Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 242109
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
409 PM CDT SUN APR 24 2016

.SHORT TERM...(TONIGHT)
ISSUED AT 408 PM CDT SUN APR 24 2016

INTENSE UPPER LEVEL LOW PRESSURE LOCATED ACROSS SOUTHWEST SOUTH
DAKOTA AT MID AFTERNOON...WITH LOBE ROTATING NORTHEAST THROUGH
CENTRAL KANSAS AND SOUTH CENTRAL NEBRASKA. DRYLINE REMAINS FROM NEAR
KMHE TO WEST OF KBVN...SEPARATING 40S DEW POINTS WEST FROM 50S EAST.
CONCERN FOR TONIGHT IS WITH SEVERE WEATHER THREAT...AS UPPER ENERGY
ROTATES NORTHWARD ALONG THE DRY LINE.

A BIT MESSY ON INITIATION THIS AFTERNOON AS HAVE HAD A TRAJECTORY
ELEVATED MOISTURE KEEPING SCATTERED SHOWERS AND A FEW RUMBLES OF
THUNDER GOING MAINLY NEAR/EAST OF I-29...AND HAS DECREASED POTENTIAL
INSTABILITY SOMEWHAT THROUGH MID AFTERNOON. WILL LIKELY SEE SOME
ENHANCEMENT OF ELEVATED BAND JUST WEST OF SIOUX CITY SOUTHWARD INTO
EASTERN NEBRASKA...AS AIRMASS AHEAD HAS HEATED OUT WELL ACROSS
SOUTHWEST AND WEST CENTRAL IOWA. ALSO LOOK FOR MORE SCATTERED
DEVELOPMENT ALONG THE DRY LINE AS UPPER LIFT RIPPLES UP THE BOUNDARY
FROM THE SOUTH. SHEAR IS STILL FORMIDABLE AT 35-40 KNOTS 0-6KM DEEP
LAYER OVER AREAS NEAR/SOUTH OF I 90...A BIT LESS TO THE NORTH...
WITH A FAIRLY DISTRIBUTED SHEAR PROFILE. SHEAR SOMEWHAT ORTHOGONAL
TO BOUNDARY WILL HELP TO KEEP INITIAL STORMS MORE SPREAD...BUT
STRAIGHT LINE ALSO SUGGESTS THAT COULD GET LEFT/RIGHT SPLIT AND
MERGERS...WORKING TOWARD A MORE BROKEN LINEAR STRUCTURE. INCREASE IN
LOW LEVEL JET IS SUGGESTED THIS EVENING AHEAD OF THE LINE WITH
ENHANCEMENT OF THE 0-1KM SHEAR...BUT WITH MOST RECENT HIGH
RESOLUTION MODELS SPEEDING UP THE INITIAL LINE A BIT...COULD VERY
WELL BE THAT THIS INCREASE WILL NOT OCCUR WITHIN THE FSD CWA. MAIN
THREATS WOULD BE HAIL AND DAMAGING WIND...AND MAINLY HAIL NORTH OF
I-90.

OVERNIGHT...THE UPPER LEVEL LOW WILL PUSH EAST...REACHING THE
EASTERN BORDER OF SD LATE NIGHT. ANOTHER AREA OF SHOWERS AND
THUNDERSTORMS EXPECTED TO WRAP AROUND THE MAIN LOW TOWARD SOUTH
CENTRAL SD AND WESTERN MISSOURI RIVER AREA DURING THE EVENING...
AND WILL STRETCH OUT ALONG THE UPPER LOW PATH LATER TONIGHT.
ELEVATED INSTABILITY REMAINS GENERALLY AHEAD OF THE FEATURE...AND
WILL GRADUALLY TRIM BACK THUNDER CHANCES WITH CENTER OF MID LEVEL
WAVE. LOWER CLOUDS WILL EVENTUALLY WRAP BACK SOUTHWARD BEHIND
SURFACE WAVE THROUGH MUCH OF SOUTHEAST SOUTH DAKOTA BY DAYBREAK.


