Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 170441
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
941 PM MST TUE DEC 16 2014

.SHORT TERM...THIS EVENING THROUGH WEDNESDAY NIGHT
ISSUED AT 241 PM MST TUE DEC 16 2014

WATER VAPOR IMAGERY SHOWS UPPER TROUGH ACROSS THE GREAT LAKES WITH
SECONDARY UPPER LOW OVER MINNESOTA. THE NEXT STRONG TROUGH IS
PUSHING INTO THE PACIFIC COAST...AND IN BETWEEN THE NRN PLAINS ARE
SITTING IN WEAK RIDGING. SURFACE ANALYSIS SHOWS THE FRONTAL BOUNDARY
SITTING OVER CNTRL MT TO THE BLKHLS AREA AND SOUTH INTO WRN/CNTRL
NEB. TEMPS HAVE RISEN INTO THE 20S ACROSS MOST LOCATIONS. LOW CLOUDS
ARE MAINLY AFFECTING THE WRN SD PLAINS THOUGH SOME BREAKING APART OF
THE CLOUD DECK HAS OCCURRED IN THE LAST HOUR OR TWO OVER NE WY AND
WRN SD FTHLLS. CLOUDS WILL BUILD BACK IN TONIGHT OVER THE WRN SD
PLAINS AND NE WY AS S/SE RETURN FLOW CONTINUES ACROSS THE AREA. THE
BKLHLS WILL REMAIN CLEAR OVERNIGHT AS THE MOISTURE REMAINS LIMITED
TO THE LOW LEVELS.

MODELS SHOW AN UPPER WAVE CROSSING THE MT/WY BORDER TOMORROW WITH
LOW LEVEL RETURN FLOW CONTINUING OVER THE REGION. LOW CLOUDS ARE
EXPECTED TO CONTINUE OVER THE WRN SD PLAINS THROUGH THE DAY...WHILE
SOME DECREASING IN CLOUD COVERAGE IS POSSIBLE OVER THE NE WY PLAINS.
WEAK FORCING FROM THE UPPER WAVE MAY BRING SOME FLURRIES/-SHSN TO
PORTIONS OF NE WY INTO NW SD THROUGH THE DAY...BUT LITTLE TO NO
ACCUMULATION IS EXPECTED. TEMPS WILL BE NEAR OR SLIGHTLY WARMER THAN
TODAY WITH HIGHS IN THE 20S TO MID 30S. WAVE WILL CROSS THE AREA
LATE WEDNESDAY SO HAVE REMOVED MENTION OF -SHSN WED NIGHT.

.LONG TERM...THURSDAY THROUGH TUESDAY
ISSUED AT 241 PM MST TUE DEC 16 2014

SPLIT FLOW WILL REMAIN IN THE PERIOD...WITH SEASONAL WESTERLY
FLOW. WEAK SHORTWAVE IMPULSES WILL CROSS REGION THROUGH THE
WEEKEND...BRINGING NOTHING MORE THAN SOME MID CLOUDS AND A WIND
SHIFT. A MORE ORGANIZED SYSTEM IS ON TRACK FOR THE FIRST PART OF
NEXT WEEK AS THE WESTERN NOAM RIDGE BUILDS AND ACTIVE NW FLOW
DEVELOPS. INCREASING LL PAC ORIGIN MOISTURE COUPLED WITH NW FLOW
IMPULSES WILL BRING CHANCES FOR RAIN OR SNOW SHOWERS...WITH THE
BEST CHANCES FOR ANY PRECIP IN NE WY AND THE NORTHERN BLACK HILLS
PER UPSLOPE PROCESSES. WARMER WEATHER IS ALSO EXPECTED FRI-SUN AS
THE UPPER RIDGE SPREADS EAST SOME AND WAA ENSUES.
HOWEVER...CONTINUED TRAIN OF IMPULSE WILL EVENTUALLY SETTLE COOLER
AIR INTO THE REGION EARLY NEXT WEEK. TENDENCIES FOR A STRONG
WESTERN NOAM TROUGH REMAIN PRESENT IN MEAN ENSEMBLES AND
DETERMINISTIC SOLUTIONS PER ANOTHER EXTENSION OF THE EAST ASIAN
UPPER JET. THIS TROUGH WOULD LIKELY LEAD TO VIGOROUS CYCLOGENSIS
ON THE PLAINS NEXT WEEK...WITH THE LATITUDINAL LOCATION HINGING ON
THE DEGREE OF UPPER JET DIGGING OVER THE SW CONUS AND POSSIBLE
DOWNSTREAM RIDGE AMPLIFICATION. THIS SYSTEM COULD POTENTIALLY
BRING SIG SNOW AND WIND TO A PORTION OF THE PLAINS TOWARD THE
MIDDLE OR END OF NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 939 PM MST TUE DEC 16 2014

WIDESPREAD IFR/LIFR CIGS WILL CONTINUE ACROSS WRN SD AND INTO
NERN WY OVERNIGHT AND THROUGH MUCH OF WEDNESDAY. LOW CLOUDS WILL
BE IN AND OUT OF THE KGCC AREA ON THE WRN EXTENT...AND THE BLKHLS
SHOULD REMAIN ABOVE THE LOW CLOUDS FOR THE MOST PART. ALSO...WITH
THE SHALLOW SUPERCOOLED CLOUDS THERE MAY BE SOME FZFG...BUT LACK
OF SHEAR IN THE CLOUD LAYER SHOULD PREVENT FZDZ FROM OCCURRING.
GRADUAL CLEARING IS EXPECTED OVER NERN WY ON WEDNESDAY...BUT
CLOUDS WILL HANG TOUGH OVER THE WRN/CNTRL SD THROUGH MOST IF NOT
ALL OF THE DAY.

&&

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

$$

SHORT TERM...13
LONG TERM...JC
AVIATION...BUNKERS





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