413
FXUS63 KUNR 282032
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
232 PM MDT THU MAY 28 2026
KEY MESSAGES
- CONTINUED WARM AND BREEZY CONDITIONS TODAY AND FRIDAY WITH A
VERY MODEST INCREASE DAY-BY-DAY IN THE POTENTIAL FOR A COUPLE
ISOLATED SHOWERS OR THUNDERSTORMS; MOST AREAS TO REMAIN DRY.
- SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY AFTERNOON AND
EVENING WITH MUCH MORE WIDESPREAD DEVELOPMENT AND PRIMARY
HAZARDS OF LARGE HAIL QUARTER TO GOLF BALL SIZE, DAMAGING WINDS
IN EXCESS OF 60 MPH, AND HEAVY RAINFALL.
- UNSETTLED CONDITIONS WITH DAILY CHANCES OF SHOWERS AND
THUNDERSTORMS CONTINUE THROUGH AT LEAST TUESDAY NEXT WEEK.
DISCUSSION
(THIS EVENING THROUGH THURSDAY)
ISSUED AT 232 PM MDT THU MAY 28 2026
THAT WARM AND BREEZY HIGH PLAINS LIFE CONTINUES! BUT, SOME CHANGES
ARE ON OUR DOORSTEP. TODAY INTO FRIDAY, A SHORTWAVE-STYLE "TONGUE"
OF LOW PRESSURE WILL BE LIFTING NORTHWARD ACROSS KANSAS AND NEBRASKA
WITH VERY GRADUALLY INCREASING MOISTURE AND INSTABILITY OVER OUR
REGION, SUPPORTING A MODEST INCREASE DAY-BY-DAY IN ISOLATED SHOWER
AND THUNDERSTORM POTENTIAL. CLOUD COVER WILL BE A LIMITING FACTOR TO
OUR DESTABILIZATION (ESPECIALLY TODAY BUT PERHAPS FRIDAY AS WELL)
WITH MODEL FORECAST SOUNDINGS GENERALLY SUPPORTING LESS THAN 1,000
J/KG MLCAPE. LIFT WILL BE LACKING TOO AND CONTINUED VERY POOR SHEAR
PARAMETERS WILL DO NOTHING TO HELP US BEST UTILIZE THAT CAPE OR
SUPPORT/SUSTAIN ANY STORM ORGANIZATION. THE RESULT WILL BE WEAKER
"PULSE" ACTIVITY WITH LIMITED COVERAGE, MOSTLY FOCUSED ON FRIDAY
AFTERNOON/EVENING WITH SOME CELLS AFFECTING NORTHEAST WYOMING AND
PERHAPS FIRING OFF THE BLACK HILLS GENERALLY AFTER 2-3PM. MOST OF
OUR FORECAST AREA IS STILL LIKELY TO REMAIN DRY BOTH DAYS (ALTHOUGH
SOME GUIDANCE TRIES TO GENERATE SOME SHOWERS LATE SATURDAY NIGHT
INTO SUNDAY MORNING, ESPECIALLY ACROSS OUR SOUTH DAKOTA PLAINS).
GENERALLY HELD WITH NBM GUIDANCE FOR OUR FORECAST, BUT SHAVED A FEW
DEGREES OFF HIGH TEMPS THIS AFTERNOON GIVEN WIDESPREAD CLOUD COVER
AND TRENDS IN SFC OBS, AND CONTINUED OUR THEME FROM PREVIOUS DAYS IN
SLIGHTLY REDUCING WINDS/WIND GUSTS AS THE NBM CONTINUES TO RUN HOT.
