Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 232336
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
636 PM CDT SAT APR 23 2016

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 418 PM CDT SAT APR 23 2016

WARM AND WINDY DAY TODAY TO BE FOLLOWED BY A MILD AND BREEZY NIGHT
AS SOUTHERLY FLOW REMAINS STOUT BENEATH INCREASING LOW LEVEL JET.
QUESTION FOR TONIGHT WILL BE MOISTURE AVAILABILITY FOR CONVERGENT
AREA ON THE NOSE OF THE LOW LEVEL JET. PERSISTENT BUT WEAKENING WARM
ADVECTION WILL AID IN STEEPENING MID LEVEL LAPSE RATES ACROSS THE
AREA...AND WITH SOME MODEST MID LEVEL MOISTURE AVAILABLE...POTENTIAL
FOR SPOTTY ACCAS SHRA/TSRA OVER MUCH OF THE CWA BY LATE TONIGHT.
THINK MORE FOCUSED AREA WILL BE NEAR/NORTH OF HIGHWAY 14...NEAREST
THE NOSE OF THE LOW LEVEL JET/850MB WARM FRONT...BUT EVEN THERE
CONFIDENCE NOT HIGH ENOUGH IN MEASURABLE PRECIP THREAT AT THIS TIME
TO GO MUCH HIGHER THAN SLIGHT CHANCE POPS AFTER 06Z...WITH BETTER
CHANCE NORTH OF OUR FORECAST AREA. STEADY SOUTHERLY BREEZE AND
MODEST LOW LEVEL MOISTURE SHOULD HOLD OVERNIGHT LOWS IN THE MID 50S
TO AROUND 60.

ANY EARLY MORNING ACCAS ACTIVITY LIKELY TO WANE AS THE LOW LEVEL JET
WEAKENS THROUGH THE MORNING...AND FOCUS THEN SHIFTS TO DETERMINING
JUST HOW FAR EAST THE DEVELOPING DRY LINE WILL PROGRESS THROUGH THE
AFTERNOON. QUITE A BIT OF DISAGREEMENT AMONG THE MODELS ON EVENTUAL
PLACEMENT...THOUGH OVERALL HAVE TRENDED A BIT FARTHER WEST WITH THIS
FEATURE OVER RECENT RUNS. NAM MUCH FARTHER WEST THAN MOST MODELS...
HOLDING THE DRY LINE WEST OF THE JAMES RIVER VALLEY THROUGH 00Z...
WHILE GFS MORE AGGRESSIVE IN PUSHING THE DRY LINE NEAR/EAST OF I-29
BY 21Z BEFORE PULLING IT BACK TO THE WEST AS A SURFACE LOW BECOMES
MORE ORGANIZED IN SOUTH CENTRAL SOUTH DAKOTA. HIGHER-RESOLUTION
ARW/NMM MODELS APPEAR A GOOD COMPROMISE WITH A LOCATION NEAR/JUST
WEST OF I-29 IN THE LATE AFTERNOON...AND HAVE FAVORED THIS SOLUTION
WHICH KEEPS BEST CHANCE FOR DEVELOPMENT EAST OF A VERMILLION-SIOUX
FALLS-BROOKINGS LINE AFTER 21Z. WITH CONTINUED STEEP MID LEVEL LAPSE
RATES...ALONG WITH LOW LEVEL DEW POINTS CLIMBING INTO THE MID-UPPER
50S AND DEEP LAYER SHEAR PUSHING 40-45KTS...CANNOT ARGUE WITH SLIGHT
RISK AS HIGHLIGHTED BY SPC ACROSS NORTHWEST IOWA. INCREASED MOISTURE
AND GREATER CLOUD COVERAGE COULD HOLD TEMPERATURES EAST OF I-29 DOWN
A BIT FROM FULL MIXING POTENTIAL...AND HAVE LOWERED HIGHS A COUPLE
OF DEGREES INTO THE MID 70S. MEANWHILE LOCATIONS WEST OF THE DRY
LINE SHOULD BE WELL-MIXED WITH HIGHS AGAIN CLOSE TO 80 DEGREES.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 418 PM CDT SAT APR 23 2016

