Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 010240
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
840 PM MDT FRI JUL 31 2015

.UPDATE...
ISSUED AT 828 PM MDT FRI JUL 31 2015

WATER VAPOR IMAGES SHOW SUBTLE SIGNS OF A WEAK SHORT WAVE IN THE
YELLOWSTONE VICINITY...WHICH WOULD CROSS NORTHEASTERN WY AND
SOUTHWESTERN SD AFTER MIDNIGHT. KUDX AND KLNX VAD WIND PROFILERS
SHOWING VEERING WINDS...BUT LOW LEVEL JET HAS NOT DEVELOPED YET...
WHILE RETURN FLOW ON THE SURFACE IS STARTING TO BRING HIGHER
DEWPOINTS TO THE AREA. ISOLATED THUNDERSTORMS MORE LIKELY TO FORM
AFTER MIDNIGHT...WITH BEST CHANCES EAST OF PHP-IEN ALONG A THETA-E
RIDGE THROUGH EARLY MORNING.

&&

.SHORT TERM...THIS EVENING THROUGH SATURDAY NIGHT
ISSUED AT 204 PM MDT FRI JUL 31 2015

A 25-30KT LL JET WILL DEVELOP OVER FAR WRN SD THIS EVENING
INCREASING THE MID-LEVEL THETA-E ADVECTION AND INCREASING THE
INSTABILITY ALOFT. MAY SEE ISOLATED ELEVATED THUNDERSTORMS DEVELOP
OVER FAR NERN WY/THE BLKHILLS THIS EVENING WHICH COULD POSSIBLY
CONTINUE THOUGH MUCH OF THE NIGHT IN THE ELEVATED UNSTABLE
LAYER...MOVING GRADUALLY SOUTHEAST OVERNIGHT. A WEAK FRONTAL
BOUNDARY WILL MOVE SOUTHWARD ACROSS THE FORECAST AREA ON SATURDAY.
DUE TO INSTABILITY AND LL FORCING ALONG AND NEAR THE FRONT WILL
INCLUDE A LOW CHANCE OF THUNDERSTORMS OVER SOUTHWESTERN AND SOUTH
CENTRAL SOUTH DAKOTA THROUGH THE DAY ON SATURDAY. HAVE ALSO
INCLUDED A SLIGHT CHANCE OF THUNDERSTORMS OVER THE CENTRAL AND
SOUTHERN BLACK HILLS ON SATURDAY AFTN AS CONVERGENCE ALONG THE
BOUNDARY COMBINED WITH DIURNAL HEATING MAY BE STRONG ENOUGH TO
OVERCOME THE SUBSIENCE BEHIND THE FRONT. HIGH TEMPERATURES ON THE
PLAINS ON SATURDAY ARE EXPECTED TO RANGE FROM THE UPPER 80S TO THE
UPPER 90S

.LONG TERM...SUNDAY THROUGH FRIDAY
ISSUED AT 204 PM MDT FRI JUL 31 2015

GFS/ECMWF STILL IN DECENT AGREEMENT WITH THE OVERALL
PATTERN FOR MUCH OF NEXT WEEK. HOWEVER...TIMING DIFFERENCES REMAIN
WITH IMPULSES MOVING THROUGH THE NORTHERN PLAINS...ESPECIALLY
FURTHER OUT IN TIME.

SUNDAY WILL BE WARM AND DRY AS UPPER RIDGE BUILDS ACROSS THE HIGH
PLAINS. HIGHS WILL BE IN THE 90S ON THE PLAINS WITH RELATIVE
HUMIDITY DROPPING TO AROUND 15 PERCENT AGAIN OVER NORTHEAST WY AND
FAR WESTERN SD. WINDS SHOULD STAY RELATIVELY LIGHT ACROSS THE AREA.

CHANCES FOR THUNDERSTORMS WILL BEGIN TO INCREASE EARLY IN THE
WEEK...STARTING LATE ON MONDAY...AS RIDGE WEAKENS ENOUGH TO ALLOW A
SERIES OF DISTURBANCES TO CROSS THE REGION. LOW LEVEL MOISTURE WILL
INCREASE AS EAST-SOUTHEAST WINDS BECOME RATHER PERSISTENT ACROSS THE
AREA THROUGH MIDWEEK...ESPECIALLY OVER AND EAST OF THE BLACK HILLS.
TIMING FOR BETTER CHANCES OF STORMS IS STILL UNCERTAIN AT THIS
POINT...BUT THE MIDDLE PART OF THE WEEK LOOKS TO BE THE MOST
FAVORABLE PERIOD. TEMPERATURES WILL BE NEAR AVERAGE THROUGH MUCH OF
THE WEEK.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING
ISSUED AT 529 PM MDT FRI JUL 31 2015

SCT CLDS OVR NERN WY AND BLK HLS WL DISSIPATE THIS EVENING. ISOLD TSTMS
MAY DVLP OVR SWRN SD TONITE AND MOV ACRS SCNTRL SD. LGT WNDS WL SHIFT
TO THE NW SAT MRNG BEHIND A COLD FRONT.


&&

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

$$

UPDATE...55
SHORT TERM...10
LONG TERM...26
AVIATION...55



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