Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 310520
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1120 PM MDT SAT AUG 30 2014

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 312 PM MDT SAT AUG 30 2014

CURRENT SURFACE ANALYSIS SHOWS LOW PRESSURE OVER FAR NORTHEAST
WY...WITH COLD FRONT FROM FAR EASTERN MT INTO CENTRAL WY. UPPER
LEVEL ANALYSIS SHOWS WEAK RIDGING OVER THE DAKOTAS WITH BROAD TROF
COVERING MUCH OF THE WESTERN CONUS. NUMEROUS SHORTWAVES ARE NOTED
WITHIN THE TROF...WITH THEM CURRENTLY OVER NORTHEAST MT...CENTRAL
WY AND SOUTH CENTRAL MT...AND EASTERN OR AND SOUTHWESTERN ID.
SKIES ARE VARIABLY CLOUDY OVER NORTHEAST WY...WITH MOSTLY SUNNY
SKIES TO THE EAST. ISOLATED SHOWERS AND STORMS HAVE STARTED TO
DEVELOP OVER NORTHEAST WY IN THE VICINITY OF THE COLD FRONT. TEMPS
RANGE FROM THE UPPER 70S TO UPPER 80S ACROSS THE AREA. WINDS ARE
SOUTH-SOUTHEAST...BREEZY AT TIMES OVER MOST OF THE AREA...EXCEPT
FOR NORTHWESTERLY WINDS OVER CAMPBELL CO BEHIND THE FRONT.

CHANCES FOR SHOWERS AND STORMS WILL INCREASE THROUGH THE LATE
AFTERNOON AND EVENING FROM WEST TO EAST...ESPECIALLY ACROSS NORTHERN
PORTIONS OF THE CWA...AS THE SHORTWAVE OVER WY MOVES EAST-NORTHEAST
THROUGH THE REGION. THE STRONGEST FORCING WITH THE WAVE MOVES ACROSS
NORTHERN PORTIONS OF THE CWA AND POINTS FURTHER TO THE NORTH THIS
EVENING. THIS IS WHERE THE BEST CHANCES FOR PCPN WILL BE...AS WELL
AS THE RISK FOR ISOLATED SEVERE STORMS. CHANCES FOR PCPN AND SEVERE
WEATHER WILL DECREASE FURTHER SOUTH ACROSS THE CWA...WITH ONLY
SLIGHT CHANCES FOR A SHOWER OR STORM OVER FAR SOUTHERN SD THROUGH
THE EVENING. THINKING FROM PREVIOUS FORECAST GENERALLY HOLDS...WITH
THE BEST THREAT FOR STRONG TO SEVERE STORMS GENERALLY NEAR OR NORTH
OF A LINE FROM GILLETTE TO NEAR SPEARFISH...TO FAITH AND DUPREE.
HOWEVER...THE SLIGHTLY LATER TIMING OF THIS WAVE ADDS SOME
UNCERTAINTY TO THE RISK...ESPECIALLY OVER EASTERN PORTIONS OF THE
RISK AREA LATER ON. INSTABILITY IS FAIRLY STRONG ACROSS THE
AREA...ESPECIALLY TO THE NORTH AND EAST OF THE BLACK HILLS LATE THIS
AFTERNOON INTO THE EVENING. SHEAR WILL ALSO BE STRONGEST TO THE
NORTH AND EAST OF THE SURFACE LOW AS IT SLOWLY TRACKS FROM NORTHEAST
WY THROUGH WESTERN SD THIS EVENING. THE MAIN THREATS FROM ANY SEVERE
STORMS WILL BE LARGE HAIL AND STRONG WIND GUSTS...BUT AN ISOLATED
TORNADO CANNOT BE TOTALLY RULED OUT OVER EXTREME NORTHEAST WY INTO
NORTHWEST SD. LOCALLY HEAVY RAINFALL IS ALSO POSSIBLE...ESPECIALLY
ACROSS FAR NORTHWESTERN SD. MOST OF THE ACTIVITY WITH THIS WAVE WILL
EXIT EAST OF THE CWA AROUND 06Z...WITH LINGERING ISOLATED LIGHTER
ACTIVITY POSSIBLE INTO THE OVERNIGHT OVER THE CWA. GUSTY NORTHWEST
WINDS WILL DEVELOP ACROSS THE WESTERN SD PLAINS DURING THE
EVENING...AFTER THE FRONT PASSES. THE STRONGEST WINDS WILL GENERALLY
BE IN THE RAPID CITY AREA...AS WELL AS THE NEARBY PLAINS TO THE
NORTH AND EAST. WINDS WILL GRADUALLY DECREASE AFTER MIDNIGHT.

