Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 260853
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
353 AM CDT TUE MAY 26 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 352 AM CDT TUE MAY 26 2015

MAIN FOCUS TODAY IS ON RAIN CHANCES. SYNOPTICALLY...THE EVER PRESENT
UPPER LOW WHICH HAS INFLUENCED THE PLAINS WEATHER FOR DAYS...IS
FINALLY OPEN AND MOVING EASTWARD SQUARELY ACROSS OUR FORECAST AREA
TODAY. IT WILL BE EAST OF OUR AREA TONIGHT. SHOWERS AND ISOLATED
THUNDERSTORMS HAVE BEEN OCCURRING THE PAST SEVERAL HOURS MAINLY IN
NORTHWEST IA...EXTREME NORTHEAST NEB...AND EXTREME SOUTHEAST SD
RIGHT ALONG THE 925MB WIND SHIFT LINE. AS THE UPPER LOW IS MOVING
SLOWLY EASTWARD...THE 925MB SHEAR AXIS FOLLOWS SUIT BUT AT A SNAILS
PACE THIS MORNING. THEREFORE THERE IS A DECENT CHANCE FOR SHOWERS
AND ISOLATED STORMS MAINLY IN NORTHWEST IA THIS MORNING...AND
ESPECIALLY IN THE EASTERN SECTIONS OF NORTHWEST IA BETWEEN 12Z AND
18Z. THE RAIN CHANCES THEN WANE THIS AFTERNOON IN OUR SOUTHEAST
ZONES AS THE WIND SHEAR CONTINUES TO MOVE EAST...LEADING INTO WHAT
WILL FINALLY BE A TOTALLY DRY NIGHT TONIGHT ACROSS THE FORECAST
AREA. CONCERNING HIGHS...THEY ARE RATHER BENIGN TODAY BUT PREFERRED
THE GUIDANCE VALUES WHICH HAD COOL VALUES IN THE 60S ACROSS OUR FAR
EASTERN ZONES DUE TO THE INCREASED CLOUD COVER. CONVERSELY A GOOD
PORTION OF OUR WESTERN ZONES SHOULD WARM INTO THE MID 70S. TONIGHT
WITH CLEARING OR CLEAR SKIES AND LIGHT WINDS...TEMPERATURES SHOULD
FALL TO 50 TO 55 DEGREES.


.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 352 AM CDT TUE MAY 26 2015

WEDNESDAY MORNING STARTS OFF FAIRLY TRANQUIL WITH CLEAR SKIES AND
LIGHT WINDS...HOWEVER...SURFACE RIDGE SHIFTS EAST AND FORECAST
SOUNDINGS INDICATE STRONG MIXING UNDER INCREASING SOUTHERLY FLOW.
WITH STEEP LAPSE RATES FROM AROUND 925 TO 700 MB LEADS TO
INSTABILITY ALOFT.  MODELS SUGGEST THE GREATEST INSTABILITY WILL BE
ACROSS SOUTHWEST MINNESOTA...WHERE BOTH THE CANADIAN AND SREF
DEVELOP PRECIPITATION.  BOTH NAM AND GFS INDICATE A FEW HUNDRED J/KG
OF UNCAPPED CAPE...BUT DO NOT PRODUCE PRECIP.  FOR NOW...KEPT
FORECAST DRY DUE TO A LACK OF A TRIGGER...BUT WILL NEED TO WATCH THE
POTENTIAL FOR AIRMASS THUNDERSTORM DEVELOPMENT IN THE EASTERN CWA
WEDNESDAY AFTERNOON.

WEDNESDAY NIGHT HAS BECOME EVEN MORE UNCLEAR WITH SHORT WAVES MAINLY
STAYING SOUTH OF THE FORECAST AREA...HOWEVER...MODEST 20-30 KNOT LOW
LEVEL JET DEVELOPS ACROSS THE PLAINS.  NOT A LOT OF CONVERGENCE
ACROSS OUR AREA...WITH THE CONVERGENCE FOCUSED FURTHER NORTH.  WITH
THE UNCERTAINTY ON FOCUS...DROPPED POPS BACK TO CHANCE.

APPEARS THAT DIRTY SOUTHWEST FLOW USHERS ADDITIONAL SHORTWAVES
ACROSS THE AREA ON THURSDAY.  HAVE RAISED POPS TO HIGH CHANCE/LOW
LIKELY ON THURSDAY.

ON FRIDAY...STRONG COLD FRONT MOVES ACROSS THE AREA WITH 925 HPA
TEMPS FALLING TO AROUND 5 C BEHIND THE FRONT.  WITH MUCH COOLER AND
STABLE AIR BEHIND THE FRONT...EXPECT CONVECTION TO BE CONTAINED
MAINLY ALONG AND AHEAD OF THE FRONT.

HOW FAR THE FRONT SURGES SOUTH IS UP FOR DEBATE...WITH MODELS IN
GENERAL STALLING THE FRONT STALLING THE FRONT BETWEEN HIGHWAY 20 AND
INTERSTATE 80.  WITH THE FRONT REMAINING IN THE VICINITY THROUGH THE
WEEKEND...COULD BE ACTIVE THOUGH FORECAST AREA IS ON THE COOL SIDE
OF THE FRONT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1032 PM CDT MON MAY 25 2015

ISOLATED CONVECTION WILL CONTINUE TO PERCOLATE SOUTH OF THE I-90
CORRIDOR OVERNIGHT. THE OTHER CONCERN TOWARDS DAYBREAK WILL BE THE
EXPANSION OF STRATUS SOUTHWARD. MVFR STRATUS CONTINUES TO LINGER
ALONG AND MN/SD BORDER...HOWEVER BROKEN MID-LVL CLOUDS FROM
CONVECTION ARE HOLDING IT AT BAY. THERE IS SOME POTENTIAL THAT
THIS STRATUS WILL SINK SOUTHWARD INTO FSD TOWARDS DAYBREAK...BUT
UNSURE IF IT WILL BE PREVAILING.

OTHERWISE...SHOWERS WILL LINGER NEAR SUX THROUGH MID-MORNING...BUT
SOME SIGNS POINT TO DRIER CONDITIONS FOR TUESDAY
AFTERNOON...ESPECIALLY FOR FSD/HON. KSUX IS MORE UNCERTAIN.


&&

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

$$

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



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