Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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245
FXUS63 KFSD 281959
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
259 PM CDT THU APR 28 2016

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 257 PM CDT THU APR 28 2016

A FEW SHOWERS BEHIND THE SLOWLY EXITING LOW SHOULD END AROUND THE
END OF THE DAY...AND GENERALLY TONIGHT WILL BE RAIN FREE.
HOWEVER...THE SYSTEM WILL LEAVE ONLY A WEAK NORTHERLY TO
NORTHEASTERLY LOW LEVEL FLOW BEHIND IT AND SEE ONLY A LITTLE OF
THE DRIER AIR TO THE NORTH MAKING IT INTO THE AREA. SKIES ARE
EXPECTED TO STAY CLOUDY TONIGHT. CEILINGS WILL LIKELY LOWER A
LITTLE LATE AFTER LIFTING SOME THIS AFTERNOON INTO THE START OF
THIS EVENING...AND AM CLOSE ON WHETHER OR NOT THERE WILL BE ENOUGH
LIGHT FOG DEVELOPMENT TO MENTION IN THE FORECAST. FOR NOW HAVE NO
MENTION...DO NOT EXPECT DENSE FOG IN ANY EVENT...BUT WILL
COORDINATE ON THE IDEA.

FRIDAY MAY BRING A LITTLE DECREASING CLOUD COVER IN THE FAR
NORTH...WELL NORTH OF I-90...OTHERWISE CLOUDS SHOULD HANG IN. THE
APPROACHING RAIN SYSTEM LOOKS SLOWER THAN IT DID YESTERDAY. CHANCE
POPS FOR RAIN LATE IN THE DAY FROM 9V9 TO SUX AND SOUTHWEST LOOK
TOPS AND I COULD SEE THE RAIN HOLDING OFF DURING THE DAY...WHICH OF
COURSE IS WHAT I AM SAYING WITH ONLY CHANCE POPS.

LOW TONIGHT IN THE MID TO UPPER 30S LOOK EASY. HIGHS FRIDAY SHOULD
BE IN THE 50S EXCEPT UPPER 40S SOUTHWEST UNDER THICKENING CLOUDS AND
POSSIBLE LATE DAY RAIN.


.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 257 PM CDT THU APR 28 2016

SEEING A SOUTHWARD TREND IN SOME MODELS WITH THE SYSTEM AFFECTING
US THIS WEEKEND...ALTHOUGH AS IS TYPICAL WITH ANY SUCH SHIFT...
SOME MODELS ARE MORE AGGRESSIVE WITH THE TREND THAN OTHERS. IN
THIS CASE THE 12Z DETERMINISTIC RUNS OF THE GFS AND GEM ARE MOST
AGGRESSIVE... TRACKING THE UPPER LOW THROUGH NORTHERN/CENTRAL
KANSAS AND REALLY LIMITING ANY PRECIP THREAT TO AREAS SOUTH OF
I-90 THROUGHOUT THE PERIOD. NAM/ECMWF ARE STILL FARTHER TO THE
NORTH...WITH ECMWF THE FARTHEST NORTH SOLUTION WITH THE UPPER LOW
IN SOUTHERN NEBRASKA... AND THOUGH NOT QUITE AS FAR AS PREVIOUS
RUNS...BULK OF THE PRECIP STILL REMAINS SOUTH OF HIGHWAY 14. IN
ALL CASES...LOW IS SLOWEST AND STRONGEST AS IT SPINS THROUGH THE
WESTERN HIGH PLAINS THROUGH EARLY SATURDAY...THEN GRADUALLY
WEAKENS AS IT SHIFTS EAST TOWARD MISSOURI SATURDAY NIGHT.

