Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KFSD 202033
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
333 PM CDT WED AUG 20 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 331 PM CDT WED AUG 20 2014

PLENTY OF COMPLEX INTERACTIONS ARE OCCURRING WITH THE CURRENT
SITUATION. FIRST OF ALL...A MID LEVEL SHORT WAVE FOCUSED NEAR 700MB
AND AN ELEVATED WARM FRONT...HAS CONTINUALLY SPARKED ELEVATED
CONVECTION IN OUR SOUTHERN ZONES...GREATLY STABILIZING THE
ATMOSPHERE THROUGH OUR SOUTHERN AND EASTERN ZONES. SYNOPTICALLY...
THE MAIN SHORT WAVE LIFTS TO THE NORTHEAST...WELL WEST AND NORTH OF
OUR FORECAST AREA. ONE WARM FRONT SETS UP SHOP FOR MUCH OF THE NIGHT
GENERALLY FROM THE SHORT WAVE IN NORTH DAKOTA...SOUTHEASTWARD
THROUGH NORTHEAST SD AND INTO THE NORTHERN PARTS OF SOUTHWEST MN. TO
THE SOUTH...A SECOND AND PRIMARY WARM FRONT EXISTS TO THE SOUTH OF
THE CONVECTION IN NEBRASKA...WHERE SOUTHERN NEBRASKA IS CURRENTLY IN
THE 90S...AND ONLY MID 70S IN SIOUX CITY. CURRENT THOUGHTS ARE THAT
WHEN THE SOUTHERN WARM FRONT LIFTS INTO OUR MO RIVER VALLEY ZONES
THIS EVENING...THAT THE PORTION OF IT ROUGHLY FROM YANKTON...TO
SIOUX CITY AND STORM LAKE MAY BE CAPPED OFF DUE TO THE ONGOING
STABILITY. THEREFORE AM INITIALLY FOCUSING ON THE WESTERN PORTION OF
THE WARM FRONT NEAR OUR SOUTH CENTRAL SD ZONES FOR A POTENTIAL FOR
SEVERE WEATHER THIS EVENING...COUPLED WITH SURFACE LOW PRESSURE A
BIT FURTHER WEST. IT APPEARS MORE AND MORE THAT THE STORMS MAY HAVE
A DIFFICULT TIME GETTING TIED TO THE SURFACE OR BOUNDARY LAYER...
LOWERING OUR CHANCES FOR TORNADIC ACTIVITY. BUT IF STORMS WERE TO
BECOME BASED CLOSE TO THE SURFACE...IT WOULD LIKELY HAPPEN TOWARD
SOUTH CENTRAL SD WHERE INSTABILITY TO OUR WEST MEETS OUR HUMID AIR
AROUND CHAMBERLAIN. BELIEVE THIS IS THE LOCATION WHERE AN ISOLATED
TORNADO COULD FORM THIS EVENING. LARGE HAIL IS ALSO CERTAINLY A
THREAT WITH ENHANCED UPDRAFTS...ESPECIALLY IN OUR WESTERN ZONES THIS
EVENING WHERE GREATER INSTABILITY EXISTS...AND ALONG THE NORTHERN
WIND SHIFT IN OUR NORTHERN ZONES AND SOUTHWEST MN LATER TONIGHT. IN
EXTREME SOUTHEAST SD SOUTH OF SIOUX FALLS...AS WELL AS MOST OF
NORTHWEST IA AND EXTREME NORTHEAST NEB...SEVERE CHANCES MAY BE REAL
TOUGH TO REALIZE DUE TO THE CURRENT STABILITY...AND THEIR FAR
PROXIMITY FROM THE MAIN SHORT WAVE.

LATER...SOME STRATUS MAY DEVELOP DUE TO SOME GUIDANCE FROM THE
LATEST 12KM NAM IN OUR NORTHERN ZONES AND INTO SOUTHWEST MN...BUT SO
FAR LEFT FOG OUT OF THE GRIDS. BUT JUST A HEADS UP THAT FOG COULD
DEVELOP IN THE VERY MOIST AIR GENERALLY ALONG AND NORTH OF I 90.
SKIES WILL GENERALLY CLEAR THURSDAY MORNING. BY THURSDAY AFTERNOON...
WOULD NOT BE SURPRISED TO SEE AN ISOLATED THUNDERSTORM FROM SIOUX
CITY NORTHEASTWARD IN FRONT OF A SLOWLY ADVANCING SURFACE WIND
SHIFT. AND IT REMAINS VERY HUMID IN OUR EASTERN ZONES SO IT WILL NOT
TAKE MUCH OF A FOCUS TO FIRE OFF A FEW STORMS. IN ADDITION...THE
SIOUX CITY AREA WILL PRESS HEAT INDEX CRITERIA FOR A COUPLE OF HOURS
THURSDAY AFTERNOON...WITH A LOT OF 95 TO 100 DEGREE HEAT INDEX
READINGS THROUGHOUT NORTHWEST IA AND SOUTHEAST SD.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 331 PM CDT WED AUG 20 2014

ANTICIPATE MOST OF THE AREA REMAINING DRY ON THURSDAY NIGHT...THOUGH
WITH A LINGERING BOUNDARY LOCATED ROUGHLY THROUGH THE SIOUX CITY TO
SPENCER CORRIDOR CANNOT RULE OUT AN ISOLATED THUNDERSTORM EARLY IN
THE NIGHT OVER OUR LOWER NORTHWESTERN IOWA ZONES. IT WILL BE A MILD
AND RELATIVELY MUGGY NIGHT WITH LOWS IN THE MID AND UPPER 60S.

