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000
FXUS63 KFSD 100255
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
955 PM CDT SUN MAR 9 2014

.UPDATE...
ISSUED AT 926 PM CDT SUN MAR 9 2014

JUST A QUICK GLANCE AT THE LATEST INFORMATION. THE 18Z NAM AND NOW
0Z NAM SEEM TO HAVE A BETTER HANDLE...AT LEAST WITH QPF...THAN DID
THE 12Z RUNS. EVEN THOUGH THE 12Z RUNS HAD UPPER LEVEL SUPPORT
WORKING SOUTHEAST FROM WESTERN SD INTO CENTRAL NEBRASKA LATE
MONDAY NIGHT INTO TUESDAY MORNING THEY WERE SPREADING THE BETTER
QPF AMOUNTS EASTWARD ALONG THE HIGHWAY 14 CORRIDOR AND EVEN
FARTHER POINTS NORTHWARD. THE 18Z NAM AND 0Z NAM NOW WORK THIS QPF
MORE SOUTHEASTWARD HINTING AT A POTENTIAL PIVOT POINT SETTING UP
SOMEWHERE LIKELY BETWEEN SIOUX FALLS AND MITCHELL. A LITTLE EARLY
TO PICK THE EXACT SPOT BUT WITH WHAT LOOKS LIKE THE INTERACTION OF
THE UPPER LEVEL SUPPORT AND THE 750-700MB FRONT IT WOULD MAKE
SENSE THAT SOMETHING LIKE THIS MIGHT OCCUR. WHILE INSTABILITY IS
NOT GREAT THERE IS STILL ENOUGH TO MAKE THIS BAND POTENTIALLY
INTERESTING...ESPECIALLY GIVEN HOW DRY THE 750MB TO 950MB LAYER
IS.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 430 PM CDT SUN MAR 9 2014

CIRRUS CONTINUES TO STREAM ACROSS THE CWA...AND IS ACTUALLY EXPECTED
TO GET A LITTLE THICKER THROUGH THE EVENING BEFORE THINNING/CLEARING
FOR A BIT DURING THE LATTER HALF OF THE NIGHT. THE THICKER CLOUDS...
ALONG WITH MODEST WINDS IN MOST AREAS AND INCREASED MOISTURE IN THE
LOWER LEVELS...WILL HELP KEEP TEMPS ABOVE FREEZING OVERNIGHT. MAIN
QUESTION DURING THE OVERNIGHT WILL BE WHETHER SNOWMELT TODAY WILL
LEAD TO ANY FOG DEVELOPMENT TONIGHT. TOUGH CALL WITH A WESTERLY LOW
LEVEL FLOW...AS THIS TYPICALLY IS NOT FAVORABLE FOR EXTENSIVE FOG.
BUT GIVEN THE EXPECTED CLEARING LATE /SHOULD ALLOW NORTH CENTRAL
AREAS TO COOL CLOSER TO DEW POINT/ AND SOMEWHAT LIGHTER WINDS IN THE
SLIGHT UPSLOPE FLOW AREA EAST OF THE JAMES RIVER...OPTED TO ADD IN A
MENTION OF PATCHY FOG BETWEEN THE JAMES RIVER AND HIGHER ELEVATIONS
OF THE BUFFALO RIDGE LATE TONIGHT/EARLY MONDAY.

MILD START WILL LEAD TO ANOTHER VERY MILD DAY...THOUGH NOT AS MUCH
AS TODAY IN MOST AREAS. WITH MORE SUNSHINE AND NORTHWEST LOW LEVEL
FLOW WHICH SHOULD STILL BE FAVORABLE FOR DECENT MIXING...DID BUMP
SOUTHWEST MN TEMPS UP A LITTLE HIGHER THAN THEY HAVE REACHED TODAY
WHILE WESTERN AREAS SHOULD STAY A LITTLE COOLER AS MID-HIGH CLOUDS
BEGIN TO MOVE IN THROUGH THE AFTERNOON IN ADVANCE OF MONDAY NIGHT
WAVE. EXPECT PRECIP TO REMAIN WEST OF THE CWA THROUGH 00Z...THOUGH
COULD BE GETTING CLOSE TO OUR NORTHWEST CORNER VERY LATE IN THE DAY.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 430 PM CDT SUN MAR 9 2014