PRIMARY EFFECTS OF THIS ARE A SLOWER AND LESS EXTENSIVE NORTHWARD
PUSH OF THE RAIN FRIDAY NIGHT/SATURDAY...AND A QUICKER EXIT TO THE
PRECIP ON SUNDAY. IN FACT...GFS/GEM/NAM HAVE ALL ARE NOW COMPLETELY
DRY FOR THE DAYTIME HOURS SUNDAY...WHILE ECMWF HANGS ONTO SOME VERY
LIGHT PRECIP SOUTH OF I-90. THUS HAVE ATTEMPTED TO TIGHTEN UP THE
NORTHERN GRADIENT IN PRECIPITATION CHANCES...CONFINING LIKELY OR
BETTER POPS TO THE I-90 CORRIDOR AND POINTS SOUTH...WITH LOW CHANCE
POPS AT BEST FOR AREAS NORTH OF HIGHWAY 14. WILL LIKELY STILL SEE
FURTHER TIGHTENING OF THE NORTH-SOUTH RAINFALL GRADIENT ACROSS THE
FORECAST AREA BY THE TIME ALL IS SAID AND DONE...THOUGH FOR NOW WE
ARE STILL LOOKING AT POTENTIAL FROM LESS THAN A QUARTER INCH NORTH
OF HIGHWAY 14...TO NEAR 1.5 INCHES IN THE MISSOURI RIVER VALLEY.

SLOWER/SOUTHWARD TREND SHOULD ALSO ALLOW FOR A LITTLE MORE WARMING
ACROSS THE NORTHERN PORTIONS OF THE AREA ON SATURDAY...AND AFTER
LOWS IN THE LOWER TO MID 40S FRIDAY NIGHT...ANTICIPATE HIGHS ON
SATURDAY RANGING FROM MID-UPPER 40S IN THE MISSOURI VALLEY...TO MID
50S NORTH OF I-90. EXITING RAIN AND DECREASING CLOUDS SUNDAY SHOULD
ALLOW FOR WARMER TEMPERATURES ALL-AROUND...WITH HIGHS GENERALLY IN
THE MID-UPPER 50S.

WARMING/DRYING TREND STILL ON TRACK FOR NEXT WEEK AS STRONG UPPER
RIDGE BUILDS OVER THE INTERMOUNTAIN WEST. WEAK LOBES OF ENERGY COULD
CLIP PARTS OF OUR MINNESOTA/IOWA COUNTIES AS THEY SLIDE DOWN THE
EAST SIDE OF THE RIDGE...THOUGH AT THIS TIME WOULD BE HARD-PRESSED
TO ADD ANY MENTION OF PRECIP. SEEING MUCH GREATER MODEL DIVERGENCE
TOWARD THE END OF THIS PERIOD...WITH 12Z GFS TAKING SHIFT TOWARD A
COLDER END TO THE WEEK AS A BACKDOOR COOL FRONT DROPS THROUGH THE
EASTERN DAKOTAS AND MINNESOTA WEDNESDAY NIGHT/THURSDAY. THIS IS A
SIGNIFICANTLY DIFFERENT SOLUTION THAN THE 12Z ECMWF...WHILE BUILDS
THE UPPER RIDGE EVEN FURTHER EASTWARD INTO THE MISSISSIPPI VALLEY.
GIVEN THE LARGE DISCREPANCIES AND LACK OF CONTINUITY IN THE GFS AS
OF YET...DID NOT STRAY MUCH FROM THE GREATER MODEL CONSENSUS WHICH
KEEPS MILD AND DRY CONDITIONS IN PLACE THROUGH THURSDAY.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1220 PM CDT THU APR 28 2016

CEILINGS 1-3K FEET. PATCHY CEILINGS BLO 1K FEET THROUGH 20Z. SCT
-SHRA THROUGH 22Z. AREAS CEILINGS BLO 1K FEET DEVELOPING AGAIN
AFTER 29/09Z WITH AREAS VISIBILITY 3-5SM/BR. VISIBILITIES
IMPROVING TO P6SM AGAIN AFTER 29/15Z.


&&

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

$$

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



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