Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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684
FXUS63 KFSD 190913
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
413 AM CDT TUE MAY 19 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 413 AM CDT TUE MAY 19 2015

LINGERING LOW CLOUDS AND WIND RESURGENCE WILL CONTINUE TO KEEP THE
FREEZE AND FROST OUT MUCH OF THE AREA. THE ONLY CLEARING THROUGH
DAYBREAK WILL BE IN THE FAR NORTHEAST IN SOUTHWEST MINNESOTA WHERE
STRONGER WINDS WILL KEEP OUT THE FREEZE AND FROST AS FORECAST. THE
FREEZE WARNING WILL STAY UNDER THE MOSTLY CLEAR SKIES AND LIGHTER
WINDS SOUTHWEST OF HON/MHE...AND A FROST ADVISORY WILL STAY ONLY
FOR BON HOMME COUNTY/SPRINGFIELD.

THE LOW CLOUDS WILL BE DRIED OUT STEADILY LATER THIS MORNING AS THE
DRIER AIR SQUEEZES THEM OUT FROM BOTH THE NORTHWEST AND NORTHEAST.
THIS WILL LEAVE THE DAY WITH STEADILY INCREASING CLOUDS FROM THE
SOUTHWEST AND A RAPID DEVELOPMENT OF LIGHT RAIN SOUTHWEST IN THE
AFTERNOON. TEMPERATURES WILL BE COOL...THOUGH NOT AS COOL AS
MONDAY...WITH HIGHS IN THE LOW TO MID 50S.

RAIN WILL CONTINUE TO DEVELOP EAST AND NORTHEAST TONIGHT AND SHOULD
GET TO ABOUT FSD AND INTO NORTHWEST IOWA BY THE END OF THE NIGHT.
MODELS ARE SURPRISINGLY CONSISTENT ON THE RAIN THREAT EXCEPT FOR THE
NAM WHICH OVERDOES IT...MORE ON AMOUNTS THAN COVERAGE. STILL...IT
LOOKS WORTH GOING FOR UNQUALIFIED POPS FOR LIGHT RAIN SPREADING
ACROSS THE SOUTH THROUGH TONIGHT...AND OF COURSE A SHARP NORTH TO
SOUTH POP GRADIENT IN THE AREA AS THE PRECIPITATION LACKS SUPPORT TO
MAKE IT TO THE FAR NORTHERN PART OF THE AREA. LOW TEMPERATURES
SHOULD BE IN THE UPPER 30S TO LOWER 40S...AND TEMPERATURES UPSTAIRS
ARE NOT QUITE COLD ENOUGH TO WORRY ABOUT MIXED SNOW WHERE A LITTLE
HEAVIER PRECIPITATION FALLS...ESPECIALLY WITH THE BEST SYSTEM
DYNAMICS HEADED WELL SOUTH OF THE AREA.


.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 413 AM CDT TUE MAY 19 2015

ANTICIPATE COVERAGE OF PRECIPITATION TO BE DECREASING FAIRLY QUICKLY
AFTER 12Z...AND ESPECIALLY BY 18Z...AS ISENTROPIC DOWNGLIDE BECOMES
DOMINANT IN THE MID LEVELS. SHOULD SEE CLEARING WORK INTO NORTHERN
PARTS OF THE FORECAST AREA BY LATE AFTERNOON...PROGRESSING TO THE
SOUTH THROUGH WEDNESDAY NIGHT. THEN ASIDE FROM SOME AFTERNOON/EARLY
EVENING CUMULUS POTENTIAL ON THURSDAY...MOSTLY CLEAR SKIES SHOULD
PREVAIL THROUGH FRIDAY MORNING. THE LINGERING SHOWERS/CLOUDS ACROSS
THE SOUTH WILL HOLD DAYTIME TEMPERATURES WEDNESDAY IN THE MID 50S...
WITH READINGS CLIMBING CLOSER TO 60 IN OUR NORTHERN AREAS. WARMER
AIR FINALLY RETURNS BY THURSDAY...AND WHILE STILL BELOW NORMAL...
SHOULD SEE TEMPERATURES TOP OUT IN THE 60S/NEAR 70.

CLOUD INCREASE FRIDAY AFTERNOON...LEADING INTO PERIOD OF UNSETTLED
WEATHER THROUGH THE HOLIDAY WEEKEND AS DISORGANIZED UPPER TROUGH
MEANDERS SLOWLY EAST THROUGH THE WESTERN CONUS. WEAK LEAD WAVE
SWINGS OUT OF THE TROUGH INTO THE NORTHERN PLAINS FRIDAY NIGHT...
AND WHILE SOMEWHAT MOISTURE STARVED AT THIS POINT...COULD SEE SOME
LIGHT SHOWERS DEVELOP AS THE WAVE PASSES THROUGH. INSTABILITY PRETTY
LIMITED...BUT NOT NON-EXISTENT...SO WORTH ISOLATED THUNDER MENTION.

