Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 221656
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1056 AM MDT FRI AUG 22 2014

.UPDATE...
ISSUED AT 1056 AM MDT FRI AUG 22 2014

LATEST KUDX RADAR SHOWS SHOWERS SLOWLY DISSIPATING OVER
PERKINS/ZEIBACH COUNTIES AND QUIET ELSEWHERE. PLENTY OF LOW CLOUDS
OVER THE SD PLAINS ARE KEEPING TEMPERATURES COOL. CLOUDS ARE
EXPECTED TO LIFT THROUGH THE DAY...BUT PLENTY OF CLOUDINESS WILL
REMAIN AS DEEP PACIFIC MOISTURE STREAMS IN. HAVE TWEAKED TEMPS TO
ACCOUNT FOR THIS...AND ADJUSTED POPS WITH LATEST INPUT FROM THE
HRRR. NO OTHER CHANGES NEEDED AT THIS TIME.

UPDATE ISSUED AT 627 AM MDT FRI AUG 22 2014

MOISTURE OVERNIGHT HAS LED TO AREAS OF FOG FROM THE NORTHERN BLACK
HILLS AND BEAR LODGE MOUNTAINS INTO NORTHWESTERN SOUTH DAKOTA AND
SOUTH CENTRAL SOUTH DAKOTA. THUS UPDATED TO ADD THE FOG. NO OTHER
CHANGES WERE MADE.

&&

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
ISSUED AT 242 AM MDT FRI AUG 22 2014

SOUTHWEST FLOW OVER THE AREA WILL CONTINUE TO BRING SEVERAL UPPER
LEVEL DISTURBANCES TO THE NORTHERN PLAINS AS AN APPROACHING UPPER
LEVEL LOW DEEPENS AND CLOSES OFF OVER THE NORTHERN ROCKIES. AT THE
SURFACE...A FRONTAL BOUNDARY EXTENDS FROM LEMMON TO FAITH TOWARDS
PINE RIDGE. THIS FRONTAL BOUNDARY WILL REMAIN NEARLY STATIONARY
THROUGH THE SHORT TERM...WHICH WILL HELP SUPPORT THE CHANCES FOR
SHOWERS AND THUNDERSTORMS. LATEST RADAR IMAGERY CONTINUES TO SHOW
SHOWERS AND THUNDERSTORMS ACROSS NORTHWESTERN SOUTH DAKOTA...WHICH
ARE ASSOCIATED WITH THE FIRST DISTURBANCE PUSHING THROUGH.

FOR TODAY...WILL SEE ADDITIONAL SHOWERS AND THUNDERSTORMS AS THE
NEXT IMPULSE CLIPS THE NORTHERN AND WESTERN PORTION OF THE FORECAST
AREA THIS MORNING. HAVE LOWERED POPS A LITTLE FROM PREVIOUS FORECAST
DUE TO LINGERING SUBSIDENCE BEHIND THE FIRST WAVE. HOWEVER BY THIS
AFTERNOON...PACIFIC MOISTURE WILL ADVECT INTO THE AREA...WHICH WILL
COMBINE WITH A STRONG JET STREAK...BRINGING WIDESPREAD SHOWERS AND
THUNDERSTORMS...SOME WITH HEAVY RAINFALL.

OVERALL MODELS CONTINUE TO SHOW A CHANGE IN THE OVERALL PATTERN FOR
TODAY THROUGH THE WEEKEND. THE UPPER LEVEL TROUGH NEAR SOUTHERN
CALIFORNIA EJECTS NORTHEASTWARD ACROSS THE AREA. THE NAM TRACK IS
FURTHER WEST...THUS RAINFALL AMOUNTS IN THE MODEL ARE QUITE A BIT
HIGHER THAN THE GFS. ALSO PW AMOUNTS VARY FROM AROUND 150 PERCENT OF
AVERAGE IN THE GFS TO OVER 200 PERCENT OF AVERAGE IN THE NAM.
DEPENDING ON WHICH SOLUTION VERIFIES...COULD NEED A FLASH FLOOD
WATCH FOR TONIGHT INTO SATURDAY...ESPECIALLY FOR THE HILLS AND
EASTERN FOOTHILLS WHERE IT HAS BEEN WETTER OVER THE PAST FEW WEEKS.
AT THIS TIME DECIDED TO MENTION LOCALLY HEAVY RAIN POSSIBLE AND WILL
LET FUTURE SHIFTS FURTHER EVALUATE THE NEED FOR ANY FLOOD
HIGHLIGHTS.

ON SATURDAY AND SATURDAY NIGHT...LINGERING SHOWERS AND STORMS WILL
CONTINUE AS THE MAIN NORTHWEST UPPER TROUGH EJECTS NORTHEASTWARD.
BUFKIT MODEL SOUNDINGS INDICATE A DEEP MOISTURE PROFILE UP TO 300 MB
WITH MOIST EASTERLY LOW LEVEL FLOW. THIS SHOULD KEEP CHANCES FOR
STORMS IN THE FORECAST...ESPECIALLY IN NORTHERN AND WESTERN AREAS
CLOSER TO THE UPPER LOW.

&&

.LONG TERM...SUNDAY THROUGH THURSDAY
ISSUED AT 242 AM MDT FRI AUG 22 2014

MODELS CONTINUE TO SHOW THE UPPER LOW LIFTING INTO EASTERN MONTANA
ON SUNDAY...WITH A DRY SLOT MOVING INTO WESTERN AND CENTRAL SOUTH
DAKOTA. THE BEST SUPPORT FOR PRECIPITATION ON SUNDAY WILL BE NORTH
OF THE FORECAST AREA. POST FRONTAL STRATUS WILL KEEP TEMPERATURES
OVER NORTHEASTERN WYOMING AND FAR NORTHWESTERN SOUTH DAKOTA COOLER
THAN AVERAGE FOR THIS TIME OF YEAR. THE UPPER LOW WILL CONTINUE TO
LIFT NORTHEASTWARD INTO MANITOBA AND WESTERN ONTARIO ON
MONDAY...FOLLOWED BY A SLOW MOVING UPPER TROUGH CROSSING THE
NORTHERN PLAINS ON TUESDAY AND WEDNESDAY. COOLER THAN AVERAGE
TEMPERATURES WILL CONTINUE THROUGH MID WEEK...ALONG WITH A DAILY
CHANCE OF SHOWERS AND THUNDERSTORMS. AN UPPER RIDGE WILL BUILD OVER
THE REGION FOR THE END OF THE WEEK...LEADING TO DRY WEATHER AND A
RETURN TO WARMER TEMPERATURES.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING
ISSUED AT 242 AM MDT FRI AUG 22 2014

AN AREA OF MVFR STRATUS WITH LCL IFR CIGS WILL BE LOCATED OVER PARTS
OF NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA THROUGH MID
MORNING. VFR CONDITIONS WILL THEN PREVAIL THROUGH THE REST OF THE
DAY AND INTO THE EARLY EVENING. HIGH COVERAGE SHRA/TSRA WILL DEVELOP
THIS AFTERNOON AND CONTINUE OVERNIGHT. WIDESPREAD IFR CIGS WILL
DEVELOP AFT 03Z AND WILL CONTINUE THROUGH MUCH OF SATURDAY MORNING.


&&

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

$$

UPDATE...13
SHORT TERM...MLS
LONG TERM...10
AVIATION...10





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