Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 292320
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
520 PM MDT FRI AUG 29 2014

.SHORT TERM...THIS EVENING THROUGH SATURDAY NIGHT
ISSUED AT 300 PM MDT FRI AUG 29 2014

CURRENT SURFACE ANALYSIS SHOWS LOW PRESSURE OVER WESTERN MN...
WITH COOL FRONT NOW SOUTH AND EAST OF THE CWA. UPPER LEVEL
ANALYSIS SHOWS SLOW MOVING LOW OVER SOUTHWEST IA...WITH SHORTWAVE
ENERGY BEHIND IT MOVING ACROSS THE WESTERN INTO CENTRAL DAKOTAS.
KUDX RADAR SHOWS ISOLATED TO SCATTERED SHOWERS FROM NORTH CENTRAL
INTO SOUTHWEST SD...WITH THE STRONGEST CELL OVER THE SOUTHEAST
SLOPES OF THE BLACK HILLS. A FEW LIGHTNING STRIKES HAVE BEEN NOTED
WITH THE CELL OVER FALL RIVER COUNTY. NORTHWEST WINDS REMAIN
BREEZY ACROSS PORTIONS OF THE SD PLAINS...BUT ARE GRADUALLY
DECREASING. TEMPS ARE IN THE LOWER 70S TO MID 80S.

A UNSETTLED WEATHER PATTERN CAN BE EXPECTED THROUGH THE HOLIDAY
WEEKEND...WITH NUMEROUS DISTURBANCES IN NEAR ZONAL FLOW BRINGING
OCCASIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS. THE BEST CHANCES
IN THE NEAR TERM LOOK TO BE LATE SATURDAY AND DURING THE DAY ON
SUNDAY. TEMPERATURES WILL BE A BIT ABOVE AVERAGE SATURDAY AND
SLIGHTLY BELOW AVERAGE FOR SUNDAY AND MONDAY.

FOR TONIGHT...ANY LINGERING SHOWERS OVER SOUTH CENTRAL SD WILL END
EARLY IN THE EVENING...WITH MOSTLY CLEAR SKIES INTO THE OVERNIGHT.
HOWEVER...SOME LOW CLOUDS COULD DEVELOP ON THE EASTERN EDGES OF THE
CWA AFTER MIDNIGHT...WITH PATCHY FOG ALSO LIKELY LATE
TONIGHT...ESPECIALLY IN THE VALLEYS. LOWS WILL MOSTLY BE IN THE
50S WITH LIGHT AND VARIABLE WINDS OVERNIGHT.

CLOUDS WILL GENERALLY INCREASE FROM WEST TO EAST ON SATURDAY...
ESPECIALLY IN THE AFTERNOON...AS THE NEXT DISTURBANCE APPROACHES.
THE BEST FORCING WILL PASS TO THE NORTH OF THE AREA ACROSS EASTERN
MT AND ND LATE IN THE DAY AND EVENING. SOUTH-SOUTHEAST WINDS WILL
DEVELOP AHEAD OF THE NEXT COLD FRONT...BRINGING WARMER AND MOISTER
AIR INTO THE AREA DURING THE DAY. HIGHS WILL BE IN THE UPPER 70S AND
80S ACROSS MOST OF THE AREA...WITH DEWPOINTS CREEPING BACK INTO THE
UPPER 50S AND LOWER 60S ACROSS THE SD PLAINS BY LATE IN THE DAY.
THIS WILL PRODUCE MODERATE INSTABILITY OVER THE AREA...ESPECIALLY
OVER NORTHWESTERN SD...WITH CAPE VALUES OF 1000 TO OVER 1500 J/KG BY
00Z. TIMING OF THE DISTURBANCE WILL BE IMPORTANT WITH REGARD TO
COVERAGE AND SCOPE OF POTENTIAL FOR SEVERE WEATHER. AS IT STANDS
NOW...THE BEST THREAT FOR A SEVERE STORM OR TWO WILL BE ACROSS
NORTHWESTERN SD...WHERE SHEAR WILL BE MOST FAVORABLE. THE THREAT
WILL DIMINISH FURTHER TO THE SOUTH WHERE THE FORCING IS WEAKER AND
CIN COULD BE SUFFICIENT ENOUGH TO KEEP STORM CHANCES TO A MINIMUM.
THE BEST CHANCE FOR STORMS WILL HOLD OFF UNTIL LATE AFTERNOON OR
POSSIBLY EARLY EVENING OVER WESTERN PORTIONS OF THE CWA...WITH THE
BEST CHANCE ELSEWHERE DURING THE EVENING. ACTIVITY WITH THIS WAVE
SHOULD MOVE OUT OF THE AREA FROM WEST TO EAST BY THE OVERNIGHT. THE
NEXT SYSTEM WILL APPROACH NORTHEAST WY LATE SATURDAY NIGHT AND MOVE
ACROSS THE FORECAST AREA ON SUNDAY.

&&

.LONG TERM...SUNDAY THROUGH FRIDAY
ISSUED AT 300 PM MDT FRI AUG 29 2014

CYCLONIC FLOW ASSOCIATED WITH UPPER TROUGH WILL MOVE THROUGH THE
CWA SUNDAY/MONDAY. FORCING WITH EMBEDDED SHORTWAVES AS WELL AS
STEEP MID-LEVEL LAPSE RATES WILL SUPPORT SCATTERED
-SHRA/-TSRA...ESPECIALLY SUNDAY/SUNDAY EVENING. TEMPERATURES WILL
BE FAIRLY CHILLY SUNDAY GIVEN CLOUD COVER AND LOW LEVEL COLD AIR
ADVECTION THROUGHOUT THE DAY.

AN UPPER LEVEL RIDGE TRIES TO POKE INTO THE NORTHERN PLAINS FOR THE
MIDDLE OF NEXT WEEK AS AN UPPER TROUGH DIGS INTO WESTERN
CANADA/NORTHWEST US. AMOUNT OF AMPLIFICATION BECOMING UNCERTAIN WITH
POSSIBLE FLAT RIDGE AND EMBEDDED SHORTWAVES MOVING ACROSS THE
US/CANADIAN BORDER. THIS COULD BRING A FEW WIND SHIFTS THROUGH THE
AREA...BUT IN GENERAL...A WARMER/DRIER TREND IS EXPECTED AS THERMAL
RIDGE BUILDS OVERHEAD.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING
ISSUED AT 515 PM MDT FRI AUG 29 2014

MVFR CIGS ARE EXPECTED BETWEEN 09Z AND 15Z SATURDAY MORNING.
SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE OVER
NORTHEASTERN WYOMING AND FAR WESTERN SOUTH DAKOTA ON SATURDAY
AFTERNOON. OTHERWISE...VFR CONDITIONS WILL PREVAIL.

&&

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

$$

SHORT TERM...26
LONG TERM...HELGESON
AVIATION...10






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