Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 020831
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
231 AM MDT SAT MAY 2 2015

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
ISSUED AT 218 AM MDT SAT MAY 2 2015

WATER VAPOR SHOWS UPPER TROF WORKING THROUGH THE PAC NW INTO THE
NRN ROCKIES EARLY THIS MRNG. AT THE SFC...AN ASSOCIATED LEE TROF
IS PUSHING INTO ERN MT/ERN WY SUPPORTING SLY BL FLOW OVER THE
CWFA.

TODAY...UPPER TROF WILL CONTINUE ITS EWD PROGRESSION...WITH SFC
TROF ADVANCING THROUGH THE WRN DAKOTAS DURING THE AFTN. MOISTURE
POOLING ALONG/AHEAD OF THIS SFC TROF WILL RESULT IN A CORRIDOR OF
NEAR 1000J/KG MLCAPE EXTENDING NWD INTO CNTRL SD. OVERALL MOISTURE
WILL BE RATHER SCANT AND MID LVL WINDS RELATIVELY LIGHT...SO
PROBABLY NOT MORE THAN A FEW PULSE TYPE STRONG STORMS IN THE LATE
AFTN/EARLY EVE. TEMPS WILL BE VERY WARM TODAY GIVEN THERMAL RIDGE
PASSING OVERHEAD...AND BEHIND THE SFC TROF DEEP MIXING AND VERY
DRY AIR WILL RESULT IN MINIMUM RELATIVE HUMIDITIES OF 10 TO 15
PERCENT...AND POSSIBLY IN THE SINGLE DIGITS OVER PARTS OF NERN WY.

SUNDAY...HIGH PRESSURE WILL BUILD INTO THE WRN DAKOTAS WITH
NOTICEABLY COOLER TEMPS AND BREEZY N/NE WINDS EXPECTED. SOME LATE
DAY STORMS POSSIBLE IN NERN WY AND THE BLKHLS GIVEN STEEP LO LEVEL
LAPSE RATES AND WEAK CYCLONIC FLOW ALOFT. BETTER CHANCE FOR
SHRA/TSRA ACRS NERN WY AND FAR WRN SD LATE SUNDAY NIGHT AS AREA
COMES UNDER INFLUENCE OF RIGHT REAR QUAD OF JET STREAK OVER ND.

.LONG TERM...MONDAY THROUGH FRIDAY
ISSUED AT 218 AM MDT SAT MAY 2 2015

NEARLY ZONAL UPPER FLOW WILL CONTINUE INTO TUESDAY WITH
NEAR TO SLIGHTLY ABOVE AVERAGE TEMPERATURES IN THE 60S AND LOWER
70S. SEVERAL DISTURBANCES EMBEDDED IN THE FLOW WILL BRING DAILY
CHANCES FOR SHOWERS AND THUNDERSTORMS...ESPECIALLY DURING THE
AFTERNOON/EVENING HOURS. BREEZY SOUTHEASTERLY RETURN FLOW IS
EXPECTED MONDAY AS HIGH PRESSURE SLIDES OVER MN.

UPPER FLOW THEN BECOMES SOUTHWESTERLY BY MID WEEK AS A DEEP TROUGH
DEVELOPS OVER THE WESTERN CONUS. BOTH GFS/ECMWF CONTINUE TO SHOW A
STRONG DISTURBANCE EJECTING INTO THE CENTRAL/NORTHERN PLAINS WED/THU
WHICH WOULD BRING INCREASING CHANCES FOR PRECIPITATION. GFS AND ECM
ARE SHOWING AROUND AN INCH OF QPF FOR MANY LOCATIONS ACROSS WRN SD.
CYCLONIC FLOW IS EXPECTED TO CONTINUE ACROSS THE REGION FOR THE END
OF NEXT WEEK...WITH CHANCES OF PRECIP PERSISTING.

&&

.AVIATION...FOR THE 12Z TAFS THROUGH 12Z SATURDAY NIGHT
ISSUED AT 218 AM MDT SAT MAY 2 2015

VFR CONDITIONS ARE EXPECTED THROUGH EARLY THIS
AFTERNOON. ISOLATED SHOWERS/THUNDERSTORMS ARE POSSIBLE THIS
AFTERNOON AND EVENING...MAINLY ACROSS CENTRAL SD. COULD BE SOME
LOCAL MVFR CIGS/VSBY AND STRONG WINDS WITH THE SHOWERS/THUNDERSTORMS.

&&

.FIRE WEATHER...
ISSUED AT 218 AM MDT SAT MAY 2 2015

VERY WARM TEMPS COMBINED WITH DEEP MIXING WILL RESULT IN DEWPOINTS
TO DROP INTO THE 20S ACROSS NERN WY AND FAR WRN...WITH SOME TEENS
POSSIBLE OVER NERN WY AND THE BLKHLS. THIS WILL RESULT IN RELATIVE
HUMIDITIES OF 10 TO 15 PERCENT...AND POSSIBLY LOWER OVER PARTS OF
NERN WY. WINDS WILL GENERALLY BE IN THE 10 TO 20 MPH RANGE.

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

$$

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


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