825
FXUS63 KUNR 092316
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
516 PM MDT WED SEP 9 2026
KEY MESSAGES
- WARM AND DRY CONDITIONS CONTINUE THIS WEEK, WITH 90S RETURNING
TO THE FORECAST THURSDAY AND FRIDAY.
- ELEVATED TO NEAR-CRITICAL FIRE WEATHER CONDITIONS CONTINUE TO
RESULT; FOCUS REMAINS ON THURSDAY AND FRIDAY, ALTHOUGH LACK OF
OVERLAP BETWEEN THE LOWEST HUMIDITIES AND STRONGEST WINDS
SUPPORT LOW CONFIDENCE IN MEETING RED FLAG WARNING CRITERIA.
- HIGH CONFIDENCE IN NO PRECIPITATION UNTIL AT LEAST FRIDAY
EVENING, IF NOT SATURDAY EVENING.
- NEXT ORGANIZED STORM SYSTEM REMAINS EXPECTED THIS WEEKEND INTO
MONDAY, BUT SIGNAL FOR COOLER TEMPERATURES SLIGHTLY MODERATING.
DISCUSSION
(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 156 PM MDT WED SEP 9 2026
OUR MAIN WEATHER CONCERN THIS WEEK REMAINS HOT, DRY, AND AT TIMES
BREEZY CONDITIONS RESULTING IN ELEVATED TO NEAR-CRITICAL FIRE
WEATHER, WITH ALL EYES THEN TURNING TO THIS WEEKEND'S STORM
SYSTEM. THE PREVIOUSLY NOTED TREND IN A QUICKER ARRIVAL TO COOLER
AIR FRIDAY REMAINS ON TRACK, SUPPORTING COOLER HIGH TEMPERATURES
IN THE 70S IN THE NORTHWEST CWA (ESPECIALLY CAMPBELL AND HARDING
COUNTIES), RANGING UP INTO THE UPPER 80S AND LOWER 90S TO THE
SOUTHEAST. FORECAST CONFIDENCE IS HIGH IN NO PRECIPITATION UNTIL
AT LEAST FRIDAY EVENING, IF NOT SATURDAY EVENING.
LONG-RANGE DETERMINISTIC MODELS CONTINUE TO KEY IN ON TWO PRIMARY
FEATURES THIS WEEKEND. THE FIRST IS A LARGE LOW PRESSURE CENTER
CROSSING CANADA TO OUR NORTH, WHICH WILL ASSIST IN TIGHTENING THE
PRESSURE GRADIENT AND INCREASING NORTHWESTERLY WINDS FRIDAY
AFTERNOON AND EVENING (GUSTS 25-40 MPH ACROSS THE REGION). THIS
WILL ESPECIALLY BE A FIRE WEATHER CONCERN...STILL NOT EXPECTING
WIND ADVISORY-LEVEL WINDS AT THIS TIME. SOME HINT OF TROUGHING
EXTENDING SOUTHWESTWARD FROM THIS PARENT LOW MAY ALSO HELP SUPPORT
SOME ISOLATED SHOWER/THUNDERSTORM POTENTIAL STARTING LATE FRIDAY
AFTERNOON INTO THE FIRST PART OF FRIDAY NIGHT, ALTHOUGH CONFIDENCE
IN THIS PERIOD IS LOW (AND NBM-BASED POPS ARE TRENDING A BIT
LOWER). MEANINGFUL OR WIDESPREAD QPF IS UNLIKELY, IF IT RAINS AT
ALL. THE SECOND PRIMARY FEATURE WILL BE ANOTHER CLOSED LOW
ROTATING DOWN THE BACK SIDE OF THIS CANADIAN PARENT LOW AND THEN
SWINGING EASTWARD/INLAND ACROSS THE NORTHERN ROCKIES. MOISTURE
ADVECTING IN ON SOUTHWEST FLOW AHEAD OF THIS LOW, ALONG WITH
INCREASING UPPER-LEVEL SUPPORT, WILL BRING US A BETTER CHANCE OF
MORE ORGANIZED PRECIPITATION SOMETIME IN THE SATURDAY
EVENING/SUNDAY/MONDAY TIMEFRAME, ALONG WITH COOLER TEMPERATURES
AND INCREASED HUMIDITIES. LOOKING AT TEMPERATURES...THE NEWS ISN'T
GREAT FOR THOSE LOOKING FOR THEIR FIRST TASTE OF FALL, AS NBM HIGH
TEMPERATURES HAVE MODERATED A BIT...GENERALLY NOW HOLDING IN THE
70S SATURDAY, SUNDAY, AND MONDAY (ALTHOUGH SOME HIGH TEMPS AS LOW
AS THE 60S MAY STILL BE POSSIBLE UP IN THE BLACK HILLS AND ACROSS
THE NORTHWESTERN SOUTH DAKOTA PLAINS). OVERNIGHT LOWS WILL REACH
THE 40S. LOOKING AT RAINFALL...FORECAST TOTALS CURRENTLY RANGE
FROM AS LOW AS 0.10" ACROSS NORTHWEST WYOMING, TO POTENTIALLY
0.50-0.75" ACROSS THE PLAINS OF CENTRAL SOUTH DAKOTA. CONTINUE TO
KEEP IN MIND THAT OUR ACTUAL EVENTUAL TEMPERATURES (AND QPF
AMOUNTS) WILL BE TIED TO THE STRENGTH AND TRACK OF THIS LOW, AND
500MB HEIGHT CLUSTER ANALYSIS CONTINUES TO HIGHLIGHT SOME
DIFFERENCES/ENSEMBLE UNCERTAINTY TIED TO SPEED AND PROGRESSION OF
THE LOW (ALTHOUGH SO FAR NO MAJOR TRENDS AFFECTING OUR FORECAST).
