Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 160441
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1041 PM MDT WED OCT 15 2014

.SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT
ISSUED AT 540 PM MDT WED OCT 15 2014

THE MAIN FORECAST CONCERN IS THE PACIFIC COLD FRONTAL PASSAGE
OVERNIGHT AND EARLY THURSDAY...AND THE RESULTANT GUSTY WEST TO
NORTHWEST WINDS. IT ALSO SHOULD BE A VERY MILD NIGHT AHEAD OF THE
COLD FRONT AS WE ARE UNDER A THERMAL RIDGE.

A STRONG SHORT-WAVE TROUGH WILL MOVE ACROSS THE NORTHERN HIGH PLAINS
TONIGHT AND ACROSS NODAK ON THURSDAY. THE NAM IS A LITTLE SLOWER
WITH THE UPPER LOW BUT OTHERWISE ALL MODELS ARE SIMILAR ON THE
STRENGTH OF THE SYSTEM...AS WELL AS STRONG SUBSIDENCE ACROSS THE NRN
2/3 OF THE CWA LATE TNGT AND THURSDAY.

AHEAD OF THE TROUGH AND COLD FRONT THIS EVNG THERE WILL BE SOME
DOWNSLOPE FLOW ACROSS THE NERN BLKHLS...AND THIS MAY PRODUCE
ADVY-LEVEL WINDS. THE SFC MSLP GRADIENT IS ONLY PROGGED TO BE 3-4 MB
ACROSS THE NRN BLKHLS...WHICH TYPICALLY IS TOO WEAK FOR WRNG
CRITERIA DOWNSLOPE WINDS.

THE PACIFIC FRONT SHOULD PASS INTO NWRN SD BTWN 03-06Z...AND WITH
850-MB WINDS OF 50-55 KT AND 3-HR SFC PRES RISES OF 3-5 MB THERE
SHOULD BE 1-3 HR OF STRONG WINDS BEHIND THE FRONT. THE FRONT THEN
WILL SWEEP ACROSS THE REST OF NWRN/WCNTRL SD BTWN 06-12Z. THE MAIN
NEGATIVE FACTOR FOR STRONG WINDS IS THE TIME OF DAY (I.E. LACK OF
HEATING)...WHICH FAVORS DECOUPLING OF THE PBL. AS A RESULT...HAVE
OPTED FOR A WIND ADVY IN LIEU OF A HIGH WIND WRNG. BUT THERE COULD
BE A FEW SPOTS THAT BRIEFLY HIT GUSTS OF 50 KT WITH THE FROPA.

THE STRONGEST 850-MB COLD ADVECTION (-1 TO -3 C/HR) WILL OCCUR AT
12Z OVER CNTRL SD...WITH WEAKENING COLD ADVECTION THEREAFTER. THIS
AGAIN WILL LIMIT THE POTENTIAL FOR MAXIMUM WIND PRODUCTION...AND
ALSO SHOULD RESULT IN DIMINISHING WINDS THRU THE AFTN. THUS...WILL
END THE WIND ADVY AT 21Z.

THE TROUGH EXITS THURSDAY NIGHT WITH LIGHTER WINDS AND NEAR-AVERAGE
TEMPS PREVAILING.

&&

.LONG TERM...FRIDAY THROUGH TUESDAY
ISSUED AT 540 PM MDT WED OCT 15 2014

.LONG TERM...MEAN UPPER RIDGE WILL PREVAIL THROUGH THE PERIOD AS IT
SLOWLY MOVES FROM WESTERN NORTH AMERICA TO CENTRAL NORTH AMERICA
FRIDAY THROUGH TUESDAY. COOLEST DAY SHOULD BE FRIDAY AS SURFACE HIGH
RESTS OVER CWA. SURFACE HIGH SHIFTS EAST OVER THE WEEKEND RESULTING
IN RETURN FLOW/WARM AIR ADVECTION AND THE DEVELOPMENT OF LEE TROUGH
FROM MT INTO WESTERN NE. RESULT WILL BE A SLOW WARMING TREND WITH
TEMPERATURES 10-15F ABOVE NORMAL BY TUESDAY. MOST GUIDANCE SHOWS
UPPER TROUGH/SHORTWAVE MOVING THROUGH FOR WEDNESDAY...BUT MOISTURE
MAY BE LIMITED SO WILL FORGO POPS AT THIS POINT.

&&

.AVIATION...FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT
ISSUED AT 1040 PM MDT WED OCT 15 2014

VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD. A STRONG COLD
FRONT WILL BRING GUSTY NORTHWEST WINDS TO THE ENTIRE AREA TONIGHT
AND THURSDAY MORNING...PARTICULARLY ON THE WRN SD PLAINS WHERE
GUSTS AROUND 40KTS ARE LIKELY.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY UNTIL 4 PM MDT THURSDAY FOR SDZ002-013-014-026-031-
     032-072-073.

     WIND ADVISORY UNTIL 4 PM MDT THURSDAY FOR SDZ001-012-025.

WY...NONE.
&&

$$

SHORT TERM...BUNKERS
LONG TERM...HELGESON
AVIATION...10






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