON.

THREE PRIMARY AREAS OF SEVERE STORM POTENTIAL ARE EXPECTED THIS
AFTERNOON AND EVENING.

...ERN MO ACROSS CENTRAL PARTS OF IL AND INDIANA...
THIS REGION IS AHEAD OF THE MCV CURRENTLY OVER NWRN MO.  A BAND OF
ASCENT IMMEDIATELY IN ADVANCE OF THE MCV WILL MOVE EWD INTO AN
INCREASINGLY UNSTABLE AIR MASS THIS AFTERNOON AND MAY PROVIDE A
FOCUS FOR RENEWED STORM DEVELOPMENT.  AS THE CAP WEAKENS...
CONVECTION IS EXPECTED TO FORM WITHIN A FAVORABLY SHEARED
ENVIRONMENT /EFFECTIVE SHEAR AROUND 40 KT/ WHICH WILL ENHANCE STORM
ORGANIZATION AND INTENSITY.  STRONGER STORMS WILL BE CAPABLE OF
PRODUCING DAMAGING WIND GUSTS AND MARGINALLY SEVERE HAIL AS THEY
SPREAD EWD INTO CENTRAL IL LATER THIS AFTERNOON AND POSSIBLY
CONTINUE INTO CENTRAL INDIANA THIS EVENING BEFORE WEAKENING.

...LOWER GREAT LAKES FROM EXTREME SERN LOWER MI ACROSS PARTS OF NRN
OH INTO WRN PA...
CONSENSUS OF MODEL GUIDANCE IS THAT STORMS WILL DEVELOP THIS
AFTERNOON ACROSS SERN LOWER MI OR NRN OH AND SPREAD INTO PARTS OF
WRN PA BY THIS EVENING.  THIS DEVELOPMENT APPEARS ASSOCIATED WITH
SEVERAL VORTICITY MAXIMA AND A MID-LEVEL JET STREAK THAT ARE
EXPECTED TO MOVE ACROSS THIS REGION DURING THE LATER AFTERNOON AND
EVENING.

CLOUDS ARE DIMINISHING ACROSS NRN OH INTO SWRN NY AND WRN PA AND
THIS SHOULD SUPPORT FURTHER DESTABILIZATION THIS AFTERNOON.  STORMS
ARE EXPECTED TO DEVELOP AND SPREAD ACROSS THE SLIGHT RISK STARTING
IN THE MID/LATE AFTERNOON WITH A THREAT FOR PRIMARILY DAMAGING WIND
GUSTS GIVEN THE STRONGER WESTERLY FLOW AND 35-45 KT VERTICAL SHEAR
OVER THE AREA.

...TX PANHANDLE INTO WRN/NORTH CENTRAL OK AND EXTREME SRN KS...
THE SWD PROGRESSION OF THE FRONT OVER WRN TX IS LIKELY TO END
SHORTLY WITH MODELS INDICATING DEVELOPMENT OF AN ELY/SELY COMPONENT
OF LOW-LEVEL WINDS TO THE NORTH OF THE BOUNDARY BY LATER THIS
AFTERNOON.  THINNING OF CLOUDS OVER PARTS OF THE TX PANHANDLE IS NOW
EVIDENT IN VISIBLE IMAGERY AND THIS WILL SUPPORT GRADUAL
DESTABILIZATION THIS AFTERNOON.  MODEL GUIDANCE INCLUDING CAM
FORECASTS ARE CONSISTENT INITIATING STRONG CONVECTION OVER THE TX
PANHANDLE WITH ACTIVITY DEVELOPING/SPREADING EWD/NEWD THROUGH THE
EVENING HOURS.  MODERATE SWLY WINDS ALOFT WILL CONTRIBUTE TO ZONE OF
30-40 KT VERTICAL SHEAR SUPPORTIVE OF A FEW SEVERE STORMS CAPABLE OF
DAMAGING WINDS AND LARGE HAIL.

$$



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