Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KFSD 190023
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
723 PM CDT THU SEP 18 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 359 PM CDT THU SEP 18 2014

LOW LEVEL MOISTURE CONTINUES TO MIGRATE NORTHWARD THROUGH THE
MISSOURI AND JAMES RIVER VALLEY THIS AFTERNOON. THE PRIMARY FORECAST
CONCERNS THROUGH FRIDAY ARE FOCUSED ON STRATUS...WINDS...AND
TEMPERATURES. OVERNIGHT...STRATUS SHOULD BEGIN TO REFORM LATE THIS
EVENING OR EARLY FRIDAY MORNING...GRADUALLY ADVECTING EASTWARD
THROUGH THE NIGHT.  CANNOT RULE OUT A BIT OF LIGHT FOG...BUT SREF
PROBABILITIES OF DENSE FOG REMAIN LOW. ISENTROPIC LIFT ALONG THE
305K SURFACE INCREASES AS NOSE OF A STOUT EML ADVECTS NORTHEAST.
MODELS NOT INDICATING ANY QPF...BUT WOULD NOT RULE OUT AN ISOLATED
SHOWER/THUNDERSTORM AFTER MIDNIGHT IN EASTERN SD TRACKING INTO
MN/IA BY DAYBREAK.

THE STORY FOR FRIDAY WILL BE TEMPERATURES AND WINDS.  A 40-50 KNOT
LLJ WILL PERSIST INTO FRIDAY MORNING...AND WHILE A THICK INVERSION
MAY PREVENT MOST OF THIS WIND FROM REACHING THE GROUND...WOULD NOT
RULE OUT A FEW STRONGER WIND GUSTS TOWARDS AND AFTER DAYBREAK.  BY
THE AFTERNOON...850MB TEMPERATURES ARE EXPECTED TO PEAK AOA
26C...NEAR 2 SD ABOVE CLIMATOLOGY.  OUR MIXING WILL NOT BE DEEP
ENOUGH TO MAXIMIZE THESE TEMPERATURES...BUT I WOULD STILL ANTICIPATE
90 DEGREES IN SOUTH CENTRAL SD...WITH LOWER TO MIDDLE 80S FURTHER
EAST.   THIS STRONG CAPPING INVERSION WILL PREVENT ANY SFC BASED
CONVECTION UNTIL THE EVENING.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 359 PM CDT THU SEP 18 2014

ONLY PRECIPITATION EVENT OF THE SHORTER TERM WILL BE FRIDAY NIGHT
AND VERY EARLY SATURDAY. OVERALL...THE MODEL TREND...OUTSIDE AN
OUTLIER NAM AND ASSOCIATES...HAS BEEN FOR ACTIVITY TO FOCUS MORE
AND MORE SOUTHWARD...PERHAPS WITH AN ORIGIN ACROSS NORTHERN
NEBRASKA DURING THE EARLY TO MID EVENING...EXPANDING ACROSS THE
NEAR/POST FRONTAL AREAS MAINLY SOUTHEAST OF A YKN TO MJQ LINE
THROUGH 06-09Z AS UPPER LEVEL FORCING WITH JET TO NORTH SLIDES
SOUTHEASTWARD...CONTINUING TO SHIFT SOUTHWARD AND DIMINISHING
LATER AT NIGHT.

NOT SEEING A VERY HIGH SEVERE WEATHER THREAT WITH SETUP WITH POST
FRONTAL ENVIRONMENT MEANING MAINLY ELEVATED STORMS WITH DIMINISHED
EFFECTIVE SHEAR AS VEERED LOW LEVEL JET AND POSITIVELY TILTED
SYSTEM DRASTICALLY REDUCE THE DIRECTIONAL SHEAR. AN ISOLATED
MARGINAL HAIL OR WIND EVENT ACROSS MAINLY EXTREME NORTHEAST
NEBRASKA AND SOUTHEAST SOUTH DAKOTA...AND NORTHWEST IOWA...WOULD
BE ON THE HIGHER END OF EXPECTATIONS... GIVEN THE INITIALLY STEEP
MID LEVEL LAPSE RATES.