ON FRIDAY WILL SEE INCREASING CHANCES OF THUNDERSTORMS...BECOMING
LIKELY BY FRIDAY NIGHT...AS LOW PRESSURE DEEPENS OVER THE WEST
CENTRAL PLAINS AND LIFTS NORTHWARD...AND SYNOPTIC LIFT INCREASES
ACROSS THE REGION AS A SHORTWAVE EJECTS OUT OF A WESTERN U.S. UPPER
LEVEL TROUGH. DOES APPEAR TO BE PLENTY ENOUGH INSTABILITY AND SHEAR
AROUND THAT SEVERE STORMS WILL AGAIN BE A POSSIBILITY IN THE LATER
AFTERNOON AND EVENING. APPARENT TEMPERATURES WILL BE RATHER
UNPLEASANT FOR FRIDAY AFTERNOON...WITH HIGHS IN THE MID AND UPPER
80S AND DEWPOINTS MAINLY LOWER AND MID 70S...CREATING A HEAT INDEX
OF LOWER TO MID 90S SOUTH OF INTERSTATE 90. THUNDERSTORM CHANCES
THEN CONTINUE SATURDAY INTO AT LEAST EARLY ON SUNDAY AS THE
AFOREMENTIONED LOW PRESSURE AND ASSOCIATED WARM FRONT LIFT UP INTO
OUR AREA...THOUGH THERE ARE SOME MODEL DIFFERENCES ON HOW THIS PLAYS
OUT EXACTLY.

WITH THE PASSAGE OF THE ABOVE MENTIONED SHORTWAVE...COOLER AIR LOOKS
TO FILTER INTO THE REGION...WITH BELOW NORMAL TEMPERATURES FOR
MONDAY THROUGH WEDNESDAY. MONDAY MAY END UP BEING MOSTLY
DRY...THOUGH MODEL CONSENSUS WOULD IMPLY BETTER PRECIPITATION CHANCES
FOR TUESDAY AND WEDNESDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1253 PM CDT WED AUG 20 2014

FOR STARTERS...VERY COMPLEX PATTERN IS NOT LENDING A LOT OF
CONFIDENCE TO THE 18Z TAFS. THE PRIMARY WARM FRONT IS STILL WELL
SOUTH OF OUR FORECAST AREA AT THIS TIME...WITH AN ELEVATED WARM
FRONT CONTINUING TO LIFT NORTHWARD. CONVECTION IS CURRENTLY FIRING
ALONG THE ELEVATED WARM FRONT...COUPLED WITH A SHORT WAVE NEAR
700MB ALONG OUR MO RIVER VALLEY ZONES. THOUGHTS ARE THAT THIS
ACTIVITY WILL LIFT NORTHEASTWARD THROUGH THE AFTERNOON. THEREFORE
PUT IN A CHANCE FOR THUNDERSTORMS FOR THE SIOUX FALLS TAF SITE VERY
LATE THIS AFTERNOON AND VERY EARLY IN THE EVENING...BASED ON THE
TIMING OF THE ELEVATED WARM FRONTAL PASSAGE. DYNAMICS SHOULD BE
COMING TO A CLOSE AROUND SIOUX CITY BY MID AFTERNOON AS THE
ELEVATED WARM FRONT LIFTS NORTHWARD. THEREFORE ENDED THE PRECIP
THREAT FOR SIOUX CITY BY THAT TIME. AS THE PRIMARY UPPER SHORT
WAVE LIFTS THROUGH NORTHERN SD AND NORTH DAKOTA THIS EVENING...
CONTINUED TO PLACE THUNDERSTORM CHANCES FOR THE KHON TAF SITE
DURING THE EVENING HOURS. BUT FURTHER SOUTH...THERE COULD BE A
BREAK IN THE KFSD TAF SITE AFTER EARLY EVENING UNTIL THE OVERNIGHT
HOURS. RIGHT DURING THE MIDDLE OF THE NIGHT...AS THE MAIN SHORT
WAVE LIFTS NORTH OF KFSD...THERE COULD BE A PERIOD OF SHOWERS AND
STORMS WHICH WERE MENTIONED IN THE KFSD TAF ASSOCIATED WITH THE
MAIN WAVE IN NORTHERN SD...AS CONVECTION COULD DEVELOP SOUTHWARD
INTO A STOUT LOW LEVEL JET. BUT KSUX MAY BE TOO FAR SOUTH FOR
NOCTURNAL ACTIVITY TONIGHT...OR AT LEAST LESS CONFIDENT OF
CONVECTION...SO LEFT KSUX DRY FOR TONIGHT.

LASTLY...THE LATEST HIRES NAM IS HINTING AT STRATUS DEVELOPMENT
FOR KHON AND KFSD LATE TONIGHT AND EARLY THURSDAY BEHIND THE SHORT
WAVE DEPARTURE. IF RAIN PANS OUT TONIGHT...THIS IS A DISTINCT
POSSIBILITY AS WINDS ARE LIGHT WITH RESIDUAL MOISTURE LINGERING.
FOR NOW...HEDGED MVFR CONDITIONS FOR THOSE TWO LOCATIONS FOR THIS
POSSIBILITY.


&&

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

$$

SHORT TERM...MJ
LONG TERM...JM
AVIATION...MJ






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.