634 
FXUS63 KFSD 181146
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
546 AM CST WED NOV 18 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 410 AM CST WED NOV 18 2015

BAND OF PRECIP...WITHIN TROWAL OF STRONG UPPER LEVEL SYSTEM LIFTING
NORTH-NORTHEAST THROUGH FAR WESTERN IOWA THIS MORNING...HAS BEEN
FAIRLY WELL-BEHAVED THUS FAR THIS MORNING. LOW-MID LEVEL FLOW OF
DRIER AIR HOLDING WESTERN EXTENT OF PRECIP NEAR DE SMET TO LAKE
ANDES LINE. EXPECT THIS WESTERN EDGE TO SLOWLY WORK EASTWARD THROUGH
THE DAY AS THE UPPER WAVE LIFTS INTO MINNESOTA AND ASSOCIATED TROWAL
SHIFTS EAST OF I-29. CANNOT COMPLETELY REMOVE POPS FROM OUR WESTERN
AREAS THOUGH...AS APPROACHING NORTHERN STREAM WAVE AND ASSOCIATED
COLD FRONT WILL KEEP POTENTIAL FOR SCATTERED SHOWERS ACROSS OUR WEST
INTO THE AFTERNOON. THIS CHANCE WILL DIMINISH WITH PASSAGE OF THE
FRONT...SLATED TO ENTER OUR FAR WEST IN THE EARLY AFTERNOON...AND
PUSH THROUGH FAR EASTERN PORTIONS OF THE CWA BY EARLY EVENING. WITH
WESTERN EDGE OF PRECIP SHIELD FARTHER EAST THAN EARLIER THOUGHT...
POTENTIAL FOR SNOW IS EVEN MORE LIMITED AND SHOULD SEE LITTLE IF ANY
SNOW IN OUR AREA WITH THIS SYSTEM TODAY.

POST-FRONTAL CONCERNS TURN TO WINDS...WIND GUSTS IN PARTICULAR AS
FORECAST SOUNDINGS SHOW 40-45KT MIXED LAYER WINDS DEVELOP ACROSS OUR
WESTERN COUNTIES AS COLD AIR ALOFT PUSHES INTO THE AREA AFTER 21Z...
EVEN STRONGER IN THE HIGHER ELEVATIONS OF GREGORY COUNTY. STRONGEST
COLD ADVECTION SHIFTS EAST ACROSS THE CWA THROUGH 03Z THIS EVENING
AND ANTICIPATE WINDS WILL DIMINISH SOME AFTER THAT TIME. HOWEVER
WITH WINDS EXPECTED TO RAMP UP AGAIN THURSDAY MORNING...WILL CARRY
WIND ADVISORY FOR LOCATIONS ALONG/WEST OF KBKX-KYKN LATE THIS
AFTERNOON ALL THE WAY THROUGH TONIGHT. LOWER CONFIDENCE EAST OF THIS
LINE THAT WINDS WILL REACH ADVISORY CRITERIA WITH THE PASSAGE OF THE
FRONT THIS EVENING. THUS DECIDED TO HOLD OFF START OF ADVISORY FOR
THESE AREAS UNTIL AFTER DAYBREAK THURSDAY. DAY SHIFT WILL HAVE TO
REEVALUATE THIS THOUGH...ESPECIALLY SOUTHWEST MINNESOTA WHERE HIGHER
ELEVATION MAY FAVOR ADVISORY LEVEL WINDS REACHING THE SURFACE DURING
THE NIGHT.

AS FOR TEMPERATURES...EXPECT LITTLE MOVEMENT TODAY WITH WIDESPREAD
CLOUDS/PRECIP HOLDING READINGS PRETTY STEADY. EXCEPTION WILL BE IN
THE WEST WHERE DRIER AIR HAS ALLOWED FOR MORE COOLING THIS MORNING
AND POST-FRONTAL MIXING SHOULD BRIEFLY WARM READINGS INTO THE UPPER
40S THIS AFTERNOON. STEADY DOWNWARD FALL BEHIND THE FRONT TONIGHT
WITH LOWS IN THE MID-UPPER 20S.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 410 AM CST WED NOV 18 2015

