Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 192055
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
255 PM MDT TUE AUG 19 2014

.SHORT TERM...THIS EVENING THROUGH WEDNESDAY NIGHT
ISSUED AT 255 PM MDT TUE AUG 19 2014

CURRENT SURFACE ANALYSIS SHOWS HIGH PRESSURE CENTERED OVER
EASTERN NEB...WITH LEE TROF LOCATED FROM CENTRAL MT INTO NORTHEAST
WY. UPPER LEVEL ANALYSIS SHOWS TROF OVER THE WESTERN GREAT LAKES
REGION...HIGH PRESSURE OVER THE SOUTHERN PLAINS...AND A TROF ALONG
THE CA COAST. SKIES ARE MOSTLY SUNNY TO PARTLY CLOUDY ACROSS THE
AREA. ISOLATED SHOWERS AND STORMS HAVE DEVELOPED OVER THE CENTRAL
AND NORTHERN BLACK HILLS. OTHER ISOLATED ACTIVITY IS TRYING TO
DEVELOP NEAR THE SURFACE TROF OVER PORTIONS OF EASTERN WY AND
SOUTHEAST MT. TEMPS ARE CURRENTLY IN THE 80S AND LOWER 90S WITH
SOUTH-SOUTHEAST WINDS.

AN UNSETTLED PATTERN WILL TAKE SHAPE OVER THE REGION FOR THE REST OF
THE WEEK AS A BROAD UPPER TROF CONTINUES TO DEVELOP OVER THE WESTERN
CONUS AND BRINGS DISTURBANCES NORTHEASTWARD ACROSS THE NORTHERN
PLAINS. DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS ARE EXPECTED
ACROSS MOST OF THE AREA.

FOR LATE TODAY AND TONIGHT...A SHORTWAVE OVER SOUTHWEST WY WILL MOVE
SLOWLY NORTHEAST INTO THE AREA...WITH SOME SIGNS OF THE WAVE
SPLITTING INTO TWO PIECES AS IT DOES. ONE PIECE WOULD MOVE ACROSS
MOSTLY SOUTHERN PORTIONS OF THE CWA THIS EVENING...WITH THE SECOND
AND STRONGER PIECE OF ENERGY MOVING ACROSS WESTERN AND NORTHERN
PORTIONS OF THE CWA TONIGHT INTO WEDNESDAY. ISOLATED STRONG
STORMS WITH SOME HAIL AND GUSTY WINDS ARE POSSIBLE INTO THIS
EVENING...MAINLY ACROSS SOUTHERN PORTIONS OF THE CWA...BUT THE
THREAT FOR SEVERE STORMS WILL BE RELATIVELY LOW. WILL KEEP BEST
CHANCES FOR PCPN ACROSS SOUTHERN AREAS IN THE EVENING...AND THEN
WESTERN AREAS OVERNIGHT. LOWS WILL BE IN THE MID 50S TO MID 60S.

CHANCES FOR SHOWERS AND STORMS WILL BE HIGHEST ON WEDNESDAY ACROSS
NORTHWESTERN SD AS THE WAVE MOVES SLOWLY NORTHEAST AND EVENTUALLY
INTO ND BY LATE IN THE DAY. CHANCES WILL GENERALLY DECREASE FURTHER
SOUTH ACROSS THE CWA. SKIES WILL BE VARIABLY CLOUDY...WITH THE MOST
CLOUDS ACROSS NORTHERN AREAS. HIGHS WILL RANGE FROM THE LOWER 80S
ACROSS NORTHWESTERN SD TO THE LOWER 90S ACROSS PORTIONS OF SOUTHERN
SD. THE SURFACE TROF WILL SLOWLY MOVE ACROSS THE AREA...SWITCHING
WINDS TO THE WEST BEHIND IT. THE FOCUS FOR POTENTIAL STRONG TO
SEVERE STORMS WILL BE MAINLY ACROSS CENTRAL SD DURING THE
AFTERNOON...AHEAD OF THE TROF AND IN REGION OF STRONGER INSTABILITY.
THIS WOULD MAINLY BE NEAR AND EAST OF A LINE FROM LEMMON TO MARTIN.
PCPN CHANCES SHOULD TAPER OFF FROM SOUTHWEST TO NORTHEAST DURING THE
LATE AFTERNOON AND EVENING HOURS.