COULD SEE A BREAK IN PRECIPITATION SATURDAY MORNING WITH CHANCES
RETURNING BY LATER IN THE DAY AS FLOW THROUGH THE PLAINS BECOMES
MORE OPEN TO THE GULF AND ALLOWS BETTER MOISTURE TO WORK INTO OUR
AREA. WHILE MODELS ARE IN FAIR AGREEMENT IN TIMING THIS FIRST WAVE
THROUGH BY LATE FRIDAY NIGHT...ENOUGH UNCERTAINTY AT THIS RANGE TO
STICK WITH A GENERAL ALL DAY PRECIP CHANCE FOR SATURDAY FOR NOW.

A LITTLE STRONGER WAVE SLATED TO KICK OUT INTO THE REGION SOMETIME
IN THE SATURDAY NIGHT/SUNDAY TIME FRAME...AND WITH DEEPER MOISTURE
BECOMING AVAILABLE...WILL STICK WITH HIGHER END PRECIP CHANCES FOR
THIS PERIOD. THIS WAVE BEGINS TO EJECT ACROSS THE NORTHERN PLAINS
TOWARD THE END OF THIS FORECAST PERIOD...KEEPING PRECIPITATION
CHANCE AROUND INTO THE MEMORIAL DAY HOLIDAY. STILL SEEING FAIRLY
SIGNIFICANT MODEL DIFFERENCES WITH REGARD TO POSITION OF SURFACE LOW
AND ASSOCIATED BOUNDARIES...WITH OPERATIONAL GFS REMAINING FARTHER
NORTH/WARMER/MORE UNSTABLE THAN ECMWF. QUITE A RANGE OF SOLUTIONS
AMONG THE GFS ENSEMBLE MEMBERS AS WELL...SO DIFFICULT TO PIN DOWN
ANY POTENTIAL SEVERE THREAT AT THIS TIME. THE WIDE RANGE IN THESE
SOLUTIONS WILL ALSO HAVE AN IMPACT ON TEMPERATURES FOR THE LATTER
HALF OF THE HOLIDAY WEEKEND...AND WITH THE UNCERTAINTY EXPRESSED
ABOVE...WILL STICK WITH BLENDED MODEL CONSENSUS FOR NOW.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1053 PM CDT MON MAY 18 2015

EDGE OF STRATUS HAS SETUP JUST WEST OF A HURON SD...TO SIOUX FALLS
TO STORM LAKE IA LINE. WITH THE WINDS OFF THE SURFACE IN THE CLOUD
LAYER REMAINING OUT OF THE NORTH ALL NIGHT...IT REMAINS TO BE SEEN
AT THIS POINT JUST HOW QUICKLY THE STRATUS WILL ERODE IF AT ALL.
MOST OF THE STRATUS IS IN THE MVFR LAYER...AND IS BEGINNING TO
EDGE EVER SO SLOWLY WESTWARD AND SOUTHWARD ON THE LATEST COUPLE OF
SATELLITE IMAGES. CONFIDENCE IS NOT REAL HIGH FOR THE 06Z SET OF
TAFS AS THE VARIOUS MODELS ARE NOT HANDLING THE CURRENT SITUATION
WELL AT ALL. THE NAM HAS CLEARED THE STRATUS OUT OF MOST LOCATIONS
ALREADY AS WELL AS THE GFS...WHEREAS THE RAP13 KEEPS STRATUS GOING
INTO MIDDAY TUESDAY. THE TRUTH MAY LIE SOMEWHERE IN BETWEEN. THERE
IS CLEARING AND DRIER AIR NOTED IN EASTERN ND WHICH IS HEADING
SOUTHWARD...SO THE CLEARING MAY HAVE TO TAKE PLACE FROM NORTH TO
SOUTH. KHON IS CURRENTLY EXHIBITING CEILINGS JUST INSIDE VFR AND
IF THE CLEARING TO THE NORTH CONTINUES SOUTHWARD...THEY COULD
SCATTER OUT BY ABOUT 08Z TUESDAY. KFSD IS A DIFFERENT STORY.
CURRENT THOUGHTS ARE THAT IT COULD TAKE QUITE A WHILE FOR THE
CLEARING LINE TO GET TO KFSD...SO KEPT MVFR CONDITIONS GOING UNTIL
12Z FOR NOW. KSUX WILL NEED TO BE WATCHED CLOSELY AS THEY ARE
CURRENTLY CLEAR...AND IT IS PROBLEMATIC IF THE STRATUS WILL MOVE
ENOUGH SOUTHWARD TO IMPACT THEIR LOCATION AS WELL. IF IT DOES...
THEY TOO WILL GO MVFR BY THE PRE DAWN HOURS.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...FROST ADVISORY UNTIL 8 AM CDT THIS MORNING FOR SDZ068.

     FREEZE WARNING UNTIL 8 AM CDT THIS MORNING FOR SDZ050-052-057-
     058-063-064.

MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...
LONG TERM...JH
AVIATION...MJ



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