281
FXUS63 KFSD 242342 AAA
AFDFSD
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SIOUX FALLS SD
642 PM CDT THU JUN 24 2021
SHORT TERM
(THIS EVENING THROUGH FRIDAY)
ISSUED AT 335 PM CDT THU JUN 24 2021
THE FOCUS OF THE SHORT-TERM FORECAST IS THE POTENTIAL FOR
CONVECTION TONIGHT AND FRIDAY. THE SURFACE FRONT HAS NOW SETTLED
OVER FAR SOUTHERN NEBRASKA AND INTO SOUTHERN IOWA. THE 850 MB
FRONT EXTENDS FROM THE NEBRASKA AND SOUTH DAKOTA BORDER INTO
NORTHWESTERN IOWA. AS THE JET STREAK COMES INTO THE PLAINS LATER
THIS AFTERNOON, STORMS ARE EXPECTED TO DEVELOP NEAR THE SURFACE
BOUNDARY. THIS SHOULD REMAIN THE FOCUS OF CONVECTION MUCH OF THE
NIGHT. TOWARD SUNRISE ON FRIDAY, ANOTHER JET STREAK WILL MOVE
INTO CENTRAL NEBRASKA WITH THE EXIT REGION APPROACHING THE SIOUX
CITY AREA. LAPSE RATES ARE LESS THAN 7 C/KM AND EVEN ELEVATED
INSTABILITY IS LIMITED BUT INTERACTION WITH THE 850 MB FRONT
RESULT IN ISOLATED SHOWERS OR THUNDERSTORMS ON FRIDAY MORNING. AS
THE JET STREAK CONTINUES TO TRACK NORTHEAST THROUGH THE DAY, THERE
WILL BE A CONTINUED CHANCE FOR STORMS FROM CENTRAL SD EASTWARD
ALONG THE NEBRASKA AND SOUTH DAKOTA BORDER INTO NORTHWESTERN IOWA.
INSTABILITY REMAINS VERY LIMITED SO ANY STORMS WILL NOT BECOME
SEVERE WITH VERY LIMITED COVERAGE THROUGH FRIDAY AFTERNOON.
RAINFALL WILL GENERALLY BE LESS THAN A TENTH OF AN INCH ALTHOUGH
ISOLATED AMOUNTS OVER A QUARTER OF AN INCH WILL BE POSSIBLE IF
STRONGER UPDRAFTS CAN DEVELOP.
ELSEWHERE SKIES WILL BE PARTLY TO MOSTLY CLOUDY. WITH DRIER AIR
FILTERING SOUTH THROUGH THE EVENING ON NORTHEASTERLY WINDS, LOWS
OVERNIGHT WILL DROP INTO THE UPPER 50S NORTH OF I90 WITH MID 60S
ALONG HWY 20 WHERE CLOUDS AND DEEPER MOISTURE ARE EXPECTED. AT
LEAST SOME SUN THROUGH MUCH OF FRIDAY, TEMPERATURES DURING THE DAY
WILL GENERALLY BE IN THE 80S, EXCEPT IN SOUTH CENTRAL SOUTH DAKOTA
WHERE CLOUDS AND A FEW SHOWERS BY AFTERNOON WILL KEEP HIGHS IN THE
MID TO UPPER 70S.
LONG TERM
(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 335 PM CDT THU JUN 24 2021
THE NEXT CHANCE OF RAIN WILL COME ON FRIDAY NIGHT THROUGH THE
WEEKEND. THE BEST MOISTURE AND INSTABILITY WILL REMAIN CONFINED
ACROSS KANSAS AND MISSOURI. HOWEVER, THE 850 MB FRONT WILL REMAIN
ACROSS NORTHWESTERN IOWA ON FRIDAY NIGHT. A COMBINATION OF LARGE
SCALE ASCENT WITH THE JET STREAK AND FRONTOGENETICAL LIFT ALONG
THE FRONT IS EXPECTED TO DEVELOP SCATTERED SHOWERS AND
THUNDERSTORMS OVERNIGHT. THE BEST CHANCE WILL BE ACROSS
NORTHWESTERN IOWA SOUTHEAST OF A LINE FROM SPENCER TO SIOUX CITY.
