Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 110035
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
735 PM CDT WED SEP 10 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 332 PM CDT WED SEP 10 2014

NORTH TO NORTHEAST WINDS CONTINUE TO DRAW DRIER AIR INTO THE REGION.
LOW LYING STRATUS IS EXPECTED TO THIN...BUT WITH FAIR AMOUNT OF
MID CLOUDS ACROSS THE AREA OVERNIGHT...HAVE NUDGED OVERNIGHT LOWS
UP SLIGHTLY A DEGREE OR TWO IN MOST LOCATIONS. WITH 925 HPA TEMPS
OF 3 TO 4 C...HAVE NOT SEEN FORECAST LOWS IN THE LOWER 40S SINCE
MAY.

SHORT WAVE APPROACHING FROM THE NORTH AND WEST WILL LEAD TO A FAIR
AMOUNT OF CLOUD COVER ACROSS THE AREA ON THURSDAY. WAVE DYNAMICS
WILL BE FIGHTING A VERY LIMITED AMOUNT OF NEAR SURFACE
MOISTURE...AND HAVE CONTINUED TO LIMIT POPS THROUGHOUT THE DAY TO
THE JAMES RIVER VALLEY AND WEST.  RAIN AMOUNTS SHOULD BE QUITE
LIGHT...TOTALING A FEW HUNDREDTHS OF AN INCH OR LESS. HIGHS WILL
CONTINUE TO BE NEAR RECORD LOW MAX GENERALLY IN THE LOWER 50S.
WITH THE SELF DESTRUCTIVE SUNSHINE ACROSS SOUTH CENTRAL SOUTH
DAKOTA...TEMPERATURES WILL STRUGGLE TO GET OUT OF THE 40S.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 332 PM CDT WED SEP 10 2014

POSITIVE TILTED UPPER TROUGH WORKS THROUGH OUR FORECAST AREA
THURSDAY NIGHT AND FRIDAY MORNING. THE DETERMINISTIC NAM/GFS/ECMWF
ARE IN GOOD AGREEMENT WITH THE PLACEMENT OF THE UPPER QG FORCING
BOTH IN SPACE AND TIME. HOWEVER THE ECMWF CONTINUES TO BE A RATHER
STRONG OUTLIER IN BEING THE MOST BULLISH ON PRECIP POTENTIAL
DURING THAT 18 HOUR PERIOD. IT REALLY HOOKS UP A STRONG 850-700MB
MOISTURE FETCH OF AIR...WHEREAS THE NAM AND GFS...AS WELL AS THE
HIRES MODELS BRING IN DRIER AIR FROM THE NORTH AND NORTHWEST. THE
MODELS HAVE ALL BEEN LOCKED ONTO THEIR RESPECTIVE SOLUTIONS...SO
IT IS DIFFICULT TO TELL AT THIS POINT WHICH SOLUTION IS MORE
CORRECT. CURRENT THOUGHTS ARE WHEN LOOKING AT THE OVERALL MOISTURE
PROFILE...EVEN ON THE DRIER NAM AND GFS...THE HIGHER POPS SHOULD
FAVOR OUR SOUTHERN ZONES THURSDAY NIGHT...EXITING VIA NORTHWEST IA
ON FRIDAY. BUT TONED DOWN THE QPF AMOUNT OF THE ECMWF...AS MANY
TIMES THE DRIER AIR INTRUDING DOWN FROM THE LARGE HIGH PRESSURE
SYSTEM FROM THE NORTH...OVERCOMES THE MOISTURE FETCH FROM THE
SOUTH OR AT LEAST PUSHES IT FURTHER SOUTH THAN WHAT THE MODELS
INDICATE. CURRENTLY HAVE THE I 90 CORRIDOR ON THE NORTHERN EDGE OF
THE ACCUMULATING RAINFALL THURSDAY NIGHT...WITH LIKELY POPS AROUND
SIOUX CITY AND STORM LAKE IA...WITH DECENT CHANCE POPS REMAINING
AROUND STORM LAKE INTO FRIDAY...ESPECIALLY IN THE MORNING.

HAVE TEMPERATURES COMFORTABLY ABOVE FREEZING THURSDAY NIGHT...BUT
WOULD NOT RULE OUT SOME PATCHY FROST IN THE RIVER BOTTOMS AROUND
THE HURON AND CHAMBERLAIN AREAS. FEEL IT WILL BE TOO ISOLATED FOR
NOW TO WARRANT A MENTION IN THE GRIDS...BUT THOSE LOCATIONS WILL
BE THE FIRST TO SEE A DECREASE IN CLOUDS. LOWS ARE VARYING BETWEEN
THE MID 30S AROUND HURON...TO THE LOWER 40S IN OUR EASTERN ZONES
WHERE CLOUD COVER WILL VERY LIKELY HANG ON. THIS WILL BE FOLLOWED
BY A MODEST REBOUND IN TEMPERATURES ON FRIDAY MAINLY INTO THE MID
50S.

NOW FRIDAY NIGHT IS A BIT CONCERNING IN TERMS OF FROST POTENTIAL.
THE SURFACE RIDGE OF HIGH PRESSURE WILL MOVE EASTWARD WHICH WILL
GIVE OUR FORECAST AREA A RETURN FLOW OF AIR...BUT POSSIBLY TOO
LATE TO HELP NORTHWEST IA. THE RAW GUIDANCE VALUES ALONG AND EAST
OF A SIOUX CITY IA TO WINDOM MN LINE LOOKED THE BEST...IN HAVING A
LOT OF VALUES OF ONLY 33 TO 34 DEGREES. LOWS SHOULD THEN MODERATE
INTO THE UPPER 30S TOWARD CHAMBERLAIN SD. THEREFORE PLACED SOME
PATCHY FROST WHEREVER THE LOWS ARE 34 DEGREES OR LESS...BUT THE
FROST SHOULD NOT LAST VERY LONG AT ANY RATE.

AFTER A WEEKEND OF HIGHS IN THE 60S...THE NEXT SYSTEM AFFECTS OUR
AREA SUNDAY NIGHT. ITS A WAVE DIVING DOWN THE NORTHWEST FLOW ALOFT
WHICH IS SIMILAR TO THE WAVE WE WILL HAVE THURSDAY NIGHT AND
FRIDAY MORNING. DRY CONDITIONS THEN FOLLOW UNTIL POSSIBLY MID WEEK
NEXT WEEK. HIGHS BY TUESDAY AND WEDNESDAY SHOULD FINALLY MODERATE
INTO THE UPPER 60S AND 70S AS THERE APPEARS TO BE NO REINFORCING
SHOT OF COOL AIR BEHIND SUNDAY NIGHTS WAVE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 717 PM CDT WED SEP 10 2014

LOW STRATUS ARUOND 1500 FEET IS BEGINNING TO LIFT ALONG OUR
WESTERN FRINGE AND SHOULD GRADUALLY ERODE TO MID AND HIGH STRATUS
DECK THROUGH AROUND 03Z. MVFR CEILINGS WILL WORK BACK INTO THE
WESTERN FORECAST AREA AFTER 12Z...WITH LIGHT RAIN SPREADING INTO
AREAS WEST OF THE JAMES VALLEY DURING THE DAYTIME ON THURSDAY.

&&

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

$$

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


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