Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 150417
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1017 PM MDT TUE APR 14 2015

.UPDATE...
ISSUED AT 810 PM MDT TUE APR 14 2015

HAVE ALLOWED THE RED FLAG WARNING TO EXPIRE AS HUMIDITIES WILL
SLOWLY RISE AS TEMPS FALLS. GUSTY SOUTHERLY WINDS WILL CONTINUE
MUCH OF THE NIGHT ON THE SD PLAINS AND WILL LEAVE THE WIND
ADVISORY IN PLACE AT THIS TIME.

&&

.SHORT TERM...THIS EVENING THROUGH WEDNESDAY NIGHT
ISSUED AT 324 PM MDT TUE APR 14 2015

UPPER RIDGING COVERS THE CENTRAL CONUS...AND TROUGH IS
DIGGING INTO THE WEST COAST. TIGHT PRESSURE GRADIENT IS DEVELOPING
ACROSS THE REGION AS LOW PRESSURE PUSHES IN FROM THE WEST. SOUTHERLY
WINDS OF 30 TO 40 KTS ARE FOUND ACROSS THE SD PLAINS. UNDER MOSTLY
SUNNY SKIES...TEMPS ARE WARMING INTO THE 70S AND 80S.

VERY TIGHT PRESSURE GRADIENT WILL KEEP SOUTHERLY WINDS GUSTY
OVERNIGHT...GENERALLY 20 TO 35 MPH WITH GUSTS UP TO 50 MPH. WITH
850MB WINDS 40 TO 50 KTS...SOME STRONGER GUSTS MAY MIX DOWN. A 4MB
PRESSURE DIFFERENCE WILL DEVELOP OVER THE BLACK HILLS
TONIGHT...CREATING SOME GUSTY DOWNSLOPING WINDS OVER THE NORTHERN
AND NORTHEASTERN FOOTHILLS...SO ADDED THOSE AREAS TO THE WIND
ADVISORY. COLD FRONT BEGINS MOVING INTO THE REGION TONIGHT...AND
NORTHWESTERLY WINDS BEHIND THE FRONT WILL ACTUALLY BE WEAKER THAN
THE SOUTHERLY WINDS AHEAD OF THE FRONT...WITH THE EXCEPTION OF SOME
GUSTY WINDS ACROSS PARTS OF NORTHEASTERN WYOMING. WINDS WILL STILL
BE BREEZY ON WEDNESDAY...AROUND 15 TO 20 KTS.

GFS IS STILL THE OUTLIER IN THE TRACK OF THIS SYSTEM. ECM/NAM/GEM
HAVE A CLOSED LOW OVER THE FOUR CORNERS AREA BY 06Z THURSDAY. THE
GFS HAS A SIMILAR CLOSED LOW...BUT ALSO AN ADDITIONAL CLOSED LOW
FORMING OVER WESTERN SD...RESULTING IN A GREATLY OVERESTIMATED
PRECIPITATION FORECAST. GFS HAS 20 INCHES OF SNOW OVER NORTHEASTERN
WYOMING...WHILE THE NAM HAS 1 TO 5 INCHES. HAVE 1 TO 3 INCHES IN THE
FORECAST...WITH THE GREATER AMOUNTS OVER SOUTHERN CAMPBELL
COUNTY...WHICH ALIGNS WITH THE SREF.

MODELS HAVE SLOWED DOWN THE ONSET OF PRECIPITATION IN THE
CWA...LIKELY NOT BEGINNING UNTIL EARLY WEDNESDAY MORNING. RAIN/SNOW
WILL GRADUALLY SPREAD ACROSS WESTERN SD WEDNESDAY. A FEW ISOLATED
THUNDERSTORMS ARE ALSO POSSIBLE OVER THE SD PLAINS WITH SOME MINIMAL
INSTABILITY AROUND. PRECIP WILL CHANGE TO SNOW ACROSS THE WESTERN
HALF OF THE CWA WEDNESDAY NIGHT...AND THERE MAY BE SOME PATCHY
BLOWING SNOW WITH THE STRONGER WINDS OVER NORTHEASTERN WYOMING.

