974  
FXUS63 KFSD 182256  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
556 PM CDT FRI JUL 18 2025  
   
KEY MESSAGES  
 
- STRONG TO SEVERE STORMS ARE POSSIBLE THIS EVENING AND NIGHT.  
STORMS LOOK TO DEVELOP ALONG AND NORTH OF HIGHWAY 14 LATE THIS  
AFTERNOON. INITIAL STORMS TRACK SOUTHEAST, WITH RENEWED  
DEVELOPMENT NEAR I-90 LATE IN THE EVENING.  
 
- LARGE HAIL UP TO 2 INCHES, DAMAGING WINDS TO 70 MPH, A BRIEF  
TORNADO, AND BRIEF LOCALLY HEAVY RAINFALL ARE ALL POSSIBLE.  
STORMS LOOK TO EXIT THE AREA BY 3-4 AM.  
 
- SATURDAY LOOKS TO BE A MOSTLY DRY DAY WITH LOW RISK (20%) FOR  
THUNDERSTORMS NEAR THE MISSOURI RIVER/HIGHWAY 20 LATE IN THE  
DAY.  
 
- ADDITIONAL CONVECTION DEVELOPS SUNDAY NIGHT INTO MONDAY AND  
SLIDE EAST, SOME OF WHICH COULD BE STRONG TO SEVERE.  
 
- AN ACTIVE PATTERN PERSISTS ALOFT MONDAY THROUGH FRIDAY NEXT  
WEEK WHICH LOOKS TO BRING DAILY CHANCES FOR SHOWERS AND  
STORMS. MACHINE LEARNING GUIDANCE SUGGESTS THAT THE STORMS  
COULD BE STRONG TO SEVERE.  
 
 
   
DISCUSSION  
 
ISSUED AT 211 PM CDT FRI JUL 18 2025  
 
THIS AFTERNOON: WE'RE CONTINUING TO SEE MID-LVL ACCAS DRIFT THROUGH  
THE REGION AT MID-AFTERNOON AS 850:700 MB WINDS REMAIN VEERED TO THE  
SOUTHWEST. SATELLITE AND SURFACE OBSERVATIONS SHOW A SURFACE LOW  
WEST OF VALENTINE WITH AN ELONGATED FRONTAL BOUNDARY LIFTING  
NORTHWARD THROUGH CENTRAL SOUTH DAKOTA AND THEN CURVING EASTWARD  
JUST NORTH OF HIGHWAY 14. STABLE STRATUS LAYER CONTINUES TO  
INDICATE FAIRLY WIDESPREAD STABILITY THROUGH THE REGION, WITH NARROW  
CORRIDOR OF LOWER STABILITY FORMING ALONG THE HIGHWAY 14 CORRIDOR  
NEAR SURFACE BOUNDARY. 30 KNOT SURFACE GUSTS INTO THIS BOUNDARY ARE  
SERVING TO ENHANCE LOW-LVL CONVERGENCE AND SHOULD FURTHER  
DESTABILIZE THE ATMOSPHERE BY 5PM. ALOFT, FORCING MECHANISMS  
HAVE BEEN MORE DIFFICULT TO PICKUP, BUT WV SHOWING CLEAR  
SHORTWAVE LEAVING EASTERN MONTANA AND MOVING INTO NORTHWESTERN  
SODAK THIS AFTERNOON. THIS WAVE SHOULD HELP DEVELOP CONVECTION  
LATE THIS AFTERNOON OR EARLY EVENING.  
 
FRIDAY EARLY EVENING AND NIGHT: A MODESTLY UNSTABLE ENVIRONMENT  
REMAINS IN PLACE SOUTH OF THE AFOREMENTIONED BOUNDARY, WITH  
EXPECTATIONS OF 1500 TO 2500 J/KG MLCAPE FORMING THROUGH THE  
EVENING. A STUBBORN EML WILL REMAIN PROBLEMATIC AND MAY DELAY  
DEVELOPMENT FURTHER SOUTH TOWARDS I-90 TOWARDS THE LATE EVENING  
HOURS. WHILE THERE HAS BEEN CONSIDERABLE BOUNCING AROUND OF CAMS  
TODAY, A FEW MORE CONSISTENT SIGNALS FOR CONVECTIVE DEVELOPMENT  
NEAR OR NORTH OF HIGHWAY 14 LATE THIS AFTERNOON CONTINUE,  
FOCUSING AT THE APEX OF INCREASES SURFACE AND DEEP MOISTURE  
CONVERGENCE. EVENTUAL STORMS WILL BE SHIFTING EAST AND SOUTHEAST  
ALONG THE EDGE OF THE EML INTO WESTERN AND SOUTHWESTERN  
MINNESOTA INTO EARLY/MID EVENING. EFFECTIVE SHEAR OF 40 TO 45  
KNOTS (ESPECIALLY MID-UPPER COLUMN) SHOULD SUPPORT A FEW  
ROTATING SUPERCELLS CAPABLE OF GOLF BALL OR LARGER HAIL. AS THE  
EVENING PROGRESSES ONWARD, ADDITIONAL DEVELOPMENT MAY BEGIN TO  
FORM NEAR THE I-90 CORRIDOR IN THE 8-10PM TIMEFRAME AS LOW-LVL  
FLOW BEGINS TO INCREASE. WHILE HAIL WILL BE THE PRIMARY RISK IN  
CONVECTION THROUGH MIDNIGHT, MODEST COLD POOL DEVELOPMENT ALONG  
WITH INTRUSION OF MID-LVL DRY AIR COULD FORCE CONVECTION  
TOWARDS A WIND RISK AS STORMS FORM DEEPER INTO THE NIGHT AND  
SHIFT INTO SOUTHERN SOUTH DAKOTA AND IOWA. ONE ASPECT OF THIS  
EVENT WE'LL HAVE TO MONITOR IS THE EVENTUAL RAMP-UP OF LOW-LVL  
FLOW AND RAPIDLY INCREASING 0-1KM HELICITY, ESPECIALLY AS THE  
BOUNDARY LAYER REMAINS MOSTLY MIXED AND LCLS STAY LOW DEEP INTO  
THE NIGHT ALONG AND SOUTH OF I-90. THIS COULD INCREASE THE  
TORNADIC RISK TOWARDS LATE EVENING AND EARLY OVERNIGHT.  
CONVECTION WILL DRIFT SOUTHEAST AND SHOULD EXIT BY 3AM.  
 
