Damaging Winds in South Dakota, September 19, 2004

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
300 PM MDT SUN SEP 19 2004

.DISCUSSION...20Z SURFACE ANALYSIS PLACES LOW PRESSURE CENTER OVER
WESTERN WYOMING WITH FRONTAL BOUNDARY EXTENDING EAST TO NORTHEASTERN
WYOMING...THEN NORTHEAST INTO NORTHWESTERN NORTH DAKOTA. FRONTAL
BOUNDARY HAD DROPPED SOUTHWARD AS COLD FRONT THIS MORNING...AND IS
CURRENTLY BEING NUDGED BACK TO THE NORTH AS A WARM FRONT AS STRONG
SOUTHERLY WINDS INCREASE LOW LEVEL WARM ADVECTION ACROSS THE REGION.
TIGHT SURFACE PRESSURE GRADIENT WAS PRODUCING VERY WINDY CONDITIONS
ACROSS PORTIONS OF CENTRAL AND SOUTH CENTRAL SOUTH DAKOTA THIS
AFTERNOON. WINDY CONDITIONS WILL CONTINUE INTO THE EVENING
HOURS...AND SHOULD GRADUALLY DIMINISH LATE THIS EVENING...FALLING
BELOW ADVISORY CRITERIA BY MIDNIGHT. HAVE CONTINUED WIND ADVISORY IN
THOSE AREAS FOR THIS EVENING.

WATER VAPOR IMAGERY SHOWS JET STREAK HAS ROUNDED THE BASE OF THE
UPPER TROUGH OVER THE WESTERN US AND IS CURRENTLY STEAMING TOWARD
THE NORTHERN PLAINS INCREASING SYNOPTIC LIFT OVER THE AREA AND
LEADING TO A CHANCE OF SHOWERS AND THUNDERSTORMS OVERNIGHT.

IN PREVIOUS MODEL RUNS...THE GFS WAS MOVING THE UPPER TROUGH THROUGH
FASTER THAN THE GFS...NOW ON THE 12Z RUNS...THE ETA IS DIGGING A
CLOSED LOW FURTHER SOUTH THAN THE GFS AND IS SLOWER THAN THE GFS IN
BRINGING THE UPPER TROUGH THROUGH. 12Z ETA SOLUTION WOULD BE WARMER
AND WETTER THAN THE 12Z GFS.

06Z GFS WAS THE CONSENSUS CHOICE OVERNIGHT AND STILL REPRESENTS A
COMPROMISE BETWEEN THE NEW ETA AND GFS RUNS. LOW PRESSURE CENTER
SCOOTS ALONG THE COLD FRONT INTO CENTRAL ND BY 12Z MONDAY...DRAGGING
THE SURFACE BOUNDARY SOUTH AS A COLD FRONT. EXPECT A CHANCE OF TSRA
ALONG THE COLD FROTN AS IT DROPS SOUTH...WITH POPS INCREASING ON
MONDAY NIGHT AS SYNOPTIC SUPPORT INCREASES MID LEVEL FRONTOGENESIS.

MONDAY NIGHT THROUGH WEDNESDAY...HAVEN/T MADE ANY SIGNIFICANT
CHANGES TO THESE PERIODS TO AVOID FLIP FLOPPING AND TO WAIT FOR THE
MODELS TO COME INTO BETTER AGREEMENT. CURRENT THINKING IS THAT THE
UPPER LOW WILL CLOSE OFF OVER THE CENTRAL ROCKIES AND WILL TRACK
SLOWLY NORTHEAST. THE BEST CHANCE OF RAIN WILL BE MONDAY NIGHT AS
ANOTHER LOW MOVES UP COLD FRONT AND LIFTS MOISTURE OVER SFC-700MB
BAROCLINIC ZONE. MUCH COOLER TEMPERATURES ARE EXPECTED WITH READINGS
STRUGGLING OUT OF THE 50S FOR TUESDAY.

THURSDAY THROUGH SUNDAY WILL FEATURE DRY WEATHER AND AND MORE
SEASONABLE TEMPERATURES.

&&

.UNR...WATCHES/WARNINGS/ADVISORIES...
.SD...WIND ADVISORY THIS EVENING FOR SDZ032-043>044-046>047-049.
.WY...NONE.

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
615 AM MDT SUN SEP 19 2004

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-201300-
BENNETT-BUTTE-CENTRAL BLACK HILLS-CUSTER CO PLAINS-FALL RIVER-HAAKON-
HARDING-HERMOSA FOOT HILLS-JACKSON-MELLETTE-NORTHEASTERN CROOK-
NORTHERN BLACK HILLS-NORTHERN CAMPBELL-NORTHERN FOOT HILLS-
NORTHERN MEADE CO PLAINS-PENNINGTON CO PLAINS-PERKINS-RAPID CITY-
SHANNON-SOUTHERN BLACK HILLS-SOUTHERN CAMPBELL-SOUTHERN FOOT HILLS-
SOUTHERN MEADE CO PLAINS-STURGIS/PIEDMONT FOOT HILLS-TODD-TRIPP-
WESTERN CROOK-WESTON-WYOMING BLACK HILLS-ZIEBACH-
615 AM MDT (715 AM CDT) SUN SEP 19 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN SOUTH DAKOTA AND
NORTHEASTERN WYOMING.

.DAY ONE...TODAY AND TONIGHT

A COLD FRONT WILL BE NEAR THE REGION TODAY...PROVIDING THE FOCUS FOR
SHOWER AND THUNDERSTORM ACTIVITY OVER NORTHEASTERN WYOMING AND
WESTERN SOUTH DAKOTA. SEVERE THUNDERSTORMS ARE NOT EXPECTED.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A COLD FRONT WILL MOVE THROUGH THE REGION MONDAY CREATING SHOWERS AND
THUNDERSTORMS. SEVERE THUNDERSTORMS ARE NOT EXPECTED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY.