AFOS product AFDFSD
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Displaying AFOS PIL: AFDFSD
Product Timestamp: 2012-04-24 03:40 UTC

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FXUS63 KFSD 240340
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1040 PM CDT MON APR 23 2012

.DISCUSSION...
QUIET NIGHT AHEAD AS WINDS GENERALLY REMAIN SOUTHERLY...THEN 
DECREASE A BIT TOWARDS 12Z AS A WEAK LOW PRESSURE DEVELOPS OVER 
WESTERN SD. WITH THE LIGHTER WINDS BUT FAIRLY MILD LOW LEVEL THERMAL 
FIELD LOWS IN MAINLY THE MIDDLE 40S LOOKS GOOD. /08

&&

.AVIATION.../FOR THE 06Z TAF ISSUANCE/
VFR CONDITIONS WILL PREVAIL THROUGH 06Z WEDNESDAY...WITH VARIABLE 
WINDS REMAINING BELOW 12KTS.

&&

.PREV DISCUSSION.../ISSUED AT 325 PM CDT/
WARM FRONT ACROSS THE FAR WESTERN PLAINS WILL SLIDE EASTWARD 
TONIGHT...WITH PREFRONTAL SOUTHERLY GRADIENT. MOST OF THE WINDS FROM 
AFTERNOON ARE STRONGLY SUPPORTED BY DEEPER MIXING...SO EXPECT THAT 
WINDS WILL DROP OFF QUITE A BIT...WITH SOMEWHAT SLOWER EASING ON 
HIGHER SOUTH DAKOTA ELEVATIONS. WITH DRY AIR...A SMALL WINDOW FOR 
TEMPS TO DROP TOWARD THE COOLER SIDE OF THE ENVELOPE FOR TONIGHT 
EXISTS ESPECIALLY THROUGH THE EAST.

WEAK NORTHWEST FLOW WAVE ALONG WARM FRONT WILL STALL BOUNDARY AND 
PERHAPS BACK A BIT WESTWARD DURING THE MORNING...BUT PROBABLY NOT 
ENOUGH TO MAKE A DIFFERENCE IN OVERALL WITH WARMING TEMPS ALOFT.
FLOW WILL BE WEAK...BUT ENOUGH SUNSHINE AND POTENTIAL TO BE A BIT 
SUPERADIABATIC...AND WILL SHADE JUST A BIT TOWARD WARMER SHALLOW 
MIXING START WEST...AND A BIT CLOSER TO COOLER MIXING IN THE EAST.
/CHAPMAN

A WEAK WAVE IS EXPECTED TO DROP SOUTHEAST ACROSS THE SOUTHWEST 
MINNESOTA TUESDAY NIGHT. LOW LEVEL MOISTURE REMAINS FAIRLY 
LIMITED...BUT MID LEVEL LAPSE RATES ARE STEEP ENOUGH TO RESULT IN 
SOME ELEVATED INSTABILITY LIFTING FROM NEAR 700 MB. HAVE CONTINUED 
MENTION OF THUNDERSTORMS ACROSS NORTHEAST HALF OF THE CWA FOR THE 
SECOND HALF OF THE OVERNIGHT.  MODELS ALSO INDICATED A VERY SUBTLE 
WAVE MOVING THROUGH THE AREA DURING THE DAY ON WEDNESDAY. DEEP 
NORTHWEST FLOW ACROSS THE AREA...WITH WEAK INSTABILITY ALOFT.  HAVE 
KEPT MENTION ON THUNDERSTORMS...BUT AM UNSURE COOLING ALOFT WILL BE 
ENOUGH TO ALLOW THE ATMOSPHERE TO TAP INTO THE INSTABILITY.  COLD 
AIR ADVECTION IN THE LOW LEVELS CONTINUES TO SLOW DOWN WITH EACH 
MODEL ITERATION...SO WENT AHEAD AND WARMED UP HIGHS ON WEDNESDAY.  
KEPT SOUTHWEST MINNESOTA SLIGHTLY COOLER DUE TO CLOUD COVER 
CONSIDERATIONS. 

THURSDAY INTO FRIDAY ARE MUCH COOLER AS LOW LEVEL COLD AIR ADVECTION 
BECOMES WELL ESTABLISHING IN LOW LEVEL EAST TO NORTHEAST FLOW ACROSS 
THE AREA.  TIMING OF THE PRECIPITATION LATE THIS WEEK CONTINUES TO 
BE PROBLEMATIC AS TWO PHASED WAVES CREATING A LONG WAVE TROUGH BREAK 
DOWN WITH THE SOUTHERN PIECE OF ENERGY LIFTING NORTHEAST AHEAD OF 
THE OTHER PORTION OF THE UPPER TROUGH. THESE TWO SYSTEMS HANG AROUND 
THE NORTHERN PLAINS THROUGH THE BETTER PORTION OF THE WEEKEND 
CREATING UNSETTLED WEATHER. HAVE RAISED POPS FRIDAY NIGHT INTO 
SATURDAY WHICH APPEAR TO BE THE TWO TIME PERIODS WHERE THERE IS A 
GREATEST CHANCE FOR PRECIP. THE GFS CONTINUED TO BE COLD ENOUGH TO 
SUPPORT SNOW ACROSS THE AREA ON SATURDAY MORNING...AND EVEN THE 
ECMWF MIGHT SUGGEST SOME RAIN MIXED WITH SNOW.  HAVE NOT ADDED 
MENTION OF SNOW AT THIS POINT...BUT WILL NEED TO WATCH THIS IN 
FUTURE PACKAGES.  WITH REX BLOCK DEVELOPING FRIDAY INTO 
SATURDAY...FEEL THAT DRY AIR WILL BE AN ISSUE ESPECIALLY LATER IN 
THE DAY ON SATURDAY AS EASTERLY FLOW DRAWS DRY AIR INTO THE REGION. 
FORECAST SOUNDINGS FOR SUNDAY HINT AT THE POTENTIAL OF INSTABILITY 
SHOWERS DEVELOPING IF THERE IS AMPLE LOW LEVEL HEATING. HAVE LOWERED 
TEMPERATURES IN THE EXTENDED QUITE A BIT CLOSER TO 925HPA 
MIXOUT...ESPECIALLY ON SATURDAY AND SUNDAY. FORECAST TEMPERATURES 
ARE MUCH CLOSER TO CONSRAW THAN CONSALL. WILL START TO SEE 
TEMPERATURES RECOVER ON MONDAY...THOUGH WILL STILL BE WELL BELOW 
NORMAL. 
&&

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

&&

$$