Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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506
FXUS63 KFSD 170354
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1054 PM CDT SAT MAY 16 2015

.UPDATE...
ISSUED AT 935 PM CDT SAT MAY 16 2015

WENT AHEAD AND TWEAKED THE POPS BASED ON A BLEND OF THE HRRR AND
LATEST 00Z NAM FOR THE REST OF TONIGHT AND ALSO FOR SUNDAY DAY
PERIOD. A LULL IN THE ACTION IS GREETING THE FORECAST AREA AT THIS
TIME...AND THIS TREND WILL LIKELY REMAIN THIS WAY FOR THE REST OF
THE EVENING. HOWEVER AFTER MIDNIGHT AND SUNDAY MORNING...THE HRRR
AND NAM12 ARE BOTH IN VERY GOOD AGREEMENT IN BRINGING ANOTHER
ROUND OF RAINFALL NORTHWARD FIRST INTO OUR EASTERN ZONES...THEN
TAILING BACK WESTWARD IN A COMMA HEAD SHAPE FOLLOWING THE MID
LEVEL TROWALING AHEAD OF THE UPPER AND SURFACE LOW. THIS SEEMS
VERY REASONABLE SO HOOKED ONTO THOSE SOLUTIONS...AND THE BLOB OF
RAINFALL IN EASTERN KS MOVING INTO EXTREME SOUTHEAST NEB IS
CERTAINLY HARD TO IGNORE. THE RAINFALL SHOULD EVENTUALLY
RETROGRADE BACK INTO OUR WESTERN ZONES VERY LATE TONIGHT AND
SUNDAY MORNING WHERE SOME BENEFICIAL RAINFALL SHOULD OCCUR. DOUBT
THERE WILL MUCH IN THE WAY OF SEVERE WEATHER IF ANY AT ALL DUE TO
A PERSISTENT LACK OF DIRECTIONAL WIND SHEAR AND ALSO A LOSS OF LOW
LEVEL HEATING AS THE NIGHT PROGRESSES.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 310 PM CDT SAT MAY 16 2015

JET MAX LIFTING NORTH OVER THE WESTERN HIGH PLAINS WILL SWING THE
ENTRANCE REGION THROUGH THE AREA LATE THIS AFTERNOON. A SMALL
MCV/WEAK WAVE IS LIFTING NORTH THROUGH THE WESTERN CWA THIS
AFTERNOON. ISOLATED THUNDERSTORMS HAVE DEVELOPED WITHIN AND AHEAD OF
THIS FEATURE AND TO THE SOUTH OF IT LITTLE IF ANYTHING IS OCCURRING.
THIS TENDS TO MAKE SENSE AS THERE IS LITTLE TO NO CONVERGENCE BEHIND
THIS WEAK FEATURE. SO WILL CONTINUE TO BACK OFF OF POPS THROUGH THE
AFTERNOON AND EVENING. SO...EXPECT A BETTER CHANCE TO THE WEST OF
OUR AREA AND OF COURSE TO THE SOUTH. THE ACTIVITY TO THE SOUTH WILL
BE THE MOST IMPORTANT TO WATCH AS THAT WILL LIKELY ADVECT/DEVELOP
NORTH THROUGH THE EVENING. AGAIN...INSTABILITY MARGINAL SO QUARTERS
TO MAYBE HALF DOLLARS WILL BE THE MAIN THREAT. WILL ALSO NEED TO
WATCH FOR A SMALL CHANCE FOR SOME FLASH FLOODING...ESPECIALLY FAR
SOUTHEAST SD...NORTHWEST IA AND SOUTHWEST MN WHERE HEAVY RAIN HAS
FALLEN AS OF LATE AND OR THE MODELS ARE HINTING AT SOME HIGHER
RAINFALL POTENTIAL. THE 3 HOUR FLASH FLOOD GUIDANCE IN THESE
LOCATIONS RUNNING GENERALLY LESS THAN 2 INCHES.

