Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 242033
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
233 PM MDT THU APR 24 2014

.SHORT TERM...THIS EVENING THROUGH FRIDAY NIGHT
ISSUED AT 232 PM MDT THU APR 24 2014

DEEP UPPER TROUGH WILL CONTINUE TO DIG INTO THE
WESTERN CONUS...WITH MEAN HEIGHT RISES PUSHING EAST INTO THE
NORTHERN PLAINS THROUGH FRIDAY. TWO WEAK IMPULSES WILL EJECT OUT OF
THE MEAN UPPER UPPER LOW...AND INTO THE REGION...POSSIBLY SUPPORTING
A FEW SHOWERS ACROSS THE NW HALF OF THE FA...ESP FRI NIGHT. WAA
ONGOING ACROSS THE REGION TODAY...AND WILL CONTINUE THROUGH FRIDAY
AHEAD OF THE DEEP UPPER TROUGH. SFC PRESSURE FALLS EXPECTED THROUGH
THE PERIOD WITH WINDS SHIFTING SE AND INCREASING PER LEE SIDE
TROUGHING...WHICH WILL BE ENHANCED BY THE APPROACHING UPPER
LOW.

TONIGHT...WEAK ELEVATED THETA-E ADV /EVIDENCED WELL AT H7/ WILL
SUPPORT AN AREA OF WEAK LIFT ACROSS THE NW ZONES THIS
EVENING...POSSIBLY SUPPORTING A FEW SPRINKLES WHEN COUPLED WITH A
WEAK UPPER LEVEL IMPULSE. DRY LL PROFILES AND LACK OF SUFFICIENT
MOISTURE PRECLUDES A SHRA MENTION. OTHERWISE...EXPECT INCREASING
HIGH CLOUDS THROUGH THE PERIOD...WITH LOWS GENERALLY IN THE 30S /40S
IN THE LEE OF THE BH/.

FRIDAY...SW FLOW WITH INCREASING ELEVATED MOISTURE WILL SUPPORT
SCT-BKN MID AND HIGH CLOUDS...ESP IN THE AFTERNOON/EVENING. STILL
EXPECTING ENOUGH INSOLATION TO SUPPORT FAIRLY DEEP MIXING...PUSHING
TEMPS INTO THE 70S MOST PLACES. DEEP MIXING OVER THE HIGHER TERRAIN
OF NE WY AND THE WESTERN BH WITH INCREASING MID LEVEL MOISTURE
COUPLED WITH AN ADVANCING UPPER LEVEL IMPULSE MAY BE SUFFICIENT FOR
A FEW ISOLD HIGH BASED SHRA THERE LATE FRI AFTERNOON. NAM LI/S
CERTAINLY HINT AT THIS AND A FEW HIRES MODELS DO GENERATE
CONVECTION. HAVE ADDED A LOW POP FOR THIS. SLIGHTLY BETTER CHANCES
FOR SHRA ARRIVE LATER FRIDAY NIGHT...MAINLY THE NW HALF...ALBEIT
ONLY ISOLD TO SCT. HAVE RETAINED A SHRA MENTION FRIDAY
NIGHT...SHIFTING THE HIGHER CHANCES AFTER MIDNIGHT. INCREASING SFC
PRESSURE FALLS WILL HELP MAINTAIN A PARTIALLY MIXED BL THROUGH THE
NIGHT MOST PLACES...WITH LOWS IN THE 40S EXPECTED MOST PLACES. HAVE
BUMPED LOWS UP A COUPLE DEGREES.

&&

.LONG TERM...SATURDAY THROUGH THURSDAY
ISSUED AT 232 PM MDT THU APR 24 2014

UPPER LEVEL TROUGH WILL MOVE OVER THE ROCKIES ON
SATURDAY. SURFACE LOW OVER EASTERN CO WILL CREATE BREEZY SOUTHEAST
WINDS...ESPECIALLY ACROSS CENTRAL SD...BRINGING IN WARM AND MOIST
AIR. INSTABILITY AND MOISTURE INFLUX WILL ALLOW SHOWERS AND
THUNDERSTORMS TO DEVELOP SATURDAY AFTERNOON AND EVENING AS THE LOW
APPROACHES. HIGHS ON SATURDAY WILL BE IN THE LOWER 60S TO LOWER 70S.

TRACK OF THE UPPER LOW IS STILL UNCERTAIN AT THIS POINT...WITH THE
GFS BRINGING IT INTO SD SUNDAY NIGHT AND THE ECMWF KEEPING IT
FARTHER SOUTH IN NEBRASKA. BOTH WRAP COOLER AIR BACK INTO THE CWA
BEHIND THE LOW...BUT TEMPS SHOULD STAY WARM ENOUGH FOR THE EVENT TO
BE MAINLY RAIN...ESPECIALLY ON THE SD PLAINS. SNOW IS MORE POSSIBLE
ACROSS NORTHEAST WYOMING AND THE BLACK HILLS WHERE LOWS DIP BELOW
FREEZING SUNDAY AND MONDAY NIGHTS. ALSO HAVE SOME ISOLATED
THUNDERSTORMS IN THE FORECAST ACROSS CENTRAL SD WHERE INSTABILITY IS
BETTER.

MODELS ARE INDICATING THAT WHEN THE UPPER LOW SHIFTS
EASTWARD...ENERGY NORTHEAST OF IT WILL BE TAKEN IN AND CIRCULATED
BACK AROUND THE LOW...SLOWING IT DOWN AND ACTUALLY CAUSING THE
SYSTEM TO RETROGRADE. THEREFORE...PRECIPITATION AND COOL WEATHER MAY
STICK AROUND FOR THE FIRST HALF OF THE WEEK. OVERALL THE SYSTEM
LOOKS VERY MOIST...WITH PWATS 180-200% OF NORMAL. MANY AREAS MAY
RECEIVE MORE THAN AN INCH OF QPF...WITH THE BLACK HILLS POSSIBLY
RECEIVING MORE THAN TWO INCHES. ADDED MODERATE PRECIPITATION WORDING
IN THE WEATHER GRIDS.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING
ISSUED AT 232 PM MDT THU APR 24 2014

VFR CONDITIONS EXPECTED FOR THE NEXT 24 HOURS. GUSTY
WEST TO NORTHWEST WINDS WILL CONTINUE THROUGH THE
AFTERNOON...BECOMING LIGHT THIS EVENING.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...RED FLAG WARNING UNTIL 6 PM MDT THIS EVENING FOR SDZ265.

WY...NONE.
&&

$$

SHORT TERM...JC
LONG TERM...POJORLIE
AVIATION...POJORLIE






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