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000
FXUS63 KFSD 020341
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
941 PM CST SUN DEC 1 2013

.UPDATE...
ISSUED AT 941 PM CST SUN DEC 1 2013

INITIAL PRECIPITATION BAND WITH LEADING WAVE WORKING NOW ACROSS
THE SOUTHWEST MINNESOTA PORTION OF THE CWA. BROAD WARM AIR
ADVECTION ALONG WITH APPROACH OF NEXT PV IMPULSE CURRENTLY BACK
ACROSS FAR NORTHWEST SOUTH DAKOTA AND SOUTHWEST NORTH DAKOTA.
CHANNELED ADVECTION WITH THIS FEATURE IS PRIMARILY NORTH OF THE
CWA DURING THE LAST HALF OF THE NIGHT...BUT DOES BRUSH THE FAR
NORTH AND INTO SW MN ON THE SOUTHERN FRINGES. STILL FAIRLY DRY
AT LOW LEVELS BELOW THE MID LEVEL CLOUD BASE...AND HAS KEPT ANY
PRECIPITATION OF NOTE FROM REACHING THE GROUND IN FSD CWA THUS FAR
INTO THE EVENING...AND THIS WILL CONTINUE TO BE A CHALLENGE TO ANY
PRECIPITATION WITH THE SECOND WAVE. HENCE...SEE NO REASON TO
DEVIATE FROM THE VERY LOW POPS FROM EARLIER FORECAST.

WOULD EXPECT BASED ON COMPOSITE OF FORECAST SOUNDINGS ALONG WITH
KABR EVENING GROUND TRUTH...THAT SLEET WOULD LIKELY BE THE FAVORED
PRECIPITATION TYPE WITH THE MID TO LATE EVENING ACTIVITY IN SW MN...
PERHAPS WITH A SHADE OF SNOW IF RATE CAN COME UP ENOUGH TO WET
BULB THE TEMPS DOWN A DEGREE OR SO. FARTHER WEST WITH THE LIFT
ENHANCEMENT APPROACHING WITH THE SECONDARY WAVE...TEMPS ALOFT
CONTINUE TO WARM...AND EVEN THE KABR/KBIS/KUNR RAOBS WOULD START
TO LOOK TOWARD A LIQUID/FREEZING MIX...DEPENDENT ON SURFACE TEMPS
WHICH SHOULD BE SLOW TO MOVE MUCH WITH CLOUDS AGAIN THICKENING
FROM THE WEST. BUT AGAIN...FOR EMPHASIS...PROSPECT OF ANYTHING
MEASURABLE IS QUITE LOW.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 304 PM CST SUN DEC 1 2013

MAIN CONCERN THE NEXT 24 H IS THE SMALL POTENTIAL FOR
PRECIPITATION...PRIMARILY OVER SOUTHWEST MINNESOTA.

