Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 292322
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
522 PM MDT FRI APR 29 2016

.SHORT TERM...THIS EVENING THROUGH SATURDAY NIGHT
ISSUED AT 251 PM MDT FRI APR 29 2016

UPPER ANALYSIS AND WATER VAPOR IMAGERY SHOW UPPER TROUGH ACROSS THE
WRN THIRD OF THE CONUS...WITH A CUT OFF LOW NEAR THE CO/NM BORDER.
SURFACE HIGH PRESSURE SITS ACROSS CNTRL CANADA...WHILE LOW PRESS
ASSOCIATED WITH THE TROUGH IS STRENGTHENING ACROSS NM/OK/TX BORDERS.
THE RESULTING ERLY FLOW ACROSS THE NRN PLAINS IS KEEPING COOL/MOIST
AIRMASS OVER THE REGION.

UPPER LOW IS STILL PROGGED TO SWING N/NE AS THE TROUGH BECOMES NEG
TILTED...THEN STALL OUT ACROSS THE NEB/KS BORDER THROUGH SATURDAY.
MODELS STILL SHOWING WRAPAROUND PRECIP SETTING UP MAINLY OVER IA AND
NEB INTO ERN WY. SOME OF THIS PRECIP IS STILL PROGGED TO REACH
PORTIONS OF THE CWA TONIGHT AND CONTINUE THROUGH SAT/SAT NIGHT. MAIN
FORECAST CHALLENGE IS HOW MUCH OF THIS PRECIP WILL FALL AS
SNOW...HOW COLD TEMPS WILL GET AT THE SURFACE AND THROUGH THE LOW
LEVELS...AND HOW MUCH SNOW ACCUMULATION CAN OCCUR. NAM/GFS SHOW
850MB TEMPS GETTING CLOSE TO FREEZING OVERNIGHT ACROSS SW/SCNTRL
SD...BUT SURFACE TEMPS STRUGGLE TO REACH NEAR FREEZING. HOWEVER
HIGHER RES MODELS DO SHOW COLDER TEMPS FARTHER SOUTH...LIKELY DUE TO
DYNAMIC COOLING. MEDIUM RANGE MODELS ARE STILL SHOWING HIGH SNOWFALL
AMOUNTS OF OVER 10 INCHES...BUT THINK THIS IS WAY OVERDONE. OVERALL
THINK TEMPS WILL STAY NEAR TO JUST ABOVE FREEZING...TOO WARM FOR ANY
SIGNIFICANT ACCUMULATION. BUT SNOWFALL RATES COULD BE HIGH ENOUGH TO
OVERCOME A SLOW CONTINUAL MELTING...SO COULD SEE SOME SNOW BEGINNING
TO ACCUMULATE. THINKING THE BEST WAY TO HANDLE SW/SCNTRL SD WILL BE
TO ISSUE A WINTER WEATHER ADVISORY FOR COUNTIES BORDERING
NEB...THOUGH ACTUAL SNOWFALL AMOUNTS MAY VARY WIDELY OVER A SHORT
DISTANCE. WILL MENTION 2 TO 6 INCHES OF SNOW ACCUMULATION ACROSS
THOSE AREAS. ALSO BELIEVE SNOW WILL FALL AND ACCUMULATE ACROSS THE
HIGHER TERRAIN OF THE BLKHLS...WITH HIGHER QPF AMOUNTS ACROSS THE
ERN HALF OF THE HILLS WHERE SOME UPSLOPE ENHANCEMENT IS EXPECTED
WITH THE PERSISTENT ERLY FLOW. THINKING ACCUMULATION WILL BE LIMITED
TO 5000 FT ELEVATIONS AND HIGHER WITH 3 TO 6 INCHES POSSIBLE. SNOW
WILL CONTINUE THROUGH SAT MORNING...BEFORE STRONGER SUN ANGLES THIS
TIME OF YEAR HELP WITH MELTING SNOW...TEMPS RISING ABOVE
FREEZING...AND SNOW EVENTUALLY CHANGING TO RAIN. HOWEVER PRECIP IS
EXPECTED TO CONTINUE SAT AFTN THROUGH SAT NIGHT MAINLY SOUTH OF
INTERSTATE 90 WITH TOTAL QPF AMOUNTS FOR THIS EVENT REACHING ONE TO
2 INCHES.

.LONG TERM...SUNDAY THROUGH FRIDAY
ISSUED AT 251 PM MDT FRI APR 29 2016

UPPER LOW PULLS OUT OF THE AREA ON SUNDAY WITH UPPER RIDGE
BUILDING INTO THE REGION FOR MUCH OF NEXT WEEK. THIS WILL BRING
DRY AND WARMER CONDITIONS. NEXT UPPER LOW SHIFTS INTO THE DESERT
SW TOWARDS THE TAIL END OF THE WEEK WHICH COULD BRING SW FLOW AND
MORE MOISTURE BACK INTO THE REGION BY NEXT WEEKEND.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING
ISSUED AT 520 PM MDT FRI APR 29 2016

WDSPRD MVFR AND LOCALIZED IFR CIGS WILL PERSIST OVERNIGHT...WITH
FAR NWRN SD AND PARTS OF NERN WY REMAINING VFR. WDSPRD RAIN/SNOW
WILL MOVE NORTHWARD FROM NEB INTO NERN WY AND WRN SD THIS EVE AND
OVERNIGHT...ESPECIALLY ALONG AND SOUTH OF I90. THIS WILL BRING
WDSPRD IFR CONDITIONS...AND LOCALIZED LIFR CONDITIONS IN THE
HIGHER TERRAIN. FAR NWRN SD LIKELY TO REMAIN MVFR OR VFR.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL NOON MDT /1 PM CDT/ SATURDAY FOR
     SDZ024-027>029-041-042-044-047.

WY...NONE.
&&

$$

SHORT TERM...13
LONG TERM...JOHNSON
AVIATION...10



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