984
FXUS63 KFSD 221718
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1218 PM CDT FRI OCT 22 2021
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 305 AM CDT FRI OCT 22 2021
LATEST WATER VAPOR LOOP SHOWS A WELL DEFINED WAVE MOVING INTO
WESTERN ND WITH A FAIRLY STRONG UPPER LEVEL JET DIVING INTO CENTRAL
AND EASTERN SD. THIS IS PRODUCING WEAK RETURNS ON RADAR OVER CENTRAL
AND NORTHERN SD EARLY THIS MORNING, BUT MODEL SOUNDINGS ARE SHOWING
A BIT OF A STRUGGLE TO SATURATE IN THE LOWER LEVELS. HOWEVER
COMPARED TO YESTERDAYS MODEL RUNS THE LOWER LEVELS ARE NOT NEARLY AS
DRY, SO PRECIPITATION CHANCES WILL BE A BIT HIGHER THAN PREVIOUSLY
THOUGHT. FORCING IN THE DENDRITIC LAYER MAXIMIZES ACROSS THE AREA,
ESPECIALLY SOUTHEAST SD, THIS MORNING. FOR THE MOST PART IT APPEARS
THAT RAIN SHOWERS WILL BE THE PREDOMINANT WEATHER TYPE, BUT A FEW
SNOWFLAKES ARE NOT IMPOSSIBLE. THE WET BULB TEMPERATURE NOT QUITE
COLD ENOUGH TO SUPPORT SNOW WHERE THE STRONGEST FORCING IS, BUT
PARTS OF SOUTHWEST MN WOULD HAVE THE BETTER CHANCE IF PRECIPITATION
ENDS UP BEING A LITTLE FARTHER NORTH AND EARLY THIS MORNING IN PARTS
OF SOUTHEAST SD BEFORE A TOUCH OF WARMING DEVELOPS. MOST OF THE
PRECIPITATION WILL BE OUT OF THE AREA BY MORNING, POSSIBLY LINGERING
IN NORTHWEST IA THROUGH EARLY AFTERNOON. COOL EASTERLY FLOW IN THE
WAKE OF THIS WAVE WILL LEAVE THE AREA WITH HIGHS AGAIN IN THE UPPER
40S TO MID 50S. BUT WITH LIGHTER WINDS THIS WILL NOT FEEL TOO BAD.
MID AND UPPER LEVEL RIDGING WILL BUILD ACROSS THE AREA TONIGHT SO
EXPECT EAST TO SOUTHEAST FLOW TO SLOWLY INCREASE. STILL SOME
QUESTION ON LOWS BUT SHOULD SEE QUITE A FEW AREAS AROUND OR A COUPLE
OF DEGREES BELOW FREEZING, ESPECIALLY EAST OF THE JAMES RIVER. THIS
SHOULD ALLOW SOME FROST TO DEVELOP. SUSPECT THAT THERE COULD BE A
LITTLE FOG AS WELL WITH A RELATIVELY WET GROUND AND LIGHT WINDS.
LONG TERM
(SATURDAY THROUGH THURSDAY)
ISSUED AT 305 AM CDT FRI OCT 22 2021
AS A STRONG UPPER LEVEL TROUGH DEVELOPS OVER THE WEST COAST AND
SHIFTS EAST INTO THE ROCKIES ON SATURDAY, SOUTHEAST FLOW WILL
INCREASE WITH MARGINALLY BREEZY CONDITIONS EXPECTED. CLOUDS WILL
INCREASE LATE IN THE DAY AS THE TROUGH APPROACHES THE WESTERN HIGH
PLAINS. THE LOW LEVEL THERMAL FIELD NOT OVERLY WARM, BUT SHOULD
SUPPORT MOST LOCATIONS REACHING THE LOW TO MID 50S. ALL IN ALL A BIT
OF A CHILLY DAY.
