Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 241147
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
647 AM CDT THU JUL 24 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 420 AM CDT THU JUL 24 2014

FAIRLY SHARP RIDGE WITH AXIS JUST EAST OF THE ROCKIES EARLY THIS
MORNING. ON WATER VAPOR LOOP...CAN SEE SEVERAL WAVES ROTATING
THROUGH THE RIDGE...ALL RIDING ON THE EDGE OF A FAIRLY STRONG MID
LEVEL FRONTAL BOUNDARY. STRONGEST WAVE BACK OVER PAC NW...BUT ONE
NICE WAVE PUSHING FROM ERN MT INTO WRN ND.  PATCHY CLOUDS IN THE
9-10 KFT RANGE HAVE DEVELOPED FROM SOUTH CENTRAL ND TOWARD
SOUTHEASTERN SD...AND INCREASING LOW LEVEL JET WINDS ON MRR
PROFILER.  ALL RECENT RUNS OF HRRR AND WRF-ARW HAVE BEEN FAIRLY
INSISTENT ON DEVELOPMENT OF CONVECTION OVER THE NEXT COUPLE HOURS
FROM 09Z-11Z OUT FROM THE JAMES VALLEY WESTWARD...AND MOST SOLUTION
HAVE AT LEAST SOME DEVELOPMENT OCCURRING THIS MORNING. GIVEN A DECENT
MID LEVEL THETA E ADVECTION FOCUS...AND MID LEVEL FRONTOGENETIC
AXIS...SEEMS WOULD BE FAVORED FOR A FEW STORMS DEVELOPING THIS
MORNING. HOWEVER...WILL BE INCREASINGLY DIFFICULT FOR ACTIVITY TO
BUILD EASTWARD AS FORCING WITH WEAK MID LEVEL WAVES DROPS SOUTHEAST

MOST LIKELY LOCATION FOR CONVECTION LOOKS TO BE THE MID TO SOUTHERN
JAMES VALLEY THEN SOUTHEAST TOWARD KSUX AREA DURING THE MORNING
HOURS. BY AFTERNOON...CONTINUED BUILDING HEIGHTS AND WARMING TEMPS
ALOFT AS WAVE MOVES PAST WILL START TO WEAR ON CONVECTIVE THREAT
WITH COVERAGE EXPECTED TO DWINDLE AS BUILDS EAST.

WITH ELEVATED INSTABILITY PERHAPS AS HIGH AS 1000 J/KG AND 2-6KM
SHEAR OF 30-40 KNOTS...POTENTIAL IS THERE FOR SOME ORGANIZED STORM
DEVELOPMENT AND UPDRAFT HELICITY ON HRRR INDICATES SOME NEED FOR
CONCERN FOR MARGINALLY SEVERE HAIL WITH ANY STRONGER STORMS THROUGH
AT LEAST MID TO LATE MORNING.

A PRETTY SHARP GRADIENT WILL AGAIN TODAY BE PRESENT BETWEEN WARM AND
HUMID LESS MIXED CONDITIONS...WITH A HOT...DRY...AND MORE MIXED
AIRMASS... LIKELY TO REMAIN JUST WEST OF THE CWA. HAVE RAISED TEMPS
MANY AREAS BY A COUPLE DEGREES...WITH MAINLY 80S...BUT SOME UPPER
70S IN MORE PERSISTENT CLOUDS/POTENTIAL PRECIP AXIS. HAVE LOWER 90S
CRAWLING BACK INTO THE WEST...AND WITH RECENT DRY CONDITIONS AND
WINDS GUSTING 25 TO 35 MPH...WILL START TO BRING A BIT MORE CONCERN
TO FIRE BEHAVIOR...BUT STARTS WILL STILL BE VERY DIFFICULT WITH
DEWPOINTS IN THE MID TO UPPER 60S HOLDING BACK TO LOWER BRULE AREA.

