Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 270348
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1048 PM CDT TUE APR 26 2016

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 352 PM CDT TUE APR 26 2016

COPIOUS MOISTURE WILL STREAM INTO THE NORTHERN PLAINS TONIGHT AND
WEDNESDAY AS THE STRONG SOUTHERN LOBE OF THE APPROACHING UPPER LOW
ROTATES AROUND A WY AXIS. THE FLOW WILL STEADILY GO FROM
SOUTHERLY TO EASTERLY AS THIS LOBE APPROACHES AND ACTUALLY
BECOMES THE MAIN UPPER LOW. WEAK WAVES STREAMING OVER THE AREA FROM
THE SOUTH AHEAD OF THE BULK OF THE MOISTURE TRIGGERED LIGHT
CONVECTION EARLIER TODAY AND THAT HAS MOSTLY DISSIPATED. WE
ARE LEFT WITH AWAITING THE DECENT BATCH OF SHOWERS AND STORMS
WHICH WILL COME UP DURING THE EVENING AND BRING WIDESPREAD WET
WEATHER BY LATE TONIGHT.

ENOUGH ELEVATED INSTABILITY LOOKS TO STREAM INTO THE MISSOURI RIVER
AREA TO BRING A FEW THUNDERSTORMS TO THE SOUTHERN PART OF THE AREA
TONIGHT...WITH THE THUNDER CHANCE SLOWLY TRANSLATING TO THE EASTERN
EDGE OF THE AREA WEDNESDAY. SEVERE STORMS ARE SEEN AS VERY UNLIKELY
WITH PERHAPS AN ISOLATED SMALL HAIL THREAT MAINLY UP TO THE SIOUX
CITY AREA.

REPEATING SMALL SCALE UPPER IMPULSES ADDED TO THE COPIOUS MOISTURE
BEING LIFTED WILL BRING A HEAVY RAIN THREAT. THIS FOR NOW IS NOT
SEEN OVER TIME RANGES SHORT ENOUGH TO BRING ANY FLASH FLOOD
THREAT...BUT MOST OF THE AREA WILL GET PRETTY SOAKED BY LATE
WEDNESDAY. IT APPEARS THAT THE HEAVIEST RAIN WILL LIKELY BE ALONG
AND WEST OF THE JAMES RIVER...ALTHOUGH CONVECTION PATTERNS MAY
AFFECT THAT.

PRECIPITATION COVERAGE COULD TEMPORARILY DECREASE OVER THE SOUTHERN
PART OF THE AREA WEDNESDAY...ESPECIALLY IN NORTHWEST IOWA AND
EXTREME SOUTHEAST SD...BUT THIS WILL BE PARTLY DUE TO THE MORE
CONVECTIVE NATURE OF THE RAIN AND WILL NOT SHAVE POPS TOO MUCH.

WINDS WILL INCREASE...BECOME EASTERLY... AND CONCEIVABLY COULD GET
CLOSE TO WIND ADVISORY CRITERIA LATE TONIGHT OR WEDNESDAY. NO
ADVISORY PLANNED FOR NOW.

NOT TOO MUCH PROBLEM WITH TEMPERATURES GIVEN THE WARM SECTOR SHOULD
STAY WELL OUT. LOWS IN THE 40S TO LOWER 50S TONIGHT AND HIGHS IN THE
40S WEST AND NORTH TO THE 50S SOUTHEAST WEDNESDAY. A LITTLE MORE
NORTHERN SURGE OF THE SYSTEM COULD PUT SUX INTO THE 60S BUT WILL NOT
PLAN ON THAT FOR NOW.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 352 PM CDT TUE APR 26 2016

WRAPPED UP UPPER WAVE PUSHES OUT ACROSS EASTERN NEBRASKA ON
WEDNESDAY NIGHT. SOMEWHAT QUIETER COVERAGE TO SHOWERS AND
THUNDERSTORMS SHOULD QUICKLY GIVE WAY TO NEXT LOBE WRAPPING
NORTHWARD AROUND THE WAVE EARLY EVENING...AND MUCH OF THE CWA
REMAINS IN A PERSISTENT EASTERLY TRAJECTORY OF MOISTURE TRANSPORT
AND GRADUALLY WEAKENING THETA E ADVECTION...WRAPPING ALL THE WAY
BACK THROUGH SOUTH CENTRAL SD AREAS. A WEE BIT OF ELEVATED
INSTABILITY REMAINS NEAR/AHEAD OF THE UPPER WAVE WRAPPING INTO PARTS
OF NW IA/NE NEBRASKA/EXTREME SE SD MAINLY THROUGH THE EVENING
HOURS...AND LIKELY NO MORE THAN ISOLATED RUMBLES ALONG WITH IT.

