932  
FXUS63 KFSD 191743  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
1243 PM CDT TUE MAR 19 2019  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 412 AM CDT TUE MAR 19 2019  
 
WARM AIR ADVECTION AHEAD OF A SHORT WAVE DROPPING SOUTH ACROSS THE  
WESTERN HALF OF THE STATE WILL LEAD TO PRECIPITATION ACROSS  
NEBRASKA, POSSIBLY SNEAKING AS FAR NORTH AS THE MISSOURI RIVER  
VALLEY. EARLY TODAY, THERE MAY BE SOME RADAR ECHOES ACROSS THE  
MISSOURI VALLEY, BUT WILL BE FIGHTING A FAIR AMOUNT OF DRY AIR IN  
THE LOW LEVELS. HOWEVER, ATMOSPHERE CONTINUES TO SATURATE IN THE  
LOWER LEVELS, AND BY THIS AFTERNOON, SHORT TERM HI RES MODELS  
INDICATE SOME WEAK INSTABILITY SOUTH OF HIGHWAY 18. COULD SEE AN  
ISOLATED SHOWER THROUGH THE EARLY EVENING HOURS.  
 
FAIR AMOUNT OF CLOUDS ACROSS THE AREA TONIGHT WILL KEEP TEMPERATURES  
FROM FALLING TOO FAR BELOW FREEZING.  
   
LONG TERM
 
(WEDNESDAY THROUGH MONDAY)  
ISSUED AT 412 AM CDT TUE MAR 19 2019  
 
MODELS ARE DISAGREEING WITH THE AMOUNT OF COOLING IN NORTHWEST FLOW  
ON WEDNESDAY. ECMWF IS THE WARMEST, NAM IS THE COOLEST WITH THE GFS  
IN THE MIDDLE. HEDGED THE FORECAST TOWARDS THE MIDDLE, RESULTING IN  
HIGHS SIMILAR TO TODAY.  
 
WARMING TREND IS EXPECTED THURSDAY THROUGH SUNDAY ACROSS THE AREA.  
LARGE UPPER TROUGH IS EXPECTED TO MOVE ONSHORE ACROSS THE WEST COAST  
ON WEDNESDAY, AND MOVE INTO THE PLAINS THIS WEEKEND. AS THIS WAVE  
LIFTS NORTHEAST, IT RUNS INTO AN ELONGATED UPPER RIDGE EXTENDING  
FROM CENTRAL CANADA INTO THE SOUTHEASTERN US. THIS KEEPS THE  
DISTURBANCE FROM ADVANCING, AND WITH IT HANGING AROUND THE REGION  
THROUGH AT LEAST EARLY NEXT WEEK, COULD SEE SCATTERED SHOWERS ACROSS  
THE REGION. WITH THE MILD AIR MASS, AND DEW POINTS IN THE 40S, AM  
ANTICIPATING A RAPID MELT AND A RAPID RISE ALONG AREA RIVERS AND  
STREAMS. ADDITIONAL PRECIPITATION FROM THE SYSTEM WILL ONLY ADD TO  
THE FLOODING CONCERNS.  
 
SECOND SYSTEM IS EXPECTED TO FOLLOW ON THE HEELS OF THE FIRST SYSTEM  
MOVING ON SHORE FRIDAY NIGHT. THIS SYSTEM IS EXPECTED TO SLIDE  
ACROSS THE SOUTHERN TIER OF STATES, BUT AS IT MOVES BY, DISLODGES  
THE UPPER LOW LINGERING ACROSS THE NORTHERN PLAINS. AS THIS SYSTEM  
STARTS TO SHIFT SOUTH ON MONDAY, NORTHEAST WINDS DEVELOP DRAWING  
COOLER AIR INTO THE REGION. HAVE LOWERED HIGHS COMPARED TO THE  
GUIDANCE, BUT AM NOT AS COOL AS MIXING WOULD SUGGEST.  
 
TEMPERATURES LOOK TO REBOUND NEXT WEEK, POTENTIALLY LEADING TO EVEN  
WARMER WEATHER THAN IS EXPECTED THIS WEEKEND.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)  
ISSUED AT 1232 PM CDT TUE MAR 19 2019  
 
MVFR CEILINGS OVER CENTRAL SD WILL CONTINUE TO PROGRESS EAST-  
SOUTHEAST ALONG THE MISSOURI RIVER THIS AFTERNOON AND EVENING.  
EXPECT MVFR CONDITIONS AT KHON INTO LATE EVENING. LOW CLOUDS AND  
POSSIBLY SOME FOG ARE EXPECTED NORTH OF I-90 LATE TONIGHT, BEFORE  
WIDESPREAD STRATUS SPREAD SOUTHWARD INTO THE REGION LATE WEDNESDAY  
MORNING.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 412 AM CDT TUE MAR 19 2019  
 
WHILE THE FIRST CREST TO AREA RIVERS HAS PASSED, THE FLOODING  
CONTINUES FOR MANY AREAS. IN FACT, MELTING CONDITIONS EARLY THIS  
WEEK SHOULD RESULT IN FLUCTUATING RIVER STAGES AS DIURNAL MELT  
WORKS INTO THE SYSTEMS. MUCH WATER REMAINS IN SNOWPACK NORTH OF  
I-90 (3 TO 8 INCHES OF LIQUID EQUIVALENT ACCORDING TO NOHRSC  
ANALYSIS), SO THE CONTINUED TREND TOWARD WARMER TEMPS AND ALSO  
OVERNIGHT LOWS MODERATING ABOVE FREEZING LATE WEEK WILL ACCELERATE  
THE MELT. SIGNIFICANT RIVER FLOODING WILL AGAIN RESULT FROM  
RUNOFF BY THIS WEEKEND INTO NEXT WEEK, INITIATING TOWARD THE  
HEADWATERS OF EACH BASIN. WILL ALSO BE KEEPING AN EYE ON WEEKEND  
PRECIPITATION, BUT AT THIS POINT ENOUGH UNCERTAINTY IN  
TIMING/AREAS/AMOUNTS TO TIE DOWN ANY POTENTIAL INFLUENCE ON THE  
OVERALL INCREASING FLOOD THREAT FROM THE MELT.  
 

 
   
FSD WATCHES/WARNINGS/ADVISORIES
 
 
SD...NONE.  
MN...NONE.  
IA...NONE.  
NE...NONE.  

 
 

 
 
SHORT TERM...BT  
LONG TERM...BT  
AVIATION...05  
HYDROLOGY...CHAPMAN  
 
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