OVERALL, NO DEVIATIONS WERE MADE FROM NBM AND WPC GUIDANCE IN THE
FORECAST FROM FRIDAY ONWARD AT THIS TIME.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 516 PM MDT WED SEP 9 2026
VFR CONDITIONS THROUGH THE TAF PERIOD.
FIRE WEATHER
ISSUED AT 156 PM MDT WED SEP 9 2026
WE CONTINUE TO MONITOR HOT, DRY, AND PERIODICALLY BREEZY
CONDITIONS TODAY THROUGH FRIDAY, RESULTING IN ELEVATED TO NEAR-
CRITICAL FIRE WEATHER. FOR TODAY, AFTERNOON MINIMUM RELATIVE
HUMIDITY VALUES WILL RANGE FROM 12-25 PERCENT...DRIEST ACROSS
NORTHEAST WYOMING...BUT OVERLAP WITH CRITICAL WINDS SEEMS LIMITED
WITH MOST AREAS GUSTING 20-25 MPH (SLIGHTLY STRONGER ACROSS THE
NORTHWESTERN SOUTH DAKOTA PLAINS).
THURSDAY AND FRIDAY CONTINUE TO LOOK SOMEWHAT CONCERNING COMPARED
TO OTHER DAYS THIS WEEK, BUT A FEW NUDGES AND TRENDS IN THE
FORECAST ARE NOTED TODAY PRECLUDING ANY RED FLAG WARNINGS AT THIS
TIME. THURSDAY...RH VALUES PLUMMET TO 6-18 PERCENT AND
TEMPERATURES HEAT INTO THE 90S, BUT COVERAGE OF WIND GUSTS
EXCEEDING 25 MPH IS VERY LIMITED. A FEW SPOTS MAY REACH THAT
THRESHOLD BASED ON THE (USUALLY HIGHER) NBM GUIDANCE, BUT OTHER
GUIDANCE HAS TRENDED A BIT LOWER, INCLUDING THE HREF MEAN WHICH
KEEPS GUSTS BELOW 20 MPH, AND EVENING THE HREF ENSEMBLE MAX ONLY
BRUSHES 25 MPH IN A FEW SPOTS. OF COURSE, THE HOT AND DRY
CONDITIONS WILL STILL DO NOTHING TO HINDER BURNING. VERY POOR
OVERNIGHT RH RECOVERY ALSO REMAINS EXPECTED THURSDAY NIGHT INTO
FRIDAY MORNING (ONLY 20-30 PERCENT FROM THE BLACK HILLS AND FALL
RIVER COUNTY AREA WESTWARD ACROSS NORTHEASTERN WYOMING).
FRIDAY...WINDS REALLY RAMP UP WITH GUSTS REACHING 25-40 MPH
REGIONWIDE, BUT AFTERNOON RH VALUES HAVE TRENDED SLIGHTLY
HIGHER COMPARED TO YESTERDAY'S FORECAST...NOW ONLY BOTTOMING OUT
AT 15 PERCENT (SOUTH/NE BORDER) TO 30 PERCENT (NORTH/ND AND MT
BORDER). IT REMAINS POSSIBLE A FEW ZONES MAY EVENTUALLY NEED RED
FLAG WARNINGS FRIDAY, BUT CONFIDENCE IS LOW AT THIS TIME.
FORECAST CONFIDENCE IS HIGH IN NO PRECIPITATION UNTIL AT
LEAST FRIDAY NIGHT, IF NOT HOLDING UNTIL SATURDAY EVENING AS OUR
NEXT SYSTEM APPROACHES. THIS SYSTEM STILL LOOKS TO POTENTIALLY
SUPPORT COOLER TEMPERATURES AND HIGHER HUMIDITY STARTING SATURDAY,
BUT THE POTENTIAL FOR WETTING RAINS REMAINS UNCERTAIN.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...KSMITH
AVIATION...JC
FIRE WEATHER...KSMITH
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