CONTINUED STRETCHING OUT OF UPPER TROUGH AXIS WILL MAKE FOR A
GRADUALLY LESS AND LESS FAVORABLE ENVIRONMENT FOR LIGHT RAIN/SHOWERS
PASSING THROUGH THURSDAY. ECMWF REMAINS A BIT FURTHER SOUTHWARD WITH
LINGERING MID LEVEL VORTICITY AXIS COMPARED TO GFS/CANADIAN... BUT
EXPECT THE AFTERNOON TO SEE MORE RAPID DECREASE TO SHOWERS SOUTH
COMPARED TO NORTH...DESPITE CLOUDS REMAINING PREVALENT.

THURSDAY NIGHT AND MUCH OF FRIDAY SHOULD PROVIDE A BRIEF BREAK FROM
THE RAINFALL.  CLOUDS WILL LARGELY REMAIN WITH FLOW WEAK BETWEEN
EXITING SYSTEM...AND THE NEXT LARGER SCALE UPPER LOW LIFTING ACROSS
THE CENTRAL AND SOUTHERN ROCKIES BY LATE DAY.  A SMALL CHANCE FOR
SHOWERS WILL RETURN TOWARD EVENING UPON STRENGTHENING AND FOCUS OF
WARM AIR ADVECTION AGAIN TOWARD THE MISSOURI CORRIDOR...WITH UPPER
FLOW STARTING TO INCREASE IN DIVERGENCE AHEAD OF APPROACHING WAVE.

IT WILL BE A SIMILAR STORY PLAYING OUT AGAIN GOING FROM FRIDAY NIGHT
THROUGH THE WEEKEND...AS THE NEXT UPPER WAVE WOBBLES OUT INTO THE
MID PLAINS SATURDAY AND AGAIN SHEARS OUT WEST TO EAST OVER THE AREA
ON SUNDAY. IF ANYTHING...THE POTENTIAL FOR ELEVATED INSTABILITY WILL
BE EVEN LOWER THIS TIME AROUND CREEPING INTO THE FAR SOUTHERN CWA AS
THE SYSTEM IS LIKELY TAKING JUST A BIT MORE SOUTHWARD TRACK. STILL
WILL SEE A DRY PUNCH ALOFT WRAPPING IN LATER SATURDAY AND SATURDAY
EVENING...AND HAVE MAINTAINED ISOLATED THUNDER CHANCES INTO
NORTHEAST NEBRASKA...FAR SOUTHEAST SOUTH DAKOTA...AND NORTHWEST IOWA
THROUGH SATURDAY EVENING. AGAIN HIGH CONFIDENCE FOR RAINFALL...BUT
NOT AS MUCH AMBIENT MOISTURE LEADING INTO THIS SYSTEM. WILL HAVE TO
SEE HOW HYDROLOGICAL SITUATION SETTLES AFTER MID WEEK SYSTEM TO SEE
WHAT IMPACTS THIS SECOND UPPER LOW MAY HAVE ON AREA RIVERS AND
TRIBUTARIES.

ONE THING FOR SURE...OTHER THAN PERHAPS A SNEAKY SLIGHT CLIMB TO
TEMPS ON FRIDAY WITH LACK OF PRECIP...TEMPS WILL EXHIBIT MINIMAL
DIURNAL CHANGES OVER THE NEXT 4-5 DAYS. BY THE TIME MONDAY COMES
ABOUT...SHOULD SEE TEMPS START A TREND TO RETURN TOWARD NORMAL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1047 PM CDT TUE APR 26 2016

WIDESPREAD MVFR-IFR CONDITIONS EXPECTED THROUGH THIS TAF PERIOD AS
RAIN AND ISOLATED THUNDERSTORMS OVERSPREAD THE REGION. CONFIDENCE
IN TIMING OF THUNDER THREAT AT ANY ONE LOCATION IS LOW...AND THUS
OPTED TO NOT MENTION IN TAFS AT THIS TIME.

GUSTY EAST WINDS WILL ACCOMPANY THE RAIN THROUGH THE DAY WEDNESDAY
WITH GUSTS AT OR ABOVE 25KT AT TIMES.

&&

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

$$

SHORT TERM...
LONG TERM...CHAPMAN
AVIATION...JH



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