Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 131714
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1214 PM CDT SUN APR 13 2014

.UPDATE...
ISSUED AT 657 AM CDT SUN APR 13 2014

GROWING CONCERN ABOUT A POTENTIAL HEAVIER SNOW BAND SETTING UP BY
EARLY AFTERNOON FROM NORTHEAST NEBRASKA INTO NORTHWEST IOWA.
STRONGER PV ADVECTION WILL BE MOVING IN TOWARD MIDDAY...AND
ALREADY SHOWING A GOOD SURGE OF ELEVATED INSTABILITY INTO NEBRASKA
NEAR AND SOUTH OF I 80. PRECIPITATION SHOULD BECOME FAIRLY
WIDESPREAD BY MIDDAY...WITH TEMPS COOLING ENOUGH BY MIDDAY TO
FORCE A CHANGE TO ALL SNOW. POSSIBILITY OF CONVECTIVE SNOWFALL
WITHIN THE BAND. INITIAL BAND LOOKS TO BE WEAKENING IN FAVOR OF
NEW BANDING TO THE SOUTHEAST...BUT ALSO STARTING A DISTINCT CHANGE
TO SNOW ACROSS THE FAR WEST. UPDATES OUT SHORTLY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 411 AM CDT SUN APR 13 2014

CONFLUENT SOUTHWEST FLOW ACROSS THE REGION EARLY THIS MORNING.
NORTHERN STREAM FEATURING BROAD CYCLONIC FLOW ALONG THE NORTHERN
TIER WITH DISTINCT DOWNSTREAM JET STREAK ACROSS EASTERN NORTH DAKOTA
AND NORTHERN MINNESOTA. WEAK WAVE IN SOUTHERN STREAM ACROSS THE
CENTRAL HIGH PLAINS AREA. MID LEVEL FRONTAL BOUNDARY WITHIN
CONFLUENCE ZONE WORKING SLOWLY EASTWARD...WHILE THE LOW LEVELS ARE
DOMINATED BY STRONG COLD AIR ADVECTION WITH TEMPS WELL BELOW ZERO AT
850 HPA SLIPPING SOUTHWARD INTO NORTHERN/WESTERN SOUTH DAKOTA.

QUITE A CHANGE EXPECTED TODAY AS COLD AIR ADVECTION WILL CONTINUE
THROUGH THE DAY...WITH A FAIRLY INTERESTING DEVELOPMENT OF
PRECIPTIATION AS SOUTHERN STREAM WAVE LIFTS INTO THE AREA AS MID
LEVEL FRONT DRIFTS ACROSS. INITIAL PUSH OF SATURATION WILL COME FROM
THE SOUTH/WEST THIS MORNING INTO THE SOUTHWESTERN CWA AND TOWARD THE
LOWER MISSOURI VALLEY...REACHING A LIMITATION TO THE NORTH AS MID
LEVEL FRONT SLIPS SOUTHWARD...AND DRYING AT LOWER LEVELS WITH COLD
ADVECTION ERODES ADVANCING MOISTURE ALOFT.  PRECIPITATION COVERAGE
SHOULD CONTINUE TO INCREASE ACROSS THE SOUTHEASTERN HALF OF THE AREA
GOING INTO THE AFTERNOON...AS BETTER PV FORCING WITH SOUTHERN STREAM
ALONG WITH IMPACTS OF NORTHERN STREAM JET ENTRANCE/MID LEVEL
FRONTOGENESIS SLIDE SOUTHEAST. FOR THESE LOCATIONS WHERE STRONGER
FORCING SLIPS INTO THE SOUTHEASTERN THIRD OF THE CWA THIS AFTERNOON
WITH TIME FOR THE BULK COOLING TO ALSO PUSH SOUTHEAST...LOOKS TO BE
A BIT HIGHER PROBABILITY OF GETTING A PERIOD OF OUTRIGHT SNOWFALL
COMPARED TO A LIGHTER RAIN/SNOW MIX. THE GOOD NEWS WOULD BE THAT
ACCUMULATIONS WOULD STILL BE LIGHT...GENERALLY AN INCH OR
LESS...WITH MUCH MELTING AS FALLING WITH SURFACE TEMPS LIKELY NO
COOLER THAN THE MID 30S AT TIME OF ANY SNOWFALL. ELSEWHERE...TEMPS
SHOULD CONTINUE TO FALL FOR A WHILE THIS MORNING...THEN STEADYING TO
RISING A FEW DEGREES WHERE PRECIPITATION IS VACANT. FAIRLY
WIDESPREAD STRATUS TO THE NORTH SUGGESTED TO BECOME SOMEWHAT MORE
RAGGED PUSHING SOUTHWARD THROUGH THE DAY...BUT WILL HELP SUPPORT A
GENERAL STEADY/FALLING TREND.