NOT BUYING IN TO DEVELOPMENT OF COMPLEX OF STORMS TONIGHT ACROSS
SOUTHEAST SOUTH DAKOTA...WHICH WOULD ALMOST REQUIRE THAT DEVELOPMENT
TO STORMS OCCURS BACK TO THE WEST WHERE TERRAIN/CONVERGENCE WOULD
HAVE A BETTER CHANCE TO OVERCOME THE MASSIVE WARM LAYER ALOFT /+15
TO +16 C AT 700 HPA/ BY EVENING. RETAINED A LOW POPS DURING THE
EVENING IN THE EVENT OF OUTSIDE CHANCE DEVELOPMENT CAN EVOLVE TOWARD
MORE ELEVATED AS SPREADS EAST. A MUCH BETTER CHANCE THAT A MORE
ORGANIZED COMPLEX WILL TAKE SHAPE JUST NORTH AND EAST OF THE CWA...
WITHIN WARM ADVECTION ZONE AHEAD OF LOW PRESSURE PUSHING INTO THE
EASTERN DAKOTAS...WITH PERHAPS A SCATTERED TO LOW LIKELY CHANCE BY
LATER EVENING AND EARLY OVERNIGHT IN EASTERN PARTS OF SW MN/NW IA.
FAIRLY SOUTH SOUTHERLY GRADIENT AND VERY WARM AIRMASS WAS CONVINCING
ENOUGH TO RAISE OVERNIGHT LOWS A FEW DEGREES.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 420 AM CDT THU JUL 24 2014

EXPECT CONVECTIVE ACTIVITY TO PRETTY MUCH BE EAST OF OUR CWA AFTER
12Z FRIDAY. SHOULD THUS BE A PARTLY TO MOSTLY SUNNY SKY...WITH JUST
SOME CUMULUS POSSIBLE. WILL HAVE QUITE A BIT OF INSTABILITY...BUT A
STRONG INVERSION ALOFT WILL KEEP US CAPPED. MODEL THERMAL FIELDS
HAVE A DECENT SPREAD...BUT OVERALL HAVE SHOWN A WARMING TREND ON
RECENT RUNS. A BIT CONCERNED THAT THE STRONG INVERSION ALOFT AND
DECENT LOW LEVEL MOISTURE OF 60S AND 70S DEWPOINTS...WILL PREVENT US
FROM FULLY MIXING...ESPECIALLY ACROSS OUR EASTERN AREAS. SO DID GO
AHEAD AND WARM HIGHS A FEW DEGREES ACROSS THE BOARD INTO THE MID 80S
AND LOW 90S...BUT DID NOT GO TOO EXTREME YET. WILL HAVE TO MONITOR
THOUGH...AS FULL MIXING WOULD RESULT IN HIGHS A FEW DEGREES WARMER
THAN CURRENTLY FORECAST. THIS SEEMS MOST PROBABLE WEST OF INTERSTATE
29...AND THINKING WE MAY NEED TO WARM THAT AREA UP ON FUTURE
FORECASTS IF TRENDS CONTINUE.

CONVECTIVE ACTIVITY MAY BECOME MORE ACTIVE FRIDAY NIGHT INTO
SATURDAY MORNING. A STRONG MID AND UPPER JET WILL PUSH ACROSS THE
NORTHERN PLAINS...ACCOMPANIED BY PRETTY GOOD PV ADVECTION AS WELL.
THIS LARGE SCALE FORCING WILL INTERACT WITH A LOW LEVEL BOUNDARY AND
EASTERLY UPSLOPE FLOW ACROSS CENTRAL SOUTH DAKOTA. THUS THINKING IS
WE MAY SEE AN AREA OF ELEVATED CONVECTION FORM...WITH STORM MOTIONS
TAKING THIS ACTIVITY EAST SOUTHEAST INTO OUR CWA. ACTUALLY PRETTY
GOOD AGREEMENT BETWEEN THE ECMWF...NAM AND SREF ON THIS SOLUTION.
GFS IS A DRY OUTLIER...AND SEEMS TO REPRESENT A LESS LIKELY
SOLUTION. THUS DID GO AHEAD AND INCREASE POPS...MOVING INTO SOUTH
CENTRAL SOUTH DAKOTA AFTER MIDNIGHT...PUSHING TOWARDS THE INTERSTATE
29 CORRIDOR THROUGH THE MORNING. AMOUNT OF INSTABILITY AVAILABLE TO
THIS ELEVATED PARCEL REMAINS UNCERTAIN...BUT COULD END UP AROUND OR
JUST ABOVE 1000 J/KG. GIVEN THE STRONG JET...SPEED SHEAR SHOULD BE
PRETTY GOOD. THUS SHOULD STORMS FORM...AT LEAST SOME SEVERE HAIL
THREAT WOULD SEEM TO EXIST...POSSIBLY A WIND THREAT TOO WITH THE DRY
SUB CLOUD LAYER POSSIBLY HELPING ORGANIZE STORMS ALONG AN OUTFLOW.
THESE ELEVATED NOCTURNAL THUNDERSTORMS ARE TOUGH TO
FORECAST...THUS CONFIDENCE ON EVOLUTION REMAINS LOW...BUT
SOMETHING TO KEEP AN EYE ON.

