Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 161709
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1109 AM MDT THU APR 16 2015

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT
ISSUED AT 334 AM MDT THU APR 16 2015

WATER VAPOR IMAGERY SHOWS LARGE CUT OFF CENTERED ALONG THE UT/CO
BORDER...WITH SEVERAL WAVES MOVING NORTHWARD ACROSS THE CNTRL TO NRN
HIGH PLAINS. SURFACE ANALYSIS SHOWS A NEARLY STATIONARY FRONT
STRADDLED ACROSS THE WRN SD PLAINS...WITH TEMPS IN THE 30S OVER NE
WY TO UPPER 40S/LOW 50S OVER CNTRL SD. KUDX RADAR SHOWS RAIN FALLING
ACROSS PORTIONS OF NW SD...AND A BAND MOVING INTO SW SD. IR SAT/OBS
SHOW MORE PRECIP FALLING OVER NE...WITH GCC REPORTING SNOW WHILE
HULETT AND NEWCASTLE ARE REPORTING RAIN. NE WY SPOTTERS HAVE
REPORTED SNOW FALLING WITH LITTLE TO NO ACCUMULATION AS MOST OF IT
MELTED UPON REACHING THE GROUND. THE MULE CREEK JUNCTION AND HIGHWAY
59 REST STOP WEB CAMS BOTH SHOW ACCUMULATIONS OF AROUND AN INCH.
TEMPERATURES ARE RIGHT AT FREEZING OR JUST ABOVE...SO LITTLE
ADDITIONAL ACCUMULATION IS EXPECTED. WILL CANCEL THE WINTER WEATHER
ADVISORY WITH THE MORNING PACKAGE. UPPER LOW WILL DRIFT E/SE
TODAY...BUT MAKE VERY LITTLE MOVEMENT OVERALL AS WEAK RIDGING
DEVELOPS OVER THE CNDN ROCKIES SETTING UP A REX BLOCK TONIGHT.
PRECIP WILL GRADUALLY DECREASE TODAY...BUT STILL LINGER IN SOME
AREAS. TEMPS WILL REACH THE MID TO UPPER 40S OVER NE WY TO THE 60S
ACROSS CNTRL SD.

DEFORMATION ZONE WILL CO/KS/NEB TODAY AND TONIGHT...BUT MODELS ARE
SHOWING A NORTHWARD PUSH WITH THE LOW AS THE NEXT SHORTWAVE TROUGH
CROSSES THE CNDN HIGH PLAINS...BEGINNING A PHASE IN PROCESS IN THE
LONG TERM. THE RESULT IS THE DEFORMATION ZONE SLOWLY MOVING
NORTHWARD INTO THE CWA. HAVE RAISED POPS QUITE A BIT ACROSS THE AREA
TO ACCOUNT FOR THIS. QPF AMOUNTS ARE VARYING...BUT IT WILL BE
POSSIBLE THE MANY LOCATIONS WILL HAVE AN INCH OR MORE OF LIQUID
ACROSS SW SD BY LATE FRI NIGHT...WITH MORE IN THE EARLY LONG TERM.
LOW LEVELS WILL BE WARM ENOUGH TO KEEP THIS AS RAIN...BUT HIGHER
ELEVATIONS OF THE BLACK HILLS MAY SEE LIGHT ACCUMULATIONS OF SNOW
FRIDAY NIGHT.

.LONG TERM...SATURDAY THROUGH WEDNESDAY
ISSUED AT 334 AM MDT THU APR 16 2015

ACTIVE NORTHWEST FLOW WILL CONTINUE IN THE PERIOD. FORECAST
MODELS CONTINUE TO TREND TO PHASING OF THE CLOSED CENTRAL CONUS
LOW WITH A STRONGER NORTHERN STREAM TROUGH SAT...SUPPORTING PRECIP
CHANCES ACROSS THE REGION. DEEP SOUTHERLY FLOW AHEAD OF THE CLOSED
CENTRAL CONUS UPPER LOW WILL SUPPORT AMPLE MOISTURE WITH THIS
SYSTEM...ALLOWING A DECENT CHANCE FOR PRECIP ACROSS MUCH OF THE
FA. IN FACT...THE GFS AND ECMWF BOTH SUPPORT OVER AN INCH OF QPF
OVER WESTER SD...WITH THE GFS PROGGING OVER 2 INCHES IN SOME
AREAS. GIVEN GROWING SUPPORT ACROSS MODEL AND ENSEMBLE
SPECTRUMS...HAVE INCREASED POPS SAT. SOME SNOW LOOKS POSSIBLE
ACROSS THE HIGHER TERRAIN. HOWEVER...ATTM GIVEN WARM THERMAL
FIELDS...PRECIP LOOKS TO FALL AS RAIN OVER MUCH OF THE FA. THIS
WILL NEED TO BE MONITORED FOR THE HIGHER TERRAIN OF THE BLACK
HILLS...AS A SLIGHT SHIFT IN THERMAL FIELDS COULD SUPPORT DECENT
SNOWS. CAA AND DRY NW TRAJECTORIES WILL BRING DRY WEATHER TO MOST
OF THE AREA THROUGH THE REMAINDER OF THE PERIOD...SAVE TOWARD THE
END OF NEXT WEEK WHEN AN EASTERN NOAM CLOSED LOW MAY RETROGRADE
BACK WEST INTO THE REGION PER LONGWAVE FLOW RETROGRESSION OVER
WESTERN NOAM. MUCH UNCERTAINTY PER THE EVOLUTION OF THE LARGE
SCALE FLOW TOWARD THE END OF THE PERIOD GIVEN CONCERNS ON CLOSED
UPPER LOWS AND WILDLY DIFFERENT SOLUTIONS PER EASTERN PAC FLOW
EVOLUTION. THUS...KEPT POPS LOW AND CLOSE TO PREVIOUS FORECAST
NUMBERS UNTIL STRONGER SIGNALS MATERIALIZE. OVERALL...COOL CONDS
CAN BE EXPECTED FOR MOST OF THE LONG TERM PERIOD GIVEN A STRONG
INFLUENCE OF THE EXPECTED EASTERN NOAM UPPER LEVEL TROUGH AND
ASSOCIATED BLOCKED FLOW.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY)
ISSUED AT 1106 AM MDT THU APR 16 2015

MAINLY VFR CONDITIONS EXPECTED THROUGH FRIDAY MORNING. SCT-
BKN040-060 WILL SLOWLY DISSIPATE WITH SCT-BKN100 LEFTOVER TONIGHT.
EXCEPT WILL BE SOME LINGERING MVFR CIGS THIS AFTERNOON ACROSS THE
HIGHER TERRAIN OF NORTHEAST WY/BLACK HILLS.

&&

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

$$

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


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