SEVERE WEATHER THREAT WILL CONTINUE THROUGH THE EARLY EVENING HOURS.
WILL HAVE TO MONITOR POTENTIAL FOR STORMS TO BECOME A BIT MORE
THREATENING ACROSS PARTS OF NW IA...WITH MODELS INDICATING AN
INCREASE IN WINDS ABOUT A KM OR SO OFF THE SURFACE ALREADY BY EARLY
EVENING. WITH PERIOD OF MAIN PV ADVECTION LASTING INTO EARLY
EVENING...WILL MAXIMIZE POTENTIAL AROUND 00Z OR SHORTLY
THEREAFTER...AND BY 03Z LIKELY TO SEE DOWNWARD TREND IN INTENSITY
AND EASTWARD PUSH TO MAIN BROKEN LINE...FAVORED BY ORIENTATION OF
SHEAR VECTOR CROSS BOUNDARY. OTHER CONVECTION WILL BE POSSIBLE BACK
TOWARD THE CONVERGENCE AREA WANDERING THROUGH THE MID JAMES VALLEY.
WHILE A MUCH LESS LIKELY TO SUPPORT AN ISOLATED SEVERE STORM NORTH
OF I-90...IT IS CERTAINLY A NON ZERO THREAT.

AS MAIN UPPER LOW BEGINS TO SLIDE/SHEAR EAST/NORTHEASTWARD
OVERNIGHT...PRECIPITATION SHOULD WRAP/SETTLE BACK MAINLY THROUGH THE
NORTHERN HALF OF THE AREA...ROUGHLY NORTH OF I 90. SHOULD BE MAINLY
RAIN...BUT A TOUCH OF ELEVATED INSTABILITY REMAINS AHEAD OF THE WAVE
AND HAVE MAINTAINED A MENTION OF THUNDER SLIPPING EASTWARD THROUGH
THE NIGHT EAST OF I-29.

BEHIND THE SYSTEM...WILL SEE FAIRLY EXPANSIVE STRATUS SHIELD PUSH
SOUTHWARD. AS A RESULT...TEMPS WILL STRUGGLE OVER MUCH OF THE
AREA...BUT PERHAPS CLOUDS COULD SPARE PARTS OF FAR NORTHWEST IOWA
LONG ENOUGH INTO THE DAY TO HAVE TEMPS MODERATE INTO THE MID 60S.
LOCATIONS HEADING PROGRESSIVELY NORTH AND WEST WILL HAVE READINGS
MAINLY STEADY TO A MODEST CLIMB AT BEST...MOSTLY IN THE 50S...
ESPECIALLY WHERE SOME LIGHT RAIN COULD LINGER AROUND KBKX AND KMML.
PLENTY OF CLOUDS HOLDING AROUND MONDAY NIGHT...AS NORTHERLY WINDS
WORK TOWARD NORTHEAST...A TRAJECTORY IN FAVOR OF HOLDING MORE FIRM
WITH LOW CLOUD COVERAGE.

ON TUESDAY...WILL HOLD OUT HOPE THAT PERSISTENT AND TREND TO
EASTERLY FLOW WILL EVENTUALLY HELP TO BREAK OUT LOW CLOUDS AT
LEAST THROUGH SOME AREAS EAST OF I 29...BUT UNFORTUNATELY THE NEXT
SYSTEM WILL ALREADY BE TRUDGING OUT OF THE ROCKIES AND INTO THE
CENTRAL HIGH PLAINS. MEAN SOLUTIONS A BIT SLOWER THAN PREVIOUS FEW
SETS OF MODEL RUNS...AND RIDGING TO THE EAST SHOULD BE ABLE TO HOLD
OFF PRECIP TO JUST AREAS MAINLY JAMES VALLEY AND MISSOURI VALLEY
THROUGH AFTERNOON. ELEVATED INSTABILITY RETURNS WITH SOLID WARM AIR
ADVECTION IN THE MID LEVELS...AND AGAIN WILL START TO WORK THUNDER
INTO THE SOUTH LATER IN DAY.

