Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 232340
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
440 PM MST SUN NOV 23 2014

.SHORT TERM...THIS EVENING THROUGH MONDAY NIGHT
ISSUED AT 240 PM MST SUN NOV 23 2014

PHASING CENTRAL CONUS UPPER TROUGHS CONTINUE TO SUPPORT STOUT SFC
PRESSURE FALLS OVER THE MIDWEST...AND RAPID CYCLOGENESIS THERE.
BACKSIDE LL CAA AND ISOBARIC ADJUSTMENT CONTINUES TO SUPPORT
STRONG NW WINDS ACROSS MOST OF THE FA...WHICH WILL BE THE CASE
INTO THE EVENING. ADVECTING UPPER LEVEL TROUGH AND ASSOCIATED COLD
POCKET COUPLED WITH DIURNAL HEATING HAS SUPPORTED A FEW SNOW
SHOWERS ACROSS THE REGION...WITH UPSLOPE FORCING SUPPORTING MORE
PERSISTENT ACTIVITY IN THE NORTHERN BLACK HILLS. ACTIVE NW FLOW
WILL SUPPORT ANOTHER COMPACT SHORTWAVE INTO THE REGION...WHICH
WILL RIDE NEAR THE LL BAROCLINIC ZONE SETTLING JUST SW OF THE FA.
THIS WILL CREATE A WESTERN SHIFT IN THE MID LEVEL IMPULSE
TRACK...SUPPORTING PRECIP CHANCES MAINLY OVER THE WESTERN THIRD
MONDAY. COLDER CONDITIONS WILL PREVAIL AS THE FA WILL MAINLY
REMAIN ON THE COLD SIDE OF THE LL FRONTAL ZONE.

TONIGHT...LARGE SCALE DECENT WILL OVERSPREAD THE REGION WITH SOME
LL DRYING THIS EVENING. THIS WILL SUPPORT A WANE IN ANY SNOW SHRA
ACTIVITY...ESP THE NORTHERN BLACK HILLS. WINDS WILL REMAIN GUSTY
MOST OF THE NIGHT...FALLING BELOW ADV CRITERIA THIS EVENING.
STRONGEST WINDS AND BEST DOWNWARD MOMENTUM TRANSPORT HAS OCCURRED
EARLIER THIS AFTERNOON...HENCE DECIDED TO CANCEL THE HWW AND
REPLACE WITH AN ADV. THE NEXT IMPULSE IN ACTIVE NW FLOW WILL
ARRIVE TOWARD DAWN...SUPPORTING A WEAK FGEN RESPONSE. HAVE
CONTINUED AN UPTICK IN POPS EARLY MONDAY MORNING...WITH CHANCES
FOR SNOW INCREASING ACROSS NE WY.

MONDAY...COMPACT SW TROUGH WILL ADVECT MAINLY OVER THE WESTERN
FA...SUPPORTING RENEWED FGEN WITH CHANCES FOR SNOW WESTERN HALF.
OVERALL...CHANCES FOR SNOW SHOWERS WILL BE LOW OUTSIDE OF THE
NORTHERN BLACK HILLS AND PORTIONS OF NE WY NEAR THE BLACK HILLS
GIVEN THAT THE BULK OF FORCING FOR ASCENT WILL REMAIN WELL SW OF THE
FA. HOWEVER...ENOUGH UPPER LEVEL SUPPORT WILL BE IN PLACE FOR
UPSLOPE FORCING WITH STEEP LL LAPSE RATES AND 20-30 KNOTS OF FLOW
IN INCREASING MOISTURE AND FROUDE. THIS WILL SUPPORT A DECENT
SETUP FOR SNOW SHOWERS WITH SOME ACCUMS IN THE NORTHERN BLACK
HILLS...WITH GENERALLY 1 TO 3 INCHES POSSIBLE...MAINLY FROM THE BEAR
LODGE MOUNTAINS TO AROUND CHEYENNE CROSSING. ANY SNOW ACCUMS OUTSIDE
OF THE BLACK HILLS WILL BE AN INCH OR LESS. BREEZY CONDITIONS CAN BE
EXPECTED ACROSS THE ENTIRE REGION...STRONGEST OVER NE WY GIVEN
PRESSURE RISE/FALL COUPLET WITH THE PASSING IMPULSE.

&&

.LONG TERM...TUESDAY THROUGH SUNDAY
ISSUED AT 240 PM MST SUN NOV 23 2014

AN ACTIVE PATTERN ASSOCIATED WITH DEEP CYCLONIC FLOW ALOFT WILL
CONTINUE ACROSS THE NORTHERN PLAINS INTO MIDWEEK. SEVERAL WEAK
DISTURBANCES WITHIN NORTHWEST FLOW WILL SLIDE THROUGH...BRINGING A
GOOD DEAL OF CLOUDINESS AND CHANCES FOR SNOW SHOWERS AT TIMES FROM
TUESDAY THROUGH WEDNESDAY NIGHT. THE BEST CHANCES FOR SNOW WILL
GENERALLY BE ACROSS FAR NORTHEAST WY AND THE NORTHERN BLACK HILLS
AREA...WHERE SOME LIGHT ACCUMULATIONS ARE A GOOD POSSIBILITY.

FOR THE HOLIDAY PERIOD...LONGER RANGE MODELS CONTINUE TO HAVE A VERY
DIFFICULT TIME SETTLING ON A CONSISTENT SOLUTION FROM THANKSGIVING
DAY INTO THE HOLIDAY WEEKEND. SIGNIFICANT RUN TO RUN INCONSISTENCIES
PERSIST...WITH THE LATEST 12Z RUNS OF THE GFS AND ECMWF NOW MUCH
WARMER FOR LATE THIS WEEK...WITH THE CANADIAN MODEL STILL ON THE
COLDER SIDE. WILL CONTINUE WITH MORE OF A BLEND OF THE MODELS FOR
NOW AND KEEP IT COLDER THAN LATEST 12Z GUIDANCE. IT STILL LOOKS
MAINLY DRY FROM THANKSGIVING DAY INTO THE WEEKEND...BUT A FEW
SHOWERS DO LOOK POSSIBLE THANKSGIVING DAY AND NIGHT IF A FRONTAL
BOUNDARY HAPPENS TO BE IN THE AREA.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 436 PM MST SUN NOV 23 2014

GUSTY NORTHWEST WINDS WILL CONTINUE THROUGH THIS EVENING. ISOLATED
TO SCATTERED SHSN/MVFR CIGS ARE MOST LIKELY ACROSS NORTHWEST
SD...THE NORTHERN BLACK HILLS...AND PORTIONS OF NORTHEAST WY INTO
THE EVENING HOURS. LOCALIZED IFR CONDITIONS ARE EXPECTED WITH
UPSLOPE ENHANCED SHSN OVER THE NORTHERN BLACK HILLS THIS
AFTERNOON. VFR CONDITIONS THEN EXPECTED OVERNIGHT WITH MVFR
CIGS/VSBYS STARTING VERY LATE TONIGHT OVER NORTHEAST WY INTO
WESTERN SD WHERE -SN DEVELOPS LASTING THROUGH MONDAY AFTERNOON.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY UNTIL 8 PM MST /9 PM CST/ THIS EVENING FOR SDZ001-
     002-012>014-025>027-031-032-041-043-044-046-047-049-072-073.

WY...NONE.
&&

$$

SHORT TERM...JC
LONG TERM...26
AVIATION...HELGESON





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