ALL MODELS SHOW TWO WAVES MOVING ACROSS THE DAKOTAS AND MINNESOTA
THE NEXT 24 H. THE FIRST WAVE IS ALREADY INTO CENTRAL SD PER WATER
VAPOR IMAGERY AND WILL LIKELY BE INTO SW MN AND NW IA BY 00Z. THERE
ARE FEW ECHOES ASSOCIATED WITH THIS SYSTEM AND THOSE ARE PRIMARILY
ACROSS FAR NORTHERN SOUTH DAKOTA. WITH VERY DRY AIR BELOW 10000 FT
AND BEST FORCING FOR ASCENT IN NORTHERN SD...HAVE REMOVED ANY CHANCE OF
PRECIPITATION WITH THIS WAVE. CLOSE ON ITS HEELS THOUGH IS A SECOND
WAVE. THE NAM IS FASTER AND FARTHER NORTH THAN EITHER THE RAP OR GFS
WITH THIS WAVE. CURRENT TRAJECTORY FROM WATER VAPOR FAVORS THE GFS
AND RAP AND FOLLOWED FOR LATER TONIGHT. THIS PUTS SAME STRONG
PRESSURE ADVECTION ON THE 1.5 PV SURFACE OVER THE CWA BY MIDNIGHT AND
CONTINUING THROUGH SUNRISE. AGAIN...MOISTURE IS A BIG ISSUE AS ALL
MODELS SHOW A 5000 TO 10000 FT DRY LAYER ABOVE THE SURFACE. FOR MUCH
OF SE SD AND NW IA...THIS DRY AIR EXPECTED TO EVAPORATE ANY
PRECIPITATION THAT DOES REACH THE SURFACE. THE ONLY PLACE THE DRY
AIR MAY BE OVERCOME IS IN SW MN WHERE IT MAY INTERACT WITH THE 850
MB BOUNDARY AND ENHANCE THE LIFT AND SATURATION. WHILE THE DRY AIR
LIKELY WILL LIMIT PRECIPITATION EVEN THERE...DID KEEP A SLIGHT CHANCE OF
PRECIPITATION FROM LATE EVENING THROUGH 12Z IN SW MN. TEMPERATURES
ALOFT ARE WELL ABOVE FREEZING...EVEN THE WET BULB TEMPERATURE WILL
BE ABOVE ZERO AND SHOULD MELT ANY PRECIPITATION ALOFT. TEMPERATURES
AT THE SURFACE THIS EVENING EXPECTED TO DROP TO AROUND 30 AND THEN
STEADY OUT AS CLOUDS AND SOUTH WINDS INCREASE. WHILE THERE IS A
POSSIBILITY TEMPERATURES COULD RISE ABOVE FREEZING AS ANY
PRECIPITATION MOVES IN...BELIEVE IT IS MOST LIKELY TO STAY JUST
BELOW FREEZING MOST OF THE NIGHT. SO ANY PRECIPITATION WILL LIKELY
BE A MIX OF FREEZING RAIN AND SLEET. AMOUNTS WILL BE LIGHT...A TRACE
TO A COUPLE HUNDREDTHS...BUT ENOUGH THAT IT COULD SLICK UP ROADS
SHOULD IT FALL.

OTHERWISE...THE PRECIPITATION WILL MOVE OFF BY MONDAY MORNING. THERE
WILL BE A LOT OF CLOUDS AROUND...ESPECIALLY EAST OF THE JAMES RIVER.
IT WILL ALSO BE VERY WARM ALOFT WITH +10C AT 925 MB IN SOUTH CENTRAL
SD WHERE THERE WILL ALSO BE SOME SUN. THEREFORE...EXPECT HIGHS TO
WARM INTO THE LOWER TO MID 50S IN SOUTH CENTRAL SD...WITH UPPER 40S
POSSIBLE OVER MUCH OF SE SD AND INTO NORTHEAST NEBRASKA AND
NORTHWEST IOWA. THE COLDEST TEMPS WILL BE IN SW MN WHERE CLOUDS WILL
BE AROUND MOST OF THE DAY AND WINDS WILL REMAIN S OR SE. BUT EVEN
THERE HIGHS WILL REACH THE LOWER 40S.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 304 PM CST SUN DEC 1 2013

THERE SEEMS TO BE LITTLE SUPPORT FOR PRECIPITATION MONDAY NIGHT
AHEAD OF THE APPROACHING LOW AND COLD FRONT. WITH SOME MID LEVEL
MOISTURE LIKELY TO BE PRESENT...HAVE GONE WITH JUST A SLIGHT
CHANCE OF LIGHT RAIN/FREEZING RAIN FOR LATE MONDAY NIGHT...THAT IS
AFTER MIDNIGHT/06Z. THIS IDEA CONTINUES INTO TUESDAY AS THE LOW
AND FRONT MOVES INTO THE AREA. THE GFS...EC...AND GEM/CANADIAN ARE
FAIRLY CLOSE TO EACH OTHER ON THE PATH AND MOVEMENT OF THE
LOW/FRONT AS IT ENTERS THE AREA AND ARE ACCEPTED OVER THE
NAM...WHICH SEEMS TO BE TOO FAST AND TOO FAR NORTH. EITHER
WAY...ANY STEADY OR WIDESPREAD PRECIPITATION SHOULD STAY NORTH OF
THE AREA...AND AM GOING FOR ONLY A CHANCE OF LIGHT
PRECIPITATION...WITH THE CHANCE INCREASING SLOWLY FROM THE
NORTHWEST IN THE INCOMING COLD AIR. AHEAD OF THE COLD AIR THE
SLIGHT PRECIPITATION THREAT WILL BE LIGHT RAIN/SNOW OR JUST LIGHT
RAIN...AND OF COURSE AS THE COLD AIR ARRIVES THE CHANCE WILL BE
FOR JUST LIGHT SNOW. THIS COOLING SHOULD BE COMPLETE BY EARLY
TUESDAY EVENING...AGAIN SHOWER THAN THE NAM WOULD SUGGEST.

