Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 240152
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
752 PM MDT SAT AUG 23 2014

.UPDATE...
ISSUED AT 749 PM MDT SAT AUG 23 2014

STRONG CONVECTION PRODUCING VERY HEAVY RAINFALL ACROSS SCNTRL SD
ATTM...WITH SCT ACTIVITY FROM NERN WY INTO NWRN SD. HAVE UPDATED
POPS BASED ON TRENDS...MOST NOTABLE TO RAISE POPS FOR SCNTRL SD.
WILL CONTINUE TO MONITOR THE FLOODING POTENTIAL ACROSS OUR NRN
CWFA...BUT IT IS APPEARING THAT THE FLOOD WATCH MAY BE ABLE TO
CANCEL WITHIN THE NEXT HOUR OR TWO.

&&

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 246 PM MDT SAT AUG 23 2014

UPPER LOW CONTINUES TO SPIN ACROSS WY/MT/ID WITH SEVERAL WAVES
ROUNDING THE BASE OVER WY INTO THE DAKOTAS. THE STRONGEST WAVE THAT
PRODUCED THE HEAVY RAINFALL THIS MORNING ACROSS PORTIONS OF WRN SD
HAS SLIDE NRD ALMOST INTO ND. HEAVY RAIN HAS ENDED ACROSS MOST OF
THE AREA. SEVERAL REPORTS OF +2 INCHES OF PRECIP OVER HARDING TO
ZIEBACH AND HAAKON COUNTIES. THE NEXT UPPER WAVE IS CROSSING FAR NE
WY THROUGH SW SD WITH A LINE OF STORMS DEVELOPING AHEAD OF IT. MORE
STORM DEVELOPMENT WILL BE POSSIBLE ACROSS WRN SD THROUGH TONIGHT.
MODELS CONTINUE TO SHOW THE LINE OF STORMS CONTINUING EWD THIS EVNG
THROUGH SCNTRL SD. INSTABILITY IS GENERALLY WEAK OVER MUCH OF THE
CWA EXCEPT 1000 TO 2000 J/KG MLCAPE OVER SWRN/SCNTRL SD. SHEAR ISNT
IMPRESSIVE...BUT SOME STORMS COULD STILL END UP BEING STRONG AS
EVIDENCED BY THE CURRENT STORM IN FALL RIVER COUNTY. CANT RULE OUT A
COUPLE SEVERE STORMS EITHER THROUGH THE EVENING. STORMS THAT DO
DEVELOP ACROSS AREAS THAT HAVE RECEIVED HEAVY RAINFALL LAST NIGHT
AND THIS MORNING WILL HAVE THE POTENTIAL TO PRODUCE LOCALIZED
FLOODING IF THEY BEGIN TRAINING. WILL EXTEND THE FLOOD WATCH THROUGH
NW SD TO PORTIONS OF NE WY UNTIL 12Z TONIGHT TO ACCOUNT FOR THIS
POTENTIAL...EVEN THOUGH POTENTIALLY IS GENERALLY LOW.

DRY AIR WILL WORK ITS WAY INTO MUCH OF THE AREA TOMORROW AS THE
WRAPPED UP LOW SWINGS NORTH OF THE CWA. NO PRECIP IS EXPECTED
TOMORROW EXCEPT OVER FAR NE WY/NW SD WHERE WRAP AROUND PRECIP MAY
CLIP THE NW CWA CORNERS. CLOUDS ELSEWHERE WILL DECREASE WITH
SUNSHINE RETURNING. MUCH COLDER AIR WILL ALSO ADVECT IN THE BACKSIDE
OF THE LOW BRINGING FALL LIKE TEMPERATURES TO THE AREA. AT THIS TIME
IT LOOKS LIKE HIGHS WILL BE IN THE UPPER 50S/MID 60S OVER NE WY/NW
SD WHERE CLOUDS WILL LIKELY PERSIS OVER MUCH OF THE DAY. OTHERWISE
TEMPS SHOULD GET INTO THE UPPER 60S TO UPPER 70S WHERE SKIES ARE
MOSTLY SUNNY.

&&

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 246 PM MDT SAT AUG 23 2014

GFS/GEM/ECMWF IN DECENT AGREEMENT FOR THE FIRST HALF OF THE WEEK.
UPPER TROF DIGS ACROSS THE WESTERN CONUS ON MONDAY...WITH WEAK
SHORTWAVE RIDGE IN SOUTHWEST FLOW ALOFT. SOME QUESTION AS TO HOW
MUCH THUNDERSTORM ACTIVITY THERE WILL BE MONDAY...AS SURGE OF WARM
MID LEVEL AIR RESULTS IN DECENT CAP. BETTER CHANCE COMES MONDAY
NIGHT WITH INCREASING 700MB THETA-E ADVECTION. ECMWF/GEM HINTING
AT UPPER LOW CUTTING OFF ACROSS THE CENTRAL ROCKIES TUESDAY...WITH
STRONG UPPER DIVERGENCE ACROSS WESTERN SOUTH DAKOTA
TUESDAY/WEDNESDAY. POTENTIAL FOR ADDITIONAL HEAVY RAIN AS PWAT
INCREASES TO AROUND 1.5 INCHES. GEM/ECMWF TRENDING SLOWER WITH
EJECTING LOW/TROF WEDNESDAY NIGHT INTO THURSDAY. IF TREND
CONTINUES...THUNDERSTORMS COULD LINGER INTO THURSDAY. DRIER AND
WARMER FOR FRIDAY/SATURDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 502 PM MDT SAT AUG 23 2014

SCATTERED SHOWERS/THUNDERSTORMS WILL BE FOUND ACROSS THE AREA
THIS EVENING...WITH BEST CHANCES EAST OF THE BLKHLS. WIDESPREAD
IFR VSBY WITH THE PRECIPITATION. MVFR/LCL IFR CIGS WILL PERSIST
ACROSS MUCH OF NORTHEAST WYOMING/WESTERN SOUTH DAKOTA THROUGH
TONIGHT.


&&

.HYDROLOGY...
ISSUED AT 246 PM MDT SAT AUG 23 2014

A LARGE STORM SYSTEM WILL CONTINUE CROSSING THE NORTHERN PLAINS
THROUGH TONIGHT. THOUGH THE HEAVIEST RAINFALL HAS ENDED ACROSS
THE AREA...ADDITIONAL SHOWERS AND THUNDERSTORMS MAY DEVELOP THIS
AFTERNOON AND EVENING. WITH SATURATED GROUNDS FROM LAST NIGHTS AND
THIS MORNINGS HEAVY RAINFALL...ANY ADDITIONAL RAINFALL WILL HAVE
THE POTENTIAL TO PRODUCE FLOODING OVER PORTIONS OF NORTHEAST
WYOMING AND NORTHWEST SOUTH DAKOTA. SO HAVE EXTENDED THE FLOOD
WATCH THROUGH 12Z FOR NW SD TO FAR NE WY.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...FLOOD WATCH UNTIL 6 AM MDT SUNDAY FOR SDZ001-002-012>014.

WY...FLOOD WATCH UNTIL 6 AM MDT SUNDAY FOR WYZ054-056-071.

&&

$$

UPDATE...JOHNSON
SHORT TERM...13
LONG TERM...7
AVIATION...JOHNSON
HYDROLOGY...13






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