&&

.LONG TERM...THURSDAY THROUGH TUESDAY
ISSUED AT 255 PM MDT TUE AUG 19 2014

MEAN WESTERN NOAM TROUGHING WILL PERSIST IN THE PERIOD...WITH
MASSIVE EASTERN NOAM RIDGING ENSUING TOWARD THE END OF THE WEEK.
THIS WILL SUPPORT A LOCAL PATTERN CHANGE AS LOWER HEIGHTS AND MUCH
COOLER TEMPS SPREAD OVER THE NORTHERN PLAINS BY THE END OF THIS
WEEKEND...PER THE WESTERN CONUS TROUGH PHASING WITH A LONG WAVE
NORTHERN STREAM TROUGH. ACTIVE SW FLOW CAN BE EXPECTED TO SUPPORT
NEAR DAILY CHANCES FOR PRECIP THROUGH THE PERIOD...WITH THE
WESTERN CONUS TROUGH SHIFTING EAST OVER THE NORTHERN PLAINS BY
LATE THIS WEEKEND. THIS WILL THEN LIKELY SUPPORT CYCLOGENESIS OVER
THE CENTRAL PLAINS...WITH INCREASING CHANCES FOR WIDESPREAD RAIN
SAT NIGHT EASTERN HALF. ANOTHER STRONG UPPER LEVEL IMPULSE MAY
EJECT EARLY NEXT WEEK...SUPPORTING ANOTHER DEEPENING SFC CYCLONE
OVER THE CENTRAL/NORTHERN PLAINS ONCE AGAIN.

HAVE RETAINED DAILY CHANCES FOR SHRA/TS WITH A WAVERING FRONTAL ZONE
OVER THE REGION THROUGH SUN. GROWING INDICATIONS FOR A STRONGER SFC
CYCLONE PROGRESSING THROUGH THE REGION SAT NIGHT INTO SUN...WHICH
COULD SUPPORT WIDESPREAD MODERATE TO HEAVY RAINS EASTERN HALF THEN.
CYCLONIC DISTURBED SW FLOW WILL PERSIST INTO EARLY NEXT WEEK.
HOWEVER...GIVEN SIGNALS FOR MORE DIURNALLY DRIVEN CHANCES FOR
CONVECTION...HAVE BIASED POPS MORE TOWARD CLIMO NUMBERS EARLY NEXT
WEEK...ESP GIVEN CONVECTIVE NATURE TO PRECIP.

AS FOR TEMPS...SEASONAL NUMBERS WILL PERSIST THROUGH FRI...WITH
COOLING CONDITIONS SAT-SUN. TEMPERATURES ARE PROGGED TO BE 5 TO 15
DEGREES BELOW SEASONAL NORMS BY SUNDAY...ESP HIGH TEMPERATURES. HAVE
CONTINUED TO ADD A NEGATIVE BIAS PER TEMPS SAT-SUN...WITH MANY
PLACES LIKELY STRUGGLING TO REACH 70 ACROSS THE NORTHERN HALF SUNDAY.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY
ISSUED AT 255 PM MDT TUE AUG 19 2014

SCT/ISOLD TSRA WILL DEVELOP LATE THIS AFTN OVER NERN WY AND
THE BLKHLS...THEN SPREAD EWD ACROSS THE PLAINS OF WRN SD TONIGHT.
MVFR/IFR CONDS EXPECTED IN HEAVIER STORMS...ESPECIALLY TONIGHT.
VFR CONDITIONS WILL CONTINUE OUTSIDE OF ANY TSRA.

&&

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

$$

SHORT TERM...26
LONG TERM...JC
AVIATION...JC





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