IF ANY SIGNIFICANT RAINFALL WILL OCCUR, IT LOOKS TO BE AT THIS
TIME IN PORTIONS OF NORTHWESTERN IOWA. NORTH OF THE BOUNDARY, DRY
AIR WILL CONTINUE TO BE ADVECTED SOUTHWESTWARD AND THIS WILL
REALLY LIMIT ANY CHANCE FOR RAIN OVER MOST OF SOUTHEASTERN SOUTH
DAKOTA AND SOUTHWESTERN MINNESOTA. A TROUGH WILL REMAIN OVER THE
AREA THIS WEEKEND. SHORT WAVES WILL ROTATE AROUND THE LONG WAVE
TROUGH SATURDAY AND SUNDAY. AS MENTIONED ABOVE, THE DEEP MOISTURE
WILL BE CONFINED WELL SOUTH OF THE AREA. BUT WITH RELATIVELY COLD
AIR ALOFT, THE COMBINATION OF SURFACE HEATING DURING THE DAY AND
LARGE SCALE ASCENT MAY PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS
DURING THE AFTERNOON AND EVENING. THERE IS NO GUARANTEE THAT ANY
LOCATION WILL SEE RAIN AND RAINFALL AMOUNTS THIS WEEKEND LOOK TO
BE LIGHT AS WELL. WITH THE UPPER TROUGH IN PLACE AND LOTS OF
CLOUDS, TEMPERATURES WILL BE BELOW NORMAL IN THE MID TO UPPER 70S.
IN THE EXTENDED PERIOD (MON - THU), THE BIG NEWS IS THE
DEVELOPMENT OF AN EXTREMELY STABLE UPPER AIR PATTERN OVER NORTH
AMERICA. BOTH THE ECMWF AND GFS/CANADIAN (NAEFS) ENSEMBLES SHOW
THE DEVELOPMENT OF A STRONG RIDGE ALONG THE WEST COAST OF NORTH
AMERICA. THE ENSEMBLE MEAN HEIGHTS AT 200 AND 500 MB ARE EXPECTED
TO BE NEAR OR ABOVE RECORD VALUES THROUGH ALL OF NEXT WEEK. AT THE
SAME TIME, A VERY STRONG RIDGE IS PROJECTED TO SET UP OFF THE
EAST COAST OF NORTH AMERICA THIS WEEKEND. WHILE NOT AS
CLIMATOLOGICALLY ANOMALOUS AS THE WEST COAST RIDGE, HEIGHTS ARE
WELL ABOVE NORMAL OFF NEW ENGLAND AT LEAST THROUGH THE MIDDLE OF
NEXT WEEK - PERHAPS LONGER IF THE ECMWF ENSEMBLE IS CORRECT. WHAT
THIS MEANS LOCALLY IS THAT A PERSISTENT TROUGH IS EXPECTED TO SIT
OVER THE NORTHERN PLAINS AND GREAT LAKES WELL INTO NEXT WEEK. HOW
LONG AND HOW FAR WEST THE TROUGH IS LOCATED IS DEPENDENT ON THE
STRENGTH OF THE EAST COAST RIDGE. THE GENERAL CONSENSUS IS THE
TROUGH AXIS WILL BE CENTERED OVER MN OR EASTERN DAKOTAS EARLY NEXT
WEEK AND THEN SLOWLY SHIFT EAST TOWARD THE GREAT LAKES AS THE
EAST COAST RIDGE BREAKS DOWN BY MID TO LATE NEXT WEEK. AS THE
TROUGH SHIFTS TO THE EAST, HEAT WILL BEGIN TO RETURN TO THE AREA
LATE NEXT WEEK. AS FOR PRECIPITATION, THE BEST CHANCE FOR RAIN
WILL BE EAST OF THE TROUGH AXIS FROM IOWA INTO THE GREAT LAKES.
WHILE INDIVIDUAL SHORT WAVES MOVING SOUTHWARD ON THE BACKSIDE OF
THE TROUGH COULD BRING CHANCES FOR RAIN EARLY NEXT WEEK, THE
TIMING AND LOCATION OF THESE SHORT WAVES IS VERY UNCERTAIN. THAT
MEANS THAT BEYOND THIS WEEKEND, THE CHANCE OF A SIGNIFICANT
RAINFALL APPEARS LOW.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 642 PM CDT THU JUN 24 2021
VFR CONDITIONS WILL PREVAIL THROUGH THE MAJORITY OF THE PERIOD. SCATTERED
SHOWERS WILL EXIT NORTHWEST IOWA EARLY THIS EVENING. OTHERWISE
ANVIL CIRRUS WILL SPREAD THROUGH THE REGION TONIGHT AS STORMS
CONTINUE IN EASTERN NE AND WESTERN SD. WINDS REMAIN LIGHT
OVERNIGHT, MAINTAINING AN EASTERLY COMPONENT WELL INTO FRIDAY.
ANOTHER ROUND OF SCATTERED SHOWERS AND STORM IS POSSIBLE FRIDAY
AFTERNOON ALONG AND SOUTHEAST OF THE SUX TO SPW CORRIDOR, BUT
CONFIDENCE IS TOO LOW TO INCLUDE IN THE TAF AT THIS TIME.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
SHORT TERM...SCHUMACHER
LONG TERM...SCHUMACHER
AVIATION...BP
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page