LATE SATURDAY NIGHT INTO SUNDAY A STRONG TROUGH WILL SPREAD ACROSS
THE PLAINS WITH WARM ADVECTION INCREASING SIGNIFICANTLY. THE MAIN
CHALLENGE FOR PRECIPITATION IN THE AREA WILL BE THE POTENTIAL FOR
CONVECTION SOUTH OF INTERSTATE 80 REDIRECTING THE STRONG LOW TO MID
LEVEL MOISTURE ADVECTION. WHILE THIS MAY BE A PROBLEM STILL BELIEVE
THAT MOST LOCATIONS ALONG AND EAST OF INTERSTATE 29 WILL SEE SOME
RAINFALL. THE GFS IS A BIT OF A NORTHERN OUTLIER WHILE THE ECMWF AND
CANADIAN SUPPORT A BIT MORE OF A SOUTHERN TRACK. ALL MODELS FAIRLY
AGREEABLE ON A STRONG DEEPENING LOW PRESSURE WHICH SHOULD ALLOW FOR
SOME EASTERLY WRAP AROUND IN THE LOW TO MID LEVELS. STILL APPEARS TO
BE THE CHANCE FOR SOME THUNDER IN MAINLY NORTHWEST IA BUT NOT
ANTICIPATING SEVERE. LOWS WILL BE MORE MILD SUNDAY MORNING, MOSTLY
UPPER 30S TO LOWER 40S, BUT DAYTIME TEMPERATURES LIKELY TO NOT RISE
MUCH SO LOWERED HIGHS A TOUCH, AND ONLY EXPECT ABOUT A 5 TO 8 DEGREE
DIURNAL RISE.
MONDAY INTO MONDAY NIGHT WILL SEE UPPER LEVEL RIDGING BRING DRY
CONDITIONS AS THE NEXT STRONG PIECE OF ENERGY MOVES INTO THE
ROCKIES. HIGHS WILL BE ON THE COOL SIDE, MOSTLY UPPER 40S TO LOWER
50S, WITH TUESDAY MORNING LOWS IN THE MID 30S TO LOWER 40S. IF THE
TIMING PANS OUT COULD SEE SOME DRIZZLE DEVELOP MONDAY NIGHT INTO
TUESDAY MORNING AS THE DENDRITIC LAYER APPEARS TOO DRY TO SUPPORT
RAIN, BUT A POTENTIALLY DEEP SURFACE TO 4-5 KFT SATURATED LAYER
COULD DEVELOP.
TUESDAY INTO WEDNESDAY MORNING WILL BE A GOOD CHANCE FOR RAINFALL AS
THE TROUGH MOVES THROUGH. CONFIDENCE NOT OVERLY HIGH AS THE MODELS
ARE TRYING TO RESOLVE WHAT ALL OF THIS ENERGY MOVING ON TO THE WEST
COAST IS GOING TO DO, BUT IF THE WAVE DOES MOVE OUT OF THE AREA
WEDNESDAY MORNING IT APPEARS THAT IT WILL BE A BIT WINDY WEDNESDAY
AND THURSDAY WITH NEAR NORMAL TEMPERATURES.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1214 PM CDT FRI OCT 22 2021
SHOWERS CONTINUE SLIDING TO THE SOUTHEAST THIS AFTERNOON ACROSS
FAR SOUTHEASTERN SD, NORTHEASTERN NE, AND NORTHWESTERN IA. EXPECT
THESE TO CONTINUE TO MOVE OUT OF THE AREA BY 20Z, WITH CEILINGS
AND VISIBILITY IMPROVING FROM MVFR TO VFR AS WELL.
SKIES ARE CLEARING BEHIND THIS PRECIPITATION, LEADING TO VFR
CONDITIONS. VFR IS EXPECTED THROUGH THE REST OF THE PERIOD. SOME
MODEL GUIDANCE LATE THIS MORNING/EARLY THIS AFTERNOON CONTINUES TO
HINT AT FOG/STRATUS DEVELOPMENT AGAIN TONIGHT; HOWEVER, CONFIDENCE
IS TOO LOW AT THIS TIME TO INCLUDE AT ANY SITE.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
SHORT TERM...08
LONG TERM...08
AVIATION...SG
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