Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 230932
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
332 AM MDT THU APR 23 2015

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT
ISSUED AT 332 AM MDT THU APR 23 2015

CURRENT SURFACE ANALYSIS SHOWS LOW PRESSURE OVER SOUTHERN
AB...WITH FRONT EXTENDING SOUTHWESTWARD INTO SOUTHERN ID. WARM
FRONT EXTENDS SOUTHEASTWARD ACROSS CENTRAL MT INTO EASTERN WY.
UPPER LEVEL ANALYSIS SHOWS LARGE TROF REMAINING ACROSS THE EASTERN
CONUS...WITH WEAKENING RIDGE OVER THE ROCKIES AND SHORTWAVE ENERGY
MOVING ACROSS WESTERN MT AND ID. SKIES ARE MAINLY CLEAR NOW...BUT
CLOUDS TO THE WEST WILL MOVE INTO THE AREA THIS MORNING. REGIONAL
RADARS SHOW SHOWERS WELL NORTH AND WEST OF THE CWA...OVER CENTRAL
AND NORTHEAST MT...MOVING TO THE EAST-NORTHEAST. TEMPS ARE MOSTLY
IN THE 30S...EXCEPT FOR 40S IN THE GILLETTE AREA WHERE WINDS HAVE
STAYED BREEZY FROM THE SOUTH MOST OF THE NIGHT. WINDS ELSEWHERE
ARE MOSTLY FROM THE EAST TO SOUTHEAST AT 5 TO 15 MPH...WITH
OCCASIONALLY STRONGER WINDS OVER NORTHWEST SD.

AS RIDGE BREAKS DOWN TO THE WEST...THIS WILL ALLOW A SERIES OF
SHORTWAVE DISTURBANCES TO CROSS THE AREA LATE THIS WEEK...BRINGING
CHANCES FOR SHOWERS AND THUNDERSTORMS. SHORT RANGE MODELS IN
DECENT AGREEMENT ON OVERALL PATTERN...WITH MOSTLY SMALL DIFFERENCES
ON TIMING AND TRACK OF SHORTWAVES AND AREAS OF PCPN. THE BEST
CHANCES WILL GENERALLY BE IN THE AFTERNOON AND EARLY EVENING HOURS
DURING PEAK HEATING...BUT AT LEAST ISOLATED ACTIVITY SHOULD LINGER
INTO THE OVERNIGHT...AND POSSIBLY THE MORNING HOURS IN SOME
AREAS...AS UPPER ENERGY PASSES ACROSS.

FOR TODAY...CLOUDS WILL INCREASE THROUGH THE DAY FROM THE
WEST...WITH MOSTLY CLOUDY CONDITIONS BY MID TO LATE AFTERNOON. WARM
FRONT WILL MOVES EAST ACROSS THE AREA DURING THE DAY...WHILE COLD
FRONT WILL APPROACH NORTHEAST WY BY EARLY AFTERNOON AND THE BLACK
HILLS LATE IN THE AFTERNOON. SECONDARY LOW WILL DEVELOP ALONG THE
COLD FRONT OVER NORTHEAST WY IN THE AFTERNOON. HIGHS WILL BE IN THE
60S AND LOWER 70S THIS AFTERNOON...WARMEST TO THE SOUTH AND EAST OF
THE BLACK HILLS WHERE THE MOST SUN IS EXPECTED. INCREASING SOUTH TO
SOUTHEAST WINDS AHEAD OF THE FRONT WILL BRING LOW LEVEL MOISTURE
INTO THE AREA...WITH DEWPOINTS INTO THE 40S OVER A GOOD PORTION OF
WESTERN SD BY LATE IN THE DAY. MOST OF THE SHOWER AND THUNDERSTORM
ACTIVITY SHOULD HOLD OFF UNTIL THE MID AND LATE AFTERNOON...THOUGH
COULD GET GOING EARLIER IN THE AFTERNOON OVER NORTHEAST WY AND THE
BLACK HILLS. THE MILD TEMPS AND INCREASING MOISTURE WILL ALLOW FOR
AN AREA OF 500 TO AROUND 1000 J/KG CAPE OVER SOUTHWESTERN SD THIS
AFTERNOON...WITH FORECAST SOUNDINGS SHOWING DECENT SHEAR OVER
SOUTHWEST SD AS WELL. A COUPLE OF STRONG TO MARGINALLY SEVERE STORMS
CERTAINLY LOOK POSSIBLE LATE THIS AFTERNOON OR EARLY EVENING IN THAT
AREA. ACTIVITY SHOULD BEGIN TO TAPER OFF AND MOVE EAST OF THE AREA
LATE IN THE EVENING...BUT WILL KEEP LOW POPS THROUGH THE NIGHT FOR
MOST AREAS.

LOW PRESSURE AND FRONTAL BOUNDARY WILL REMAIN OVER THE AREA ON
FRIDAY. TEMPS WILL BE SLIGHTLY COOLER WITH MORE CLOUD COVER...BUT
STILL IN THE 60S TO NEAR 70 DEGREES ACROSS THE PLAINS. CHANCES FOR
SHOWERS WILL INCREASE INTO THE AFTERNOON AS ATMOSPHERE
DESTABILIZES...BEST CHANCES GENERALLY OVER THE BLACK HILLS INTO
SOUTHWESTERN SD. A FEW THUNDERSTORMS ARE EXPECTED AS WELL...
ESPECIALLY ACROSS SOUTHERN PORTIONS OF THE CWA. A STRONG STORM OR
TWO IS POSSIBLE AGAIN OVER SOUTHWEST INTO SOUTH CENTRAL SD IN THE
AFTERNOON.

.LONG TERM...SATURDAY THROUGH WEDNESDAY
ISSUED AT 332 AM MDT THU APR 23 2015

GFS/GEM/ECMWF CONTINUE TO SHOW STRONG UPPER TROF DIGGING FROM THE
PACIFIC NORTHWEST THROUGH THE CNTRL ROCKIES THIS WEEKEND. UPPER
FLOW SPLITS...WITH LOW CLOSING OFF OVER THE SOUTHERN PLAINS AND
WEAKER NORTHERN STREAM TROF SLIDING THROUGH THE NRN PLAINS. MODELS
IN DECENT AGREEMENT WITH A GOOD PCPN POTENTIAL FOR THE WEEKEND
INTO MONDAY. THERMAL PROFILES SUPPORT POTENTIAL FOR RAIN/SNOW MIX
IN HIGHER ELEVATION OF THE BLACK HILLS BY SUNDAY NIGHT. UPPER
LEVEL RIDGE BUILDS ACROSS THE ROCKIES EARLY NEXT WEEK...WITH DRY
WEATHER AND WARMER TEMPERATURES.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING
ISSUED AT 332 AM MDT THU APR 23 2015

A FEW SHOWERS/THUNDERSTORMS POSSIBLE THIS AFTERNOON INTO
TONIGHT. LCL MVFR CIGS/VSBY WITH THE PRECIPITATION.

&&

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

$$

SHORT TERM...26
LONG TERM...7
AVIATION...7


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