ONLY SMALLEST CHANCES FOR EARLY DAY POPS IN THE SOUTHEAST...THEN
SHOULD BE A DRY AND MIXY DAY ON SATURDAY. MAIN COOLING REMAINS
BOTTLED UP BEHIND SECONDARY WAVE PUSHING INTO CENTRAL MINNESOTA BY
LATE DAY...SO POTENTIAL FOR ANOTHER ABOVE NORMAL DAY WITH UPPER
70S TO MID 80S...WITH MUCH REDUCED HUMIDITY FROM THAT ON FRIDAY.
COOLER READINGS BY SUNDAY BEHIND SECONDARY FRONT...BUT A SOMEWHAT
LESS WINDY DAY. SURFACE RIDGE SETTLES ACROSS THE HEART OF THE AREA
ON SUNDAY NIGHT FOR COOLEST NIGHT...BUT SHOULD REMAIN FROST FREE.

MODELS CONTINUE TO SOLIDIFY CONSENSUS OF LARGE SCALE RIDGE
PUSHING EAST ACROSS THE AREA THROUGH MIDWEEK...BUT CONTAMINATING
WITH A SLOW MOVING UPPER WAVE. LOW LEVEL FLOW WOULD START TO
INCREASE MOISTURE BY LATER MONDAY NIGHT INTO THE FAR WEST...AND
PERSISTENT SOUTHERLY FLOW AND SLOW ADVANCEMENT OF TROUGH AXIS
THROUGH THE END OF THE PERIOD WOULD EVENTUALLY ALLOW PRECIPITATION
CHANCES TO IMPACT THE ENTIRE CWA. PROBABLY MORE OF A SHOWER THREAT
THAN THUNDER...WITH INSTABILITY FAIRLY MEAGER WITH SYSTEM. TREND
EXPECTATIONS...AS LONG AS THERE IS NOT A MASS ABANDONMENT OF THIS
SOLUTION /WHICH WOULD NOT BE OUT OF CHARACTER GIVEN THE THREE DAY
CHANGE/ IS FOR A LOWER DIURNAL RANGE WITH MAINLY COOLER HIGHS AND
SLIGHTLY MILDER LOWS...ALONG WITH MUCH HIGHER PRECIPITATION
CHANCES. FOR NOW...HAVE STARTED WITH FIRST PRECIP CHANCE IN THE
FAR WEST ON LATER MONDAY NIGHT...WITH STABLE AND DRIER TRAJECTORY
KEEPING FAR EAST DRY INTO EARLY WEDNESDAY. DAYTIME TEMPS LIKELY AT
OR BELOW NORMAL...WITH OVERNIGHT LOWS ABOVE AFTER A COOLER NIGHT
EAST ON MONDAY NIGHT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU SEP 18 2014
MVFR STRATUS ACROSS EASTERN NEBRASKA INTO WESTERN IOWA IS EXPECTED
LOWER AND BROADEN THROUGH THE OVERNIGHT. WITH THE LOW LEVEL JET
INCREASING AND ADVECTING THESE CLOUDS NORTH...HAVE KEPT IFR
CEILINGS IN THE TAFS. ADDED MENTION OF LOW LEVEL WIND SHEAR AT
KHON WHERE LOW LEVEL JET IS A FEW KNOTS STRONGER THAN KSUX AND
KFSD. STILL SHOULD BE A BREEZY NIGHT ESPECIALLY THROUGH THE LOWEST
2K FEET. WINDS WILL SHIFT SOUTHWEST DURING THE DAYLIGHT HOURS ON
FRIDAY AS A COLD FRONT APPROACHES FROM THE WEST. STRATUS SHOULD
GRADUALLY SCOUR OUT...BUT NOT UNTIL AFTER 18Z.

&&

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

$$

SHORT TERM...DUX
LONG TERM...CHAPMAN
AVIATION...



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.