161
ACUS01 KWNS 201630
SWODY1
SPC AC 201629
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT SUN APR 20 2025
VALID 201630Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTHERN ARKANSAS AND MISSOURI VICINITY...
..SUMMARY
SEVERE THUNDERSTORMS ARE EXPECTED TODAY ACROSS PARTS OF THE ARKLATEX
INTO THE OZARKS AND MID MISSISSIPPI VALLEY, MAINLY THIS AFTERNOON
AND EVENING. THE BEST CORRIDOR FOR TORNADOES (SOME OF WHICH COULD BE
STRONG) AND SCATTERED TO NUMEROUS DAMAGING WINDS SHOULD EXIST FROM
CENTRAL/NORTHERN ARKANSAS INTO MISSOURI.
..SYNOPSIS
A COMPACT UPPER LOW CURRENTLY MOVING INTO WESTERN OKLAHOMA WILL
SHIFT QUICKLY NORTHEASTWARD THIS AFTERNOON AND TONIGHT, CROSSING
EASTERN KANSAS AND WESTERN MISSOURI THIS EVENING AND THEN CONTINUING
NORTHEASTWARD ACROSS IOWA AND INTO WISCONSIN TONIGHT. FAST
SOUTHWESTERLY FLOW ALOFT WILL EXIST IN ADVANCE OF THIS SYSTEM,
WITHIN THE TIGHT HEIGHT GRADIENT BETWEEN THIS FEATURE AND THE
PERSISTENT RIDGE CENTERED OVER THE SOUTHEAST.
AT THE SURFACE, A DEVELOPING LOW ANALYZED OVER WESTERN OKLAHOMA AT
15Z IS FORECAST TO PROGRESS NORTHEASTWARD ACROSS SOUTHEASTERN KANSAS
AND MISSOURI THROUGH THE AFTERNOON, AND THEN SHOULD CONTINUE
NORTHWARD TOWARD -- AND EVENTUALLY INTO -- SOUTHERN WISCONSIN BY
EARLY MONDAY MORNING. WHILE A WARM FRONT LIFTS NORTHWARD ACROSS THE
MID MISSISSIPPI VALLEY/MIDWEST, A COLD FRONT TRAILING FROM THE LOW
WILL SWEEP EASTWARD INTO/ACROSS MISSOURI AND ARKANSAS THIS AFTERNOON
AND EVENING, AND THEN ACROSS THE MID AND LOWER MISSISSIPPI VALLEYS
THROUGH THE END OF THE PERIOD.
...NORTHEASTERN TEXAS NORTHEASTWARD TO THE WESTERN ILLINOIS
VICINITY...
AN EXPANSIVE AREA OF MULTI-LEVEL CLOUD COVER, ALONG WITH ONGOING
CONVECTION, IS EVIDENT ACROSS WESTERN AND NORTHERN PORTIONS OF THE
RISK AREA LATE THIS MORNING, WHICH CONTINUES TO RETARD MORE
SUBSTANTIAL HEATING AT THIS POINT. WITH THAT SAID, SOME BREAKS IN
THE CLOUDS ARE EVIDENT PER RECENT VISIBLE IMAGERY AS FAR WEST AS
EASTERN OKLAHOMA, WITH THINNING CLOUD COVER WITH
EASTWARD/NORTHEASTWARD EXTENT INTO ARKANSAS AND THE OZARKS.
AS THE SURFACE LOW OVER OKLAHOMA DEEPENS THROUGH THE DAY IN TANDEM
WITH THE ADVANCE OF THE UPPER LOW, NORTHWARD ADVANCE OF THE WARM
FRONT WITH TIME WILL ALLOW A MOIST BOUNDARY LAYER TO LIKEWISE
OVERSPREAD MUCH OF MISSOURI AND ILLINOIS THROUGH SUNSET. THIS,
COMBINED WITH AT LEAST MODEST HEATING ACROSS PORTIONS OF THE AREA
SHOULD YIELD AN AMPLY UNSTABLE ENVIRONMENT (500 TO NEAR 1500 J/KG
MIXED-LAYER CAPE) TO GRADUALLY EVOLVE -- SUPPORTING A STEADY
INCREASE IN CONVECTIVE COVERAGE AND INTENSITY THIS AFTERNOON.
IN CONTRAST TO THE RATHER MODEST THERMODYNAMIC ENVIRONMENT, A VERY
FAVORABLE LOW-LEVEL AND DEEP-LAYER WIND FIELD IS EVIDENT, WITH
RESPECT TO DEVELOPMENT OF ORGANIZED/ROTATING STORMS. AN 80 KT
MID-LEVEL JET WILL SPREAD NORTHEASTWARD ACROSS THE RISK AREA WITH
TIME, ATOP A 50-PLUS KT LOW-LEVEL JET. THIS WILL SUPPORT VIGOROUS
UPDRAFT EVOLUTION, WITH ALL-HAZARDS SEVERE RISK EVOLVING AS A
RESULT. AT THIS TIME, IT REMAINS APPARENT THAT TORNADO POTENTIAL --
INCLUDING RISK FOR A COUPLE OF STRONG TORNADOES -- SHOULD MAXIMIZE
ACROSS THE OZARKS, AND AREAS JUST NORTH AND SOUTH, AS SURFACE WINDS
BACK TO SOUTHEASTERLY AHEAD OF THE DEEPENING/ADVANCING SURFACE LOW.
THE PRIMARY RISK SHOULD EVOLVE WITH AN ANTICIPATED, BROKEN BAND OF
STORMS WITHIN THE COLD-FRONTAL ZONE, INCLUDING EMBEDDED SUPERCELLS.
ALONG WITH THE TORNADO POTENTIAL, FAIRLY WIDESPREAD COVERAGE OF
DAMAGING WIND GUSTS IS ALSO EXPECTED, AS COMPLEX, LEWP/BOW-TYPE
STRUCTURES ARE EXPECTED WITHIN THE BAND OF STORMS, AS CONVECTION
ADVANCES EASTWARD ACROSS MISSOURI AND ARKANSAS TOWARD THE
MISSISSIPPI VALLEY THROUGH THE AFTERNOON AND INTO THE EVENING HOURS.
SEVERE RISK IS EXPECTED TO EXPAND AS FAR NORTH AS SOUTHEASTERN IOWA
AND ADJACENT WESTERN ILLINOIS THIS EVENING, WHERE WEAKER INSTABILITY
IS EXPECTED, AND AS FAR SOUTH AS EASTERN TEXAS WHERE A WEAKER WIND
FIELD WITH SOUTHWARD EXTENT SHOULD LIMIT SEVERE POTENTIAL ON THE
SOUTHERN FRINGE. RISK SHOULD VERY GRADUALLY DIMINISH OVERNIGHT AS
CONVECTION SHIFTS EASTWARD ACROSS THE MID-MISSISSIPPI VALLEY.
..GOSS/HALBERT.. 04/20/2025
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