Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 201515
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
915 AM MDT WED AUG 20 2014

.UPDATE...
ISSUED AT 915 AM MDT WED AUG 20 2014

CURRENT SURFACE ANALYSIS SHOWS WEAK LOW PRESSURE OVER WESTERN
SD...WITH WARM FRONT EXTENDING SOUTHEAST THROUGH EASTERN NEB.
A COLD FRONT ALSO EXTENDS ACROSS NORTHERN MT. UPPER LEVEL
ANALYSIS SHOWS A LOW OVER THE NORTHERN GREAT LAKES REGION...WITH
HIGH PRESSURE OVER THE SOUTHERN PLAINS. A LARGE SCALE TROF NOW
COVERS MUCH OF THE WESTERN CONUS. SOUTHWEST FLOW IN PLACE OVER THE
HIGH PLAINS IS BRINGING UNSETTLED WEATHER TO THE AREA. KUDX RADAR
SHOWS ISOLATED TO SCATTERED LIGHT SHOWERS OVER MOSTLY WESTERN SD
AT THIS TIME. TEMPS ARE IN THE UPPER 60S AND 70S AT THIS HOUR
UNDER VARIABLY CLOUDY SKIES.

THE BEST CHANCE FOR SHOWERS AND STORMS THROUGH THE AFTERNOON WILL
GENERALLY BE ACROSS AREAS NORTH AND EAST OF THE BLACK
HILLS...THOUGH ANY PART OF THE CWA COULD SEE A SHOWER OR
THUNDERSTORM THROUGH THE DAY. THE BEST INSTABILITY IS PROGGED TO
BE NEAR AND EAST OF THE SURFACE LOW...WHICH WILL REMAIN ACROSS
WEST CENTRAL SD INTO THE AFTERNOON AND THEN SLOWLY MOVE EAST-
SOUTHEAST OF THE AREA. THE SLIGHT RISK FOR SEVERE STORMS THIS
AFTERNOON GENERALLY REMAINS NEAR AND EAST OF A LINE FROM LEMMON TO
PHILIP TO MARTIN.

HAVE UPDATED TO MAKE SOME ADJUSTMENTS TO POPS FOR TODAY AND TO ADD
SLIGHT CHANCE POPS TO NORTHEAST WY AND THE BLACK HILLS AREA FOR
TONIGHT AS ANOTHER WEAK DISTURBANCE MOVES THROUGH THESE AREAS.
HAVE NOT MADE ANY ADJUSTMENTS TO HIGH TEMPS AT THIS POINT...BUT
THEY MAY NEED TO BE TWEAKED A BIT IN SOME AREAS THROUGH THE
DAY...DEPENDING ON EXTENT OF CLOUD AND SHOWER COVERAGE.

&&

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT
ISSUED AT 218 AM MDT WED AUG 20 2014

UPPER LEVEL ANALYSIS HAS RIDGE OVER THE CENTRAL CONUS WITH LARGE
TROF ACROSS THE WESTERN CONUS. RIDGE AXIS RESIDES OVER THE DAKOTAS
WITH SOUTHWEST UPPER FLOW MOVING INTO THE AREA. SKIES ARE MOSTLY
CLOUDY ACROSS MUCH OF THE FORECAST AREA WITH SCATTERED LIGHT
SHOWERS ACROSS SOUTH CENTRAL SOUTH DAKOTA...NORTHEAST
WYOMING...AND FAR WESTERN SOUTH DAKOTA. AT THE SURFACE...LOW
PRESSURE IS LOCATED ACROSS SOUTHEAST MONTANA WITH WEAK WARM
FRONTAL BOUNDARY EXTENDING INTO WESTERN SOUTH DAKOTA. TEMPERATURES
AT 2 AM ARE IN THE 60S AND 70S...WITH GENERALLY LIGHT WINDS. THE
EXCEPTION...BREEZY SOUTHWEST WINDS ACROSS PARTS OF NORTHEAST
WYOMING JUST SOUTH OF THE SURFACE LOW.

