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000
FXUS63 KUNR 160431
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1031 PM MDT SAT MAR 15 2014

.UPDATE...
ISSUED AT 713 PM MDT SAT MAR 15 2014

UPSLOPE SNOW HAS COME TO AN END SO HAVE CANCELLED THE WINTER WX
ADVISORY FOR THE NRN BLKHLS. ALSO...ISSUED AN SPS EARLIER FOR THE
-FZDZ ACROSS WCNTRL SD INCLUDING SPEARFISH STURGIS AND RAPID CITY.

UPDATE ISSUED AT 636 PM MDT SAT MAR 15 2014

GETTING SOME -FZDZ MIXED IN WITH THE SNOW AROUND THE BLKHLS AND
ADJACENT PLAINS...AND LOOKING AT THE 00Z KUNR SOUNDING THE
MOISTURE HAS BECOME QUITE SHALLOW WITH LESS SEEDING FROM ALOFT.
THUS...HAVE ADDED -FZDZ TO THE FCST FOR A FEW HOURS THIS EVE
BEFORE PCPN COMES TO AN END.

&&

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 203 PM MDT SAT MAR 15 2014

CURRENT SURFACE MAP PLACES COLD FRONT FROM EASTERN MONTANA INTO
FAR WESTERN SOUTH DAKOTA...SLOWLY BACKING WESTWARD INTO THE BLACK
HILLS. WATER VAPOR SHOWS WEAK SHORTWAVE CROSSING WESTERN SOUTH
DAKOTA...WITH MAIN WAVE DIGGING SOUTHWARD IN COLORADO. WITH
SURFACE FRONT BACKING INTO THE BLACK HILLS...COMBINATION LOW LEVEL
CONVERGENCE AND UPSLOPE ENHANCEMENT HAS LED TO AN INCREASE IN
PRECIPITATION INTENSITY OVER THE NORTHERN BLACK HILLS AND ADJACENT
PLAINS. TEMPERATURES CURRENTLY WARM ENOUGH ALONG I-90 CORRIDOR FOR
RAIN...WITH SNOW IN HIGHER BLACK HILLS.

FOR TONIGHT...PRECIPITATION WILL CONTINUE INTO THIS
EVENING...MAINLY FROM THE BLACK HILLS INTO SOUTH CENTRAL SOUTH
DAKOTA. RAPID CITY/STURGIS AREA SHOULD SEE TRANSITION TO SNOW
BEFORE PRECIPITATION ENDS. CURRENT WINTER WEATHER ADVISORY LOOKS
GOOD FOR THE BEAR LODGE/NORTHERN BLACK HILLS. CALLS AROUND THE
AREA SHOW THAT HIGHEST ACCUMULATIONS THROUGH THE DAY HAVE BEEN
ABOVE 5500FT. SNOW LEVELS WILL CONTINUE TO LOWER THROUGH THIS
EVENING. AS PRECIPITATION MOVES OUT OF THE AREA THIS
EVENING...FORECAST SOUNDINGS KEEP BL-2000KT LAYER NEARLY SATURATED
THROUGH MUCH OF THE NIGHT WITH DRYING ABOVE. WITH NE-E BL
WINDS...SOME FOG POSSIBLE OVERNIGHT WESTERN SOUTH DAKOTA.

UPPER RIDGE OVER THE NORTHERN ROCKIES BUILDS INTO THE NORTHERN
PLAINS SUNDAY/SUNDAY NIGHT. QUICK BOUNCE IN LOW LEVEL TEMPERATURES
FOR SUNDAY AS WARM FRONT PUSHES INTO THE CENTRAL DAKOTAS. MANY
LOCATIONS WILL REMAIN ABOVE FREEZING SUNDAY NIGHT WITH LOW LEVEL
THERMAL RIDGE OVER WESTERN SOUTH DAKOTA.

