Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 011944
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
244 PM CDT SUN MAY 1 2016

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 244 PM CDT SUN MAY 1 2016

STILL SEEING A FEW SHOWERS THIS AFTERNOON OVER THE LOWER PORTIONS OF
NORTHWEST IOWA...BUT EXPECT THESE TO DISSIPATE AS WE MOVE TOWARD
EVENING. OTHERWISE...HIGH PRESSURE BEGINS TO SETTLE INTO THE REGION
TONIGHT WITH CLEARING SKIES AND DYING WINDS. THIS WILL RESULT IN A
GENERALLY COOLER NIGHT...WITH TEMPERATURES FALLING BACK TO THE MID
30S TO AROUND 40. CANNOT RULE OUT SOME PATCHY FROST IN LOWER LYING
AREAS OF THE WESTERN HIGHWAY 14 CORRIDOR INTO SOUTH CENTRAL SD. WITH
THE PATCHY NATURE OF THE FROST AM THINKING THAT A HEADLINE WILL NOT
BE NEEDED. THE OTHER THING TO KEEP AN EYE ON TONIGHT WILL BE THE
POSSIBILITY OF FOG DEVELOPING WITH THE LIGHT WINDS AND WET GROUND.
MODEL VISIBILITY GUIDANCE DOES NOT SUGGEST WIDESPREAD FOG OVERNIGHT
SO STAYED WITH PATCHY WORDING...CONFINED TO THE SOUTHEASTERN
PORTIONS OF THE CWA LATE TONIGHT.

ON MONDAY WILL SEE AN INCREASE IN CLOUDS WITH SOME CU DEVELOPMENT
THROUGH THE AFTERNOON...IN ADDITION TO A THICKER CLOUD DECK THROUGH
THE WESTERN JAMES RIVER VALLEY AND SOUTH CENTRAL SD AS AN UPPER
LEVEL SHORTWAVE DROPS SOUTHWARD OUT OF NORTH DAKOTA. THIS FEATURE
WILL RESULT IN THE DEVELOPMENT OF SLIGHT INSTABILITY OVER THAT AREA
IN THE AFTERNOON...AND COULD SEE SOME ISOLATED TO SCATTERED SHOWERS
WITH POSSIBLE RUMBLES OF THUNDER INTO EARLY MONDAY EVENING. THERMAL
PROFILES DO WARM ON MONDAY...AND LOOKING AT HIGHS IN THE LOWER TO
MID 60S ACROSS THE ENTIRE CWA.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 244 PM CDT SUN MAY 1 2016

MONDAY NIGHT INTO TUESDAY WILL SEE THE WEAK UPPER LEVEL WAVE EXIT TO
THE SOUTH LEAVING BEHIND MOSTLY CLEAR SKIES AND LIGHT WINDS.
ISOLATED SHOWERS WILL BE POSSIBLE IN SOUTH CENTRAL SOUTH DAKOTA BUT
ALL SHOULD BE DIURNALLY DRIVEN. LOWS MAINLY 39 TO 44.

WEAK CONVERGENCE AND MARGINAL INSTABILITY OVER MAINLY SOUTHWEST
MINNESOTA TUESDAY AFTERNOON/EVENING AS A WAVE DIVES SOUTH THROUGH
MINNESOTA BUT AT THIS TIME NOT WORTH A MENTION OF ANYTHING.
OTHERWISE AN INCREASE IN NORTHWEST FLOW WILL LEAD TO WINDS OF 10 TO
20 MPH...LIKELY SOME GUSTS AROUND 25 TO 30 MPH. TEMPERATURES WILL BE
MILD WITH HIGHS MAINLY IN THE LOWER TO MID 70S...THE WARMER READINGS
CLOSER TO HIGHWAY 14 JUST AHEAD OF THE WEAK BACK DOOR COOL FRONT.

WEDNESDAY WILL BE COOLER BUT WINDS WILL NOT BE AS STRONG. SHOULD
ALSO SEE A LOT OF SUNSHINE AS HIGH PRESSURE MOVES SOUTHEAST. HIGHS
MAINLY IN THE 60S.

IN THE OUTER PERIODS(THURSDAY THROUGH SUNDAY)...OMEGA BLOCKING
PATTERN IN PLACE THURSDAY WITH THE AREA UNDER THE INFLUENCE OF THE
BACKSIDE OF THE EASTERN TROUGH. HOWEVER THE RIDGING TO THE WEST WILL
GRADUALLY OVERSPREAD THE AREA FRIDAY INTO SATURDAY AND AS WAS
SUSPECTED WITH YESTERDAYS TOO AGGRESSIVE ECMWF...THE MODELS ARE IN
BETTER AGREEMENT IN KEEPING THE WESTERN TROUGH TO THE WEST THROUGH
SATURDAY. THIS SHOULD ALLOW FOR A SUSTAINED SOUTHERLY FLOW IN THE
LOW LEVELS THURSDAY INTO SATURDAY SO EXPECT GRADUALLY WARMING
CONDITIONS AS WELL. RIGHT NOW SATURDAY AFTERNOON INTO SUNDAY IS THE
TRICKY CALL WHEN COOLER LOW LEVEL AIR IS EXPECTED TO DROP SOUTH INTO
NEBRASKA. THIS IS IN RESPONSE TO A NORTHERN STREAM WAVE RIDING THE
RIDGE THROUGH SOUTHERN CANADA INTO THE GREAT LAKES. THE ECMWF IS
STRONGEST AND FASTEST WITH THIS WAVE...THUS BRINGING THE COOLER AIR
TO LOCATIONS NORTH OF INTERSTATE 90 BY MID DAY...WHILE THE GFS IS A
BIT SLOWER AND WOULD ALLOW MORE WARMING TO OCCUR. THE CANADIAN IS
EVEN SLOWER WITH THIS COLDER AIR AND WOULD NOT BRING THE COOLER AIR
SOUTH UNTIL AT LEAST SATURDAY NIGHT. WILL COOL THE NORTHERN CWA A
BIT AND KEEP THE WARMER TEMPERATURES IN THE FAR SOUTH. WHILE THE
THREAT IS TOUGH TO DISCERN FOR THE WEEKEND WITH SOME VARIABILITY IN
THE MODELS...AIMING FOR A LOW END THREAT SATURDAY AND SUNDAY. SOME
OF THIS WILL DEPEND UPON THE OUTCOME OF THE NORTHERN STREAM WAVE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1207 PM CDT SUN MAY 1 2016

VFR CONDITIONS WILL LINGER AROUND KSUX INTO MID AFTERNOON WITH
SHOWER CHANCES CONTINUING. OTHERWISE...MAINLY VFR CONDITIONS
EXPECTED THROUGH THE TAF PERIOD. THE EXCEPTION WILL BE TONIGHT
WHEN WINDS WILL GO LIGHT AND WITH WET GROUND THERE IS A
POSSIBILITY OF FOG DEVELOPMENT...THOUGH MODEL GUIDANCE IS NOT
SUGGESTING WIDESPREAD FOG DEVELOPMENT.

&&

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

$$

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



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