Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 301549
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
949 AM MDT THU APR 30 2015

.UPDATE...
ISSUED AT 942 AM MDT THU APR 30 2015

LATEST SFC ANALYSIS SHOWED THE N-S ORIENTED TROUGH OVER WESTERN
SOUTH DAKOTA WITH GUSTY NORTHWEST WINDS TO THE WEST OF THE TROUGH
OVER NORTHEASTERN WYOMING AND FAR WESTERN SOUTH DAKOTA AND
SOUTHERLY WINDS EAST OF THE TROUGH OVER CENTRAL SOUTH DAKOTA. THE
COLD FRONT WAS STILL LOCATED FROM WESTERN NORTH DAKOTA INTO
SOUTHEASTERN MONTANA THEN INTO NORTH CENTRAL WYOMING. THE SFC
TROUGH WILL CONTINUE TO SHIFT EASTWARD TODAY WITH THE COLD FRONT
DROPPING SOUTHEASTWARD INTO THE FORECAST AREA. STILL EXPECT ISOLD-
SCT -SHRA/-TSRA THIS AFTN AND EVENING WITH THE BEST CHANCE OF RAIN
ALONG THE SFC TROUGH OVER SOUTH CENTRAL SD LATE THIS AFTN AND
ALSO NEAR THE FRONT OVER PARTS OF NERN WY...THE BLKHLS...AND SWRN
SD FROM LATE THIS AFTN INTO THIS EVENING.

&&

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT
ISSUED AT 307 AM MDT THU APR 30 2015

UPPER LEVEL ANALYSIS SHOWS POSITIVELY TILTED RIDGE FROM THE
DESERT SOUTHWEST INTO THE NORTHERN PLAINS...WITH SHORTWAVE TROF
CROSSING THE NORTHERN ROCKIES. SKIES ARE MOSTLY CLEAR ACROSS THE
NORTHERN PLAINS WITH CLOUD COVER INCREASING FROM THE NORTHWEST. AT
THE SURFACE...STRONG COLD FRONT IS APPROACHING THE NORTHERN PLAINS
FROM MONTANA. TEMPERATURES ARE MILD AHEAD OF THE FRONT...MAINLY IN
THE 50S. WINDS ARE OUT OF THE SOUTH TO SOUTHEAST AT 10 TO 20 MPH.

WARM CONDITIONS WILL PERSIST THROUGH THE END OF THE WEEK...WITH A
COLD FRONT MOVING THROUGH THE CWA THIS MORNING...BRINGING A
SLIGHT COOLDOWN. SHORT RANGE MODELS ARE IN GOOD AGREEMENT ON THE
TIMING OF THE FRONTAL PASSAGE THIS MORNING AND ASSOCIATED CHANCES
FOR PCPN LATER IN THE DAY WITH POST FRONTAL SHORTWAVE.

FOR TODAY...THE COLD FRONT WILL MOVE THROUGH THE FORECAST AREA
THIS MORNING...BEFORE SLOWING DOWN AS IT REACHES CENTRAL SD
AROUND MIDDAY. WINDS WILL SWITCH TO THE NORTHWEST BEHIND THE FRONT
AND BECOME BREEZY TO WINDY ACROSS THE AREA. THE STRONGEST WINDS
WILL BE FROM K2WX TO KRAP...WHERE GUSTS TO AROUND 40 MPH ARE
EXPECTED. UPPER SHORTWAVE WILL MOVE ACROSS THE AREA MOSTLY DURING
THE AFTERNOON AND EVENING HOURS. CHANCES FOR SHOWERS AND STORMS
STILL LOOK RELATIVELY LOW... ESPECIALLY ACROSS WESTERN PORTIONS OF
THE CWA...BUT AS THE WAVE TRIES TO CATCH UP WITH THE COOL
FRONT...THE CHANCES SHOULD INCREASE FURTHER EAST ACROSS THE
CWA...ESPECIALLY TOWARD SOUTH CENTRAL SD LATE IN THE DAY. CAPE
VALUES ARE FORECAST TO BE RELATIVELY LOW...SO THE CHANCES FOR ANY
STRONGER STORMS LOOK TO BE MINIMAL. HIGHS WILL RANGE FROM THE LOW
TO MID 60S OVER NORTHEAST WY AND THE BLACK HILLS TO THE UPPER 70S
OVER SOUTH CENTRAL SD. WINDS WILL DIMINISH IN THE EVENING AND ANY
LINGERING SHOWERS ACROSS FAR SOUTHERN SD WILL DISSIPATE OVERNIGHT.

ON FRIDAY...ZONAL FLOW TAKES OVER AS BROAD RIDGE SETTLES OVER THE
DESERT SOUTHWEST. WEAK SURFACE HIGH WILL SLIDE ACROSS THE DAKOTAS
DURING THE DAY...PRODUCING MOSTLY SUNNY SKIES AND RELATIVELY LIGHT
WINDS. HIGH TEMPERATURES WILL CLIMB INTO THE MID 60S TO MID 70S.
MOSTLY CLEAR SKIES WILL PERSIST THROUGH FRIDAY NIGHT WITH LOWS IN
THE 40S.

.LONG TERM...SATURDAY THROUGH WEDNESDAY
ISSUED AT 307 AM MDT THU APR 30 2015

VERY WARM CONDITIONS ARE EXPECTED ON SATURDAY WITH THERMAL RIDGE
CROSSING THE CWFA. BEST CHANCE FOR TSRA WILL BE OVER CNTRL SD
ALONG/AHEAD OF A SURFACE TROF. FLOW ALOFT WILL BE NEARLY ZONAL
SUNDAY THROUGH TUESDAY WITH COOLER AIR FILTERING INTO THE NRN
PLAINS. SEVERAL DISTURBANCES EMBEDDED IN THE FLOW WILL BRING
NEARLY DAILY CHANCES FOR SHRA/TSRA...ESPECIALLY DURING THE
AFTERNOON/EVENING HOURS. FLOW ALOFT THEN BECOMES SW BY MID WEEK AS
A DEEP TROF DEVELOPS OVER THE WRN CONUS. BOTH GFS/ECMWF SUGGEST A
STRONG DISTURBANCE EJECTING INTO THE CNTRL/NRN PLAINS ON WED WHICH
WOULD BRING INCREASING CHANCES FOR PCPN.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING
ISSUED AT 307 AM MDT THU APR 30 2015

VFR CONDITIONS ARE EXPECTED TODAY AND TONIGHT. A CDFNT MOVING
THROUGH THIS MRNG WILL BRING GUSTY NW WINDS TO AROUND 35KTS ACROSS
NERN WY AND WRN SD THROUGH THE DAY.


&&

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

$$

UPDATE...10
SHORT TERM...15
LONG TERM...JOHNSON
AVIATION...JOHNSON



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