Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 230457
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1057 PM CST SAT NOV 22 2014

.UPDATE...
ISSUED AT 940 PM CST SAT NOV 22 2014

STRATUS CONTINUES TO MOVE BACK INTO THE REGION TONIGHT. HRRR AND
RAP SEEM TO HAVE A GOOD HANDLE ON THIS...KEEPING MOST OF THE
STRATUS ALONG AND EAST OF INTERSTATE 29. SIGNAL FOR DENSE FOG IN
THE MODELS IS LESS THAN LAST NIGHT AND CURRENTLY NOT SEEING MUCH
OUT THERE. WILL KEEP FOG IN THE FORECAST...BUT PROBABILITY OF
WIDESPREAD DENSE FOG SEEMS TO BE DECREASING...ALTHOUGH WILL NEED
TO CONTINUE TO MONITOR.

OTHERWISE WATCHING SOME LIGHT PRECIPITATION THAT WILL TRY TO MOVE
ACROSS THE REGION TONIGHT INTO TOMORROW ASSOCIATED WITH A PRETTY
GOOD AREA OF MID LEVEL FRONTOGENESIS. WILL HAVE TO OVERCOME QUITE
A BIT OF DRY AIR IN THE LOW LEVELS...BUT STILL COULD SEE SOME
LIGHT PRECIPITATION WORK FROM WEST TO EAST INTO EARLY TOMORROW
AFTERNOON. DID GO AHEAD AND CHANGE PRECIPITATION TYPE TO ALL RAIN
THOUGH. EXPECT SURFACE TEMPERATURES TO REMAIN ABOVE FREEZING...AND
MODEL SOUNDINGS SUGGEST PLAIN RAIN IS THE MOST LIKELY PRECIPITATION
TYPE. SREF PROBABILITIES ALSO BACK THIS UP...SO FELT COMFORTABLE
REMOVING MENTION OF SNOW. CAN NOT COMPLETELY RULE OUT A FEW FLAKES
MIXED IN...BUT SHOULD MAINLY BE A CHILLY LIGHT RAIN IF ANYTHING.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 415 PM CST SAT NOV 22 2014

ANOTHER DIFFICULT FORECAST IN THE SHORT TERM AS LOW CLOUDS AND
STRATUS STRUGGLING TO ERODE ACROSS THE EASTERN HALF OF THE FORECAST
AREA.  WHERE THE STRATUS HAS ERODED...TEMPERATURES HAVE RECOVERED
NICELY IN THE 40S AND 50S...BUT ACROSS THE EAST UNDER THE BLANKET OF
LOW CLOUDS...TEMPERATURES HAVE REMAINED STEADY IN THE 30S.  EXPECT
THE EAST TO FILL BACK IN WITH LOW CLOUDS AND FOG TONIGHT...AND MAY
HAVE TO ISSUE A DENSE FOG ADVISORY TONIGHT FOR PORTIONS OF THE
FORECAST AREA.  BEST CHANCES APPEAR TO BE ALONG AND EAST OF A LINE
FROM VERMILLION TO MARSHALL AND EAST. EXPECT VISIBILITIES TO
IMPROVE AS SURFACE TROUGH SHIFTS EAST AND WINDS BECOME NORTHWEST
DRYING OUT THE LOW LEVELS. WITH THE PASSAGE OF THE TROUGH...COULD
HAVE A SMALL AMOUNT OF PRECIPITATION WITH STRONG 700 MB
FRONTOGENESIS COINCIDING WITH WEAK DIV Q ALOFT. PRECIP TYPE COULD
BE A REAL CONCERN THROUGH THE MORNING HOURS WITH TEMPERATURES AT
THE SURFACE NEAR FREEZING. TOUGH CALL IN TERMS OF PRECIP
TYPE...FOR NOW...KEPT PRECIP TYPES CONFINED TO RAIN OR SNOW...BUT
COULD BE POTENTIAL FOR FREEZING RAIN WITH WARM DRY LAYER IN THE
LOWEST 2000 FEET OF THE ATMOSPHERE. EXPECT PRECIP TO BE ALL RAIN
AS IT SHIFTS FURTHER EAST INTO LOCATIONS WHERE TEMPERATURES REMAIN
ABOVE FREEZING. HIGH TEMPERATURES A TOUGH CALL ON SUNDAY...WITH
925 HPA TEMPS COOLING FROM NEAR 10C DOWN CLOSER TO 5C BY 0Z
MONDAY. FURTHER BACK TO THE NORTHWEST...925 HPA TEMPS HOVER IN THE
LOWER SINGLE DIGITS LEADING TO A RELATIVELY SMALL DIURNAL
FLUCTUATION UNDER A MOSTLY CLOUDY SKY.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 415 PM CST SAT NOV 22 2014

