Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 271103
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
503 AM MDT SAT SEP 27 2014

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
ISSUED AT 231 AM MDT SAT SEP 27 2014

08Z SURFACE ANALYSIS HAD COOL FRONT/TROUGH FROM CENTRAL ND INTO
SOUTHEAST WY. LOOKS LIKE BOUNDARY HAS STALLED AS IT HAS BECOME
PARALLEL TO UPPER FLOW. WATER VAPOUR SHOWED UPPER RIDGE OVER THE
PLAINS AND UPPER LOW/TROUGH OVER THE FAR WESTERN US. DISPOSITION
OF THIS TROUGH MAIN CONCERN.

TODAY...UPPER LOW MOVES EAST SLIGHTLY AS UPPER RIDGE WEAKENS.
SURFACE TROUGH SLIPS SLIGHTLY SOUTHEASTWARD. THERMAL BOUNDARY ACROSS
TROUGH WILL BE QUITE PRONOUNCED WITH POTENTIAL FOR LARGE TEMPERATURE
BUSTS OVER CWA. HAVE TRENDED TOWARD GUIDANCE BEHIND THE FRONT AND
NEAR/SLIGHTLY ABOVE GUIDANCE AHEAD OF FRONT GIVEN POTENTIAL
TEMPERATURES PER FORECAST LOWER TROPOSPHERIC SOUNDINGS.

TONIGHT...UPPER LOW SPINS INTO NV WITH WEAKENING UPPER RIDGE STILL
OVER THE PLAINS. MOISTURE BEGINS TO ENTER WESTERN PORTIONS OF CWA
LATE WITH THE POTENTIAL FOR SHRA/TSRA LATE...BUT CONFIDENCE NOT
HIGH. TEMPERATURES WILL BE NEAR GUIDANCE.

SUNDAY...UPPER LOW DANCES INTO UT WITH UPPER RIDGE FINALLY MOVING
EAST. THIS SHOULD ALLOW MOISTURE TO SURGE INTO WESTERN PORTIONS OF
THE CWA AND SUBSEQUENT INCREASES IN POPS...ESPECIALLY LATE GIVEN
INCREASING 850-700MB THETA-E ADVECTION AND SYNOPTIC SCALE LIFT.
COOLER AIR FILTERS INTO THE NORTHWEST AS SURFACE TROUGH SLIDES
FURTHER EAST. TEMPERATURES TRICKY AGAIN WITH SHARP GRADIENT FROM
WEST TO EAST.

&&

.LONG TERM...MONDAY THROUGH FRIDAY
ISSUED AT 231 AM MDT SAT SEP 27 2014

THE UPPER LOW GRADUALLY PHASES BACK INTO THE MAIN FLOW MONDAY AS
IT BECOMES NEGATIVELY TILTED THROUGH MONDAY NIGHT. EXTENSIVE
SOUTHERLY FLOW WILL FEED MOISTURE INTO THE AREA. SHOWERS AND
ISOLATED STORMS WILL INCREASE IN COVERAGE OVER THE AREA THROUGH
THE DAY MONDAY...WITH THE BEST CHANCES MONDAY NIGHT. PRECIP WILL
CONTINUE INTO TUESDAY AS WRAP AROUND PRECIP SLOWLY EXITS THE AREA
INTO TUESDAY NIGHT. MODELS STILL WORKING ON QPF AMOUNTS...BUT IT
IS LOOKING LIKE MANY AREAS COULD SEE OVER AN INCH BY WEDNESDAY.
COOLER TEMPS PUSHING INTO THE AREA BEHIND THE SYSTEM WILL KEEP
TEMPERATURES WELL BELOW SEASONAL AVERAGES. CYCLONIC FLOW REMAINING
OVER THE REGION WILL KEEP LOW CHANCE POPS OVER THE AREA WEDNESDAY
AND THURSDAY. AT THIS TIME MODELS ARE SUGGESTING A RIDGE BUILDING
FOR THE END OF THE WEEK WHICH WOULD BRING BACK DRIER
WEATHER...WITH BELOW AVERAGE TEMPS CONTINUING.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 502 AM MDT SAT SEP 27 2014

VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD.

&&

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

$$

SHORT TERM...HELGESON
LONG TERM...13
AVIATION...13






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