470
FXUS63 KABR 151721 AAC
AFDABR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
1221 PM CDT TUE SEP 15 2026
KEY MESSAGES
- DRY CONDITIONS EXPECTED TODAY BEFORE A WEAK DISTURBANCE TRACKS
OVER THE REGION WEDNESDAY THROUGH THE WEEKEND BRINGING THE
OPPORTUNITY FOR ISOLATED TO SCATTERED SHOWERS AND WEAK THUNDERSTORMS.
- ANOTHER ROUND OF RAINFALL IS EXPECTED LATE THURSDAY THROUGH
FRIDAY. THE HIGHEST ACCUMULATIONS ARE EXPECTED OVER EASTERN SOUTH
DAKOTA, WHERE PROBABILITY TO SEE AN INCH OF RAIN OR MORE RANGES FROM
40-60%.
UPDATE
ISSUED AT 1220 PM CDT TUE SEP 15 2026
UPDATED THE AVIATION DISCUSSION FOR THE 18Z TAF ISSUANCE.
UPDATE ISSUED AT 1100 AM CDT TUE SEP 15 2026
FORECAST IS STAYING ON TRACK TODAY. WINDS HAVE DIED BACK
EARLIER IN THE MORNING AND THE WIND ADVISORY WAS EXPIRED.
UPDATE ISSUED AT 610 AM CDT TUE SEP 15 2026
SEE BELOW FOR AN AVIATION FORECAST DISCUSSION FOR THE 12Z TAFS.
DISCUSSION
ISSUED AT 239 AM CDT TUE SEP 15 2026
SATELLITE AND WEBCAM OBSERVATIONS INDICATE A COUPLE OF PATCHES OF
LINGERING FOG THIS MORNING OVER EASTERN SOUTH DAKOTA (AND ALONG I-29
IN DEUEL COUNTY IN PARTICULAR) AS OF ROUGHLY 07Z. AS WINDS INCREASE
OVER THAT AREA, THE EXPECTATION IS THAT THE REMAINING FOG WILL CLEAR
OUT OVER THE NEXT COUPLE OF HOURS. GUSTY WINDS HAVE ARRIVED OVER
NORTH CENTRAL SOUTH DAKOTA THIS MORNING, UP TO 45 TO 50 MILES PER
HOUR AT TIMES. GIVEN THE DELAYED ONSET OF THE WINDS AND THE
PERSISTENCE OF 40+ MILE PER HOUR GUSTS, HAVE EXTENDED THE WIND
ADVISORY THROUGH 12Z THIS MORNING FOR ALL COUNTIES PREVIOUSLY UNDER
THE ADVISORY. NO ADDITIONAL COUNTIES HAVE BEEN ADDED AT THIS TIME.
WINDS ARE EXPECTED TO DIE DOWN THROUGH THE DAY TODAY AS A HIGH
PRESSURE CENTER BUILDS IN. WITH THIS HIGH PRESSURE OVERHEAD, LIGHT
WINDS, AND NEARLY FULL HUMIDITY RECOVERY OVERNIGHT, ANOTHER ROUND OF
FOG WILL BE POSSIBLE EARLY WEDNESDAY MORNING, MAINLY OVER NORTHEAST
SOUTH DAKOTA AND WESTERN MINNESOTA.
OVER THE NEXT FEW DAYS, A NEGATIVELY TILTED RIDGE WILL BUILD OVER
THE NORTHERN PLAINS, WHILE AND UPPER-LEVEL LOW DEVELOPS OVER THE
WESTERN CONUS. THIS SETUP WILL ALLOW FOR A WARMER AIRMASS TO BUILD
INTO THE REGION, INCREASING HIGH TEMPERATURES BY THE END OF THE
WEEK. LATEST NBM MEDIAN VALUES SIT IN THE MID TO UPPER 70S OVER
NEARLY THE ENTIRE FORECAST AREA THURSDAY AND BEYOND, WHICH IS NEAR-
NORMAL TO SLIGHTLY ABOVE NORMAL.
THE UPPER-LEVEL SETUP WILL ALLOW FOR STRONGER WINDS ALOFT TO DEVELOP
A WEAK LOW PRESSURE CENTER WITH SOME RAIN OUT AHEAD. NO SEVERE
WEATHER IS EXPECTED WITH THESE RAIN SHOWERS, AND NEITHER IS MUCH
SIGNIFICANT PRECIPITATION. LATEST NBM PROBABILITY OF SEEING A TENTH
OF AN INCH THROUGH 06Z THURSDAY IS GENERALLY LESS THAN 20 PERCENT
ACROSS THE FORECAST AREA, WITH SOME POCKETS OF 20 TO 30 PERCENT OVER
CENTRAL SOUTH DAKOTA.