TODAY AND TONIGHT...CHANCES FOR SHOWERS AND STORMS WILL CONTINUE
TODAY WITH BEST CHANCES ACROSS NORTHWESTERN SD AS THE MAIN UPPER
SHORTWAVE MOVES SLOWLY NORTHEAST AND EVENTUALLY INTO ND BY LATE IN
THE DAY. PCPN CHANCES WILL GENERALLY DECREASE FURTHER SOUTH AND
EAST ACROSS THE CWA. SKIES WILL BE VARIABLY CLOUDY...WITH THE MOST
CLOUDS ACROSS NORTHERN AREAS. HIGHS WILL RANGE FROM THE LOWER 80S
ACROSS NORTHWESTERN SD TO THE LOWER 90S ACROSS PORTIONS OF
SOUTHERN SD. A SURFACE TROF WILL SLOWLY MOVE ACROSS THE AREA
DURING THE DAY...SWITCHING WINDS TO THE WEST/NORTHWEST BEHIND IT.
THE FOCUS FOR POTENTIAL STRONG TO SEVERE STORMS WILL BE MAINLY
ACROSS CENTRAL SD DURING THE AFTERNOON...AHEAD OF THE TROF AND IN
REGION OF STRONGER INSTABILITY. PCPN CHANCES SHOULD TAPER OFF FROM
SOUTHWEST TO NORTHEAST DURING THE LATE AFTERNOON AND EVENING
HOURS...WITH PCPN ENDING ACROSS THE AREA AFTER MIDNIGHT. LOW
TEMPERATURES WILL BE IN THE MID 50S TO MID 60S.

THURSDAY...UPPER LEVEL FLOW REMAINS SOUTHWEST AS WEAK SURFACE HIGH
PRESSURE MOVES INTO THE DAKOTAS. WEAK SHORTWAVE ENERGY WILL LIFT
THROUGH WESTERN AND NORTHERN PORTIONS OF THE FORECAST
AREA...BRINGING ANOTHER ROUND OF SHOWERS AND STORMS TO NORTHEAST
WYOMING AND FAR WESTERN SOUTH DAKOTA. HIGH TEMPERATURES WILL CLIMB
INTO THE 80S TO NEAR 90 DEGREES...WITH SOME 70S ACROSS THE BLACK
HILLS.

&&

.LONG TERM...FRIDAY THROUGH TUESDAY
ISSUED AT 218 AM MDT WED AUG 20 2014

LARGE UPPER TROF WILL WORK THROUGH THE ROCKIES ON
FRIDAY/SATURDAY...THEN PUSH INTO THE PLAINS SUNDAY THROUGH EARLY
NEXT WEEK. TEMPS WILL GRADUALLY COOL THROUGH THE WEEKEND...WITH
SUNDAY LIKELY BEING THE COOLEST DAY IN THE EXTENDED WITH TEMPS
STRUGGLING TO GET OUT OF THE 60S IN MANY AREAS...ESPECIALLY NERN
WY/BLKHLS/NWRN SD. TEMPS WILL THEN SLOWLY MODERATE EARLY NEXT WEEK
BUT STILL REMAIN WELL BELOW AVERAGE. PCPN CHANCES WILL CONTINUE
THROUGH MOST OF THE EXTENDED PERIOD...WITH THE BEST CHANCES
OCCURRING EARLY IN THE WEEKEND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 638 AM MDT WED AUG 20 2014

ISOLD/SCT -SHRA EXPECTED THIS MORNING BUT MOSTLY VFR CONDITIONS
EXPECTED EVEN WITHIN -SHRA. SCT TSRA ARE EXPECTED TO DEVELOP THIS
AFTN...WITH A DECREASE IN COVERAGE TONIGHT. THE BEST CHANCES WILL
BE FROM THE BLKHLS THROUGH NWRN SD. LOCAL IFR CIGS/VSBYS WILL
OCCUR WITH THE HEAVIEST STORMS. OUTSIDE OF STORMS...VFR CONDITIONS
WILL PREVAIL.

&&

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

$$

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






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