LOWS TONIGHT WILL BE IN THE MID 30S TO MID 40S. HIGHS WEDNESDAY WILL
RANGE FROM NEAR 40 ACROSS NORTHEASTERN WY TO THE UPPER 60S ACROSS
CENTRAL SD.

.LONG TERM...THURSDAY THROUGH TUESDAY
ISSUED AT 324 PM MDT TUE APR 14 2015

LARGE UPPER LEVEL LOW WILL MOVE OUT OF THE CENTRAL
ROCKIES ON THURSDAY...PRODUCING SOME RAIN AND SNOW ACROSS NORTHEAST
WYOMING AND WESTERN SOUTH DAKOTA EARLY IN THE DAY...WITH CONDITIONS
IMPROVING LATER IN THE DAY. HIGHS ON THURSDAY WILL BE NEAR AVERAGE.
MAINLY DRY WEATHER IS EXPECTED ON FRIDAY AND SATURDAY WITH RIDGING
IN THE NORTHERN STREAM...AND A CUT OFF UPPER LOW MOVING SLOWLY
EASTWARD ACROSS THE SOUTHERN PLAINS. THE NEXT SYSTEM SLIDES THROUGH
THE NORTHERN PLAINS WITH A CHANCE FOR SHOWERS SATURDAY NIGHT INTO
SUNDAY. TEMPERATURES WILL REMAIN NEAR AVERAGE THROUGH THE EXTENDED
PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1013 PM MDT TUE APR 14 2015


VFR CONDITIONS WILL CONTINUE OVERNIGHT WITH AN INCREASING CHANCE
OF -SHRA ACROSS NERN WY. CONDITIONS WILL DETERIORATE TO IFR
ACROSS NERN WY AND INTO PORTIONS OF FAR WRN SD INCLUDING THE
BLKHLS TOWARDS MRNG AS -RASN DEVELOPS. THESE POOR CONDITIONS WILL
CONTINUE THROUGH THE DAY WEDNESDAY. A STRONG LO LEVEL JET WILL
LEAD TO LO LEVEL WIND SHEAR ACROSS MUCH OF WESTERN SOUTH DAKOTA
OVERNIGHT.

&&

.FIRE WEATHER...
ISSUED AT 810 PM MDT TUE APR 14 2015

RELATIVE HUMIDITY WILL SLOWLY RISE TONIGHT AS TEMPERATURES
FALL...BUT POOR HUMIDITY RECOVERY IS EXPECTED FOR MOST AREAS IN
WESTERN SOUTH DAKOTA (A LITTLE BETTER HUMIDITY RECOVERY EXPECTED
FOR NORTHEAST WYOMING). EXPECT GUSTY SOUTHERLY WINDS THROUGH THE
NIGHT OVER MUCH OF WESTERN SOUTH DAKOTA. SLOW MOVING COLD FRONT MOVES
INTO NORTHEAST WYOMING/NORTHWEST SOUTH DAKOTA LATE TONIGHT...AND
THROUGH WESTERN SOUTH DAKOTA WEDNESDAY MORNING. SOME RAIN/SNOW
WILL DEVELOP BEHIND THE COLD FRONT...ACCUMULATING SNOW LIKELY
ACROSS PORTIONS OF NORTHEAST WYOMING INTO THE BLACK HILLS. RAIN
WILL SPREAD INTO SOUTHWEST/SOUTH CENTRAL SOUTH DAKOTA WEDNESDAY
AFTERNOON.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY UNTIL 6 AM MDT /7 AM CDT/ WEDNESDAY FOR SDZ001-002-
     012>014-025-030>032-041>044-046-047-049-072-073.

WY...NONE.
&&

$$

UPDATE...JOHNSON
SHORT TERM...POJORLIE
LONG TERM...15
AVIATION...JOHNSON
FIRE WEATHER...JOHNSON


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