137
FXUS63 KUNR 281135
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
535 AM MDT FRI MAR 28 2025
KEY MESSAGES
- MILD TODAY WITH ELEVATED FIRE WEATHER CONDITIONS
- TWO ROUNDS OF WIDESPREAD PRECIPITATION TONIGHT THROUGH SUNDAY
NIGHT WITH BENEFICIAL QPF FOR MUCH OF THE CWA
- LOW CONFIDENCE FORECAST FOR SNOW AMOUNTS THIS WEEKEND
DISCUSSION
(TODAY THROUGH THURSDAY)
ISSUED AT 208 AM MDT FRI MAR 28 2025
07Z SURFACE ANALYSIS HAD LOW OVER KD07 WITH COOL FRONT INTO
SOUTHERN MT. WATER VAPOUR LOOP HAD UPPER LOW SPINNING OFF THE
PACIFIC NORTHWEST COAST AND SOUTHWEST FLOW ALOFT OVER THE NORTHERN
PLAINS. WEAK EMBEDDED SHORTWAVE OVER WESTERN WY WITH SOME WEAK
REGIONAL RADAR RETURNS FROM WESTERN WY TO WESTERN ND. EFFECT OF
THE UPPER LOW THE MAIN FORECAST CONCERN FOR THE WEEKEND.
TODAY, WEAK SHORTWAVE MOVES NORTHEAST WITH SMALL POPS WARRANTED
OVER THE NORTHWEST QUARTER OF THE CWA MAINLY THIS MORNING. SURFACE
LOW SLIPS SOUTHEAST AND COOL FRONT SAUNTERS THROUGH THE CWA. WARM
TEMPERATURES EXPECTED AHEAD OF THE FRONT OVER SOUTH-CENTRAL SD,
BUT STILL MILD BEHIND IT ALBEIT WITH GUSTY NORTHERLY WINDS.
TONIGHT THROUGH SUNDAY NIGHT, UPPER LOW OFF THE PACIFIC NORTHWEST
COAST SPINS TWO DISTINCT SHORTWAVE TROUGHS INTO THE NORTHERN
PLAINS. THE FIRST ARRIVES TONIGHT, FOCUSING SYNOPTIC LIFT AS WELL
AS LOW LEVEL THETA-E ADVECTION/FRONTOGENESIS LATE TONIGHT/SATURDAY
MORNING. PWATS ~150% NORMAL. INITIAL PRECIPITATION WILL BE RAIN
WITH A CHANGEOVER TO SNOW OVER THE HIGHER ELEVATIONS OF THE BLACK
HILLS FIRST, AND THEN POSSIBLY ON THE PLAINS. CHANGEOVER ON THE
PLAINS WILL BE MODULATED BY INTENSITY OF THE QPF/DYNAMIC COOLING
AND THEN DAYTIME EFFECTS. GREAT UNCERTAINTY CONTINUES TO EXISTS,
PARTICULARLY SINCE ANTECEDENT WARM WEATHER WILL COUNTER SNOWFALL
ACCUMULATIONS, UNLESS THE SNOW COMES DOWN IN BUCKETS. IN ADDITION,
THERE WILL BE NORTHEASTERLY BOUNDARY FLOW POTENTIALLY BRINGING
DRIER AIR TO NORTHWESTERN SD, BUT FOCUSING UPSLOPE FLOW ON THE
EASTERN SLOPES OF THE BLACK HILLS. THERE WILL BE A LULL IN THE
STRONGEST PRECIPITATION LATER SATURDAY AFTERNOON/EVENING, BUT THEN
AS THE SECOND WAVE APPROACHES, ADDITIONAL QPF ENSUES. FORECAST
SOUNDINGS SUPPORT MOSTLY SNOW FOR THE SECOND WAVE, SO EXPECT
BETTER CHANCES OF SNOW ACCUMULATION ON THE PLAINS. THE MAIN STORM
TOTAL QPF AXIS HAS SHIFTED SOUTH PER THE LATEST ENSEMBLE GUIDANCE,
MAINLY FROM NORTHEASTERN WY THROUGH SOUTHERN SD WHERE CHANCE OF
>0.1" ~100%, >0.25" 80%+, >0.50" 50-80%. BENEFICIAL QPF HIGHLY
WELCOME NO MATTER WHAT FORM FALLS. 25-75TH SNOWFALL FOR THE ENTIRE
WEEKEND 4-8" FOR THE BLACK HILLS, 1-5" ON PARTS OF THE PLAINS.
FOR RAPID CITY, THE 10-90TH IS 0 TO 7" OF SNOW. HREF THE MOST
AGGRESSIVE WITH SNOW AMOUNTS, BUT CONFIDENCE IS NOT HIGH ENOUGH
EARLY THIS MORNING TO ISSUE WINTER HEADLINES. SUSPECT SOME WILL BE
NEEDED BY THE TIME THIS SPRING STORM'S INTENTIONS ARE KNOWN.
TEMPERATURES WILL BE BELOW GUIDANCE WHERE THE HIGHEST RAIN/SNOW
FALLS.
PROGRESSIVE FLOW IS EXPECTED NEXT WEEK WITH A SERIES OF
SHORTWAVES BRINGING ADDITIONAL ROUNDS OF BENEFICIAL QPF. PERHAPS
MORE SNOW, BUT TIMING/TEMPERATURES UNCERTAIN. LATEST ENSEMBLE
GUIDANCE HAS TIGHTENED TEMPERATURES RANGES FOR NEXT WEEK, BUT
STILL 20F SPREADS TUESDAY THROUGH FRIDAY.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 531 AM MDT FRI MAR 28 2025
VFR CONDITIONS ARE EXPECTED THROUGH MOST OF THE PERIOD. CLOUDS
WILL INCREASE FRIDAY EVENING AS A SYSTEM APPROACHES THE AREA.
PRECIPITATION AND MVFR CONDITIONS ARE EXPECTED TO PUSH INTO THE
REGION FROM WEST TO EAST TOWARDS THE END OF THE TAF PERIOD.
FIRE WEATHER
ISSUED AT 208 AM MDT FRI MAR 28 2025
EXPECT ELEVATED FIRE WEATHER CONDITIONS TODAY AS A COLD FRONT
MOVES THROUGH THE AREA. GUSTY WESTERLY WINDS AHEAD OF THE FRONT
WILL BECOME NORTHERLY. MINIMUM RELATIVE HUMIDITIES WILL DIP INTO
THE 20S. THE JOINT PROBABILITY OF <20% RH/>25MPH WIND GUSTS IS
LESS THAN 30% PER HREF. A COUPLE OF DISTURBANCES WILL BRING
EXCELLENT CHANCES FOR WETTING QPF STARTING TONIGHT, LASTING
THROUGH SUNDAY.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...HELGESON
AVIATION...DYE
FIRE WEATHER...HELGESON
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