800 
FXUS63 KFSD 040838
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
338 AM CDT THU SEP 4 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 337 AM CDT THU SEP 4 2014

A COLD FRONT IS SITUATED THROUGH CENTRAL SOUTH DAKOTA VERY EARLY 
THIS MORNING...WITH SCATTERED CONVECTION DEVELOPING THROUGH THE 
JAMES RIVER VALLEY IN ASSOCIATION WITH THETA E ADVECTION AIDED BY A 
STRONG LOW LEVEL JET PUSHING OUT OF EASTERN NEBRASKA. EXPECT THIS 
AREA OF CONVECTION TO LIFT TO THE NORTH AND EAST THROUGH THE MORNING 
HOURS AS THE BETTER WARM AIR ADVECTION FOLLOWS SUIT. THE COLD FRONT 
WILL PUSH ACROSS THE CWA DURING THE DAY...THOUGH WITH THE ABSENCE OF 
DEEPER MOISTURE AND BETTER UPPER LEVEL SUPPORT REMAINING TO THE 
NORTH...EXPECTING ONLY ISOLATED CONVECTION TO DEVELOP ALONG THE 
FRONT AS IT PUSHES EASTWARD. AHEAD OF THE FRONT...INSTABILITY AND 
BULK SHEAR REMAIN RATHER MEAGER...SO DO NOT ANTICIPATE AND SEVERE 
STORMS. THE MAIN EFFECTS OF THE FRONT WILL BE BREEZY NORTHWEST WINDS 
WITH THE PASSAGE OF THE SYSTEM...ALONG WITH PLUNGING DEWPOINTS AS 
DRIER AIR MOVES INTO THE AREA. WITH THE FRONT ONLY MAKING IT TO OUR 
FAR EASTERN ZONES BY LATE AFTERNOON...HIGHS THROUGH PORTIONS OF 
SOUTHWESTERN MINNESOTA AND NORTHWESTERN IOWA WILL CLIMB INTO THE 
LOWER/MID 80S...WHILE BACK TO THE WEST WHERE COOLING WILL BE 
REALIZED...HIGHS WILL ONLY BE IN THE MID AND UPPER 70S.

THE FRONT SETTLES TO THE SOUTH AND EAST OF OUR AREA BY 
TONIGHT...THOUGH THERE IS FAIRLY DECENT MODEL AGREEMENT ON 
SHOWER/THUNDERSTORM DEVELOPMENT ALONG THE MID LEVEL FRONT...SITUATED 
MAINLY TO THE SOUTH OF OUR CWA...THOUGH CANNOT RULE OUT THAT SOME OF 
THIS ACTIVITY WILL NUDGE INTO THE SIOUX CITY TO STORM LAKE CORRIDOR 
THIS EVENING. WITH STRONG COLD AIR ADVECTION TONIGHT...LOWS WILL 
FALL INTO THE UPPER 40S TO MID 50S.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 337 AM CDT THU SEP 4 2014

THE INTERMEDIATE RANGE OF THE FORECAST LOOKS PRETTY QUIET. FRIDAY
STILL HAS A STRONG SHORT WAVE MOVING SOUTHEASTWARD ACROSS THE
NORTHERN PLAINS FROM CANADA...HELPING TO USHER IN COOLER AND DRIER 
AIR WHEN COMPARED TO THURSDAY. BOTH THE DETERMINISTIC NAM AND GFS
ARE SHOWING QUITE OF BIT OF MID AND HIGH LEVEL CLOUDS WHICH MAY
ACT TO PUT A FURTHER LID ON HIGHS. BUT IN GENERAL WITH SUCH DRY
LOW LEVELS BELOW 600MB...KEPT OUR ZONES AROUND SIOUX CITY AND
STORM LAKE DRY WHERE THERE IS STILL SOME MID LEVEL CONVERGENCE TO
CONTEND WITH...AND ALSO PLACED IN THE RIGHT ENTRANCE REGION OF A
STRONG JET TO THE NORTHEAST...AT LEAST IN THE MORNING HOURS. FOR
TEMPERATURES...SOUNDINGS SHOW MIXING TO CLOSE TO 850MB WITH
NORTHERLY WINDS. THEREFORE HIGHS STILL LOOK LIKE THERE IN THE 65
TO 70 DEGREE RANGE.

FRIDAY NIGHT AND SATURDAY WILL SEE MAINLY CLEAR SKIES AND LIGHT
WINDS. LOOKS PLEASANT. FRIDAY NIGHT WILL CERTAINLY HAVE AN EARLY
AUTUMN BIT OF A CHILL IN THE AIR...WITH LOWS EASILY GETTING DOWN
INTO THE 40S. SATURDAY WILL FOLLOW WITH VERY NICE LOWER TO MID 70S
AND DRY AIR. SATURDAY NIGHT WILL HAVE A LIGHT RETURN FLOW OF AIR
WHICH WILL BEGIN TO MODERATE THE LOWS A BIT...AT LEAST WEST OF I
29. BUT ALONG AND EAST OF I 29...TEMPERATURES WILL STILL BE QUITE
CHILLY.

NEXT WEEK...THE USUAL MODEL DISCREPANCY BEGINS TO CREEP INTO THE
PICTURE. OVERALL...THE DETERMINISTIC ECMWF AND GFS HAVE THE SAME
WAVY FEATURES...BUT THE GFS PROGRESSES THE SYSTEMS MUCH QUICKER
THAN THE ECMWF WHICH IS ITS USUAL BIAS. IRONICALLY DESPITE THIS...
THEIR RESPECTIVE SURFACE PATTERNS ARE NOT ALL THAT DIFFERENT...
AT LEAST SUNDAY THROUGH TUESDAY. OFF AND ON CHANCES FOR SHOWERS
AND STORMS CONTINUE...MAINLY SUNDAY NIGHT THROUGH TUESDAY NIGHT...
ALBEIT THE LATEST ECMWF IS DRIER THAN THE GFS IN SOME PERIODS. IT
LOOKS WARM AND SLIGHTLY HUMID MONDAY AND TUESDAY...FOLLOWED BY
COOLER WEATHER ON WEDNESDAY AS A STRONG SURFACE FRONT BEGINS TO
SLOWLY OOZE DOWN FROM THE NORTH BY TUESDAY NIGHT. THIS WILL AFFECT
OUR LOCATION BY MID WEEK...BUT IT APPEARS THAT OUR FORECAST AREA
IS TOO FAR SOUTH TO FEEL THE FULL IMPACT OF THE COOL AIR. BOTH
MODELS FORECAST ONLY ZERO DEGREES CELSIUS AT 850MB CLOSE TO THE
CANADIAN BORDER BY WEDNESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1044 PM CDT WED SEP 3 2014
COLD FRONT EXPECTED TO MOVE THROUGH THE AREA 12-18Z WITH WIND
SHIFT FROM THE SOUTH TO THE NORTHWEST. COULD SEE SOME MVFR STRATUS
IMMEDIATELY BEHIND THE FRONT...ESPECIALLY AT KHON. HAVE ADDED
MENTION OF STRATUS FOR A FEW HOURS...BUT EXPECT STRATUS TO THIN AS
IT PROGRESSES EAST THROUGHOUT THE DAY...AND THUS ONLY HAVE A
SCATTERED DECK AT BEST IN KFSD AND KSUX. BREEZY NORTHWEST WINDS
SHOULD PREVAIL THROUGHOUT THE DAY BEHIND THE FRONT.


&&

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

$$

SHORT TERM...JM
LONG TERM...MJ
AVIATION...