354
ACUS03 KWNS 230727
SWODY3
SPC AC 230726
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0226 AM CDT WED SEP 23 2020
VALID 251200Z - 261200Z
..NO SEVERE THUNDERSTORM AREAS FORECAST
..SUMMARY
THE POTENTIAL FOR ORGANIZED SEVERE THUNDERSTORMS ON FRIDAY ACROSS
PARTS OF THE UPPER MIDWEST APPEARS TOO UNCERTAIN TO INCLUDE ANY RISK
AREAS AT THIS TIME.
..UPPER MIDWEST
A STRONG WESTERLY MID/UPPER-LEVEL JET IS FORECAST TO PERSIST ON
FRIDAY ACROSS MUCH OF THE PACIFIC NORTHWEST TO THE NORTHERN ROCKIES
AND NORTH-CENTRAL STATES. A SHORTWAVE TROUGH EMBEDDED WITHIN THIS
FLOW REGIME SHOULD MOVE EASTWARD ACROSS THE UPPER MIDWEST THROUGH
THE PERIOD. AT THE SURFACE, A COLD FRONT WILL LIKEWISE SWEEP
EASTWARD ACROSS THIS REGION, WITH A MODEST INCREASE IN LOW-LEVEL
MOISTURE OCCURRING AHEAD OF THE FRONT ACROSS PARTS OF EASTERN MN
INTO WESTERN WI AND VICINITY. AT THIS POINT, MOST GUIDANCE SUGGESTS
THAT WARM MID-LEVEL TEMPERATURES PRECEDING THE SHORTWAVE TROUGH WILL
KEEP THE WARM SECTOR CAPPED THROUGH THE DAY. STILL, THERE IS A
NON-ZERO CHANCE THAT NEAR-SURFACE-BASED STORMS COULD FORM ALONG OR
JUST AHEAD OF THE FRONT ACROSS PARTS OF EAST-CENTRAL MN INTO
NORTHWESTERN WI BY FRIDAY EVENING. IF THIS OCCURS, THEN SEVERE
THUNDERSTORMS APPEAR POSSIBLE GIVEN THE FORECAST COMBINATION OF WEAK
INSTABILITY WITH STRONG DEEP-LAYER SHEAR. HOWEVER, THE MORE PROBABLE
SCENARIO IS FOR MAINLY ELEVATED STORMS TO FORM NORTH OF THE WARM
SECTOR FRIDAY EVENING/NIGHT IN A LOW-LEVEL WARM ADVECTION REGIME,
WITH A MINIMAL SEVERE RISK FARTHER SOUTH. GIVEN THESE UNCERTAINTIES
AND MODEL DIFFERENCES, HAVE OPTED TO DEFER POSSIBLE INCLUSION OF LOW
SEVERE PROBABILITIES ACROSS THIS REGION TO A LATER OUTLOOK.
..SOUTHEAST
ISOLATED TO SCATTERED THUNDERSTORMS MAY OCCUR ACROSS A BROAD PORTION
OF THE SOUTHEAST ON FRIDAY AS A WEAK, POSITIVELY TILTED SHORTWAVE
TROUGH MOVES EASTWARD OVER THIS REGION. ALTHOUGH MID-LEVEL
SOUTHWESTERLY FLOW SHOULD BE MODESTLY ENHANCED, THE LACK OF ANY
DISCERNIBLE SURFACE LOW, POOR MID-LEVEL LAPSE RATES, AND WEAK
INSTABILITY ALL SUGGEST THAT ANY ORGANIZED SEVERE THUNDERSTORM RISK
SHOULD REMAIN LOW.
..GLEASON.. 09/23/2020
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