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000
FXUS63 KFSD 152346
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
646 PM CDT WED MAY 15 2013

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 339 PM CDT WED MAY 15 2013

IN THE NEAR TERM...LAST REMNANTS OF ISOLATED TO LOW END SCATTERED
SHOWERS SHOULD EXIT THE EASTERN ZONES OF OUR FORECAST AREA THROUGH
THE LATE AFTERNOON HOURS. NAM SHOWS DEPARTING SHORT WAVE PER THE MID
AND UPPER QG FORCING...WITH CLOUDS CLEARING UPSTREAM. OTHERWISE FOR
THE REMAINDER OF TONIGHT...MOISTURE FIELDS ARE POINTING TOWARD A
CLEAR TO PARTLY CLOUDY NIGHT. WINDS WILL BE LIGHT WITH A BROAD
EASTERLY FLOW OVER MANY LOCATIONS. THEREFORE TRENDED LOWS TOWARD THE
COOLER GUIDANCE READINGS...NOTING ALSO THE RELATIVE DRY SURFACE
DEW POINTS STILL IN PLACE. ON THURSDAY...WELL ADVERTISED SHORT WAVE
STILL IS PROGGED TO INFLUENCE OUR FORECAST AREA MOVING ACROSS A
QUASI ZONAL UPPER FLOW OF AIR IN THE MID SECTION OF THE COUNTRY.
SATURATION ISSUES REMAIN HEADING EASTWARD INTO OUR EASTERN ZONES.
BUT THE WAVE CERTAINLY INFLUENCES ARE SOUTHERN AND WESTERN ZONES.
BUMPED UP POPS TO THE LIKELY CATEGORY IN THOSE AREAS...AS CURRENT
THOUGHTS ARE THAT THEY MAY RECEIVE A QUARTER INCH OF RAIN OR A
LITTLE MORE DURING THE AFTERNOON HOURS. HIGHS ON THURSDAY ARE A
CHALLENGE DUE TO THE INCREASING THICK CLOUD COVER. THERE WILL BE AN
INCREASINGLY MOIST SOUTHEAST FETCH OF AIR. HOWEVER THE AIR MASS WILL
LIKELY BE TEMPERED BY ABUNDANT CLOUDS. AT THIS POINT CONSENSUS MOS
VALUES LOOKED REASONABLE GIVEN THE GFS AND NAM 850MB TEMPERATURES.
THE COOLEST SPOT WILL LIKELY BE IN OUR SOUTHWEST WHERE TEMPERATURES
COULD STRUGGLE TO GET INTO THE LOWER 70S. CONVERSELY...80 DEGREES OR
MAYBE A BIT WARMER IS A GOOD BET IN THE EASTERN SECTIONS OF
NORTHWEST IOWA.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 339 PM CDT WED MAY 15 2013

ABOVE DISCUSSED SHORT WAVE WILL TRACK ACROSS AREA AND SHOULD
PROVIDE A DECENT ROUND OF SHOWERS AND STORMS THURSDAY NIGHT.
INSTABILITY ALOFT WILL CONTINUE TO INCREASE MODESTLY THROUGH THE
EVENING...AS WILL AVAILABLE MOISTURE EVEN THOUGH MODELS CONTINUE
TO BE TOO FAST RAISING THE DEWPOINTS...AND THE WAVE WILL PROVIDE
SOME LIFT. WIND FIELD WILL NOT INCREASE NEARLY ENOUGH TO
COMPENSATE FOR THE MODERATE NATURE OF OTHER FACTORS SO SEVERE
WEATHER THREAT SEEMS NIL OVER OUR AREA...THE MORE DECENT
INSTABILITY REMAINING TO THE SOUTH. RAINFALL POTENTIAL SEEMS
MODERATE THOUGH FEEL GUIDANCE IS A LITTLE TOO LIGHT. HAVE KEPT 12
HOUR AMOUNTS LESS THAN A HALF INCH FOR NOW WITH SOME HIGH
POPS...THOUGH THESE AMOUNTS MAY HAVE TO BE LIFTED AS THE LIFT FROM
THE WAVE WILL HELP INCREASE THE PRECIPITATION EFFICIENCY. THIS
CONVECTION SHOULD ABATE FRIDAY MORNING AS THE WAVE MOVES TO THE
EAST...WITH THE AMOUNT OF RAIN LEFT FOR FRIDAY MORNING DEPENDENT
ON THE EXACT TIMING OF THE EXIT. OTHERWISE...FRIDAY SHOULD BE A
RELATIVELY QUIET DAY WITH THE ABSENCE OF LIFT THOUGH HAVE LEFT A
LITTLE CHANCE LATER IN THE DAY WEST AND NORTH GIVEN THE MOISTURE
AND INSTABILITY SHOULD STILL BE AROUND.

