Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 181709
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1209 PM CDT MON AUG 18 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 405 AM CDT MON AUG 18 2014

OVERNIGHT CONVECTION NEVER REALLY GOT GOING AS A COMPLEX ACROSS
NEBRASKA LIKELY DIVERTED FLOW AND STOLE THE SHOW. HOWEVER A WAVE
OVER SOUTHERN CANADA WILL DROP SOUTHEAST AND SWING A COOL FRONT
THROUGH THE AREA THIS AFTERNOON. THIS SHOULD KEEP A CHANCE FOR
THUNDERSTORMS OVER MAINLY THE EASTERN CWA. A DECENT AXIS OF
INSTABILITY IN THE FORM OF CAPE VALUES AROUND 2000 J/KG SHOULD
EXTEND NORTH FROM ABOUT SIOUX CITY TOWARDS JACKSON LATE THIS
AFTERNOON. ALONG AND EAST OF THIS LINE A COUPLE OF STORMS COULD COME
CLOSE TO REACHING SEVERE LIMITS. THE THREAT WILL LIKELY END QUICKLY
IN THE EVENING AS THE BOUNDARY MOVES THROUGH.

THIS WILL LEAD TOWARDS A QUIET OVERNIGHT PERIOD AS DRIER AIR FILTERS
IN AND NORTHWEST WINDS GRADUALLY DECREASE TO 5 TO 10 MPH. LOWS
SHOULD MAINLY BE IN THE UPPER 50S TO LOWER 60S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 405 AM CDT MON AUG 18 2014

TUESDAY SHOULD END UP BEING A PRETTY NICE DAY ACROSS THE AREA.
SHORTWAVE RIDGING BEHIND THE DEPARTING WAVE WILL LEAD TO SUBSIDENCE
ALOFT AND A PARTLY TO MOSTLY SUNNY DAY. LOOKING AT HIGHS MAINLY IN
THE LOW TO MID 80S. HUMIDITY WILL BE LOWER...BUT STILL A BIT ON THE
HIGHER SIDE WITH DEWPOINTS IN THE LOW TO MID 60S. RETURN FLOW
ALREADY BEGINS TO INCREASE TUESDAY NIGHT...WITH INCREASING MOISTURE
AND ISENTROPIC LIFT ACCOMPANYING IT. THUS LOOKS LIKE WE SHOULD SEE
SCATTERED ELEVATED CONVECTION BREAK OUT LATER TUESDAY NIGHT...MAINLY
FOCUSED ACROSS THE SOUTHWEST HALF OF THE AREA.

THIS MID LEVEL ISENTROPIC LIFT WILL CONTINUE INTO THE DAY
WEDNESDAY...WITH A DECENT WAVE APPROACHING THE REGION AS WELL. THUS
MAKES SENSE THAT MID LEVEL CLOUDINESS AND SCATTERED SHOWERS AND
STORMS WILL CONTINUE INTO WEDNESDAY. THE UPPER WAVE WILL ALSO DRAG A
COLD FRONT ACROSS THE AREA LATER IN THE DAY INTO THE OVERNIGHT. THIS
COMBINED WITH THE INCREASING LOW LEVEL JET MAY INCREASE COVERAGE OF
CONVECTIVE ACTIVITY WEDNESDAY NIGHT. AT THIS POINT SEEMS LIKE MOST
OF THE STORMS WILL BE ELEVATED...WHICH WOULD LIMIT THE SEVERE
THREAT. HOWEVER IF WE GET ENOUGH SUN DURING THE DAY AND STORMS
BECOME BASED NEAR THE SURFACE...THERE COULD BE A SEVERE THREAT AS
THERE WILL BE GOOD TURNING OF THE WINDS WITH HEIGHT RESULTING IN
DECENT SHEAR. SO SOMETHING TO KEEP AN EYE ON. WEDNESDAY WILL BE A
WARM AND HUMID DAY AS WELL...WITH HIGHS DEPENDENT ON CLOUD
COVER...BUT LOOKING LIKE 80S. LOOKING AT A GOOD CHANCE OF SEEING A
DRY THURSDAY BEHIND THIS WAVE. AND WITH WARMING TEMPERATURES
ALOFT...SHOULD BE LOOKING AT MID TO UPPER 80S MOST LOCATIONS.

FORECAST UNCERTAINTY INCREASES THURSDAY NIGHT INTO THE COMING
WEEKEND. THE RIDGE AXIS WILL PUSH EAST OF OUR AREA...WITH QUITE A
BIT OF ENERGY ENTERING THE WESTERN PORTION OF THE COUNTRY. MODELS
SEEM TO BE COMING INTO AGREEMENT THAT ONE WAVE WILL DRAG A FRONT
THROUGH SOMETIME FRIDAY INTO FRIDAY NIGHT...WITH ANOTHER WAVE
PUSHING ACROSS SOMETIME OVER THE WEEKEND. SO FOR NOW WILL KEEP THE
HIGHEST POPS FRIDAY INTO FRIDAY NIGHT...AND LOWER POPS OVER THE
WEEKEND GIVEN TIMING UNCERTAINTY. PROBABLY WILL BE DEALING WITH A
DECENT AMOUNT OF MID LEVEL CLOUDS AND ELEVATED STORMS IN THIS
PATTERN MAKING HIGHS TRICKY. FOR NOW WILL STICK NEAR CONSENSUS
RESULTING IN 80S MOST SPOTS...POSSIBLY BRIEFLY COOLING INTO THE 70
SOMETIME LATER THIS WEEKEND OR EARLY NEXT WEEK. DEEP LAYER SHEAR
WILL BE STRONGER FRIDAY INTO THE WEEKEND WHICH WOULD SUPPORT A
POTENTIAL SEVERE THREAT SOMETIME DURING THE PERIOD. QUESTION
BECOMES WHETHER WE CAN GET SURFACE BASED CONVECTION OR WHETHER
STORMS WILL STAY ELEVATED ABOVE THE BEST SHEAR. SO WILL JUST NEED TO
MONITOR AND FINE TUNE ANY THREATS AS WE GET CLOSER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1203 PM CDT MON AUG 18 2014

ISOLATED TO SCATTERED CONVECTION IS EXPECTED TO DEVELOP MAINLY
EAST OF INTERSTATE 29 THIS AFTERNOON...WITH TAF SITES MOST LIKELY
NOT AFFECTED. OTHERWISE...VFR CONDITIONS THROUGH THE TAF PERIOD.

&&

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

$$

SHORT TERM...08
LONG TERM...CHENARD
AVIATION...JM





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