Severe Storm Outlook Narrative (AC)
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ACUS02 KWNS 231733
SWODY2
SPC AC 231732

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 PM CDT TUE AUG 23 2016

VALID 241200Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS WEDNESDAY AFTERNOON AND EVENING
ACROSS NORTH-CENTRAL AND NORTHEAST KS...SOUTHEAST NEB...NORTHERN MO
AND SOUTHERN IA...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK
AREA FROM THE SOUTHWEST GREAT LAKES/MIDWEST REGION TO THE TX
PANHANDLE...

...SUMMARY...
SCATTERED STRONG TO SEVERE STORMS PRODUCING STRONG WIND GUSTS AND
HAIL ARE EXPECTED FROM NORTHEAST KANSAS...SOUTHEAST NEBRASKA INTO
NORTHERN MISSOURI AND IOWA WEDNESDAY AFTERNOON AND EVENING.
ISOLATED SEVERE STORMS WILL BE POSSIBLE FROM THE TEXAS PANHANDLE
NORTHEASTWARD THROUGH CENTRAL MISSOURI TO SOUTHERN
WISCONSIN...SOUTHWEST LOWER MICHIGAN...AND INDIANA.

...SYNOPSIS...
AN UPPER LOW...CURRENTLY MOVING THROUGH SOUTHERN SASKATCHEWAN PER
SATELLITE IMAGERY...WILL REMAIN PROGRESSIVE ON WEDNESDAY AS IT
TRACKS ACROSS SOUTHERN MANITOBA INTO ONTARIO...WITH STRONGEST
ATTENDANT MIDLEVEL WINDS SPREADING FROM THE DAKOTAS INTO MN AND
EVENTUALLY THROUGH NORTHERN WI AND UPPER MI.  DETERMINISTIC MODELS
TEND TO AGREE THAT THE SOUTHWEST STATES/FOUR CORNERS TROUGH WILL
WEAKEN THIS FORECAST PERIOD AS MOST OF THE REMAINING MIDLEVEL
IMPULSES EJECT TO THE NORTHEAST THROUGH NORTHERN OK AND THE CENTRAL
PLAINS TO MO/IA TOWARD THE GREAT LAKES.  THESE PERTURBATIONS WILL
TEND TO DAMPEN IN AMPLITUDE AS THEY MOVE THROUGH A CONFLUENT FLOW
REGIME LOCATED BETWEEN THE SOUTHERN CANADA UPPER LOW AND A
SUB-TROPICAL RIDGE CENTERED OVER THE GULF COAST STATES.  MODELS TEND
TO AGREE WITH ONE SUCH MIDLEVEL IMPULSE AS IT MOVES INTO NORTHEAST
KS/SOUTHEAST NEB INTO NORTHERN MO/SOUTHERN IA WEDNESDAY AFTERNOON
AND EVENING...WITH 40-50-KT SOUTHWESTERLY 500-MB WINDS.

AT THE SURFACE...A COLD FRONT ATTENDANT TO THE SOUTHERN CANADA UPPER
LOW SHOULD BE MOVING INTO EASTERN MN...WESTERN IA TO NORTH-CENTRAL
AND WESTERN KS.  THIS BOUNDARY WILL ADVANCE TO THE EAST AND MORE
SLOWLY TO THE SOUTH...AND SHOULD EXTEND BY MID-LATE WEDNESDAY
AFTERNOON FROM CENTRAL WI TO NORTHEAST THROUGH SOUTHWEST IA TO THE
EASTERN BORDER AREA OF NEB/KS...AND THEN WESTWARD INTO WESTERN KS.

...NERN KS/SOUTHEAST NEB THROUGH NORTHERN MO/SOUTHERN IA...
THE COMBINATION OF AN EXISTING MOIST WARM SECTOR /SURFACE DEW POINTS
IN THE MID 60S TO LOWER 70S AND PRECIPITABLE WATER VALUES OF 1.5-2.0
INCHES/...STEEP MIDLEVEL LAPSE RATES /7-7.5 C PER KM/ SPREADING FROM
NEB/KS INTO IA/NORTHERN MO AND SURFACE HEATING WILL RESULT IN
MODERATE INSTABILITY /MUCAPE 1500-2500 J PER KG/.  MEANWHILE...
INITIAL WESTERLY LOW-LEVEL WINDS ACROSS KS/MO ARE EXPECTED TO BACK
SOME TO SOUTH/SOUTHWESTERLY WEDNESDAY AFTERNOON...SUPPORTING AN
INCREASE IN LOW-LEVEL CONVERGENCE ALONG THE COLD FRONT AS IT MOVES
INTO THE SLIGHT RISK AREA.  THIS ASCENT COMBINED WITH WEAK HEIGHT
FALLS AND FORCING FOR ASCENT WITH THE APPROACHING SHORTWAVE TROUGH
IS EXPECTED TO RESULT IN THUNDERSTORM DEVELOPMENT IN VICINITY OF THE
FRONT.  THE FAVORABLE THERMODYNAMICS COUPLED WITH VERTICALLY VEERING
WINDS AND STRENGTHENING BULK SHEAR SUGGEST BOTH SUPERCELLS AND LINE
SEGMENTS WILL BE POSSIBLE... PRODUCING PRIMARILY STRONG WIND GUSTS
AND HAIL.

STORM COVERAGE ALONG THE EXTENT OF THE COLD FRONT WILL TEND TO SHIFT
EQUATORWARD...WITH SOME POTENTIAL FOR STRONGER STORMS TO MOVE INTO
IL WEDNESDAY EVENING.  THE EASTERN PART OF THE SLIGHT RISK AREA MAY
NEED TO BE EXTENDED INTO PART OF NORTH-CENTRAL IL IN LATER
OUTLOOKS...IF SUFFICIENT DESTABILIZATION CAN OCCUR IN THE WAKE OF
ONGOING/EARLY PERIOD CONVECTION AND ASSOCIATED CLOUDINESS EAST OF
IA. OTHERWISE...THE OVERALL SEVERE-WEATHER THREAT SHOULD GRADUALLY
DIMINISH WEDNESDAY NIGHT WITH WEAKENING INSTABILITY.

...MIDWEST TO LOWER MI...
ONE OR MORE CLUSTERS OF STORMS SHOULD BE ONGOING AT THE START OF DAY
2 ACROSS THE UPPER AND MID MS VALLEY.  THIS ACTIVITY AND ATTENDANT
CLOUDINESS WILL SPREAD EAST AS A MIDLEVEL TROUGH MOVES THROUGH THE
GREAT LAKES REGION DURING THE FIRST HALF OF THIS FORECAST PERIOD.
DESTABILIZATION MAY BE LIMITED...DUE TO EXTENSIVE CLOUDINESS...AND
THUS LIMIT THE INTENSITY OF NEW STORMS THAT MAY FORM AS THIS
ACTIVITY SPREADS EAST.

...CENTRAL KS TO THE TX PANHANDLE...
STRONG HEATING WILL OCCUR FROM SOUTHERN KS INTO THE TX PANHANDLE AND
ALSO INTO THE HIGH PLAINS OF CO AND NM.  MODELS SUGGEST INSTABILITY
WILL BE MARGINAL WITH BULK SHEAR SUFFICIENT FOR STORM ORGANIZATION.
THIS AND STEEP LAPSE RATES SHOULD SUPPORT HAIL AND LOCALLY STRONG
WINDS WITH STORMS THAT DEVELOP ACROSS THESE AREAS.

..PETERS.. 08/23/2016

$$


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