EXPECT ANY CONVECTION WOULD EXIT THE AREA BY AFTERNOON...GIVING WAY
TO PARTLY TO MOSTLY SUNNY SKIES. TEMPERATURE FORECAST PROBABLY A BIT
LOWER CONFIDENCE THAN NORMAL DUE TO DIFFERENCES IN HOW MODELS HANDLE
MORNING CONVECTION AND DEBRIS CLOUDS. FOR NOW STAYED NEAR CONSENSUS
OF LOW TO MID 80S...BUT WOULD EXPECT ADJUSTMENTS UP OR DOWN A FEW
DEGREES MAY VERY WELL BE NEEDED AS WE GET CLOSER. A STRONG UPPER
WAVE WILL DIVE SOUTHEAST OUT OF CANADA INTO THE GREAT LAKES
REGION...PUSHING A COLD FRONT THROUGH OUR AREA BY SUNDAY. THIS WILL
RESULT IN A COOLER END TO THE WEEKEND. LOOKING AT MID 70S TO AROUND
80 ON SUNDAY...WITH BLUSTERY NORTHWESTERLY WINDS GUSTING AROUND 30
MPH.

THIS COOLER AND DRIER AIR IS EXPECTED TO CONTINUE INTO THE MIDDLE OF
NEXT WEEK AS THE PATTERN BECOMES MORE STAGNANT...WITH A DEEP TROUGH
OVER THE EASTERN USA AND RIDGE OVER THE WEST. APPEARS WE WILL STAY
ON THE COOLER SIDE OF THINGS...WITH THE RIDGING UNABLE TO BUILD FAR
ENOUGH EAST. THUS TEMPERATURES SHOULD STAY SEVERAL DEGREES BELOW
NORMAL THROUGH MID WEEK...WITH HIGHS IN THE 70S AND 80S AND LOWS IN
THE 50S AND 60S. NOT MUCH FORCING...BUT MOISTURE INCREASES
ENOUGH...THAT COMBINED WITH THE COOL TEMPERATURES ALOFT...WE MAY BE
ABLE TO GENERATE ENOUGH INSTABILITY FOR A FEW DIURNALLY DRIVEN SHOWERS
AND STORMS BY WEDNESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 646 AM CDT THU JUL 24 2014

AN AREA OF SCATTERED THUNDERSTORMS WILL PUSH OUT OF THE KHON AREA
BY 13Z-14Z...AND MOVE TO IMPACT THE KFSD AND KSUX TAF SITE LATER
ON IN THE MORNING BETWEEN 13Z-17Z. A HEAVIER CORE IN STORMS WILL
LIKELY TAKE VISIBILITY TO MVFR...OTHERWISE VFR CONDITIONS ARE
EXPECTED WITH THE HIGH BASED STORMS. A FEW STORMS MAY ALSO PRODUCE
SOME SMALL HAIL. SURFACE SOUTHEAST TO SOUTH WINDS WILL INCREASE
AND WILL RESULT IN SOME STRONGER WIND GUSTS ABOVE 25 KNOTS DURING
THE MIDDAY AND AFTERNOON HOURS. IF WINDS DECOUPLE MORE THAN
EXPECTED TONIGHT...THERE COULD BE SOME LOW LEVEL WIND SHEAR FOR
KFSD OR KSUX. ANOTHER ELEMENT TO WATCH IS THE HIGH MOISTURE
CONTENT OF THE AIR...WHICH MAY ALSO LEAD TO A POTENTIAL FOR A
BRIEF PERIOD OF MVFR VISIBILITIES AROUND KSUX OF KFSD LATE.

&&

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

$$

SHORT TERM...CHAPMAN
LONG TERM...CHENARD
AVIATION...CHAPMAN





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