STILL, WIDESPREAD GUSTS OF 30-40 MPH WILL CONTINUE BOTH AFTERNOONS,
WITH A LOCALIZED GUST TO 50 MPH NOT OUT OF THE QUESTION IN NORMALLY
BREEZIER SPOTS, ESPECIALLY IN THE GILLETTE REGION AND ACROSS
NORTHWEST SOUTH DAKOTA. FOR OUR FIRE PARTNERS...MINIMUM AFTERNOON RH
VALUES ARE SLOWLY TRENDING HIGHER COMPARED TO PREVIOUS DAYS DESPITE
THE BREEZY CONDITIONS...25-35 PERCENT TODAY, AND 25-40 PERCENT
FRIDAY (EXCEPT LOWER ACROSS NORTHEAST WYOMING). MORE GOOD NEWS ON
THE MOISTURE FRONT FOLLOWS BELOW.
BY SATURDAY, SYNOPTIC-SCALE REINFORCEMENTS ARRIVE AS A LARGE, NEARLY
STATIONARY LOW PRESSURE CENTER THAT HAS BEEN RESIDING OVER
CALIFORNIA AND NEVADA LATELY FINALLY EJECTS NORTHEAST ACROSS THE
ROCKIES, WITH THE OVERALL TROUGH TAKING ON A STRONGLY NEGATIVE TILT
AND COOLING MID-LEVEL TEMPERATURES. AHEAD OF THIS FEATURE, STRONG
MOISTURE ADVECTION WILL BE UNDERWAY ON SOUTH/SOUTHEAST FLOW
THROUGHOUT THE ATMOSPHERIC COLUMN WITH SFC DEW POINTS REACHING 55-65
DEGF AND INCREASING INSTABILITY. SURFACE AND NEAR-SURFACE WINDS
BACKED TO SOUTHEASTERLY WILL ASSIST IN TRANSPORTING THIS MOISTURE
WESTWARD AT LEAST UP AGAINST THE BLACK HILLS CORRIDOR AND ENHANCE
STORM-RELATIVE INFLOW. A REVIEW OF NAMNEST AND GFS MODEL FORECAST
SOUNDINGS...EVEN USING MLCAPE OR EFFECTIVE PARCEL CAPE...SUGGEST
1,000 TO 2,000 J/KG (MODERATE INSTABILITY/FUEL FOR STORMS), ALONG
WITH PWATS INCREASING OVER 1 INCH. BOTTOM LINE...MOISTURE AND
INSTABILITY ARE LOOKING MUCH MORE SUPPORTIVE OF THUNDERSTORMS BY
SATURDAY AFTERNOON REGIONWIDE, AND THE NWS STORM PREDICTION CENTER
(SPC) HAS INTRODUCED A SLIGHT RISK (LEVEL 2 OF 5) OF SEVERE
THUNDERSTORMS ACROSS MOST OF OUR SOUTH DAKOTA COUNTIES (WHERE THESE
TWO PARAMETERS WILL BE HIGHEST) WITH A MARGINAL RISK (LEVEL 1 OF 5)
FOR THE REST OF OUR CWA. (FOR WHAT IT'S WORTH, MOST ANALOG AND
MACHINE-LEARNING SEVERE WEATHER PROBABILITIES OUT THERE SUPPORT THIS
AS WELL.) SHEAR PARAMETERS WILL IMPROVE TOO, BUT WILL STILL REMAIN
SOMEWHAT OF A LIMITING FACTOR TO A MORE ROBUST SEVERE WEATHER THREAT
AS DEEP-LAYER SHEAR DOES NOT CURRENTLY LOOK TO EXCEED 30KTS,
RESULTING IN MESSY MULTI-CELL TO LOW-END SUPERCELL STORM MODES
ALBEIT WITH SOME DECENT CELL LONGEVITY. THOSE BACKED SURFACE WINDS
INTO THE SE (ESPECIALLY ACROSS OUR SOUTH DAKOTA COUNTIES) AS WELL AS
SOME INCREASE IN 0-1 AND 0-3 KM SRH VALUES TOWARD EVENING INDICATE
THE RISK OF AN ISOLATED, BRIEF TORNADO IS LOW, BUT NOT ZERO. DECENT
CAPE IN THE HAIL GROWTH ZONE, AND INITIALLY STEEP LOW-LEVEL LAPSE