FAIRLY CONSISTENT SOLUTIONS HANDLING PACE AND TRACK OF LARGE CLOSED
LOW THROUGH THE CENTRAL AND NORTHERN PLAINS THROUGH THURSDAY. SOME
MINOR NORTH/SOUTH VARIATIONS IN TRACK OF MID LEVEL CIRCULATION...
BUT SUGGESTION THAT AREA UNLIKELY TO FULLY BREAK INTO THE WARM
SECTOR WITH SURFACE WAVE KEEPING FURTHER SOUTH IN THE VAST MAJORITY
OF SOLUTIONS. GFS AND CANADIAN KEEP WINDOW OPEN THAT WAVE/WARM FRONT
COULD SPREAD INTO FAR NORTHEAST NEBRASKA OR NORTHWEST IOWA ON
WEDNESDAY...BUT IN GENERAL WILL BE SUSCEPTIBLE FOR PERIODS OF
SHOWERS AND THUNDERSTORMS WRAPPING AROUND THE SLOW MOVING SYSTEM.
SEVERE THREAT SHOULD BE LITTLE TO NONE...WITH EXCEPTION OF PERHAPS
THAT FAR SOUTHERN TIER AROUND KSUX...AS EVEN MORE ELEVATED STORMS
COULD PRODUCE A HAIL THREAT GIVEN THE POTENTIAL STEEPER LAPSE RATES
ADVECTING AHEAD OF UPPER LOW FROM LATER TUESDAY NIGHT THROUGH
WEDNESDAY EVENING.  MORE CERTAIN WILL BE SOME APPRECIABLE RAINFALL
POTENTIAL MIDWEEK...AN INCH OR TWO IN MANY LOCATIONS.

SYSTEM PULLS EAST THURSDAY WITH LINGERING AREAS OF LIGHT RAIN... AND
WILL REPLAY THE MORE WIDESPREAD LOWER CLOUDS. SHEARING OUT THE
SYSTEM SHOULD END THE PRECIP THREAT OVER MOST OF THE AREA THURSDAY
NIGHT...PERHAPS A FEW SPITS EARLY ON IN SW MN.

FRIDAY PERHAPS THE MOST PLEASANT DAY OF THE UPCOMING WEEK IN TERMS
OF DRY WEATHER...JUST A BIT ON THE COOL SIDE OF NORMAL...AND AGAIN
STRUGGLING WITH LINGERING CLOUDS...AND INCREASE AHEAD OF YET ANOTHER
WEATHER SYSTEM FOR THE WEEKEND. WILL REPLAY THE INCREASE IN WARM
ADVECTION AND OVERSPREADING OF LIFT FORCING FRIDAY NIGHT INTO
SATURDAY...ALONG WITH INCREASING ELEVATED INSTABILITY FOR SOME
THUNDER ONCE AGAIN. TEMPS REMAINING ON THE COOL SIDE OF NORMAL.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 631 PM CDT SAT APR 23 2016

SOUTHERLY WINDS WILL BE QUITE GUSTY UNTIL SUNSET...FREQUENTLY
GUSTING TO 25 TO 30 KNOTS BEFORE SUBSIDING RELATIVELY SPEAKING
AFTER SUNSET. IT IS ANTICIPATED THAT VFR CONDITIONS WILL PREVAIL
THROUGH SUNDAY. HOWEVER THE NAM IS POINTING AT SOME POSSIBLE MVFR
CEILINGS SUNDAY MORNING. LEFT IT OUT OF THE TAFS FOR NOW AS THIS
SCENARIO WAS NOT BACKED UP BY OTHER MODELS SUCH AS THE RAP AND
GFS. BUT DID HEDGE AS A HEADS UP AND KEPT A SCATTERED DECK GOING.
FOR SUNDAY AFTERNOON...LEFT THE MENTION OF TSRA OUT OF THE KFSD
AND KSUX TAF SITES FOR NOW AS MUCH OF THE ACTIVITY MAY DEVELOP
WEST OF INTERSTATE 29.

&&

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

$$

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



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