STRONG WINDS WILL CONTINUE TO LEAD OFF THE LONGER RANGE PERIOD.
GFS AS PER USUAL HAS SOMEWHAT BETTER MIXED BOUNDARY LAYER AND THUS
SLIGHTLY STRONGER WINDS THROUGH THE LOWEST PROFILE COMPARED TO
NAM/SREF/ECMWF. EVEN IF A BIT TOO STRONG...45 TO 50 KNOT WINDS ATOP
THE MIXED LAYER...AND A DECENT 30 TO 40 KNOTS AT THE MID POINT MAKE
FOR A SOLID WIND ADVISORY...AND AS LONG AS HIGHER LOCATIONS DO NOT
START EARLIER...WILL GO WITH AN 8 AM START TIME AVERAGING BETWEEN
MORE AND LESS EXPOSED AREAS.  SHOULD GET A FAIRLY MARKED DECREASE IN
WINDS AFTER 21-22Z AS MIXING ATTEMPTS TO HOLD ON TO A RAPIDLY
WEAKENING SUPPORT NEAR SURFACE...WITH NO HELP FROM DIURNAL CYCLE AT
THAT POINT. FAIRLY CONSISTENT 925 HPA TEMP FORECAST BETWEEN MODELS
SUGGESTS UPPER 30S TO LOWER 40S FOR HIGHS.

WINDS MOST AREAS SHOULD BE FAIRLY LIGHT BY EARLY EVENING...WITH
EXCEPTION OF PARTS OF SW MN...WITH CLEAR SKIES AND VERY DRY AIRMASS
HELPING TEMPS TO FALL QUICKLY. CLOUDS WILL BEGIN TO INCREASE AS NEXT
UPSTREAM WAVE PUSHES THROUGH THE NORTHERN ROCKIES...WITH GENERALLY
CLOUDY SKIES MOST AREA BY DAYBREAK. TEMPS MAY ACTUALLY LEVEL OFF OR
RISE A BIT LATER NIGHT IN THE WEST...ESPECIALLY THE FAR SOUTHWEST
WHERE COULD START TO SEE A LITTLE LIGHT SNOW TOWARD DAYBREAK.

TO SAY THERE IS A BIT OF DIVERSITY WITH FRIDAY SYSTEM IS REALLY
MAKING A MOLEHILL OUT OF A MOUNTAIN. JET STREAK CURRENTLY WELL OUT
TO THE EDGE OF THE GULF OF ALASKA WILL BE RIDING THE NORTHWEST FLOW
INTO THE CENTRAL PLAINS ON FRIDAY. GIVEN THE LARGER SCALE PATTERN...
MUCH MORE LIKELY TO GET A MORE SOUTHWARD SOLUTION PER GFS/CANADIAN
AND TO A LESSER DEGREE THE MODERATE ECMWF...COMPARED TO THE NAM/SREF
AND OTHER DERIVATIVES. HAVE DESIGNED FORECAST OFF BLEND OF THE MORE
SOUTHERN SOLUTIONS...BUT EVEN THEN...A VAST DIFFERENCE IN TIMING
WITH GFS PRACTICALLY FINISHING UP THE PRECIPITATION IN THE EAST AS
ECMWF IS REALLY JUST GOING WELL. KEPT THINGS MORE ON A MID TIMING
PER ECMWF/CANADIAN. 

AS FAR AS FORECAST DETAILS...COOL AND QUITE DRY AIRMASS WILL BE IN
PLACE AT LOWER LEVELS TO BEGIN ON FRIDAY...WITH WELL DEFINED MID
LEVEL BOUNDARY ACROSS THE SOUTHERN CWA. FRONTOGENESIS REACTS TO
APPROACHING UPPER JET STREAK...WITH LIFT PROFILES WELL PLACED IN THE
DENDRITIC ZONE.  NO REASON TO EXPECT ANYTHING OTHER THAN A SOLID
PRECIPITATION FORM WITH WET BULB QUICKLY MAKING ANY NEAR SURFACE
WARM LAYER A MEMORY. NOT VERY UNSTABLE ABOVE THE FRONTAL ZONE...SO
NOT LOOKING FOR RATES TO GET OUT OF HAND.  SNOWFALL ALONG THE BAND
SHOULD REALLY START ENHANCING BY MID MORNING...WITH BROAD BANDING
NEAR/NORTH OF THE MISSOURI RIVER INTO NORTHWEST IOWA. MAX PRECIP
SHOULD BE IN THE EARLY TO MID AFTERNOON...BEFORE EASTWARD SHIFT OF
BETTER FRONTAL DYNAMICS AS WELL AS THE EROSION FROM RENEWED
NORTHERLY FLOW.  ON THE REALM OF POSSIBILITY WOULD BE A BIT MORE
AMPLIFICATION OF SYSTEM AND PERHAPS A BIT OF A PIVOT DEVELOPING NEAR
THE SOUTHEAST CORNER OF THE CWA. THIS COULD ENHANCE AMOUNTS EVEN A
BIT MORE TOWARD HIGHWAY 20...BUT FOR NOW AM GENERALLY LOOKING FOR 2
TO 5 INCH BAND OF SNOWFALL SOUTH OF A WAGNER TO SPENCER IOWA LINE.
ONCE MORE CONSISTENCY IN RUNS APPEARS...WOULD EXPECT THAT MAY BE
DEALING WITH THE FIRST WINTER WEATHER HIGHLIGHT FOR THE SEASON. DRY
AIR TO NORTH COULD EASILY RESULT IN A SHARPER NORTHERN CUTOFF TO
SNOW...BUT ENOUGH MID LEVEL MOISTURE/LIFT OVER THE DRIER LOW LEVELS
TO WARRANT AT LEAST LIKELY POPS TO JUST NORTH OF I 90...WHERE
AMOUNTS COULD REACH AROUND AN INCH.