THE NEXT SHORTWAVE OVER OR/ID WILL APPROACH OUR WESTERN ZONES BY
EARLY SUNDAY MORNING...WITH THIS ONE TRACKING A BIT FURTHER SOUTH
ACROSS THE CWA DURING THE DAY. THIS SYSTEM SHOULD BRING A MORE
WIDESPREAD COVERAGE OF PCPN ACROSS THE AREA...WITH COLDER AIR ALOFT
KEEPING THE ATMOSPHERE UNSTABLE. SHOWERS ARE LIKELY ACROSS THE BLACK
HILLS AREA...WITH A PRETTY GOOD CHANCE FOR SHOWERS ACROSS THE REST
OF THE CWA DURING THE DAY...ESPECIALLY IN THE LATE MORNING AND
AFTERNOON. A FEW THUNDERSTORMS ARE POSSIBLE...BUT CLOUD COVER AND
COOLER AIR WILL HELP TO KEEP CAPE VALUES RATHER LOW. HIGHS WILL ONLY
BE IN THE 70S ACROSS THE SD PLAINS...WITH 60S OVER THE BLACK HILLS
AND NORTHEAST WY. SHOWERS WILL EXIT EASTERN AREAS IN THE EVENING
WITH A COOL NIGHT ON TAP FOR MOST AREAS. YET ANOTHER DISTURBANCE IS
PROGGED TO APPROACH WESTERN PORTIONS OF THE AREA LATE SUNDAY NIGHT
OR MONDAY MORNING.

&&

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 312 PM MDT SAT AUG 30 2014

SHORTWAVE EMBEDDED IN CYCLONIC FLOW WILL BRING CONTINUED CHANCES
FOR -SHRA/-TSRA MONDAY...BUT COVERAGE SHOULD BE LOWER THAN SUNDAY
ON THE PLAINS. UPPER TROUGH WILL SHARPEN OVER THE PACIFIC
NORTHWEST TUESDAY/WEDNESDAY BRINGING A FLAT UPPER RIDGE/THERMAL
RIDGE OVER THE CWA RESULTING IN DRIER/WARMER WEATHER. LONG TERM
GUIDANCE NOW SHOWING WEST/NORTHWEST FLOW ALOFT AND A SERIES OF
FRONTS DANCING ACROSS THE REGION FOR THURSDAY THROUGH SATURDAY.
RESULT WILL BE CHANCES FOR -SHRA/-TSRA ALONG WITH COOLER
TEMPERATURES FOR THE END OF NEXT WEEK.

&&

.AVIATION...FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT
ISSUED AT 1115 PM MDT SAT AUG 30 2014

SCATTERED SHOWERS AND A FEW THUNDERSTORMS WILL CROSS WESTERN SOUTH
DAKOTA TONIGHT. ADDITIONAL SHOWERS AND THUNDERSTORMS WILL DEVELOP
OVER NORTHEASTERN WYOMING LATE SUNDAY MORNING AND WILL INCREASE IN
COVERAGE AS THE PRECIPTIATION SPREADS NORTHEASTWARD DURING THE AFTERNOON.
MAINLY VFR CIGS ARE EXPECTED...ALTHOUGH AREAS OF MVFR CONDITIONS
ARE POSSIBLE WITH THE RAIN SHOWERS AND THUNDERSTORMS. THE SHOWERS
AND THUNDERSTORMS WILL END LATE SUNDAY EVENING.

&&

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

$$

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






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