FRIDAY NIGHT AND SATURDAY SHOULD SEE THE UPPER TROUGH DEVELOPING
OVER THE WESTERN USA APPROACHING BUT MOST OF THE LIFT SHOULD WAIT
UNTIL SATURDAY NIGHT. GIVEN THE STEADY DEVELOPMENT OF A STRONG CAP
FRIDAY NIGHT INTO SATURDAY...CONVECTION SHOULD BE AT A
MINIMUM...THOUGH AGAIN AM LEAVING A LITTLE MENTION WEST AND NORTH
CLOSER TO THE APPROACHING SYSTEM AND ITS BOUNDARIES...IN CASE
SOME SMALL SCALE WAVE POSSIBLY DUE TO CONVECTION MOVES AHEAD OF
THE MAIN SYSTEM...THESE ANIMALS CAN BE IMPOSSIBLE TO TIME UNTIL
THEY ARE ALMOST HERE SINCE THEY WOULD RESULT FROM CONVECTION THAT
WILL NOT EVEN DEVELOP FOR A WHILE. SO...SATURDAY MAY BE A PRETTY
QUIET...DRY...AND EVEN NICE DAY IF WE MAT BE A BIT SUBJECTIVE.
TEMPERATURES DURING THESE PERIODS WILL BE WARMING TO MORE ABOVE
NORMAL AND HUMIDITY WILL COME A LITTLE CLOSER TO
SUMMERLIKE...THOUGH IT IS AGREED THAT MODELS ARE TOO STRONG ON
THAT MOISTURE INCREASE...AGAIN.

THE START OF SIGNIFICANT CONVECTION WILL TAKE ITS TIME BUT MAY GET
GOING WEST LATE SATURDAY...AND GO INTO HIGH COVERAGE SATURDAY NIGHT
AND SUNDAY AS THE TROUGH ACTUALLY MOVES INTO THE AREA. INCREASING
INSTABILITY WILL PROVIDE A RISK OF SEVERE STORMS...WITH TORNADOES
NOT TOO LIKELY AS WIND FIELDS WILL NOT BE THAT EXCITING...AND THIS
WOULD BE MOSTLY SATURDAY NIGHT AND SUNDAY. RAINFALL POTENTIAL
SHOULD INCREASE TO THE POINT WHERE SOME AREAS MAY SEE OVER AN INCH
WITH THE STORMS IN A SHORT TIME...BUT DO NOT SEE THE COPIOUS TWO
TO THREE INCHES IN A SHORT TIME THAT WE MAY SEE A LITTLE LATER IN
THE SPRING OR IN SUMMER. AS THE SYSTEM HANGS AROUND EARLY NEXT
WEEK...THE SHOWER AND STORM POTENTIAL WILL BE SLOW TO
DECREASE...THOUGH WITH THE COOLING LOWER ATMOSPHERE AND WEAKENING
INSTABILITY...ACTIVITY DOES NOT HAVE TO MUCH CHANCE TO BE
EXCITING. TEMPERATURES SHOULD COOL DAY BY DAY EARLY NEXT WEEK
UNTIL THE END OF THE PERIOD...NEXT WEDNESDAY...WHEN DAYTIME
TEMPERATURES SHOULD WARM BACK UP SLIGHTLY AS THE AIR DRIES OUT. BY
WEDNESDAY HAVE RAIN CHANCES DOWN TO SLIGHT CHANCE FOR MOST OF THE
AREA. OVERALL...THESE SEVERAL DAYS HAVE THE POTENTIAL TO BE A WET
PERIOD...NO SURPRISE IN OUR NORMALLY WETTEST MONTH.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 645 PM CDT WED MAY 15 2013

VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. LIGHT NORTHERLY
FLOW WILL TRASITION TO EASTERLY AND INCREASE THROUGHOUT THE DAY ON
THURSDAY. CHANCES OF THUNDERSTORMS WILL INCREASE TOWARDS 00Z
FRIDAY.

&&

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

$$

SHORT TERM...MJF
LONG TERM...
AVIATION...