Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 011746
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1246 PM CDT WED JUL 1 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 413 AM CDT WED JUL 1 2015

LOOKS TO BE A MESSY 24 HOUR PERIOD ACROSS THE AREA...AS SEVERAL
WAVES WILL BE TRAVERSING THE REGION. THE FIRST WAVE IS PUSHING
ACROSS SOUTH DAKOTA EARLY THIS MORNING...MARKED BY SOME FAIRLY
DISTINCT DRYING ACROSS THE NORTHWEST CORNER OF THE RUSHMORE STATE.
SCATTERED SHOWERS AND THUNDER HAVE POPPED ACROSS MUCH OF THE AREA...
WITH ELEVATED CAPE OF A FEW HUNDRED J/KG AVAILABLE...PERHAPS UP TO
500-700 J/KG FOR THE FAR WESTERN CWA. COUPLE STRONGER CELLS WILL
SLIDE SOUTHEAST ALONG THE AXIS OF GREATEST THETA E ADVECTION FROM
WEST OF KHON TOWARD KYKN AND KSUX EARLY THIS MORNING. WOULD NOT BE
SHOCKED TO FIND A LITTLE HAIL UP TO DIME SIZE WEST OF THE JAMES
RIVER...AS STORMS DO HAVE SOME SIGNS OF MID LEVEL ROTATION WITH
FAIRLY STRONG DIRECTIONAL SHEAR. MORE GENERAL SHOWERS AND EMBEDDED
THUNDER WILL BECOME LIKELY THIS MORNING TOWARD I29...BUT SHOULD SEE
THIS COVERAGE DROP OFF AS WAVE PUSHES QUICKLY SOUTHEAST THIS
MORNING. DESPITE WHAT MOST MODELS SHOW...WOULD STILL EXPECT A PERIOD
OF MUCH LESS PRECIPITATION POTENTIAL TO SPREAD FROM NORTHWEST TO
SOUTHEAST BEHIND INITIAL WAVE LATER THIS MORNING AND THROUGH MUCH OF
THE AFTERNOON. WHAT REMAINS IS A MARGINAL THERMODYNAMIC ENVIRONMENT
IN AN AT BEST WEAKLY FORCED ENVIRONMENT. HIGHS AGAIN DIFFICULT WITH
PRECIPITATION/CLOUDS...BUT SHOULD SHAKE OUT FROM SOME LOWER TO MID
70S ALONG MAIN AXIS OF EARLY PRECIP...TO SOME NEAR 80 IN THE FAR
WEST.

THE NEXT WAVE IS A FAIRLY STRONG IMPULSE CLIPPING ALONG THE
INTERNATIONAL BORDER BACK ACROSS NORTHERN WASHINGTON AND IDAHO...
WITH THE LEADING LIFT FORCING FROM THIS WAVE STARTING AS EARLY AS
LATE AFTERNOON IN THE FAR NORTH. INSTABILITY GRADIENT SETTING UP
BETWEEN BETTER HEATED WESTERN AREAS AND MORE CLOUDY AND STABLE EAST
REINFORCED BY DRY AIR ADVECTION INTO THE EASTERN CWA. MAY SEE UP TO
1000 J/KG INSTABILITY SET UP ACROSS THE FAR WEST...WITH PROXIMITY OF
A WEAK LOW LEVEL CONVERGENCE AXIS POTENTIALLY FOCUSING LATE DAY
DEVELOPMENT. THESE STORMS WOULD DRIFT TOWARD NEBRASKA AFTER
FORMATION...AND WOULD AGAIN BRING A THREAT FOR AN ISOLATED
MARGINALLY SEVERE STORM.

