212 
FXUS63 KFSD 091620
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1120 AM CDT MON JUL 9 2012


.DISCUSSION...
FORECAST GENERALLY IN GOOD SHAPE BUT HAVE WARMED HIGHS IN SOME 
LOCATIONS TO ACCOUNT FOR RAPID WARMING THIS MORNING.  DESPITE 
NORTHEASTERLY FETCH...DRY SURFACE CONDITIONS ALLOWING FOR 
TEMPERATURES TO WARM INTO THE MID AND UPPER 80S.  SHORTWAVE DROPPING 
DOWN FROM CENTRAL NORTH DAKOTA MAY SPARK A FEW GARDEN VARIETY 
THUNDERSTORMS IN THE JAMES AND MISSOURI RIVER VALLEY.  THESE STORMS 
ARE HANDLED WELL IN THE FORECAST AND ARE NOT EXPECTED TO BE SEVERE. 

&&
.AVIATION.../FOR THE 18Z TAF ISSUANCE/
VFR CONDITIONS THROUGH THE PERIOD. AN ISOLATED STORM OR TWO IS 
POSSIBLE WEST OF THE JAMES RIVER VALLEY AFTER 21Z.  THESE STORMS 
SHOULD DISSIPATE WITH SUNSET. 

&&
.PREV DISCUSSION.../ISSUED AT 417 AM CDT/
WEAK BACK DOOR BOUNDARY ALONG THE NORTHERN EDGE OF THE CWA EARLY 
THIS MORNING...PRETTY HARD TO FIND IN WIND FIELDS...DEFINED A BIT 
BETTER WITH 925 HPA THETA E...AND LOOKING AT THE SURFACE MOISTURE 
POOLING NEAR AND BEHIND. SUBTLETY RULES IN THIS PATTERN AS HAS BEEN 
EVIDENCED WITH PRECIPITATION OVER THE LAST COUPLE OF NIGHTS...AND 
MAY BE THAT TODAY IS NO EXCEPTION TO THIS.  WEAK CHANNELLED VORT 
AXIS STRETCHED ACROSS THE NORTHEASTERN CWA EARLY THIS MORNING...WITH 
ONE WAVE MOVING ALONG RESPONSIBLE FOR EARLIER PICKUP IN ELEVATED 
CONVECTION AROUND THE KMML AREA. OF NOTE IN LAST HOUR OR TWO IS THE 
INCREASE IN MID CLOUDINESS ALONG THIS AXIS...MAINLY ALONG AREAS IN 
ADVANCE OF NEXT SUBTLE INCREASE IN PV ADVECTION. MIGHT BE THIS IS 
WHAT NAM AND HRRR ARE TRYING TO PICK UP ON WITH DEVELOPMENT OF LIFT 
AXIS WITH NUISANCE PRECIPITATION DEVELOPMENT AS IT SHIFTS SOUTHWARD 
THROUGH MID MORNING. RETAINED SOME ISOLATED LEVEL POPS FOR REST OF 
THE NIGHT AND INTO THE MID MORNING HOURS...BUT EXPECT THAT OTHER 
THAN CLOUDS...SHOULD END UP WITH A BIT OF A QUIET PERIOD AFTER INTO 
THE EARLY AFTERNOON. AS THE AFTERNOON PROGRESSES...INDICATIONS ARE 
MOISTURE POOLING AND DEVELOPMENT OF SOME MINOR INSTABILITY THROUGH 
SOUTHWEST HALF OF THE AREA AS ENTIRE BOUNDARY SLIPS SOUTHWARD. AXIS 
OF DIV Q REMAINS LOCKED IN THROUGH THIS AREA...AND DID INTRODUCE A 
ISOLATED CHANCE FOR THUNDER SOUTHWEST OF A HURON TO SIOUX FALLS TO 
IDA GROVE LINE. DIURNAL CYCLE AND WEAKENING OF LIFT FORCING SHOULD 
END PRECIP BY AROUND SUNSET.

