Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 171557
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
957 AM MDT SUN AUG 17 2014

.UPDATE...
ISSUED AT 957 AM MDT SUN AUG 17 2014

THE MAIN FEATURE ON THE LARGE SCALE MAPS THIS MORNING
IS THE SLOW MOVING CLOSED LOW MOVING THROUGH THE SOUTHERN
CANADIAN PRAIRIE PROVINCES. IMPULSES ROTATING AROUND THE SOUTHERN
PERIPHERY OF THIS SYSTEM OVER A PERSISTENT WEAK SURFACE TROUGH ARE
THE WEATHER MAKERS FOR THE UNR CWFA TODAY. THE FIRST ONE IS
PRODUCING A FEW MODERATELY STRONG STORMS OVER NORTHWESTERN AND
WEST CENTRAL SOUTH DAKOTA THIS MORNING WHICH WILL INTO CENTRAL
SOUTH DAKOTA IN THE NEXT COUPLE OF HOURS. A STRONG SUBTROPICAL UPPER
RIDGE ACROSS THE SOUTHWESTERN TWO THIRDS OF THE CONUS IS KEEPING
THE MONSOON PLUME PUSHED OFF TO THE SOUTHEAST...LIMITING MOISTURE
ADVECTION INTO THE NORTHERN PLAINS.

THIS EVENING AND TONIGHT...THE NEXT IMPULSE...CURRENTLY MOVING
INTO NORTHEAST WYOMING IS A LITTLE STRONGER AND WILL PROVIDE
SLIGHTLY MORE SHEAR TO THE ENVIRONMENT. BULK SHEAR IS GENERALLY
FORECAST TO REMAIN BELOW 40 KTS MUCAPE BELOW 2000 J/KG SBCAPE
BELOW 1500 J/KG. HOWEVER SEVERAL SEVERE STORMS ARE POSSIBLE WITH
THE PRIMARY THREATS BEING LARGE HAIL AND LOCAL GUSTY THUNDERSTORM
WINDS. DEVELOPMENT OF THE SECOND GROUP OF STORMS IS EXPECTED
THROUGH THE EARLY TO MID AFTERNOON HOURS WITH THE CELLS
ACCOMPANYING THE UPPER LEVEL SHORT WAVE COMBINING INTO AN MCS AND
MOVING INTO NORTH CENTRAL SOUTH DAKOTA BETWEEN 22Z AND 00Z. GOOD
STORM MOTION SHOULD PRECLUDE THE THREAT OF WIDESPREAD HEAVY
RAINFALL ACCUMULATIONS.

&&

.SHORT TERM...TODAY THROUGH MONDAY NIGHT
ISSUED AT 325 AM MDT SUN AUG 17 2014

UPPER LEVEL ANALYSIS HAS RIDGE ACROSS THE SOUTHWEST CONUS WITH CUT
OFF LOW SPINNING ACROSS SOUTHERN SASKATCHEWAN. SKIES ARE MOSTLY
CLEAR WITH THE EXCEPTION OF SOME STORMS ACROSS FAR NORTHWEST SOUTH
DAKOTA. AT THE SURFACE...LOW PRESSURE HAS MOVED INTO NORTHEAST
SOUTH DAKOTA...WITH WEAK HIGH PRESSURE ACROSS WESTERN PORTIONS OF
THE FORECAST AREA. TEMPERATURES AT 3 AM ARE IN THE 60S WITH LIGHT
WINDS.

TODAY AND TONIGHT...WEAK SHORTWAVE ENERGY WILL SLIDE ACROSS
NORTHWESTERN SOUTH DAKOTA EARLY THIS MORNING...WITH SOME LIGHT
SHOWERS AND STORMS ON-GOING. SOME AREAS OF FOG WILL BE POSSIBLE
ACROSS FAR NORTHWEST SOUTH DAKOTA THIS MORNING. LATER
THIS MORNING AS UPPER LOW APPROACHES...WEAK HEIGHT FALLS WILL
BRING IN A LITTLE COOLER AIR ALOFT...HELPING TO DESTABILIZE THE
ATMOSPHERE AND PROVIDE A FEW WEAK IMPULSES DURING THE
DAY...TRIGGERING A FEW STORMS OVER THE HIGHER TERRAIN OF NORTHEAST
WYOMING...THE BLACK HILLS...AND NORTHWEST SOUTH DAKOTA. SHORTWAVE
CURRENTLY OVER IDAHO WILL MERGE WITH A SHORTWAVE TROF ROTATING
AROUND THE UPPER LOW THIS AFTERNOON...BRINGING MORE WIDESPREAD
SHOWERS AND THUNDERSTORMS TO WESTERN SOUTH DAKOTA. DECENT LAPSE
RATES AND MODEST SHEAR WILL BE IN PLACE THIS AFTERNOON...SO SOME
STRONG TO SEVERE STORMS ARE EXPECTED ACROSS WESTERN SOUTH
DAKOTA...PERSISTING INTO THE EVENING HOURS. HIGH TEMPERATURES WILL
BE IN THE 80S TO LOWER 90S.

ON MONDAY...UPPER LEVEL LOW SHIFTS EAST AS RIDGE BUILDS ACROSS THE
WESTERN CONUS. OTHER THAN AN ISOLATED SHOWER OR TWO ACROSS
NORTHWEST SOUTH DAKOTA...SKIES WILL BE MOSTLY SUNNY. HIGH
TEMPERATURES WILL BE SLIGHTLY COOLER...IN THE MID 70S TO UPPER
80S.

&&

.LONG TERM...TUESDAY THROUGH SATURDAY
ISSUED AT 325 AM MDT SUN AUG 17 2014

UPPER RIDGE PUSHES EAST OF THE REGION ON TUESDAY AS LARGE UPPER TROF
WORKS SLOWLY EWD THROUGH THE WRN CONUS. EMBEDDED SHORT WAVE ACTIVITY
IN THE SW FLOW ALOFT ACRS THE NRN PLAINS WILL BEING A NEARLY DAILY
CHANCE FOR TSTMS TO OUR REGION FROM MID WEEK INTO NEXT WEEKEND.
LATEST GFS/ECMWF SOLUTIONS SUGGEST THE UPPER TROF WILL WORK INTO THE
PLAINS SOMETIME NEXT WEEKEND. TEMPS WILL REMAIN NEAR AVERAGE THROUGH
THE WEEK...BUT SHOULD COOL OVER THE WEEKEND.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING
ISSUED AT 325 AM MDT SUN AUG 17 2014

MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD...HOWEVER SCT
MVFR/IFR CIGS ARE POSSIBLE EARLY THIS MRNG OVER PARTS OF NWRN-CNTRL
SD. SCT TSRA OVER NWRN SD EARLY THIS MRNG WILL PRODUCE LCL IFR
VSBYS. SCT TSRA WILL DEVELOP OVER THE BLKHLS AND MUCH OF WRN SD THIS
AFTN/EVE AND PRODUCE LCL IFR CIGS/VSBYS.


&&

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

$$

UPDATE...CARPENTER
SHORT TERM...15
LONG TERM...JOHNSON
AVIATION...JOHNSON





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