668
FXUS63 KUNR 182327
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
527 PM MDT THU JUN 18 2026
KEY MESSAGES
- THUNDERSTORMS WITH MODERATE TO HEAVY RAIN AND SEVERE WEATHER
POSSIBLE THIS WEEKEND.
- HIGH TEMPS IN THE 70S TO LOW 80S FOR FRIDAY AND SATURDAY.
COOLER HIGH TEMPS IN THE 60S TO LOW 70S SUNDAY AND MONDAY.
- NW WINDS UP TO 10 TO 20 MPH TOMORROW SWING TO THE EAST/SOUTHEAST
AT 5 TO 15 MPH LATE TOMORROW.
- IMPROVED FIRE WEATHER CONDITIONS GOING INTO THE WEEKEND -
LIGHTER WINDS, MINIMUM RH VALUES AROUND 25%, AND INCREASING
CHANCES OF RAIN THIS WEEKEND.
DISCUSSION
(THIS EVENING THROUGH THURSDAY)
ISSUED AT 155 PM MDT THU JUN 18 2026
LATEST SATELLITE IMAGERY SHOWS CONTINUED NORTHWEST FLOW OVER THE
CWA. A FEW SHOWERS ARE STARTING TO DOT THE LANDSCAPE BUT RAIN
AMOUNTS WILL BE NEGLIGIBLE.
LOOKING AHEAD TO TONIGHT AND TOMORROW, WE'LL CONTINUE THE CHANCES
FOR ISOLATED SHOWERS AND NON-SEVERE STORMS TRYING TO DRIFT IN
FROM THE NORTH AND NORTHWEST. TEMPERATURES WILL BE NEAR-NORMAL
WITH OVERNIGHT LOWS IN THE 40S TO LOW 50S AND AFTERNOON HIGHS IN
THE 70S TO LOW 80S.
FRIDAY NIGHT AND THE WEEKEND WILL SEE A WEATHER PATTERN CHANGE
THAT WILL BRING VERY DIFFERENT WEATHER. THE UPPER LEVEL
NORTHWESTERLY FLOW WILL SHIFT TO A MORE WESTERLY FLOW AS A HIGH
PRESSURE BUILDS OVER THE DESERT SOUTHWEST. AT THE SURFACE, A LEE
SIDE LOW LOOKS TO DEVELOP IN EASTERN COLORADO. THIS PATTERN WILL
BRING RAIN, AND THUNDERSTORMS TO THE CENTRAL PLAINS, INCLUDING
WESTERN SOUTH DAKOTA AND NORTHEAST WYOMING.
WITH FORECASTED PWATS NEARING 150% OF NORMAL IN SOME MODELS,
THERE IS POTENTIAL FOR HEAVY RAIN. THE WPC HAS PUT MOST OF WESTERN
SOUTH DAKOTA AND NORTHEAST WYOMING IN A MARGINAL RISK FOR
EXCESSIVE RAINFALL. SATURDAY MORNING TO MONDAY MORNING RAINFALL
AMOUNTS COULD BE QUITE IMPRESSIVE; THE EURO AND GFS ENSEMBLE'S
75TH PERCENTILE FOR SATURDAY AND SUNDAY RAINFALL AMOUNTS ARE
AROUND 1 TO 1.5 INCHES, HEAVIEST RAIN IN SOUTH-CENTRAL SOUTH
DAKOTA. THE 25TH PERCENTILE IS AROUND 0.50 TO 0.75 INCHES. SO
BASED ON THAT, THERE IS A SOLID CHANCE FOR WIDESPREAD 48 HOUR
RAINFALL AMOUNTS NEAR 1 INCH IN WESTERN SOUTH DAKOTA.
THE SPC HAS A SLIGHT RISK OF SEVERE WEATHER CENTERED OVER THE
KS/NE BORDER BUT THE SURROUNDING MARGINAL RISK DOES SPREAD INTO
SOUTHWESTERN SD. AT THIS TIME, MAIN CONCERNS WOULD BE GUSTY WINDS
AND HAIL.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 524 PM MDT THU JUN 18 2026
VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIODS.
ISOLATED/SCATTERED SHRA/TS WILL CONTINUE THIS EVENING ACROSS
(MAINLY) NORTHWESTERN SD AND EXTREME NORTHEASTERN WY.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...GS
AVIATION...HELGESON
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