FOLLOWING EXIT OF SYSTEM ON FRIDAY EVENING WILL BE INFLUX OF THE
COLDEST AIRMASS OF THE SEASON...850 HPA TEMPS -12 TO -14C BY
SATURDAY. HAVE TRENDED TEMPS GENERALLY DOWNWARD FROM INITIAL BLEND
THROUGH SAT NIGHT...ESPECIALLY FOR THOSE AREAS EXPECTING SNOWFALL.
NOT OUT OF THE QUESTION THAT SOME LOCATIONS COULD GET FAIRLY CLOSE
TO ZERO ON SATURDAY NIGHT WHEN GRADIENT EASES.

SUNDAY WILL START MODERATING TREND...AND THIS WILL CONTINUE UNABATED
THROUGH MIDWEEK AS UPPER LEVELS ONCE AGAIN REARRANGE TO THE FAMILIAR
WESTERN TROUGH/PLAINS RIDGE. WEAK BOUNDARY WILL SLIDE THROUGH AROUND
SUNDAY NIGHT/MONDAY MORNING...BUT LITTLE MORE THAN A BETTER MIXING
SET UP TO AID IN WARMING.  WILL HAVE TO SEE HOW QUICKLY ANY
SNOWCOVER WILL GO AWAY...AND VERY WELL MAY REQUIRE SOME SLOWING OF
WARMING TREND OVER THOSE MINOR CHANGES ALREADY MADE. BY
WEDNESDAY...MAY SEE ENOUGH DURATION TO SOUTHERLY FLOW TO RETURN
THREAT FOR STRATUS/FOG WITH A LIGHT RAIN/DRIZZLE THREAT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 546 AM CST WED NOV 18 2015

FAIRLY WIDESPREAD IFR-LIFR CEILINGS ACROSS THE AREA TO START THE
PERIOD...THOUGH SEEING POCKETS OF MVFR OR EVEN VFR CONDITIONS
NEAR EDGES OF RAIN SHIELD. EXPECT SUB-VFR CEILINGS TO BE DOMINANT
CONDITION FOR KFSD/KSUX THROUGH THIS MORNING...BUT GRADUAL UPWARD
TREND IS LIKELY AS PRIMARY RAIN SHIELD SLOWLY SHIFTS EAST INTO
MINNESOTA/IOWA. AFTER 18Z-20Z...MAIN AVIATION CONCERN WILL SHIFT
FROM SUB-VFR FLIGHT CONDITIONS TO INCREASING WEST-NORTHWEST WINDS.
EXTENDED PERIOD OF WIND GUSTS IN EXCESS OF 25KTS LIKELY SPREADING
ACROSS ALL LOCATIONS AFTER 21Z...WITH GUSTS AT OR ABOVE 35KTS
POSSIBLE FOR A FEW HOURS DURING THE LATE AFTERNOON/EVENING IN
AREAS WEST OF INTERSTATE 29. THOUGH WINDS WILL SUBSIDE SLIGHTLY
OVERNIGHT...INCREASING SPEEDS LIKELY THROUGHOUT THE AREA AGAIN
BEYOND THIS TAF PERIOD...AFTER DAYBREAK THURSDAY.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 6 PM CST THURSDAY FOR 
     SDZ038>040-050-052>055-057>061-063>065-068.

     WIND ADVISORY FROM 8 AM TO 6 PM CST THURSDAY FOR SDZ056-062-066-
     067-069>071.

MN...WIND ADVISORY FROM 8 AM TO 6 PM CST THURSDAY FOR MNZ071-072-080-
     081-089-090-097-098.

IA...WIND ADVISORY FROM 8 AM TO 6 PM CST THURSDAY FOR IAZ001>003-
     012>014-020>022-031-032.

NE...WIND ADVISORY FROM 8 AM TO 6 PM CST THURSDAY FOR NEZ013-014.

&&

$$

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