000
FXUS63 KFSD 060006
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
606 PM CST THU DEC 5 2013

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 416 PM CST THU DEC 5 2013

BREEZY NORTHWESTERLY WINDS WILL BEGIN TO SLOWLY DROP OFF LATER THIS
EVENING IN A WEAKENING GRADIENT AS HIGH PRESSURE CONTINUES TO BUILD
TO THE SOUTH AND EAST. EVEN SO...THEY WILL REMAIN CLOSE TO 10 KTS
OVERNIGHT...AND WITH NIGHT TIME LOWS EXPECTED TO DROP INTO THE LOWER
TEENS BELOW ZERO OVER SNOW COVERED AREAS WIND CHILL VALUES WILL
RANGE FROM 25 TO 30 BELOW. IN LIGHT OF THAT...GOING WIND CHILL
ADVISORY REMAINS APPROPRIATE...WITH AN EXTENSION AS NOTED BELOW.

925 MB TEMPERATURES CONTINUE TO FALL JUST A BIT INTO
TOMORROW...LOWER 20S BELOW ZERO C...THOUGH MODELS HAVE TRENDED A
LITTLE WARMER...BUT STILL REMAINED ON THE LOW SIDE OF GUIDANCE
WITH HIGHS RUNNING AROUND ZERO...TO SINGLE DIGITS ABOVE IN SNOW
FREE AREAS OF NORTHWEST IOWA. WITH HIGH PRESSURE EXERTING MORE
INFLUENCE...IT WILL BE LESS BREEZY THAN TODAY WITH NORTHWESTERLY
WINDS STAYING CLOSER TO THE 10 TO 15 KT RANGE. IGNORED THE MODEL
PROGGED LOW LEVEL MOISTURE...WHICH WOULD SUGGEST STRATUS
FORMATION...AS THE MODELS HAVE BEEN WAY OVERDOING THE LOW LEVEL RH
THROUGH THIS COLD EVENT.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 416 PM CST THU DEC 5 2013

STILL BANKING ON FRIDAY NIGHT BEING THE COLDEST OF THE NEXT FEW
WITH DYING WINDS AND ONLY SLOWLY INCREASING CLOUDS FROM THE WEST
LATE. AS MENTIONED ABOVE...MODELS ALSO TRENDED WARMER FOR THIS
PERIOD...BUT WENT BELOW GUIDANCE KEEPING LOWS UPPER TEENS BELOW
ZERO NORTH TO SINGLE DIGITS BELOW FAR SOUTHEAST. DESPITE THE LACK
OF WIND ON THIS NIGHT...EVEN MEAGER WINDS ARE RESULTING IN WIND
CHILL VALUES OF 25 TO 30 BELOW...SO EXTENDED WIND CHILL ADVISORY
THROUGH FRIDAY NIGHT INTO SATURDAY MORNING.

BY SATURDAY...AN UPPER LEVEL WAVE BEGINS TO LIFT OUT OF THE WESTERN
UNITED STATES...WITH MID LEVEL WARM AIR ADVECTION AND ISENTROPIC
LIFT INCREASING OVER OUR AREA BY AFTERNOON. THIS WILL PRESENT AS AN
INCREASE IN CLOUDS DURING THE DAY...AND WITH 925 MB TEMPERATURES
RISING A COUPLE OF DEGREES...HIGHS WILL BE MAINLY SINGLE DIGITS
ABOVE...TO 10 ABOVE FAR SOUTH. WINDS WILL CONTINUE TO BE RELATIVELY
LIGHT THROUGH THE DAY.

AS THE AFOREMENTIONED UPPER LEVEL TROUGH PUSHES INTO THE CENTRAL
PORTIONS OF THE COUNTRY DURING THE WEEKEND...WILL SEE A PROLONGED
OVERRUNNING EVENT WITH LIGHT SNOW DEVELOPING ACROSS THE AREA ON
SATURDAY NIGHT AND LINGERING INTO SUNDAY NIGHT. THE BETTER FOCUS
WILL BE IN OUR SOUTH AND EAST...WITH SNOWFALL TOTALS THROUGH THE
PERIOD RANGING FROM AROUND AN INCH THROUGH THE CHAMBERLAIN TO HURON
CORRIDOR...TO AROUND 4 INCHES THROUGH PORTIONS OF NORTHWESTERN IOWA.
WITH REGARD TO TEMPERATURES...SUNDAY LOOKS TO BE THE WARMER DAY OF
THE NEXT FEW...THROUGH STILL WELL BELOW NORMAL WITH HIGHS IN THE
LOWER TO MID TEENS.

