Area Forecast Discussion
Issued by NWS Rapid City, SD

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773
FXUS63 KUNR 161737
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1137 AM MDT SAT MAY 16 2015

.UPDATE...
ISSUED AT 1035 AM MDT SAT MAY 16 2015

DRY SLOT HAS WORKED THROUGH OUR CWFA THIS MORNING. LATEST MODELS
ARE SHOWING LESS INSTABILITY AND PCPN CHANCES FOR THE WRN TWO
THIRDS OF OUR ZONES TODAY SO HAVE CUT BACK ON POPS THESE AREAS.
BEST CHANCES FOR MORE WDSPRD ACTIVITY WILL BE ACROSS OUR ERN
ZONES THIS AFTN/EVE AS SHORT WAVE CURRENTLY EJECTING NEWD INTO ERN
CO ARRIVES. MLCAPE NEAR 1000J/KG AND PLENTY OF SHEAR WILL BE
SUFFICIENT FOR A FEW SUPERCELLS...ALTHOUGH BEST CHANCES FOR SVR
STORMS WILL RESIDE EAST OF OUR AREA.

&&

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
ISSUED AT 300 AM MDT SAT MAY 16 2015

CURRENT SURFACE MAP PLACES LOW JUST EAST OF THE BLACK HILLS...WITH
TROF EXTENDING INTO THE NEBRASKA PANHANDLE. SHOWERS/ISOLATED
THUNDERSTORMS LINGER ACROSS NORTHWEST SOUTH DAKOTA INTO SOUTH
CENTRAL SOUTH DAKOTA. LOW CLOUDS/FOG/DRIZZLE REMAIN IN VICINITY OF
BLACK HILLS.

FOR TODAY...CURRENT SHOWERS/ISOLATED THUNDERSTORMS WILL CONTINUE
TO LIFT NORTHWARD EARLY THIS MORNING...WITH MID LEVEL DRY SLOT
OVER EASTERN WYOMING/FAR WESTERN SOUTH DAKOTA. LOW CLOUDS EXPECTED
TO DISSIPATE THIS MORNING...WITH SOME SUNSHINE ACROSS THE AREA.
SHORTWAVE CROSSES THE AREA THIS AFTERNOON...WITH ANOTHER ROUND OF
SHOWERS/THUNDERSTORMS. BEST INSTABILITY/SHEAR ACROSS CENTRAL
SOUTH DAKOTA. MAY BE SOME ISOLATED SEVERE THUNDERSTORMS SOUTH
CENTRAL SOUTH DAKOTA...OTHERWISE BEST POTENTIAL FOR SEVERE
THUNDERSTORMS WILL BE EAST AND SOUTH OF THE FORECAST AREA.

STRONG SHORTWAVE EJECTS OUT OF WESTERN CONUS LOW TONIGHT...WITH
CUTOFF LOW DEVELOPING NEBRASKA TONIGHT...THEN LIFTING INTO EASTERN
SOUTH DAKOTA SUNDAY. DEFORMATION ZONE ON BACK SIDE OF LOW WILL
BRING SHOWERS TO THE AREA FOR SUNDAY...WITH THE BEST CHANCE OF
RAIN NORTH AND EAST OF THE BLACK HILLS. SHOWERS LINGER INTO SUNDAY
NIGHT...WITH THERMAL PROFILES SUPPORTING RAIN/SNOW MIX FROM THE
BLACK HILLS INTO NORTHWEST SOUTH DAKOTA.

.LONG TERM...MONDAY THROUGH FRIDAY
ISSUED AT 300 AM MDT SAT MAY 16 2015

MEDIUM RANGE MODELS IN PRETTY GOOD AGREEMENT ON GENERAL
PATTERN FOR NEXT WEEK...WITH PERSISTENT UPPER TROF ALONG THE WEST
COAST BRINGING A SERIES OF SYSTEMS ACROSS THE NORTHERN PLAINS DURING
THE WEEK. AFTER A BRIEF BREAK FROM PCPN ON MONDAY...UNSETTLED WX
WILL RETURN ON TUESDAY. THE BEST CHANCES FOR PCPN LOOK TO BE TUESDAY
AFTERNOON INTO WEDNESDAY WITH THE FIRST OF THESE SYSTEMS. COOLER AND
MORE STABLE AIRMASS IN PLACE WILL LIMIT ACTIVITY TO MAINLY SHOWERS.
TEMPERATURES LOOK COLD ENOUGH AT THIS POINT FOR SOME SNOW ACROSS AT
LEAST THE HIGHER BLACK HILLS DURING THE TUESDAY NIGHT/WEDNESDAY
MORNING PERIOD. WEAKER DISTURBANCES WILL BRING ADDITIONAL CHANCES
FOR SHOWERS AND STORMS LATE IN THE WEEK...WITH ANOTHER STRONGER
SYSTEM POSSIBLY BRINGING MORE SIGNIFICANT RAINFALL NEXT WEEKEND.
TEMPERATURES WILL STAY BELOW AVERAGE THROUGH MUCH OF THE WEEK...WITH
HIGHS MOSTLY IN THE 50S ACROSS THE PLAINS...SOME 40S OVER THE BLACK
HILLS EARLY IN THE WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY)
ISSUED AT 1131 AM MDT SAT MAY 16 2015

FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING
ISSUED AT 545 AM MDT SAT MAY 16 2015

VFR CONDITIONS WILL CONTINUE ACROSS NORTHEAST WY AND FAR WESTERN
SOUTH DAKOTA TODAY. FURTHER EAST...IFR/MVFR CEILINGS WILL
GRADUALLY IMPROVE TO VFR FROM WEST TO EAST ACROSS CENTRAL SD THIS
AFTERNOON AS SOME DRIER AIR PUSHES INTO THE AREA. SMALL CHANCES
FOR SHOWERS AND THUNDERSTORMS WILL RETURN THIS AFTERNOON...BEST
CHANCES ACROSS THE BLACK HILLS AREA AND ACROSS FAR SOUTH CENTRAL
SOUTH DAKOTA. MVFR TO IFR CONDITIONS WILL RETURN TO NORTHEAST
WYOMING AROUND MIDNIGHT...AND WESTERN SOUTH DAKOTA EARLY SUNDAY
MORNING...AS THE NEXT WEATHER SYSTEM MOVES INTO THE AREA.


&&

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

$$

UPDATE...JOHNSON
SHORT TERM...7
LONG TERM...26
AVIATION...15



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