000
FXUS63 KABR 080156 AAA
AFDABR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
856 PM CDT SUN SEP 7 2008
.UPDATE...
CURRENT FORECAST FOR TONIGHT IS ON TRACK. NO CHANGES PLANNED.
TEMPERATURES ARE GONNA BECOME INCREASINGLY CLOUD-DEPENDENT WITH
WINDS DROPPING TO NEXT TO NOTHING AS THIS SURFACE HIGH SHIFTS
SOUTHEAST OVERNIGHT AND SITS RIGHT DOWN ON TOP OF THE CWA. UPPER
LEVEL JET MAX AND MID-LEVEL FRONTOGENESIS AND LIFT FROM EMBEDDED
S/W IN NW FLOW SHOULD ALL SUFFICE TO PRODUCE ENOUGH CLOUD COVER
OVER CENTRAL SOUTH DAKOTA OVERNIGHT TO KEEP TEMPS FROM BOTTOMING
OUT IN THE MID 30S. UPPER 30S/LOWER 40S SHOULD SUFFICE
TONIGHT...SO WILL BE LEAVING OUT ANY MENTION OF PATCHY FROST.
STRONGEST FORCING AND THICKEST CLOUDS STILL LOOK TO REMAIN ALONG
OR SOUTH OF I-90 OVERNIGHT...SO CONTINUING THE INHERITED WX/POPS
FORECAST ACROSS SOUTH CENTRAL SOUTH DAKOTA WITH HIGHEST POPS SOUTH
OF PIERRE.
&&
.PREV DISCUSSION...
.SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT
ISO SHOWERS DEVELOPED THIS AFTERNOON ACROSS SOUTHERN NORTH DAKOTA
AND HAVE MOVED INTO NORTHERN SOUTH DAKOTA. MAIN AREA OF RAIN IS
ACROSS SOUTHERN SOUTH DAKOTA...MAINLY FROM I-90 AND POINTS SOUTH.
THIS AREA OF RAIN WILL REMAIN ACROSS THE SOUTHERN HALF OF THE
STATE OVERNIGHT AND LEFT LIKELY POPS ACROSS THE SOUTHWESTERN CWA
OVERNIGHT...ESPECIALLY AFTER 06Z. SYSTEM WILL EXIT THE AREA ON
MONDAY BUT WILL LEAVE MENTION OF SMALL POPS ACROSS THE EASTERN
CWA.
SURFACE HIGH PRESSURE OVER THE CENTRAL PLAINS WILL SLIDE EAST ON
TUESDAY AND ALLOW FOR WARMER AIR TO ADVECT INTO THE REGION. LOW
PRESSURE WILL STRENGTHEN OVER THE NORTHERN ROCKIES INTO TUESDAY
NIGHT...TIGHTENING THE PRESSURE GRADIENT OVER THE CWA. EXPECTING
BREEZY TO WINDY CONDITIONS TO DEVELOP BY TUESDAY
AFTERNOON...MORE SO FROM THE JAMES VALLEY AND POINTS WEST.
.LONG TERM...WEDNESDAY THROUGH SUNDAY
MEDIUM RANGE MODELS HAD BEEN DOING QUITE WELL WITH THE UPCOMING
MID WEEK WEATHER SYSTEM. TODAY SOME MAJOR DIFFERENCES HAVE CROPPED
UP. HAVE DECIDED TO SIDE WITH THE GFS FOR THIS PACKAGE BUT MAKE AS
FEW CHANGES AS POSSIBLE UNTIL MODELS SETTLE DOWN ON A SOLUTION. THE
PERIOD OPENS WITH GOOD MODEL AGREEMENT. AN H5 TROUGH ALOFT DIGS
SOUTH FROM CANADA AND COMES INTO PHASE WITH AN UPPER LEVEL LOW
OVER CALIFORNIA. BY 00Z FRIDAY THEY MOVE THE NORTHERN TROUGH
THROUGH THE REGION AND KEEP A CUT OFF LOW IN THE SOUTHWEST IN A
SPLIT FLOW REGIME. BY 00Z SATURDAY THE ECMWF WEAKENS THE SOUTHERN
STREAM LOW AND MOVES IT INTO THE ZONAL NORTHERN STREAM FLOW. THE
GFS CONTINUES THE SPLIT FLOW CUT OFF SCENARIO. BY 00Z SUNDAY THE
GFS WEAKENS THE LOW IN THE SOUTHWEST AND MOVES IT EAST. THE ECMWF
HAS ALREADY PASSED THE TROUGH THROUGH THIS AREA. THESE SOLUTIONS
ARE BOTH VERY DIFFERENT FROM YESTERDAY AND DIFFERENT FROM
PREVIOUS RUNS SO CONFIDENCE IS PRETTY LOW. ENSEMBLE SOLUTION DOES
NOT SHED MUCH LIGHT ON A SOLUTION BUT SERVES TO POINT OUT THE
UNCERTAINTY.GOING GRIDS SEEM TO HANDLE THE OLD SOLUTION WELL AND
WOULD LIKELY BE PRETTY GOOD WITH THE CURRENT ITERATION. WILL NOT
MAKE MANY CHANGES UNTIL FURTHER RUNS SETTLE IN ON A SOLUTION.
TEMPERATURES WILL ALSO BE DEPENDENT ON POSITIONS OF FEATURES SO
WILL NOT PUSH TEMPERATURES HIGHER TOWARD NEXT WEEK END. LATEST MOS
GUIDANCE ALSO IS NOT AS BULLISH ON WARM TEMPERATURES AS
YESTERDAY.
&&
.AVIATION...
SEVERAL SMALL UPPER LEVEL DISTURBANCES WILL MOVE OVER THE AREA
THROUGH TOMORROW. THESE WILL HELP KICK OFF SOME SHOWERS ESPECIALLY
SOUTH OF THIS AREA. THESE SHOWERS COULD BRIEFLY REDUCE CEILINGS OR
VISIBILITY TO MVFR CONDITIONS AT THE KPIR TERMINAL LATE TONIGHT.
HOWEVER...FOR THE REMAINDER OF THE TAF SITES...THROUGH TOMORROW
EXPECT MOSTLY VFR CONDITIONS WITH CEILINGS ABOVE 3500 FT AGL AND
UNRESTRICTED VISIBILITY.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...DORN
SHORT TERM...TMT
LONG TERM...KEEFE
AVIATION...DORN
WEATHER.GOV/ABERDEEN
