Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 212014
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
214 PM MDT MON JUL 21 2014

.SHORT TERM...THIS EVENING THROUGH TUESDAY NIGHT
ISSUED AT 159 PM MDT MON JUL 21 2014

20Z SFC ANALYSIS SHOWS LOW PRESSURE CENTERED OVER NORTHWESTERN
SOUTH DAKOTA WITH A WARM FRONT ARCING NORTHEASTWARD INTO
NORTHEASTERN NORTH DAKOTA. A DRYLINE/SFC TROUGH EXTENDS SOUTHEASTWARD
FROM THE LOW INTO SOUTHEASTERN SOUTH DAKOTA. DEWPOINTS JUST TO THE
WEST OF THE TROUGH ARE CURRENTLY IN THE MID 50S WITH DEWPOINTS IN THE LOWER
70S EAST OF THE BOUNDARY. SYNOPTIC SCALE SUBSIDENCE CURRENTLY OVER
THE FORECAST AREA HAS BEEN KEEPING A LID ON ANY CONVECTION SO FAR.
HOWEVER INSTABILITY IS INCREASING OVER THE WESTERN PART OF THE
FORECAST AREA IN ADVANCE OF THE NEXT SHORTWAVE APPROACHING FROM
THE WEST. WHILE THE BEST CHANCE OF WIDESPREAD SEVERE T-STORMS WILL
BE LOCATED ALONG AND NEAR THE WARM FRONT DURING THE REST OF THIS
AFTERNOON AND EVENING...ISOLATED SEVERE STORMS WILL BE POSSIBLE
OVER NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA. STRONG WIND
GUSTS WILL BE POSSIBLE WITH ANY THUNDERSTORMS.

ALTHOUGH SOMEWHAT DRIER AIR IS MOVING INTO SOUTH CENTRAL SOUTH
DAKOTA THIS AFTERNOON...SFC TEMPERATURES ARE WELL ABOVE 100F
DEGREES SO WILL CONTINUE THE HEAT ADVISORY THAT IS IN EFFECT FOR
THAT AREA UNTIL IT IS SCHEDULED TO EXPIRE AT 800 PM CDT.

LATER TONIGHT...CONVECTION PUSHES EAST OF THE CWA WITH WEAK COOL
AIR ADVECTION. TEMPERATURES WILL BE NEAR GUIDANCE.

TUESDAY...SURFACE HIGH PUSHES EAST OF THE MO RIVER WITH
RETURN/UPSLOPE FLOW OVER NORTHEAST WY/FAR WESTERN SD. UPPER RIDGE
REBUILDS OVER THE NORTHERN PLAINS. AS TAIL END OF COOL FRONT MORPHS
INTO LEE TROUGH OVER WESTERN PORTIONS OF THE CWA...ENOUGH
CONVERGENCE WILL BE PRESENT FOR ISOLATED LATE AFTERNOON TSRA.
INVERTED-V SOUNDINGS SUGGESTS ISOLATED SEVERE WIND GUST THREAT.
TEMPERATURES WILL BE 5-10F LOWER THAN TODAY GIVEN THICKNESS CHANGE
AND FORECAST POTENTIAL TEMPERATURES.

&&

.LONG TERM...WEDNESDAY THROUGH MONDAY
ISSUED AT 159 PM MDT MON JUL 21 2014

UPPER-LEVEL RIDGE WILL REMAIN OVER THE ROCKIES AND HIGH PLAINS
DURING THE MIDDLE AND LATTER PART OF THE WEEK...WITH VERY WARM
CONDITIONS PERSISTING. WEAK DISTURBANCES ROTATING AROUND THE UPPER
HIGH TO THE SOUTHWEST WILL BRING MOSTLY ISOLATED THUNDERSTORM
ACTIVITY TO THE REGION FROM WEDNESDAY THROUGH FRIDAY. THE BEST
CHANCES FOR PCPN LOOK TO BE WEDNESDAY AFTERNOON AND EVENING...WHEN
THERE DOES APPEAR TO BE A RISK FOR STRONG TO SEVERE STORMS OVER THE
AREA.

THE RIDGE WILL WEAKEN AND SLIDE BACK INTO THE WESTERN CONUS OVER THE
WEEKEND AS A STRONG UPPER TROF MOVES FROM SOUTH CENTRAL CANADA TO
THE GREAT LAKES REGION. THIS WILL EVENTUALLY BRING A COOLER PATTERN
WITH NEAR TO SLIGHTLY BELOW AVERAGE TEMPERATURES FOR THE REST OF THE
EXTENDED PERIOD. WILL KEEP SLIGHT CHANCES FOR SHOWERS AND
THUNDERSTORMS OVER PORTIONS OF THE AREA INTO EARLY NEXT WEEK.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z TUESDAY
ISSUED AT 159 PM MDT MON JUL 21 2014

MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIOD.
ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS NORTHEAST WY
AND MUCH OF WESTERN SD LATE TODAY AND THIS EVENING AS THE NEXT
DISTURBANCE PASSES ACROSS.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR SDZ046-047-049.

WY...NONE.
&&

$$

SHORT TERM...10
LONG TERM...26
AVIATION...26





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