338  
FXUS63 KFSD 261707  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
ISSUED BY NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN  
1207 PM CDT THU APR 26 2018  
   
UPDATE
 
 
ISSUED AT 1205 PM CDT THU APR 26 2018  
 
UPDATED TO INCLUDE 18Z AVIATION DISCUSSION BELOW.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 343 AM CDT THU APR 26 2018  
 
AN UPPER LEVEL TROUGH OF LOW PRESSURE WILL SWING THROUGH THE AREA  
TODAY, BUT AT LEAST WITH REGARDS TO PRECIPITATION LITTLE IS EXPECTED  
TO OCCUR. A LEAD SOUTHWEST TO NORTHWEST ORIENTED JET MAX SHOULD  
CONTINUE TO WEAKEN THROUGH THE MORNING AND WHILE IT WILL PROVIDE THE  
AREA WITH A LITTLE MID LEVEL CLOUD COVER DRY LOW LEVELS AND FAIRLY  
STABLE MID LEVELS WILL NOT ALLOW FOR MUCH OF ANY LIGHT RAINFALL. THE  
EXCEPTION COULD BE FAR EASTERN SD INTO SOUTHWEST MN WHERE JUST A  
HINT OF LOWER STABILITY IN THE MID LEVELS IS FORECAST AND COULD  
PROVIDE A VERY SHORT PERIOD OF VERY LIGHT RAINFALL. OVERALL, THE  
IMPACT WILL BE NEGLIGIBLE.  
 
A STRONGER NORTHERLY UPPER LEVEL JET WILL PLUNGE INTO THE AREA  
LATER THIS MORNING AND WILL AID IN ENHANCING MIXING AND THE WIND  
FIELD WHICH WILL LEAD TO A BIT OF A WINDY DAY. THERE SHOULD BE QUITE  
A BIT OF SUNSHINE SO HIGHS FROM THE UPPER 50S TO MID 60S WILL STILL  
FEEL FAIRLY PLEASANT.  
 
AS THE JET SHIFTS TO THE EAST, WEST TO NORTHWEST FLOW WILL REMAIN  
IN PLACE AT THE SURFACE TONIGHT AND WILL HELP KEEP TEMPERATURES  
ON THE MILD SIDE. LOWS GENERALLY MID 30S TO LOWER 40S.  
   
LONG TERM
 
(FRIDAY THROUGH WEDNESDAY)  
ISSUED AT 343 AM CDT THU APR 26 2018  
 
FRIDAY WILL BE ANOTHER WINDY DAY AS A COMBINATION OF GOOD MIXING AND  
DECENT COOL AIR ADVECTION WILL ALLOW FOR GUSTS TO 30 TO 35 MPH.  
TEMPERATURES WILL BE ON THE MILD SIDE AND WILL NEED TO KEEP AN EYE  
ON DEW POINTS AS THE GOOD MIXING COULD RESULT IN LOWER DEW POINTS.  
AFTERNOON RELATIVE HUMIDITY ALREADY FORECAST TO BE 25 TO 35 PERCENT  
SO COULD PROVE TO BE A PROBLEM FOR FIRE WEATHER.  
 
A FAIRLY STRONG HIGH PRESSURE AT THE SURFACE WILL SETTLE IN ON  
FRIDAY NIGHT AND CONTINUE THROUGH SATURDAY. THIS WILL BRING SOME  
COOLER TEMPERATURES BOTH FRIDAY NIGHT AND SATURDAY MORNING BUT WITH  
LIGHTER WINDS AND A LOT OF SUNSHINE SATURDAY SHOULD BE A VERY NICE  
DAY IN THE 60S.  
 
AN UPPER LEVEL RIDGE WILL STRENGTHEN OVER THE AREA ON SUNDAY AND  
MUCH WARMER TEMPERATURES WILL RESULT. ALONG WITH THE WARMER  
TEMPERATURES WILL BE MUCH WINDIER CONDITIONS WITH SOUTHERLY GUSTS  
LIKELY APPROACHING 40 MPH. DEW POINTS SHOULD INCREASE ENOUGH TO HELP  
FIRE WEATHER CONCERNS BUT WITH THAT STRONG OF A WIND AND  
TEMPERATURES IN THE 70S THERE MAY BE SOME PROBLEMS.  
 
SUNDAY NIGHT INTO WEDNESDAY WILL SEE A TROUGH DIG INTO THE ROCKIES  
BUT THIS TIME AROUND THE MODELS ARE A LITTLE MORE AGGRESSIVE IN  
COLLAPSING THE RIDGE EAST AS A SERIES OF STRONGER JET MAXES EJECT  
NORTHWARD. TOO EARLY TO REALLY GET COMFORTABLE WITH A SOLUTION BUT  
SHOULD BE A GOOD CHANCE FOR SHOWERS AND A FEW THUNDERSTORMS DURING  
THIS TIME WITH HIGHS MONDAY IN THE 70S THEN LIKELY 60S TUESDAY AND  
WEDNESDAY. LOW TEMPERATURES MONDAY AND TUESDAY MORNINGS WILL BE VERY  
WARM IN THE 50S.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)  
ISSUED AT 1205 PM CDT THU APR 26 2018  
 
WITH THE EXCEPTION OF GUSTY WINDS THIS AFTERNOON AND A FEW WIND  
SHIFTS, THE FORECAST PERIOD WILL BE QUIET ACROSS THE AREA. THE  
MID/HIGH CLOUDS ASSOCIATED WITH THIS MORNING'S FRONTAL PASSAGE  
HAVE MOVED SOUTHEAST OF THE AREA, LEAVING CLEAR SKIES. WE'LL HAVE  
A BRIEF PERIOD OF HIGH PRESSURE INTO TONIGHT BEFORE ANOTHER  
COLD FRONT DROPS INTO THE AREA LATE TONIGHT AND FRIDAY MORNING.  
WINDS WILL BACK AHEAD OF THE FRONT, THEN VEER ONCE AGAIN IN ITS  
WAKE.  
 

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

 
 

 
 
UPDATE...  
SHORT TERM...08  
LONG TERM...08  
AVIATION...  
 
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