718
FXUS63 KUNR 170921
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
221 AM MST SAT JAN 17 2026
KEY MESSAGES
- ELEVATED TO NEAR-CRITIAL FIRE WEATHER THROUGH THE WEEKEND
- STRONG WINDS POSSIBLE LATER TONIGHT INTO SUNDAY AS COLD FRONTS
SLICE THROUGH THE AREA
- MOISTURE-STARVED ACTIVE WEATHER NEXT WEEK AS NORTHWEST FLOW
OSCILLATES BAROCLINIC ZONE OVER THE NORTHERN PLAINS
DISCUSSION
(TODAY THROUGH FRIDAY)
ISSUED AT 216 AM MST SAT JAN 17 2026
09Z SURFACE ANALYSIS HAD WEAKENING LOW NEAR THE MACKINAC BRIDGE
WITH A COLD FRONT EXITING THE CWA. COMPACT HIGH BEHIND IT FROM MT
INTO CENTRAL CANADA. WATER VAPOUR LOOP SHOWED UPPER LOW OVER IA
WITH SHORTWAVE EXITING THE CWA. REGIONAL RADAR LOOP HAD SOME
LEFTOVER FLURRIES OVER SOUTHWEST SD ASSOCIATED WITH STRATOCUMULUS
ROTATING THROUGH PER NIGHTTIME RGB LOOP. LOOKING UPSTREAM, NEXT
DISTURBANCE TO AFFECT US OVER NORTHERN BC/AB.
TODAY, SURFACE ANTICYCLONE SLIPS THROUGH NORTHEAST WY/WESTERN SD
WITH ROBUST WARM AIR ADVECTION BEHIND IT. HOW MUCH OF THAT
REACHES THE GROUND DURING THE DAY IS QUESTIONABLE, SO CONFIDENCE
IN MAXT THIS AFTERNOON IS LESS THAN NORMAL.
TONIGHT/SUNDAY, 2 COMPACT SHORTWAVES WILL RACE SOUTH FROM CANADA
INTO THE NORTHERN PLAINS DROPPING A COUPLE OF COLD FRONTS THROUGH
THE CWA LATER TONIGHT INTO SUNDAY. FIRST COLD FRONT ASSOCIATED
WITH 2-4MB/3HR PRESSURE RISES/MODEST COLD AIR ADVECTION/40-60KT
LOWEST 2KM OF THE TROPOSPHERE ARRIVES OVERNIGHT. MIXING AHEAD OF
COLD FRONT LIKELY TO MAKE MANY CALENDAR DAY HIGH TEMPERATURES
OCCUR OVERNIGHT TONIGHT. SECOND COLD FRONT ARRIVES SUNDAY WITH
3-5MB/3HR PRESSURE RISES AND SIMILAR LOWEST 2KM FORECAST
SOUNDINGS. GOOD RECIPE FOR HIGH WINDS, SO HAVE HOISTED A HIGH WIND
WATCH TO ACCOUNT. HREF SEEMS TO UNDERPLAY (AS IT DID YESTERDAY)
PEAK WIND GUSTS WITH NBM GIVING 50-80% CHANCE OF >50KT WIND GUSTS,
ESPECIALLY FROM K2WX-KRAP. INTERESTING TIDBIT (AND WHY THE HIGH
WIND WATCH STARTS AT 18/03Z) IS A 6MB PRESSURE GRADIENT AND 50KT
BOUNDARY LAYER WIND ACROSS THE BLACK HILLS SUGGESTING DOWNSLOPE
ENHANCEMENT FROM SPEARFISH TO STURGIS AHEAD OF THE FIRST COLD
FRONT. MOISTURE WILL BE LIMITED WITH THIS SYSTEM, BUT CAN'T RULE
OUT SOME LIGHT SNOW, ESPECIALLY FOR THE NORTHERN BLACK HILLS.
TEMPERATURES WILL BE NEAR GUIDANCE.
NEXT WEEK LOOKS ACTIVE, BUT GIVEN SURFACE TRAJECTORIES, SYSTEMS
WILL BE MOISTURE-STARVED AS THEY RACE FROM CANADA INTO THE
NORTHERN PLAINS. THE BAROCLINIC ZONE IN PLACE WILL OSCILLATE WITH
FREQUENT BOUTS OF WIND AND TEMPERATURE VARIATION (AT LEAST 20F
PROBABILISTIC SPREADS BY THE END OF THE WEEK).
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1035 PM MST FRI JAN 16 2026
NW WINDS WILL CONTINUE TO DECREASE THROUGH THE OVERNIGHT HOURS. A
BAND OF SNOW SHOWERS IS CROSSING THE BLACK HILLS AREA THROUGH
SOUTHWEST SD. THIS WILL BRING TEMPORARILY HIGH WIND GUSTS OVER
50KT AND LOCALIZED MVFR/IFR VSBY. THESE SHOWERS WILL CONTINUE
SOUTHWARD OVER THE NEXT FEW HOURS, EXITING THE SOUTHERN SD BORDER
BY 08-09Z. VFR CONDITIONS ARE OTHERWISE EXPECTED THROUGH THE
FORECAST PERIOD. STRONG NW WINDS ARE EXPECTED TO RETURN SATURDAY
NIGHT.
FIRE WEATHER
ISSUED AT 216 AM MST SAT JAN 17 2026
VERY DRY AIR WILL BE IN PLACE OVER THE AREA TODAY AS WINDS
DIMINISH THIS AFTERNOON. MINIMUM RELATIVE HUMIDITIES WILL DROP TO
10-30% (EXCEPT 30S OVER SOUTH-CENTRAL SD). TOOK AT HARD LOOK AT
RED FLAG WARNING ISSUANCE OVER FAR SOUTHWESTERN SOUTH DAKOTA, BUT
THE JOINT PROBABILITY OF RH<15%/WIND GUSTS>25MPH FOR 3+ HOURS IS
LOW. A COUPLE OF COLD FRONTS THEN ARRIVE TONIGHT/SUNDAY WITH WIND
GUSTS FROM 40-70 MPH POSSIBLE, PARTICULARLY OVER THE WESTERN SD
PLAINS. BOTH FEATURES WILL LEAD TO ELEVATED TO NEAR-CRITICAL FIRE
WEATHER CONDITIONS FOR THIS WEEKEND.
LOOKING AHEAD TO NEXT WEEK, THE PATTERN CHANGES VERY LITTLE SO BE
PREPARED FOR FLUCTUATING TEMPERATURES AND WINDY PERIODS. EVENTUALLY,
COLDER WEATHER MAY BE MORE SUSTAINED BY NEXT WEEKEND, BUT EVEN THEN
PROBABILISTIC TEMPERATURE SPREADS INCREASE TO 30F LEADING TO LOW
CONFIDENCE IN EVENTUAL OUTCOME.
UNR WATCHES/WARNINGS/ADVISORIES
SD...HIGH WIND WATCH FROM THIS EVENING THROUGH SUNDAY AFTERNOON FOR
SDZ001-002-012-013-025-072-073-078.
HIGH WIND WATCH FROM LATE TONIGHT THROUGH SUNDAY AFTERNOON FOR
SDZ014-026-030>032-042-043-074.
HIGH WIND WATCH FROM SUNDAY MORNING THROUGH SUNDAY AFTERNOON FOR
SDZ027-041-075.
WY...HIGH WIND WATCH FROM THIS EVENING THROUGH SUNDAY AFTERNOON FOR
WYZ060.
DISCUSSION/KEY MESSAGES...HELGESON
AVIATION...13
FIRE WEATHER...HELGESON
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