LONGER TERM ISENTROPIC LIFT EVENT WILL BE WINDING DOWN ON SUNDAY
EVENING...BUT LOCATION OF TROUGH AXIS SUGGEST THAT WILL STILL BE
DEALING WITH SOME LIGHT SNOWFALL IN ABOUT THE SOUTHEAST HALF OF THE
CWA THROUGH SUNDAY EVENING. ACCUMULATIONS WILL BE MINOR AT THIS
POINT...LIKELY A HALF INCH OR LESS.

REINFORCING TROUGH CRASHING THROUGH THE NORTHERN PLAINS ON SUNDAY
NIGHT AND MONDAY...AND WILL DRIVE ANOTHER SURGE OF ARCTIC AIR
THROUGH THE REGION. WILL LIKELY BE PLAYING THE WIND CHILL GAME ONCE
AGAIN BY THIS TIME...WITH 25 TO 35 KNOTS IN THE MIXED LAYER SUNDAY
NIGHT INTO MONDAY MORNING...WILL GET 20 BELOW TO 30 BELOW WIND
CHILLS AGAIN. RIDGE AXIS PUSHES PAST DURING THE DAY...WITH FLOW
TURNING WESTERLY...AND COULD HELP MODERATE THE EXTREME WEST ON
ELEVATION ALONE INTO SOMEWHAT LESS FRIGID AIR ALOFT.

ANOTHER WAVE WILL DROP RAPIDLY SOUTHEAST MONDAY NIGHT...WITH A
CLIPPER WAVE MOVING THROUGH THE NORTHERN PLAINS. GFS A LITTLE MORE
DIGGY WITH SYSTEM...AND MAY NOT BE WRONG IN DOING THIS IF FAITH IS
PLACE IN GFS ENSEMBLES. ENOUGH EVIDENCE THAT LIFT AHEAD OF STRONG PV
PUSH MAY CLIP THE NORTHEAST TO INCLUDE A SMALL POP.  WINDS ON BOTH
SIDES OF THE SYSTEM WILL BE STRONG...AND NOT ONLY THE TRAILING
NORTHWEST WINDS OF 35 TO 45 KNOTS ALOFT...BUT THE SOUTHWEST WINDS
AHEAD COULD BE PROBLEMATIC IN PRODUCING SOME SIGNIFICANT BLOWING
SNOW...ESPECIALLY WITH THE FLUFF EXPECTED WITH THE WEEKEND SYSTEM.
EVEN WITHOUT SNOW...WILL BE A THREAT. WILL HAVE TO KEEP AN EYE ON
THIS OVER THE COMING DAYS.

FOLLOWING THE SYSTEM...ANOTHER GLANCING COLDER SHOT...BUT OVERALL
PATTERN WILL FAVOR A BROADENING AND FLATTENING OF THE TROUGH ACROSS
THE CENTRAL CONUS. EVENTUALLY WILL SEE MODERATION TO TEMPS...BUT SEE
NO REASON WITH SNOWCOVER AND THE START WITH COLDER AIR TO SHADE
TOWARD COOLER RANGE OF GUIDANCE. MAY BE ANOTHER WEAK SYSTEM ZIPPING
IN OR NEAR THE REGION WEDNESDAY NIGHT...BUT FOR THE TIME HAVE NOT
MENTIONED ANY LIGHT PRECIP THREAT WITH THIS FEATURE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 602 PM CST THU DEC 5 2013

VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGHOUT THE TAF PERIOD.
NORTHWEST WINDS WILL REMAIN AROUND 5 TO 15 KT TONIGHT...AND INCREASE
TO 10 TO 20 KT DURING THE DAY ON FRIDAY.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WIND CHILL ADVISORY UNTIL 9 AM CST SATURDAY FOR SDZ038>040-050-
     052>071.

MN...WIND CHILL ADVISORY UNTIL 9 AM CST SATURDAY FOR MNZ071-072-080-
     081-089-090-097-098.

IA...WIND CHILL ADVISORY UNTIL 9 AM CST SATURDAY FOR IAZ001>003-
     012>014.

     WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO NOON CST FRIDAY FOR
     IAZ020>022-031-032.

NE...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO NOON CST FRIDAY FOR
     NEZ013-014.

&&

$$

SHORT TERM...JM
LONG TERM...JM/CHAPMAN
AVIATION...