TEMPERATURES...QUITE MILD MONDAY NIGHT...WILL RISE JUST A LITTLE
FAR NORTHWEST...TO A FEW DEGREES SOUTHEAST...BEFORE THE COLDER AIR
TURNS THEM STEADY THEN FALLING. EVEN BY THE SLOWER GFS AND
EC...THE COLD INVASION WILL BECOME WELL ESTABLISHED BY TUESDAY
EVENING. WILL CONTINUE THE CHANCES OF LIGHT SNOW THROUGH
WEDNESDAY AND OF A FEW FLURRIES INTO THURSDAY. LACK OF SUPPORT
DOOMS ACCUMULATIONS...IF ANY...TO BE QUITE LIGHT. FRIDAY AND
SATURDAY LOOK DRY AND COLD.

THE COLD AIR WILL BE QUITE BITING WITH WIND CHILLS CURRENTLY
EXPECTED TO DROP TO BELOW ZERO FAR WEST BY WEDNESDAY MORNING. BY
THURSDAY MORNING THE WHOLE AREA SHOULD BE BELOW ZERO AND THE NORTH
PERHAPS GETTING CLOSE TO THE ADVISORY BOUNDARY OF 20 BELOW ZERO.
TEMPERATURES AND WIND CHILLS WILL BE PARTLY DEPENDENT ON WHETHER
OR NOT WE GET ANY SNOW COVER...EVEN A HALF INCH TO INCH WILL HAVE
AN EFFECT. WHAT WE WILL HAVE IN THE FORECAST COULD BE A LITTLE
COLDER OR LESS COLD DEPENDING ON THAT FACTOR.

AM GOING WITH THE EXTENDED GUIDANCE INDICATING A LOW CHANCE OF
SNOW FOR DAY 7...NEXT SUNDAY. THE EC IS THE ONLY MODEL INDICATING
ANYTHING...BUT AS FAR WEST AS IT KEEPS THE UPPER TROUGH...GOING BY
IT ALONE WOULD RATE A BIGGER THREAT...SO SLIGHT CHANCE SEEMS THE
BEST ROAD FOR NOW. THERE WILL BE SOME SLIGHT MODERATION IN THE
COLD TEMPERATURES...BUT ONLY SLIGHT AS THE COLD REGIME WILL
DOMINATE FOR A WHILE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 941 PM CST SUN DEC 1 2013

WEAKER LEAD WAVE MOVING THROUGH MINNESOTA AND IOWA...WITH
SECONDARY SYSTEM RACING INTO NORTHWEST SOUTH DAKOTA. LIFT FORCING
WITH SECONDARY WAVE LOOKS TO REMAIN MAINLY NORTH AND EAST OF THE
TAF SITES...WITH POTENTIAL FOR PERHAPS A LITTLE LIGHT FREEZING
RAIN OR RAIN NEAR THE KHON SITE AROUND 07Z-11Z WINDOW.
HOWEVER...NOT WORTH A MENTION WITH VERY LOW PROBABILITY EVENT AT
THIS TIME. EVEN WITH A BIT BETTER THREAT OF PRECIPITATION TOWARD
SW MN...CONDITIONS ARE LIKELY TO REMAIN VFR EVEN IN ANY
PRECIPITATION...GREATER THAN 6 SM AND CEILINGS ABOVE 3000 FT AGL.

&&

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

$$

UPDATE...CHAPMAN
SHORT TERM...SCHUMACHER
LONG TERM...
AVIATION...CHAPMAN