DRY SLOT SWINGS NORTH LATE TONIGHT INTO SUNDAY MORNING WITH RAIN AND
ISOLATED THUNDERSTORMS EXPECTED TO CONTINUE IN THE NORTHERN AND
WESTERN CWA. AS THE LOW PRESSURE WRAPS UP AND SHIFTS EASTWARD A COLD
FRONT AT THE SURFACE WILL WORK EAST KEEPING HIGHS IN CHECK OVER THE
WESTERN CWA. LOWS TONIGHT MAINLY UPPER 50S TO LOWER 60S WITH HIGHS
SUNDAY RANGING FROM THE MID 60S IN CENTRAL SD TO THE MID 70S IN
NORTHWEST IOWA.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 310 PM CDT SAT MAY 16 2015

COOL AND BREEZY CONDITIONS ARE EXPECTED TO BEGIN THE PERIOD AS LOW
PRESSURE CONTINUES TO LIFT OFF TO THE NORTHEAST AND STRONG
NORTHWESTERLY WINDS DRAW UNSEASONABLY COOL AIR INTO THE REGION.  850
HPA TEMPS TUMBLE THROUGHOUT THE NIGHT AND REMAIN NEAR ZERO DURING
THE DAY ON MONDAY. 12Z ECMWF HAS WARMED SLIGHTLY OVER THE 00Z
RUNS...BUT WITH LINGERING CLOUD COVER....SHOULD BE A COOL DAY ACROSS
THE AREA.

AS WINDS DROP OFF MONDAY NIGHT WILL NEED TO KEEP AN EYE ON THE
FROST/FREEZE POTENTIAL.  WITH DRY AIR MASS AND LIGHT WINDS...EXPECT
TEMPERATURES TO FALL WITHIN A FEW DEGREES OF FREEZING.

COOL TEMPERATURES CONTINUE TUESDAY INTO WEDNESDAY. MODELS SHOW A
UPPER LEVEL LOW SHEARING OUT AND MOVING ACROSS THE AREA.  NOT MUCH
IN THE WAY TO WORK WITH MOISTURE WISE...AND HAVE CUT BACK POPS ALONG
WITH THUNDER MENTION.

COOL TEMPERATURES CONTINUE THROUGH THE END OF THE WEEK WITH A MORE
ACTIVE PATTERN POTENTIALLY FOR THE WEEKEND AS LARGE UPPER LEVEL
TROUGH ACROSS THE WEST SHIFTS EAST.  WITH ONGOING WEATHER
CONCERNS...KEPT FORECAST FAIRLY CLOSE TO GUIDANCE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1051 PM CDT SAT MAY 16 2015

THE LATEST HRRR AND NAM12 MODELS CONTINUE TO BE IN PRETTY GOOD
AGREEMENT IN BRINGING THE NEXT ROUND OF RAINFALL NORTHWARD LATE
TONIGHT...THEN CURLING THE PRECIPITATION WESTWARD TOWARD DAY BREAK
SUNDAY. THERE IS A LOT OF RAINFALL UPSTREAM IN EASTERN NEB AND
WESTERN KS...SO HAVE NO REASON TO DOUBT THIS SCENARIO YET SO
INCLUDED THE RAIN IN THE TAFS. THE BIGGEST QUESTION MARK IS THE
AMOUNT OF THUNDERSTORMS. THERE COULD BE ELEVATED STORMS EMBEDDED
IN THE RAIN...SO INCLUDED THE MENTION OF TSRA ONLY IN A TEMPO
GROUP FOR OUR THREE SITES. FURTHERMORE...THE HUMIDITY TIME
SECTIONS AND MODEL SOUNDINGS SHOW WIDESPREAD MVFR TO POSSIBLE
LOWER END IFR CONDITIONS TAKING OVER LATE TONIGHT AND SUNDAY
MORNING NORTH OF I 90 IMPACTING THE KHON TAF SITE. HEADING FURTHER
SOUTHWARD...THE CEILINGS WILL BE HIGHER WITH LESS RAINFALL ON
SUNDAY. THEREFORE AM LESS PESSIMISTIC WITH THE CEILINGS IN THE
KFSD AND KSUX TAF SITES.

&&

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

$$

UPDATE...MJ
SHORT TERM...08
LONG TERM...
AVIATION...MJ



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