BY SUNDAY NIGHT...NORTHWEST WINDS INCREASE TO 20 TO 30 MPH WITH
HIGHER GUSTS TO 45 MPH. COLDER AIR BEGINS RUSHING BACK INTO THE
REGION...WITH TEMPERATURES DROPPING BACK BELOW FREEZING IN THE
EVENING AND REACHING THE TEENS AND LOWER 20S BY DAYBREAK MONDAY. AS
THE NORTHERN STREAM UPPER TROUGH DIGS INTO THE NORTHERN PLAINS AND
MERGES WITH THE SOUTHERN STREAM WAVE TO OUR EAST...SOME SCATTERED
LIGHT SNOWFALL WILL TRACK SOUTHEAST ACROSS THE FORECAST
AREA...HOWEVER THE BETTER FORCING REMAINS TO OUR EAST AND WITHOUT A
GREAT DEAL OF MOISTURE...ANY SNOWFALL WILL BE ON THE LIGHT SIDE.
COULD SEE AROUND A HALF INCH TO INCH IN SOUTHWEST MINNESOTA...
OTHERWISE A FEW TENTHS OR TRACE AT BEST. ADDITIONALLY...WITH THE
GUSTY WINDS...THE LIGHT SNOW WILL BLOW AROUND A BIT...BUT AMOUNTS
WILL BE TOO LIGHT FOR ANY BLOWING SNOW MENTION. ANY EXISTING SNOW
PACK SHOULD HAVE ENOUGH OF A CRUST TO NOT CAUSE ANY BLOWING SNOW
ISSUES EITHER.

WITH THE DEEP UPPER LEVEL TROUGH SLIDING ACROSS THE WESTERN GREAT
LAKES AND SHARP RIDGING ALONG THE WEST COAST...UPPER LEVEL NORTHWEST
FLOW SETTLES INTO THE AREA. WHILE NOT PARTICULARLY A COLD
AIRMASS...TEMPERATURES REMAIN BELOW NORMAL IN THE MID 20S TO MID 30S
ON TUESDAY AND WEDNESDAY. MODELS TRACK A CLIPPER WAVE ALONG THE
UPPER FLOW...ALTHOUGH THE TIMING...TRACK AND STRENGTH OF THIS FAST
MOVING WAVE REMAINS IN POOR AGREEMENT. THE GFS IS QUITE A BIT FASTER
THAN THE OTHER MODELS...FOLLOWED BY THE ECMWF THEN THE NAM. BUT IT
SEEMS THE GENERAL CONSENSUS IS FOR THE BEST CHANCE OF LIGHT SNOW IN
OUR NORTHEASTERN COUNTIES ON TUESDAY NIGHT.

UNCERTAINTY FURTHER INCREASES WEDNESDAY AND WEDNESDAY NIGHT AS THE
BAROCLINIC ZONE SETS UP NEAR THE FORECAST AREA AND POTENTIALLY
BECOMES THE FOCUS MECHANISM OF ADDITIONAL LIGHT PRECIPITATION AS
WARM AIR ADVECTION LIFTS INTO CENTRAL SD AND THE MID MISSOURI
VALLEY. CONFIDENCE IS FAIRLY LOW WITH WHERE THIS WILL SET UP...BUT
WILL LEAVE SOME ISOLATED LIGHT SNOWFALL MENTION WEDNESDAY AND
WEDNESDAY NIGHT.

MODELS WAVER WITH BRINGING FURTHER WAVES ALONG THE FLOW...BUT NOT A
LOT OF CONFIDENCE IN THE TIMING. THANKSGIVING LOOKS TO BE THE
COLDEST DAY IN THE EXTENDED WITH HIGHS ONLY IN THE TEENS AND LOWER
20S FOLLOWED BY THURSDAY NIGHT LOWS IN THE SINGLE DIGITS. FRIDAY
TEMPERATURES MODERATE SOME INTO THE UPPER TEENS TO NEAR 30.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY EVENING)
ISSUED AT 1055 PM CST SAT NOV 22 2014

EXPECT MVFR TO IFR CIGS AND VIS ACROSS NORTHWEST IOWA AND ADJACENT
PORTIONS OF SOUTHWEST MINNESOTA TONIGHT...SO INCLUDED MENTION IN THE
KSUX TAF. BASED ON OBS WILL KEEP KSUX MVFR...BUT IFR AND LIFR CIGS
ARE NOT TOO FAR AWAY AND COULD MOVE IN...SO SOMETHING TO WATCH.
COULD SEE SOME DENSE FOG FORM...ALTHOUGH LATEST GUIDANCE SUGGESTS
WIDESPREAD DENSE FOG IS PROBABLY BECOMING LESS LIKELY. AGAIN KFSD
WILL BE NEAR THE EDGE OF THIS STRATUS AND FOG...BUT BASED ON LATEST
MODEL GUIDANCE LEANING TOWARDS THEM STAYING VFR...BUT WILL CONTINUE
TO MONITOR. EXPECT ANY STRATUS TO CLEAR EARLY TO MID MORNING AS A
FRONT SWITCHES WINDS TO THE WEST AND NORTHWEST. COULD BE A LITTLE
LIGHT RAIN AS THE FRONT CROSSES...BUT NOT EXPECTING ANYTHING OF
SIGNIFICANCE AT THIS TIME. WINDS WILL INCREASE BEHIND THE
FRONT...AND BY LATE MORNING AND AFTERNOON EXPECTING GUSTS OF 30 TO
40 KTS TO BE COMMON AND LAST INTO THE OVERNIGHT. ALSO SHOULD SEE
STRATOCU DEVELOPMENT BEHIND THE FRONT IN THE COLD AIR ADVECTION
REGIME...WITH HEIGHTS LIKELY HIGH END MVFR OR LOW END VFR. ALSO
SHOULD BE SCATTERED FLURRIES OR SNOW SHOWERS INTO THE
OVERNIGHT...AND GIVEN THE STRONG WINDS COULD SEE BRIEF PERIODS OF
VISIBILITY REDUCTION...SO WILL HAVE TO WATCH FOR THAT AS WELL.


&&

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

$$

UPDATE...CHENARD
SHORT TERM...
LONG TERM...
AVIATION...CHENARD


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