Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 230140
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
740 PM MDT MON SEP 22 2014

.UPDATE...
ISSUED AT 735 PM MDT MON SEP 22 2014

A LOW PRESSURE SYSTEM CONTINUES TO SWING BANDS OF ISOLD-SCT -SHRA...
AND A FEW THUNDERSTORMS...ACROSS THE AREA EARLY THIS EVENING.
BEST CHANCE OF RAIN DURING THE REST OF THE NIGHT WILL BE OVER
SOUTH CENTRAL SOUTH DAKOTA WHERE THE LOW-MID LEVEL THETA-E
ADVECTION WILL INCREASE AS A LOW LEVEL JET DEVELOPS OVER THAT AREA.

&&

.SHORT TERM...THIS EVENING THROUGH TUESDAY NIGHT
ISSUED AT 257 PM MDT MON SEP 22 2014

20Z SURFACE ANALYSIS HAD LOW OVER SOUTHEAST MT WITH TROUGH FROM
CENTRAL MT THROUGH LOW INTO NORTHEAST CO. WATER VAPOUR SHOWED
UPPER LOW OVER WESTERN WY WITH LEAD SHORTWAVE SPINNING OVER
SOUTHEAST WY...HEADING EAST-NORTHEAST. ABOUT 100-500J/KG MUCAPE
HAS DEVELOPED THIS AFTERNOON AHEAD OF SHORTWAVE...AND AS IT
INTERACTS WITH SURFACE FEATURES...A FEW SHRA/TSRA WILL DEVELOP
OVER/ADVECT INTO CWA THROUGH THE EVENING HOURS. LOW LEVEL JET
DEVELOPS OVER CENTRAL NE/SD TONIGHT WITH THE MAIN FOCUS FOR
PRECIPITATION SHIFTING INTO SOUTH CENTRAL SD WHERE BEST 850-700MB
THETA-E ADVECTION EXPECTED. LOWS TONIGHT NEAR GUIDANCE.

TUESDAY...UPPER LOW SPINS INTO NORTHEAST SD AND OPENS UP INTO A
TROUGH AS IT SHIFTS INTO THE UPPER MIDWEST/SOUTHERN MB. EARLY
MORNING PRECIPITATION SOUTH CENTRAL SD WILL WANE...BUT ADDITIONAL
ACTIVITY MAY DEVELOP IN THE AFTERNOON OVER SOUTHERN PORTIONS OF SD
AS 500-750J/KG MUCAPE DEVELOPS DURING PEAK HEATING. AFTERNOON
PRECIPITATION FOCUS SHOULD BE ON LEFTOVER SURFACE TROUGH/WIND SHIFT
LINE DRAPED ACROSS SD PORTIONS OF THE CWA. TEMPERATURES WILL BE NEAR
GUIDANCE.

TUESDAY NIGHT...SYSTEM EXITS CWA WITH CLEARING SKIES AND PLEASANT
TEMPERATURES.

&&

.LONG TERM...WEDNESDAY THROUGH MONDAY
ISSUED AT 257 PM MDT MON SEP 22 2014

DRIER AIR WILL RETURN WEDNESDAY AS A RIDGE BUILDS AND SURFACE
TROF PUSHES EAST OF FORECAST AREA. LOW HUMIDITY AND SOUTHWEST FLOW
WILL ALLOW TEMPERATURES TO WARM WELL ABOVE SEASONAL AVERAGES. DEEP
TROF WILL PUSH ACROSS THE ROCKIES BY THE END OF THE WEEK...WITH A
CLOSED LOW FORMING OVER THE CENTRAL ROCKIES. PRECIPITATION WILL
MOVE INTO THE AREA BY LATE SATURDAY AND BECOME WIDESPREAD LATE
SUNDAY THROUGH MONDAY MORNING...WITH MOST PRECIPITATION BEHIND THE
SURFACE TROF. GFS IS SHOWING A DRY SLOT OVER WESTERN INTO CENTRAL
SD WITH A BAND OF PRECIPITATION ACROSS CENTRAL-EASTERN SD...BUT
MODEL BLEND HAS BROADBRUSHED POPS ACROSS THE AREA. FORECAST
SOUNDINGS ARE VERY STABLE...ALTHOUGH ENOUGH CONVERGENCE ALONG THE
SURFACE TROF AND COOL AIR WITH THE UPPER LOW CREATE ENOUGH
INSTABILITY FOR THUNDERSTORMS.

&&

.AVIATION...FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING
ISSUED AT 444 PM MDT MON SEP 22 2014

BANDS OF ISOLD TO SCT SHWRS/TSTMS WILL CROSS NERN WY AND PARTS OF
WRN AND SC SD THIS EVE. LCL MVFR CONDITIONS AND GUSTY WNDS
POSSIBLE IN THE VCNTY TSTRMS. GUSTY S WNDS ON THE SD PLAINS W WL
DCRS THIS EVEN...AND WNDS WL SWITCH TO THE NW OVR NERN WY AND FAR
WRN SD TUES MRNG AS SFC TROF MOVS INTO WRN SD.


&&

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

$$

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





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