SATURDAY: HIGH PRESSURE SINKS INTO THE REGION EARLY SATURDAY, LIKELY  
ALLOWING STRATUS TO DEVELOP AND PATCHY FOG THROUGH MID-MORNING.  
CONVECTIVE CHANCES MAY BEGIN TO REDEVELOP BY MID-LATE AFTERNOON  
SATURDAY, WITH MLCAPE PLOTS SUGGESTING THE GREATEST POTENTIAL  
ALONG AND SOUTH OF THE MISSOURI RIVER AND HIGHWAY 20 AREAS.  
INCREASING MID-LVL FLOW AND APPROACHING VORTICITY COULD SPELL  
SOME INCREASED SEVERE WEATHER RISKS FROM LATE AFTERNOON THROUGH  
MID-EVENING.  
 
SUNDAY: MID-LVL HEIGHTS INCREASE EARLY SUNDAY, WHICH SHOULD KEEP  
CONVECTION IN THE WEST RIVER AREAS THROUGH MOST OF SUNDAY. FURTHER  
EAST, HIGH PRESSURE WILL KEEP CONDITIONS COOLER. NOCTURNAL  
CONVECTION RISKS INCREASE LATE SUNDAY NIGHT INTO MONDAY AS THE LLJ  
INCREASES AND A MID-LVL SHORTWAVE MOVES THROUGH THE PLAINS. A LOW  
(MARGINAL) RISK OF SEVERE STORMS WILL BE POSSIBLE.  
 
MONDAY-FRIDAY: THE PATTERN THROUGH MOST OF NEXT WEEK REMAINS HIGHLY  
UNSETTLED WITH A BUILDING, BUT FLAT MID-LVL RIDGE MOVING OVER THE  
CENTRAL CONUS. THIS TYPICAL MID-SUMMER MCS PATTERN SHOULD BRING BOTH  
WARMER TEMPERATURES BUT ALSO SURGING SURFACE DEW POINTS. MULTIPLE  
DAYS OF SEVERE WEATHER RISKS MAY BE UPON US NEXT WEEKS, MOSTLY  
FOCUSED LATE IN THE EVENING AND THROUGH THE OVERNIGHT HOURS.  
REGARDING DEW POINTS, IT'S MOST LIKELY THE CASE THAT NBM DEW POINTS  
ARE TOO LOW GIVEN VEGETATION GROWTH, RECENT RAINFALL, AND MOISTURE  
CONVERGENCE.  
 
 
   
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/  
 
ISSUED AT 542 PM CDT FRI JUL 18 2025  
 
NO SIGNIFICANT CHANGES FROM THE PREVIOUS TAFS. A MIX OF VFR AND  
MVFR CEILINGS REMAIN IN PLACE THIS AFTERNOON. ISOLATED TO  
SCATTERED SHOWERS CONTINUE ACROSS THE AREA LATE THIS AFTERNOON.  
BEGINNING TO SEE CONVECTION FIRE NEAR AND NORTH OF US HWY 14  
(WITH THE STRONGEST CELL AT THE TIME OF THIS DISCUSSION NEAR  
KATY). EXPECT CONVECTION TO CONTINUE TO DEVELOP THIS EVENING AND  
MOVE SOUTHEAST, WITH ADDITIONAL DEVELOPMENT NEAR I-90 LATER  
TONIGHT. CONFIDENCE IN TIMING/SPREAD OF CONVECTION REMAINS LOW  
AS CAMS CONTINUE TO HANDLE CURRENT DEVELOPMENT POORLY. STORMS  
COULD BE STRONG TO SEVERE WITH ALL MODES POSSIBLE.  
 
OTHERWISE, GUIDANCE CONTINUES TO SHOW STRATUS AND/OR FOG  
DEVELOPING AFTER STORMS ROLL THROUGH TONIGHT, LEADING TO MVFR TO  
IFR OR LOWER CONDITIONS. IMPROVEMENT IS EXPECTED THROUGH THE  
LATE MORNING AND EARLY AFTERNOON HOURS.  
 
ISOLATED TO SCATTERED SHOWERS AND STORMS MAY DEVELOP ONCE AGAIN  
TOMORROW AFTERNOON, WITH THE GREATEST CHANCES SOUTH OF I-90 AND  
TOWARD US HWY 20. WILL OMIT FROM KSUX FOR NOW GIVEN LOW CHANCES  
AND LOW CONFIDENCE.  
 
 
   
FSD WATCHES/WARNINGS/ADVISORIES  
 
SD...NONE.  
MN...NONE.  
IA...NONE.  
NE...NONE.  
 
 
 
 
 
DISCUSSION...DUX  
AVIATION...SG  
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