FXUS63 KFSD 221629
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1130 AM CDT TUE JUN 22 2004

.DISCUSSION...
WEAK BOUNDARY OVER SOUTHERN NORTH DAKOTA LATE THIS MORNING WILL DROP 
INTO FAR NORTHERN CWA BY EARLY IN THE EVENING...THEN CONTINUE SLOWLY 
SOUTHEAST INTO NORTHWEST IOWA OVERNIGHT.  WILL HANG ONTO LOW CHANCE 
OF SHRA/TSRA WITH THIS BOUNDARY...AIDED BY WEAK SHORTWAVE DROPPING 
INTO EASTERN MONTANA...AND MINIMAL INSTABILITY SHOWN BY 12Z MESOETA 
WITH MUCAPE NEARING 500J/KG BY 00Z NORTH OF BKX-MML.  INSTABILITY 
WEAKENS THROUGH THE OVERNIGHT...SO SHIFT TO JUST ISOLATED THUNDER 
WITH CHANCE OF SHRA FOR TONIGHT LOOKS GOOD.  AREA MAY HAVE TO BE 
ADJUSTED A BIT NORTHEAST...AS BEST CONVERGENCE AND FORCING WITH WEAK 
WAVE APPEARS AS THOUGH IT WILL SLIDE NORTHEAST OF THE CWA...BUT WILL 
NOT MAKE ANY CHANGES AT THIS TIME.

TEMPERATURES WARMED UP MORE QUICKLY THAN FORECAST EARLIER THIS 
MORNING...BUT STARTING TO SLOW DOWN A BIT NOW.  MADE SOME TWEAKS TO 
HOURLY GRIDS TO ACCOUNT FOR THIS...BUT FORECAST HIGHS LOOK GOOD AND 
WILL LET ZFP RIDE FOR NOW.

 HACKER
&&

.PREV DISCUSSION...
TEMPERATURES AND PRECIP CHANCES WILL BE PRIMARY FORECAST CONCERN 
OVER THE NEXT FEW DAYS.

06Z WATER VAPOR IMAGERY/RUC ANALYSIS CONTINUED TO SHOW FAMILIAR 
PATTERN OF THE LAST FEW DAYS...NAMELY BLOCKING HIGH OVER THE PAC 
NORTH WEST WITH CWA UNDER BROAD NORTHWESTERLY FLOW. MAIN SHEAR 
AXIS/AREA OF SUBSIDENCE WAS JUST EXITING SOUTHERN CWA AND MOSTLY 
CLEAR SKIES PREVAILED. 

BOTH ETA/GFS HAD THERE PROBLEMS INITIALIZING THIS MORNING...MAINLY 
WITH RESPECT TO STRENGTH OF TROF CURRENTLY TO THE NW OF CWA. MODELS 
PRETTY SIMILAR THROUGH THE SHORT TERM BUT BEGIN TO DIVERGE SOMEWHAT 
WITH TIMING AND PLACEMENT OF FRONTAL BOUNDARIES AND STRENGTH OF SFC 
FEATURES. DECIDED TO LEAN MORE WITH THE ETA THROUGH THE FIRST COUPLE 
PERIODS AND GO WITH MORE OF A BLEND OF ETA/GFS/UKMET AFTER THAT.

TODAY SHOULD BE RELATIVELY WARM FOR THE WEEK AS WESTERLY WINDS...FEW 
CLOUDS AND RELATIVELY DRY BOUNDARY LAYER SHOULD ALLOW MIXING PAST 
H850. CURRENT FORECAST HAD VERY GOOD HANDLE ON HIGHS SO DIDNT MAKE A 
LOT OF CHANGES. FIRST OF A SERIES OF SHORTWAVE SHOULD ENTER THE AREA 
EARLY THIS EVENING AND SLIDE SOUTHEAST OVERNIGHT. BEST UPPER LEVEL Q 
VECTOR FORCING WOULD FAVOR THE EAST FOR THE HIGHEST POPS...BUT BROAD 
AREA OF H700 Q VECTOR FORCING WOULD INDICATE A SLIM CHANCE FARTHER 
WEST SO EXPANDED POPS A LITTLE FROM GOING FORECAST. THE 
NEXT...STRONGER SHORT WAVE WILL SLIDE OVER THE AREA WEDNESDAY NIGHT. 
MODELS REALLY SPLIT ON WHAT THE SFC REFLECTION OF THIS WAVE WILL BE. 
GFS SEEMS A LITTLE TO STRONG COMPARED TO ETA AND UKMET SO FAVORED 
THE ETA SOLUTION. DECENT H850-700 WAA BEGINS LATE OVER THE WEST AND 
THEN SPREADS SOUTH AND EAST DURING THE MORNING HOURS...SO UPPED POPS 
A BIT. NOT A WHOLE LOT OF CHANGES MADE TO THE GOING FORECAST FROM 
THURSDAY ON. MODELS A BIT MORE SIMILAR ON FRONTAL PLACEMENT FOR 
THURSDAY...BUT STILL VARY A BIT ON DEGREE OF COLD AIR OVER THE AREA. 
WENT WITH A COMPROMISE OF H850 TEMPS WHICH WAS A TAD COOLER THAN 
WHAT WAS GOING. DIDNT MAKE ANY CHANGES TO THE EXTENDED BUT SATURDAY 
MAY NEED TO BE WATCHED FOR POSSIBLE PRECIP MENTION. GFS TRIES TO 
DEVELOP MCS OVER WESTERN PLAINS THAT CLIPS SOUTHWEST CWA...DONT 
REALLY TRUST THE GFS ABILITY TO DEVELOP MCS'S IN THE LATER PERIODS 
SO WILL LEAVE OUT FOR NOW.

&&

.FSD...WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&

$$
JRM