.LONG TERM...(MONDAY THROUGH SUNDAY)
ISSUED AT 408 PM CDT SUN APR 24 2016

UPPER LOW AND ASSOCIATED SURFACE LOW PRESSURE LIFT NORTHEAST OF THE
FORECAST AREA MONDAY MORNING...TAKING ANY LINGERING PRECIPITATION
THREAT WITH IT BY MIDDAY MONDAY. SYSTEM SEEMS TO BE TRACKING JUST A
BIT FARTHER NORTH...ALLOWING FOR MORE SUNSHINE AND SOME WARMER AIR
TO WORK INTO NORTHWEST IOWA MONDAY. STILL ANTICIPATE RATHER LARGE
TEMPERATURE RANGE ACROSS THE AREA...FROM LOWER 50S UNDER WRAPAROUND
STRATUS NEAR HURON...TO NEAR 70 AT STORM LAKE IOWA. WEAK MID-UPPER
LEVEL RIDGE WORKS ACROSS THE AREA THROUGH TUESDAY. THIS WILL KEEP
AREAS EAST OF I-29 DRY...WHILE A CHANCE OF SHOWERS/THUNDERSTORMS
BEGINS TO WORK INTO AREAS ALONG/WEST OF THE JAMES RIVER. STUBBORN
LOW LEVEL CLOUDS AND A COOL EASTERLY FLOW WILL KEEP TEMPERATURES
SEASONABLY COOL IN THE 50S ACROSS MUCH OF SOUTH DAKOTA/MINNESOTA
TUESDAY...BUT NORTHWEST IOWA COULD AGAIN SEE A LITTLE MORE SUN...
HELPING THEM WARM INTO THE 60S. WITH THE ADDED HEATING IN OUR FAR
SOUTH...SOME MODEST INSTABILITY COULD WORK INTO AREAS SOUTH OF
HIGHWAY 18 BY LATE TUESDAY AFTERNOON...THOUGH FORECAST SOUNDINGS
STILL CAPPED TO ELEVATED STORMS...AND WITH FAIRLY DEEP EASTERLY
SURFACE-BASED FLOW...SEVERE THREAT THIS FAR NORTH APPEARS MINIMAL.

THE BROAD UPPER LOW THEN BEGINS TO SWINGS INTO THE CENTRAL AND
NORTHERN PLAINS TUESDAY NIGHT...SPREADING A GOOD CHANCE FOR SOME
WIDESPREAD RAINFALL ACROSS THE FORECAST AREA TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT.

LONGER RANGE DOMINATED BY COOL TEMPERATURES...WITH OVERNIGHT LOWS
LARGELY IN THE MID 30S TO LOWER 40S...AND HIGHS IN THE 50S. RAIN
SHOULD BEGIN TO DIMINISH BY THURSDAY AS THE UPPER LOW PULLS EAST
THROUGH THE GREAT LAKES. ECMWF HANGS ON TO MORE MUDDLED FLOW AND
LINGERS PRECIP AROUND THE AREA ALL THE WAY THROUGH FRIDAY. AS
ALLUDED TO IN THE LONG RANGE DISCUSSION FROM WPC...THIS SOLUTION
IS A BIT OF AN OUTLIER...SO WILL CONTINUE WITH TREND TOWARD DRIER
CONDITIONS FOR THURSDAY NIGHT/FRIDAY. GFS/GEM THEN BRING YET
ANOTHER UPPER LOW INTO THE CENTRAL PLAINS...SPREADING RAIN BACK
INTO THE FORECAST AREA FRIDAY NIGHT THROUGH THE UPCOMING WEEKEND.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1229 PM CDT SUN APR 24 2016

THUNDERSTORM CHANCES WILL INCREASE BY LATE AFTERNOON...ESPECIALLY
FOR KFSD AND KSUX TERMINALS. A FEW SEVERE STORMS WITH LARGE HAIL
AND DAMAGING WINDS POSSIBLE...AND MORE GENERAL THUNDERSTORMS WILL
AS WELL BRIEFLY REDUCE CONDITIONS INTO THE MVFR VISIBILITY/CEILING
RANGE. OTHERWISE...VERY LATE NIGHT AND EARLY MONDAY MORNING WILL
FIND IFR STRATUS WRAPPING SOUTHWARD THROUGH THE KHON AND
EVENTUALLY KFSD SITES.


&&

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

$$

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



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