RATES COUPLED WITH DCAPE SOLIDLY OVER 1,000 J/KG AND THE HIGHER
PWATS SUGGEST PRIMARY RISKS OF HEAVY RAIN, PERHAPS SOME WET
MICROBURSTS (DAMAGING WINDS OVER 60 MPH), AND LARGE HAIL OF QUARTER
TO GOLF BALL SIZE WITH MODEL SOUNDINGS PULLING SOME SEVERE HAIL
ANALOGS. SIMULATED REFLECTIVITY OFF THE NAMNEST SUGGESTS THE
STRONGER STORMS COULD INITIATE AS EARLY AS 18Z/NOON IN NORTHEAST
WYOMING, AND 21Z/3PM INTO WESTERN SOUTH DAKOTA, LIKELY CONTINUING
INTO THE FIRST PART OF THE NIGHT SATURDAY NIGHT TRENDING INTO OUR
EASTERN PLAINS WITH TIME...STORMS MAY GROW UPSCALE INTO MORE OF A
LINE OR CLUSTER DURING THEIR JOURNEY NORTHEAST GIVING EVERYONE SOME
RAIN. HIGH TEMPERATURES SATURDAY WILL TOP OUT IN THE UPPER 70S TO
LOW 80S GIVEN SOME CLOUD COVER AND STORMS RUNNING AROUND. NBM
GUIDANCE CAPTURED MOST ELEMENTS REASONABLY WELL FOR NOW AND NO
SIGNIFICANT FORECAST EDITS WERE MADE, ALTHOUGH CURRENT POPS PRIOR TO
SUNSET SATURDAY MAY BE A BIT OVERDONE. SOME LOCALES IN SOUTH DAKOTA
COULD SEE QPF EXCEEDING 0.50 INCHES BETWEEN SATURDAY AFTERNOON AND
SUNDAY MORNING! (FOR OUR FIRE PARTNERS, CHANCE OF WETTING RAIN WILL
REACH 40-80 PERCENT BY THIS PERIOD.)
THE MAIN LOW LOOKS TO SLOWLY DRIFT NORTHEAST SUNDAY THROUGH TUESDAY
WITH MULTIPLE SUBTLE SHORTWAVES/DISTURBANCES ROTATING AROUND IT,
RESULTING IN ADDITIONAL DAILY CHANCES OF MOSTLY AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS ACROSS THE REGION. IT'S POSSIBLE
WE START TO TREND DRIER AFTER THAT, BUT FORECAST CONFIDENCE IS
CURRENTLY LOW. LATEST 500MB HEIGHT ENSEMBLE CLUSTER ANALYSIS STILL
UNIVERSALLY SUPPORTS CONTINUED PRESENCE OF SOME SORT OF
LOW/TROUGHING WITH IT'S CENTER/AXIS STILL WEST/NORTHWEST OF OUR CWA
THROUGH AT LEAST TUESDAY, WITH THAT SIGNAL WEAKENING BY WEDNESDAY.
BROADLY SPEAKING, NO SIGNIFICANT COOL-DOWN IS EXPECTED AT THIS TIME
AS A RESULT OF THIS SYSTEM AND PATTERN THROUGH NEXT WEDNESDAY.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z FRIDAY)
ISSUED AT 1113 AM MDT THU MAY 28 2026
VFR CONDITIONS ARE EXPECTED THROUGH MOST OF THE FORECAST PERIOD.
ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS PORTIONS OF
NORTHEAST WYOMING, WESTERN SD, AND INTO SOUTH-CENTRAL SD.
TRANSIENT MVFR CONDITIONS ARE POSSIBLE WITH THE SHOWERS AND
THUNDERSTORMS. WIDESPREAD, GUSTY SOUTHEASTERLY WINDS (~35KTS) WILL
PERSIST INTO THE EVENING BEFORE WEAKENING DURING OVERNIGHT HOURS.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...KSMITH
AVIATION...SCHULTZ
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