010
ACUS03 KWNS 290716
SWODY3
SPC AC 290715
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0215 AM CDT THU JUL 29 2021
VALID 311200Z - 011200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL GREAT LAKES REGION AND FROM THE OZARKS INTO THE MID
MISSISSIPPI VALLEY...
..SUMMARY
MARGINALLY SEVERE THUNDERSTORMS CAPABLE OF ISOLATED DAMAGING WINDS
AND HAIL, WILL BE POSSIBLE ON SATURDAY ACROSS PARTS OF THE GREAT
LAKES REGION AND FROM THE OZARKS TO THE MID MISSISSIPPI VALLEY.
..GREAT LAKES
A BROAD CYCLONIC FLOW PATTERN WILL BE IN PLACE ACROSS THE
NORTHEASTERN THIRD OF THE UNITED STATES ON SATURDAY. AT THE SURFACE,
A COLD FRONT WILL ADVANCE SOUTHWARD ACROSS THE GREAT LAKES REGION. A
NORTHEAST-TO-SOUTHWEST CORRIDOR OF MAXIMIZED LOW-LEVEL MOISTURE WILL
BE IN PLACE AHEAD OF THE COLD FRONT FROM THE MID MISSOURI VALLEY
INTO THE CENTRAL GREAT LAKES. AS SURFACE TEMPERATURES WARM
THROUGHOUT THE DAY IN THE VICINITY OF THE FRONT, A POCKET OF
MODERATE INSTABILITY IS EXPECTED TO DEVELOP. THE INSTABILITY AXIS
SHOULD BE LOCATED FROM SOUTH-CENTRAL WISCONSIN INTO WESTERN LOWER
MICHIGAN BY AFTERNOON. CONVECTION WILL LIKELY INITIATE NEAR THE
FRONT DURING THE LATE AFTERNOON AS INSTABILITY BECOMES MAXIMIZED,
WITH THUNDERSTORMS MOVING SOUTHEASTWARD ACROSS THE CENTRAL GREAT
LAKES REGION. NAM FORECAST SOUNDINGS AT 21Z NEAR MILWAUKEE SUGGEST
THAT DEEP-LAYER SHEAR WILL BE ABOUT 30 TO 35 KT, WHICH SHOULD BE
ADEQUATE FOR AN ISOLATED SEVERE THREAT. THE STRONGER MULTICELLS
COULD GENERATE MARGINALLY SEVERE WINDS ALONG WITH HAIL.
..OZARKS/MID MISSISSIPPI VALLEY
NORTHWEST MID-LEVEL FLOW WILL BE IN PLACE ON SATURDAY FROM THE
NORTHERN PLAINS TO THE MID MISSISSIPPI VALLEY. A SURFACE LOW AND
ASSOCIATED COLD FRONT ARE FORECAST TO MOVE SOUTHWARD ACROSS THE
OZARKS, CENTRAL PLAINS AND SOUTHERN HIGH PLAINS. ALONG AND SOUTH OF
THE FRONT, SURFACE DEWPOINTS FROM THE MID 60S TO THE LOWER 70S F
WILL LIKELY RESULT IN THE DEVELOPMENT OF MODERATE INSTABILITY BY
AFTERNOON. THIS COMBINED WITH LOW-LEVEL CONVERGENCE ALONG THE FRONT
WILL PROVIDE A FOCUS FOR CONVECTIVE DEVELOPMENT. THESE STORMS ARE
FORECAST TO MOVE SOUTHWARD ACROSS CENTRAL AND SOUTHERN MISSOURI
DURING THE LATE AFTERNOON AND EARLY EVENING. MODERATE DEEP-LAYER
SHEAR ALONG WITH THE INSTABILITY SHOULD SUPPORT A POTENTIAL FOR
MARGINALLY SEVERE WINDS, ESPECIALLY AS LOW-LEVEL LAPSE RATES BECOME
STEEP.
..BROYLES.. 07/29/2021
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