538
ACUS02 KWNS 150558
SWODY2
SPC AC 150556
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT FRI AUG 15 2025
VALID 161200Z - 171200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE NORTHERN HIGH PLAINS EASTWARD TO THE GREAT LAKES...
..SUMMARY
THUNDERSTORMS WITH A POTENTIAL FOR ISOLATED SEVERE GUSTS AND HAIL
WILL BE POSSIBLE ON SATURDAY FROM PARTS OF THE CENTRAL AND NORTHERN
PLAINS EASTWARD TO THE GREAT LAKES.
..CENTRAL AND NORTHERN PLAINS
AT MID-LEVELS, A RIDGE WILL MOVE ACROSS THE NORTHERN PLAINS ON
SATURDAY, AS SOUTHWESTERLY FLOW REMAINS FROM THE NORTHERN ROCKIES
INTO THE NORTHERN HIGH PLAINS. AT THE SURFACE, AN UPSLOPE FLOW
REGIME WILL REMAIN IN PLACE FROM THE DAKOTAS INTO EASTERN MONTANA.
A SURFACE TROUGH WILL DEEPEN DURING THE DAY OVER THE NORTHERN HIGH
PLAINS. ALTHOUGH LARGE-SCALE ASCENT WILL REMAIN WEAK ACROSS THE
REGION, ISOLATED THUNDERSTORMS MAY DEVELOP IN THE AFTERNOON NEAR THE
SURFACE TROUGH. ADDITIONAL ISOLATED STORMS COULD DEVELOP NEAR AND TO
THE NORTH OF A FRONT LOCATED ACROSS NORTHERN NEBRASKA. TO THE NORTH
OF THE FRONT, A MOIST AND UNSTABLE AIRMASS IS FORECAST. MODERATE
INSTABILITY WILL BE IN PLACE OVER MUCH OF THIS AIRMASS BY AFTERNOON.
ALTHOUGH DEEP-LAYER SHEAR WILL REMAIN NEAR OR BELOW 35 KNOTS OVER
MOST OF THIS AIRMASS, LOW TO MID-LEVEL LAPSE RATES WILL BE STEEP.
THIS COULD BE ENOUGH FOR ISOLATED SEVERE GUSTS AND HAIL WITH ANY
CELL THAT CAN DEVELOP AND PERSIST IN THE LATE AFTERNOON AND EARLY
EVENING.
..UPPER MISSISSIPPI VALLEY/GREAT LAKES
WEST-NORTHWESTERLY MID-LEVEL FLOW WILL REMAIN IN PLACE ON SATURDAY
FROM THE UPPER MISSISSIPPI VALLEY INTO THE GREAT LAKES, AS A
MID-LEVEL RIDGE MOVES ACROSS THE NORTHERN PLAINS. AT THE SURFACE, A
FRONT IS FORECAST TO REMAIN IN PLACE FROM FAR NORTHERN IOWA INTO
SOUTHERN WISCONSIN. FROM NEAR THE BOUNDARY SOUTHWARD, SURFACE
DEWPOINTS ARE FORECAST TO BE IN THE LOWER TO MID 70S F. THIS WILL
CONTRIBUTE TO A STRONGLY UNSTABLE AIRMASS BY AFTERNOON. ALTHOUGH
LARGE-SCALE ASCENT WILL REMAIN WEAK ACROSS THE REGION, ISOLATED
THUNDERSTORMS MAY DEVELOP ALONG PRE-EXISTING BOUNDARIES OR ALONG
ZONES OF MAXIMIZED LOW-LEVEL CONVERGENCE. NAM FORECAST SOUNDINGS
NEAR AND TO THE NORTH OF THE FRONT ACROSS THE UPPER MISSISSIPPI
VALLEY HAVE 0-6 KM SHEAR IN THE 30 TO 40 KNOT RANGE, WITH 700-500 MB
LAPSE RATES OF 7 TO 7.5 C/KM. THIS COULD BE ENOUGH FOR ISOLATED
ROTATING STORMS WITH POTENTIAL FOR HAIL AND SEVERE WIND GUSTS. A
POTENTIAL FOR SEVERE GUSTS COULD EXTEND EASTWARD INTO PARTS OF THE
GREAT LAKES WHERE MODERATE INSTABILITY IS FORECAST, BUT DEEP-LAYER
SHEAR WILL BE MORE MODEST.
..BROYLES.. 08/15/2025
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