&&

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 230 PM MDT SAT MAR 15 2014

LONG TERM...MONDAY WILL BE A VERY MILD DAY AHEAD OF AN APPROACHING
UPPER LEVEL SYSTEM AND COLD FRONT. HIGHS WILL BE IN THE 50S AND
60S...WARMEST TO THE SOUTH AND EAST OF THE BLACK HILLS. CHANCES FOR
SHOWERS WILL INCREASE THROUGH THE AFTERNOON AND EVENING FROM WEST TO
EAST AS THE SHORTWAVE MOVES INTO THE AREA. NAM AND GFS ARE BOTH
SHOWING A WELL MIXED BOUNDARY LAYER WITH STEEP LAPSE RATES MONDAY
AFTERNOON ACROSS MUCH OF WESTERN SD. WITH SUFFICIENT LOW LEVEL
MOISTURE...MODELS ARE SHOWING ENOUGH INSTABILITY TO POTENTIALLY
PRODUCE A THUNDERSTORM OR TWO AS THE UPPER LEVEL SUPPORT ARRIVES.
HAVE ADDED A SLIGHT CHANCE FOR STORMS OVER THE BLACK HILLS AND MUCH
OF WESTERN SD FOR MONDAY AFTERNOON.

THE COLD FRONT AND MAIN FORCING WITH THE SHORTWAVE WILL PUSH THROUGH
MONDAY NIGHT AND TUESDAY MORNING...WITH RAIN AND SNOW EXPECTED
ACROSS MUCH OF THE CWA. PCPN WILL CHANGE OVER TO SNOW DURING THE
EVENING ACROSS NORTHEASTERN WY AND THE BLACK HILLS...AND ACROSS THE
REST OF THE CWA OVERNIGHT INTO EARLY TUESDAY. MANY AREAS WILL LIKELY
SEE AT LEAST A LIGHT ACCUMULATION OF SNOW...WITH THE HEAVIEST SNOWS
CONFINED TO THE NORTHERN BLACK HILLS...WHERE UPSLOPE ENHANCED SNOWS
WILL DEVELOP. SIX INCHES OR MORE IS LOOKING INCREASINGLY LIKELY OVER
THE FAVORED HIGHER ELEVATIONS OF THE NORTHERN HILLS. A WINTER STORM
WATCH MAY BE NEEDED FOR AT LEAST THE NORTHERN BLACK HILLS IF THE
LATEST MODEL TRENDS PERSIST. GUSTY NORTHWESTERLY WINDS WILL ALSO
DEVELOP ACROSS THE PLAINS LATER MONDAY NIGHT INTO TUESDAY...WHICH
COULD PRODUCE SOME BLOWING AND DRIFTING SNOW AS WELL. PCPN WILL
GENERALLY SLIDE OUT OF THE AREA LATE TUESDAY MORNING AND AFTERNOON.

BEYOND TUESDAY...NORTHWESTERLY FLOW ALOFT WILL GENERALLY PERSIST
THROUGH THE REST OF THE EXTENDED. OCCASIONAL WEAK DISTURBANCES IN
THE FLOW WILL BRING CHANCES FOR LIGHT RAIN AND SNOW...MAINLY TO
NORTHERN AND WESTERN PORTIONS OF THE CWA. TIMING OF THESE
DISTURBANCES IS UNCERTAIN AT THIS POINT...BUT THE BETTER CHANCES
LOOK TO BE LATE THURSDAY INTO FRIDAY. TEMPERATURES LOOK TO BE NEAR
AVERAGE ON WEDNESDAY AND SLIGHTLY ABOVE AVERAGE LATE IN THE WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1026 PM MDT SAT MAR 15 2014

WDSPRD MVFR/IFR CIGS WILL CONTINUE OVERNIGHT OVER PARTS OF NERN WY
AND MUCH OF THE WRN SD PLAINS...ALONG WITH AREAS OF -SN AND -FZDZ.
IFR/LIFR CIGS AND FOG ARE EXPECTED ALONG THE NRN/ERN FOOTHILLS OF
THE BLKHLS. CONDITIONS WILL IMPROVE FROM WEST TO EAST RATHER EARLY
SUNDAY MRNG.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

UPDATE...JOHNSON
SHORT TERM...7
LONG TERM...26
AVIATION...JOHNSON