ONE CONCERN TO MONITOR THROUGH THE DAY IS SOME OF THE HIGHER QPF
VALUES INDICATED BY A FEW HIGH RESOLUTION SOLUTIONS FROM KSUX TO
KEST...AND EVEN THE 00Z GFS/NAM...WHICH GIVEN A WORST CASE GREATER
COOLING COULD BE INTERPRETED TO PRODUCE A SMALLER AREA OF HEAVIER
SNOWFALL ACROSS PARTS OF EXTREME NORTHEAST NEBRASKA AND NORTHWEST
IOWA. SREF PROBABILITIES OF A QUARTER INCH QPF ARE EVEN FAIRLY HIGH
THROUGH THIS AREA...SOME OF WHICH WOULD STILL LIKELY BE RAIN.
SOME MARGINAL INSTABILITY ABOVE THE FRONTAL ZONE...BUT LOCATION OF
LIFT IN THERMAL PROFILES TOWARD WARMER AND MORE STABLE PARTS OF
SOUNDING MAKES A BIT HESITANT TO SIDE TOWARD A VERY NARROW BAND OF
HEAVY PRECIPITATION AT THIS POINT.

OTHER CONCERN FOR TODAY IS THE WIND...WHICH WILL PROBABLY GET FAIRLY
CLOSE TO WIND ADVISORY CRITERIA OF 30 MPH SUSTAINED OVER A GOOD
SHARE OF THE AREA. FOR NOW...IT LOOKS MARGINAL ENOUGH TO NOT ISSUE
AN ADVISORY.

SNOW OR A RAIN/SNOW MIX WILL LINGER EARLY EVENING ACROSS THE FAR
SOUTHEAST...BUT SHOULD COME TO A FAIRLY QUICK END AS CONTINUED DRY
AIR ADVECTION UNDERCUTS THE FRONTOGENETIC BAND. CLOUDS WILL
GRADUALLY THIN...BUT TEMPS OVERALL SHOULD BE MORE DRIVEN BY THE COLD
ADVECTION WITH CONTINUED MIXING...WHICH LOOKS TO FAVOR TEMPS MAINLY
IN THE MID 20S.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 411 AM CDT SUN APR 13 2014

MONDAY SHOULD SEE THE CHANCES FOR PRECIPITATION GONE LEAVING BEHIND
A PARTLY CLOUDY AND WINDY DAY...NOT TO MENTION COOL. HIGHS WELL
BELOW NORMAL AND EVEN WENT AHEAD AND BACKED OFF ON HIGHS A DEGREE OR
TWO AS FULL MIXING ON THE WARMER MODELS WAS STILL COMING UP A TOUCH
SHORT OF FORECAST. NAM STILL MUCH COLDER THAN THE OTHER MODELS SO
THREW THAT OUT. STILL STRUGGLING WITH WHAT TO DO FOR DEW POINTS ON
MONDAY INTO MONDAY NIGHT AS THE LATEST MODEL OUTPUT WANTS TO DROP
THEM INTO THE SINGLE DIGITS WHICH SEEMS A BIT UNLIKELY GIVEN NO SNOW
COVER. WILL MAINTAIN SOMETHING CLOSE TO THE GOING FORECAST WHICH
WOULD BE MORE IN LINE WITH THE TEENS.