WITH SURFACE RIDGE NOSING IN FROM NORTHEAST OVERNIGHT...SHOULD END 
UP WITH COOLISH NIGHT...MAINLY UPPER 50S TO AROUND 60.  PLEASANT 
CONDITIONS EXPECTED ON TUESDAY WITH LOW LEVEL RIDGE THROUGH THE 
AREA. NAM STRONGEST WITH ANOTHER SUBTLE UPPER WAVE WHICH PUSHES 
SOUTH THROUGH WESTERN CWA DURING THE DAY...BUT WITH THIS FAIRLY 
ALONE WITH DEGREE OF FORCING AND INSTABILITY...DID NOT MESS UP THE 
DRY FORECAST. TEMPS HAVE BEEN GETTING TO OR JUST ABOVE MAX MIXING 
LAST COUPLE OF DAYS...LIKELY DUE TO DRY CONDITIONS...AND HAVE KEPT 
GENERAL RULE OF FOLLOWING WARMER GUIDANCE /AND LARGER DIURNAL RANGE/ 
FOR THE SHORT TERM. IN FACT...THROUGH WEDNESDAY...HARD TO FIND A 
CONSISTENT SIGNAL TO MENTION ANY PRECIPITATION THREAT WITH AREA 
DOWNSTREAM OF STRONG RIDGE. BY LATER WEDNESDAY NIGHT...IMPACT OF 
WAVE COMING OVER RIDGE WILL START TO ENHANCE THE DIV Q ACROSS THE 
CENTRAL DAKOTAS AS THE MID LEVEL THERMAL GRADIENT ADVANCES AND LOW 
LEVEL JET STARTS TO INCREASE. STEEPER MID LEVEL LAPSE RATES WILL 
START TO MOVE EASTWARD...AND MAY NEED TO WATCH FOR A COUPLE OF 
STORMS TO APPROACH AREAS WEST OF THE JAMES RIVER TOWARD THURSDAY 
MORNING.

FOR THE EXTENDED RANGE /THURSDAY THROUGH SUNDAY/ ECMWF AND GFS...
WHILE QUITE SIMILAR ON THE LONG WAVE FORECAST...REALLY COULD NOT 
PROVE TO BE MUCH MORE DIFFERENT IN THE THERMAL STRUCTURE ACROSS THE 
AREA...WITH THE GFS MUCH MORE INTENT ON HOLDING LOWER LEVEL COOL AIR 
IN PLACE OVER THE AREA...WITH DIFFERENCES INCREASING TO 7-10C FOR 
925 HPA TEMPERATURES BY THE WEEKEND. HAVE SEEN THIS BEFORE THIS 
YEAR...AND GIVEN THE HISTORY AND DRYNESS...EXPECT THAT A WARMER 
SOLUTION SHOULD BE PREFERRED. FAIRLY COOL 700 HPA TEMPERATURES 
REMAIN EVEN INTO SATURDAY...SO AS IMPACT OF WAVE CROSSING THE RIDGE 
AND SHEARING IN THE DOWNSTREAM AREAS THROUGH THE MISSISSIPPI 
VALLEY...DIV Q LINGERS FOR QUITE A WHILE ACROSS THE AREA FROM 
THURSDAY THROUGH EARLY SATURDAY. KEPT A LOW CHANCE FOR PRECIPITATION 
GOING STARTING EARLY THURSDAY IN THE NORTHWEST...AND EXITING THE 
NORTHEAST AREAS EARLY SATURDAY WITH THE NOSE OF THE ELEVATED MIXED 
LAYER. 

IT IS ENTIRELY POSSIBLE...WITH A FORECAST SHIFT TOWARD A STRONGER 
ECMWF FLAVOR...THAT WE COULD BE SEVERAL DEGREES WARMER BY FRIDAY 
THROUGH SUNDAY...PERHAPS BRINGING BACK SOME NEAR 100 DEGREE READINGS 
TO THE WESTERN CWA.  /CHAPMAN

&&

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

&&

$$