MORE ROBUST CHANCES FOR RAIN COME INTO THE FORECAST AREA FRIDAY INTO
SATURDAY AS THE UPPER-LEVEL LOW MENTIONED IN THE ABOVE PARAGRAPH
MOVES EASTWARD INTO THE NORTHERN PLAINS. THERE IS SOME DISAGREEMENT
ON THE TIMING WITHIN MODEL GUIDANCE, BUT THERE SEEMS TO BE STRONG
AGREEMENT AMONGST THE ENSEMBLES (NBM, GFS, EURO, AND CANADIAN
SPECIFICALLY) IN THE TRACK OF THE HIGHEST PRECIPITATION TOTALS. AT
THE MOMENT, IT APPEARS THAT THE AXIS OF HEAVIEST PRECIPITATION WILL
REMAIN TO THE SOUTH, RUNNING THROUGH OR JUST NORTH OF SIOUX FALLS.
THIS MEANS THAT EASTERN SOUTH DAKOTA WILL BE THE AREA WITHIN THE
ABERDEEN CWA THAT IS SET TO RECEIVE THE MOST RAINFALL, WITH TOTALS
DECREASING MOVING TO THE NORTHWEST. STILL A FAIRLY LARGE DEGREE OF
SPREAD EXISTS OVER EASTERN SOUTH DAKOTA, WITH THE NBM 25TH/75TH
PERCENTILE RAINFALL TOTALS ENDING SATURDAY MORNING RANGES FROM 1"-3"
IN TOTAL. EURO AND CANADIAN ENSEMBLES ARE GENERALLY IN AGREEMENT
WITH THAT SPREAD, ALTHOUGH ARE PERHAPS A BIT LOWER ON THE 75TH
PERCENTILES. THE GEFS IS A BIT OF AN OUTLIER IN THAT IT IS MUCH
LOWER, HAVING A SPREAD AROUND 0.5"-1.5". GIVEN HOW IT VERIFIED WITH
RECENT RAINFALL, CONFIDENCE WOULD LEAN AGAINST TRUSTING THOSE LOWER
VALUES. ALL THIS TO SAY THAT THESE QPF TOTALS RAISE SOMEWHAT OF A
RED FLAG WITH REGARDS TO THE FLOODING POTENTIAL. WILL DIVE MORE IN-
DEPTH ON THE FLOODING RISK IN FUTURE DISCUSSIONS, BUT TO GIVE A
BRIEF OVERVIEW: STORM MOTION, WARM CLOUD LAYER, AND HIGH PWATS ALL
GIVE ADDITIONAL CREDENCE TO THE FLOODING THREAT OVER EASTERN SOUTH
DAKOTA DURING THIS EVENT. THROUGH 12Z FRIDAY, A SLIGHT RISK
EXCESSIVE RAINFALL OUTLOOK IS IN PLACE FOR PORTIONS OF EASTERN AND
CENTRAL SOUTH DAKOTA, WITH A MARGINAL THROUGH 12Z SATURDAY.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1220 PM CDT TUE SEP 15 2026
TERMINALS KABR,KATY,KPIR,KMBG
VFR CONDITIONS WILL CONTINUE THROUGH THE DAY AND INTO THE
NIGHT. SOME AFTERNOON CUMULUS CLOUDS ARE STARTING TO DEVELOP OVER
PORTIONS OF NORTHERN SOUTH DAKOTA WHICH COULD LOWER THE CLOUD BASES
TO AT TIMES DURING THE AFTERNOON TO BE BETWEEN 3500 TO 7500 FEET,
THOUGH THERE SHOULD ONLY BE A FEW CLOUDS IN THE SKY SO THERE
WILL NOT BE LOW CEILINGS. CONDITIONS SHOULD STAY VFR INTO THE
MORNING FOR MOST TERMINALS, THOUGH WITH HIGHER HUMIDITY AND
LOWER WIND SPEEDS, THERE COULD BE SOME PATCHY SPOTS OF FOG THAT
COULD DEVELOP DURING THE EARLY WEDNESDAY MORNING OVER KATY AND
KABR THAT COULD REDUCE VISIBILITIES SLIGHTLY. NORTHWESTERLY
WINDS WILL START TO TURN THIS EVENING TO BECOME MORE EASTERLY
OVERNIGHT THEN SOUTHEASTERLY DURING THE DAY WEDNESDAY. THE
WINDS WILL PICK UP WEDNESDAY MORNING INTO THE AFTERNOON AND BE
GUSTING UP AROUND 30 MPH OVER KPIR AND KMBG AND UP AROUND 20 TO
25 MPH OVER KABR AND KATY.
ABR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
UPDATE...12
DISCUSSION...BC
AVIATION...12
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