A WEAK RIDGE OF HIGH PRESSURE WILL MOVE THROUGH MONDAY NIGHT AND
WINDS SHOULD BE LIGHT FOR A GOOD CHUNK OF THE NIGHT...ESPECIALLY IN
THE EASTERN CWA. SOME GUIDANCE COMING IN WITH MID TO UPPER TEENS
WHICH SEEMS TOO LOW FOR THE MOST PART SO WILL KEEP LOWER 20S IN
PLACE.

SOUTH TO SOUTHEAST FLOW WILL DEVELOP ON TUESDAY MORNING AND
STRENGTHEN THROUGH THE DAY. LOWERED HIGHS JUST A TOUCH AS SOUTHEAST
WINDS AND AN EXITING COLD AIR MASS TO THE EAST DO NOT ALWAYS SUPPORT
GOOD MIXING. WENT FOR HIGHS VERY LATE IN THE DAY...ABOUT 23Z WITH
TEMPERATURES AT 18Z ABOUT 10 DEGREES SHORT OF HIGH TEMPERATURES...SO
LOOKING AT A LATER SURGE OF WARMTH. POTENTIALLY ONE OF THOSE DAYS
THAT SOUNDS MILD ON THE SURFACE WITH HIGHS IN THE 50S BUT WITH A
GUSTY SOUTHEAST WIND AND SLOW RISE THROUGH THE DAY WILL LIKELY FEEL
COOLER THAN MANY EXPECT.

TUESDAY NIGHT INTO WEDNESDAY CONTINUES TO BE A PERIOD OF
DISAGREEMENT...ALBEIT A LITTLE LESS THIS TIME AROUND. THE ECMWF
CONTINUES TO BE THE WARMER AND FARTHER NORTHER SOLUTION WHILE THE
GEM IS THE COLDEST AND FARTHEST SOUTH. COMPARED TO YESTERDAY THE GEM
HAS TRENDED NORTH...THE GFS WHICH WAS ALREADY IN THE MIDDLE ALSO
TRENDED A BIT NORTH AND THE ECMWF HAS COME QUITE A BIT SOUTH. IF THE
CURRENT SOLUTIONS ARE CLOSE AND TRENDING IN THE RIGHT DIRECTION WILL
LIKELY SEE SOME MORNING HIGHS WITH FALLING AFTERNOON TEMPERATURES.
STILL A GOOD CHANCE FOR PRECIPITATION WITH RAIN OR SNOW POSSIBLE
WEDNESDAY AFTERNOON AND NIGHT. STILL TOO EARLY TO GET EXCITED ABOUT
ANY PARTICULAR DETAILS.

THURSDAY THROUGH SATURDAY WILL SEE BELOW NORMAL TEMPERATURES WITH
ONLY MINOR CHANCES FOR PRECIPITATION THURSDAY AND THURSDAY NIGHT. NO
MAJOR TRENDS AT THIS POINT IN TIME TO GRAB ON TO EXCEPT CONTINUING
THE BELOW NORMAL TEMPERATURES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1210 PM CDT SUN APR 13 2014

WIDESPREAD MVFR CEILINGS ACROSS THE AREA WILL PREVAIL UNTIL
GRADUAL DRYING WORKS SOUTHWARD AT LOWER LEVELS WITH CONTINUED COLD
AIR ADVECTION. LARGER AVIATION CONCERNS WITH CONDITIONS WITHIN
PRECIPITATION BANDING WHICH MAY EVOLVE THIS AFTERNOON. MAIN BAND SHOULD
SET UP SOUTHEAST OF A KMWM TO KYKN LINE BY AFTERNOON...AND WILL
COOL ENOUGH TO CHANGE TO SNOW WITH IFR/LIFR VISIBILITIES AND
CEILINGS. ANY PRECIPITATION WILL COME TO AN END AFTER 00Z THIS
EVENING...WITH IMPROVING CONDITIONS OVERNIGHT. NORTHERLY WINDS
WILL REMAIN GUSTY THROUGH MONDAY.


&&

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

$$

UPDATE...CHAPMAN
SHORT TERM...CHAPMAN
LONG TERM...08
AVIATION...JM






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