Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 041737
SWODY2
SPC AC 041736

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1236 PM CDT SAT JUL 04 2015

VALID 051200Z - 061200Z

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF EASTERN SD AND
WESTERN MN...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NORTHERN
PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE CENTRAL HIGH PLAINS TO
UPPER MS VALLEY...

...SUMMARY...
THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS AND LARGE HAIL ARE
EXPECTED SUNDAY ACROSS PARTS OF NORTHERN PLAINS FROM NORTHERN
NEBRASKA ACROSS SOUTH DAKOTA AND INTO PORTIONS OF EASTERN NORTH
DAKOTA AND MUCH OF SOUTHERN MINNESOTA.

...OVERVIEW...
NORTHERN FLANK OF MID/UPPER RIDGE EXTENDING FROM FOUR CORNERS TO
CENTRAL PLAINS WILL BE DAMPENED CONSIDERABLY THIS PERIOD DUE IN PART
TO A PROGRESSIVE SHORTWAVE TROUGH DIGGING EAST-SOUTHEAST FROM THE
CANADIAN ROCKIES TO THE PRAIRIES. A FURTHER DAMPENING INFLUENCE IS
FORECAST TO OCCUR AS A COHERENT IMPULSE TRANSLATES EAST AROUND THE
NORTHERN PERIPHERY OF THE RIDGE...FROM THE NORTHERN GREAT BASIN TO
NORTHERN HIGH PLAINS...THROUGH SUNDAY NIGHT. RESULTANT PHASING OF
THE MIDLEVEL HEIGHT FIELD...FROM THE NORTHERN PLAINS TO UPPER MS
VALLEY...WILL CONTRIBUTE TO A BELT OF FASTER WESTERLY FLOW ALOFT AND
MODEST HEIGHT FALLS THROUGH LATE SUNDAY.

THERE IS BETTER AGREEMENT AMONGST LATEST GLOBAL MODELS AND ENSEMBLE
SYSTEMS THAT SUBSTANTIAL CONVECTIVE DEVELOPMENT WILL OCCUR ACROSS
EASTERN SD INTO MN LATE SUNDAY AS A SLOW-MOVING COLD FRONT AND LEE
CYCLONE/FRONTAL WAVE DEVELOP INTO THESE AREA AMIDST STRONG
DESTABILIZATION.

A BROAD AND LUMBERING MID/UPPER TROUGH...ACCOMPANIED BY 20-30 KT
500MB FLOW ON ITS EASTERN FLANK...WILL SPREAD VERY WEAK HEIGHT FALLS
EAST-NORTHEAST FROM THE DEEP SOUTH TO SOUTHEAST. FORWARD PROGRESS OF
THIS DISTURBANCE WILL BE SLOWED BY AN EVOLVING BLOCK IN THE FORM OF
A BENT-BACK RIDGE ACROSS THE NORTHEAST.

...NORTHERN PLAINS...
MID/UPPER JET IS FORECAST TO PROGRESS EAST ALONG THE U.S./CANADA
BORDER AS A COLD FRONT SPREADS SOUTH/SOUTHEAST ACROSS ND/WRN SD AND
ADJACENT ERN WY THROUGH THE DAY. DEEP LAYER SHEAR AHEAD OF
THE COLD FRONT WILL NOT BE PARTICULARLY STRONG AND WARM SECTOR
AIRMASS OVER THE PLAINS SHOULD REMAIN CAPPED FOR MUCH OF THE
AFTERNOON. EARLY CONVECTION APPEAR MOST LIKELY IN TWO AREAS EITHER
SIDE OF THE HIGHER SEVERE PROBABILITIES. 1) IN POST-FRONTAL/UPSLOPE
REGIME ACROSS WY/SD BORDER AREA...AND 2) ON THE EDGE OF THE CAP AND
NOSE OF DIURNALLY WEAKENING LLJ ACROSS CENTRAL AND NRN MN. HAIL WILL
BE POSSIBLE FROM SOME OF THE WY/SD BORDER STORMS WHILE ISOLATED TO
SCATTERED HAIL AND WIND WILL BE POSSIBLE WITH THE MN CONVECTION.

GREATER SEVERE WEATHER POTENTIAL IN THE FORM OF LARGE HAIL AND
DAMAGING WINDS IS EXPECTED TO EVOLVE DURING THE EVENING FROM
NORTHEAST SD INTO SOUTHWEST MN. IT IS HERE WHERE STRONGEST
DESTABILIZATION IS INDICATED IN LATEST GUIDANCE WITH SBCAPE OF
2000-3000 J/KG DEVELOPING IN THE PRESENCE OF STRONG HEATING AND EML
PLUME EMANATING FROM THE WESTERN U.S./ROCKIES. PRE-FRONTAL BOUNDARY
LAYER MOISTENING AND PERSISTENT/FOCUSED ASCENT ALONG THE SLOWLY
ADVANCING FRONT...IN CONCERT WITH INCREASING LARGE-SCALE FORCING FOR
ASCENT FROM PHASING SHORTWAVE TROUGHS...SHOULD ACT TO OVERCOME
REMAINING INHIBITION BY EVENING WITH ROBUST CONVECTION FOLLOWING.
STRONGEST UPPER DIVERGENCE WILL OVERSPREAD THE REGION THROUGH LATE
EVENING COINCIDENT WITH DIURNAL STRENGTHENING OF LLJ TO 40-60KT.
INITIAL STORMS NEAR FRONT AND ANY FRONTAL WAVE WILL HAVE THE CHANCE
AT PRODUCING LARGE HAIL. THERE IS AN INCREASING CHANCE FOR STORMS TO
ORGANIZE INTO A SMALL FORWARD PROPAGATING MCS WITH TIME. THIS SYSTEM
MAY POSE A SEVERE WIND RISK WELL INTO THE NIGHT AS IT TRACKS FROM SD
ACROSS SOUTHERN MN.

..CARBIN.. 07/04/2015



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