THE BULK OF DYNAMICS SLIDE DOWN INTO THE CWA THE LATTER HALF OF THE
NIGHT...AND WILL SEE A GREAT INCREASE IN COVERAGE OF SHOWERS AND
THUNDERSTORMS OVERNIGHT...STRUGGLING TO PRESS TOO FAR EASTWARD INTO
SOUTHWEST MINNESOTA AND NORTHWEST IOWA FOR A TIME.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 413 AM CDT WED JUL 1 2015

WATER VAPOR LOOP EARLY THIS MORNING SHOWING A NICE...COMPACT WAVE
MOVING TOWARDS NORTHERN MONTANA WHICH WILL BE THE ENERGY THAT
IMPACTS THE AREA ON THURSDAY. THE LIFT ALONG AND AHEAD OF THIS WAVE
WILL BRING RAIN AND THUNDERSTORMS BUT UNLIKELY TO BRING SEVERE
THUNDERSTORMS. WILL HAVE THE HIGHEST POPS IN SOUTH DAKOTA AND
NORTHWEST IOWA WHILE THE LOWER POPS WILL BE IN SOUTHWEST MINNESOTA.
IN REALITY A PRETTY GOOD CHANCE FOR MOST LOCATIONS TO GET AT LEAST
SOME RAINFALL SO IF TIMING AND LOCATION OF LATEST PROJECTIONS
REMAINS CONSISTENT WILL PROBABLY NEED TO RAISE POPS IN FUTURE
FORECASTS. DID LOWER HIGHS JUST A BIT AS EXTENSIVE CLOUD COVER AND
PRECIPITATION WILL KEEP THINGS ON THE COOLER SIDE.

THE LIFT WILL GRADUALLY DIMINISH THURSDAY NIGHT AND WILL HAVE THE
CHANCE FOR RAIN SHIFT SOUTHEAST THROUGH THE NIGHT. GRADUAL CLEARING
FROM NORTHWEST TO SOUTHEAST SHOULD ALLOW FOR LOWS IN THE MID 50S TO
LOWER 60S.

FRIDAY SHOULD END UP A FAIRLY NICE DAY WITH LIGHT WINDS AND PARTLY
CLOUDY SKIES. HOWEVER THE AIR MASS IN PLACE NOT REAL WARM SO WILL
MAINLY SEE HIGHS IN THE 70S.

IN THE OUTER PERIODS(SATURDAY THROUGH TUESDAY)...UPPER LEVEL ENERGY
BEGINS TO WORK ONTO THE PLAINS SATURDAY AND WILL MAINTAIN SMALL POPS
IN MAINLY THE WESTERN CWA WHERE THE BETTER INSTABILITY AND LOWER AND
MID LEVEL CONVERGENCE IS EXPECTED. SUNDAY STILL POSES SOME POTENTIAL
FOR SEVERE THUNDERSTORMS AS A WAVE MOVES INTO THE AREA AND A FRONT
SETTLES INTO CENTRAL SD. THIS TIMING IS SIMILAR TO YESTERDAYS MODEL
RUNS AND WITH A STRONG JET MAX MOVING FROM MONTANA INTO NORTH DAKOTA
IN THE AFTERNOON SO NO THOUGHTS THAT IT MIGHT COME THROUGH MORE
QUICKLY. WITH THE JET ENERGY ONLY SLOWLY MOVING ACROSS THE NORTHERN
PLAINS MORE STABLE AIR SHOULD BE IN PLACE ON MONDAY AND TUESDAY SO
LITTLE CHANCE FOR PRECIPITATION DURING THIS TIME AND TEMPERATURES
LIKELY AT OR A LITTLE BELOW NORMAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1241 PM CDT WED JUL 1 2015
ISOLATED SHOWERS MAINLY ALONG AND EAST OF I-29 COULD PRODUCE
TEMPORARY MVFR CONDTIONS AT BOTH KFSD SND KSUX BUT ARE NOT
EXPECTED TO PERSIST LONG ENOUGH TO CONTAIN IN THE TAF. AFTER
21Z...EXPECTED SCATTERED SHOWERS AND STROMS TO DEVELOP WEST OF THE
JAMES. THESE STORMS SHOULD MAINLY REMAIN VFR...BUT COULD DEVELOP
SOME LOWER CEILINGS THROUGH THE NIGHT. WITH ABUNDANT MOISTURE IN
THE NEAR SURFACE LAYER...COULD SEE A STRATUS DECK DEVELOP AROUND
15Z...THOUGH SATURATION APPEARS TO BE QUITE THIN. HAVE THEREFORE
KEPT CONDITIONS VFR THROUGH THE PERIOD.

&&

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

$$

SHORT TERM...CHAPMAN
LONG TERM...08
AVIATION...



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