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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