PERIOD OF WARMTH WILL COME TO A SHARP...BUT BRIEF...DEMISE BY
TUESDAY AS A TROUGH PROGRESSES TOWARD THE DEFORMATION ZONE ACROSS
THE CWA. SYSTEM IS EXTREMELY FRONTOGENETICAL...AND THIS USUALLY
RESULTS IN A MORE RAPID DEVELOPMENT OF BANDED PRECIPITATION. WARM
TEMPS THROUGH THE EVENING WILL RESULT IN ALL LIGHT RAINFALL...
PROBABLY SOMEWHAT SHOWERY AS THE SATURATION WORKS FROM MID LEVELS.
COVERAGE OF PRECIP SHOULD ENHANCE VERY QUICKLY GIVEN THE STRENGTH
OF THE FRONTOGENETIC FORCING SUGGESTED IN ALL GUIDANCE. WHILE
THERE HAVE BEEN SOME NOTED DIFFERENCES IN QPF LOCATION OVER THE
LAST 24-48 HOURS WORTH OF MODEL RUNS...THERE HAS BEEN LESS
DEVIATION IN WHERE FRONTOGENESIS AND RELATIVE INSTABILITY SETS UP.
LOOKS LIKE MORE FAVORABLE LEVEL FOR LIFT WILL INITIATE BETWEEN
750-700 HPA...AND THERE IS A GREAT DEAL OF INSTABILITY NEAR THIS
LEVEL AND TO THE WARM SIDE OF ELEVATED FRONTAL BOUNDARY TO THE
SOUTH. JET CORE POISED TO THE NORTHEAST FROM MONDAY NORTHERN
STREAM TROUGH WILL PROVIDE A CONSTANT SOURCE OF NORTH TO NORTHEAST
FLOW TO THE AREA WITH COOLER AND DRIER TRAJECTORY FEEDING INTO
DEVELOPING PRECIP BAND...AND SOUTHERN PORTIONS OF WAVE WILL DIG TO
PRODUCE DECENT CYCLOGENESIS IN THE CENTRAL PLAINS...AGAIN
ISALLOBARICALLY SUPPORTING THAT NORTH TO NORTHEAST COMPONENT. AS
PRECIPITATION DEVELOPS...EXPECT A VERY TIGHT BAND TO DEVELOP IN
RESPONSE TO FRONTAL FORCING AND INSTABILITY. COMBINATION OF LARGE
SCALE COOLING SETTLING SOUTHWARD...EVAPORATIVE IMPACTS...AND
HARDER TO QUANTIFY DIABATIC IMPACTS IN INTENSE BANDING WILL DRIVE
PRECIPITATION OVER TO SNOWFALL...AND INDICATIONS OFF GREATER 12Z
RUNS AND SREF ENSEMBLES IS A FASTER TRANSITION THAN EARLIER RUNS
SUGGEST. BY 12Z...EXPECT BULK OF THE PRECIPITATION BAND TO BE NEAR
AND NORTH OF I 90...WITH A STEADY AND SLOW SOUTHWARD PROGRESSION
DURING THE MORNING AND EARLY AFTERNOON. LIFT THROUGH THE MORNING
HOURS ALONG THE COULD GET EVEN A LITTLE EXTRA BOOST AS PV
ADVECTION SLIDES IN ALOFT OVER THE FRONTAL BOUNDARY. FOR NOW...
HAVE A BAND OF GENERALLY 2 TO 4 INCHES FORECAST OVER THE NORTHERN
TWO THIRDS OF THE CWA...AND AN INCH TO TWO IN THE SOUTH. CERTAIN
THAT THE FORECAST WILL EVOLVE IN TERMS OF SNOWFALL AMOUNTS... AS
IN ALL LIKELIHOOD WILL BE A TIGHT BAND OF HEAVIER SNOWFALL WHICH
COULD EXCEED 3 OR 4 INCHES IN A HARD TO DEFINE LOCATION AT THIS
RANGE. GOOD NEWS IS THAT TEMPS WILL LIKELY BE IN THE 30-33 AT
COLDEST DURING SNOW...AND THIS WILL HELP TO LIMIT TOTAL AMOUNTS AS
WELL AS THE TRANSIENCE OF THE BANDING.

TUESDAY NIGHT...SECONDARY COLD FRONT WILL BACK SOUTHWARD INTO THE
AREA AS ENERGY IN NORTHERN STREAM WRAPS THROUGH THE GREAT LAKES
AND PHASES INTO THE TROUGH TO THE EAST. INCREASING LOW LEVEL
HUMIDITY ALONG THE BOUNDARY AND SHALLOW LIFT FORCING COULD BRING A
FEW FLURRIES OR EVEN A LIGHT SNOW SHOWER OVER ABOUT THE EASTERN
HALF OF THE AREA AS TEMPS FALL TOWARD ICE CRYSTAL FAVORED NUMBERS.
HAVE NOT ADDED IN THIS COMPLEXITY YET AT THIS TIME. BOUNDARY WORKS
BACK EASTWARD THROUGH WEDNESDAY NIGHT...WITH CLOUDS AND AGAIN EVEN
A MEAGER SNOW THREAT...IF ANY DEEPER LIFT CAN DEVELOP. EVEN A
LITTLE FREEZING DRIZZLE MAY BE SOMETHING TO WATCH FOR DURING THE
WED NIGHT/EARLY THU PERIOD.

EXPECT THAT A FAIR AMOUNT OF THE SNOWFALL WILL MELT ON WEDNESDAY
WITH HIGH MOISTURE CONTENT TO SNOWFALL...AND WHILE IMPACTING HIGHS
TO THE LOWER SIDE ON WEDNESDAY ALONG WITH CLOUDS...BUT SHOULD HAVE
LITTLE IMPACT ON POTENTIAL THURSDAY. ALLBLEND TEMPS DID NOT EVEN
REFLECT ISOTHERMAL FROM 925 HPA FOR THE WESTERN HALF OF THE AREA...
AND GIVEN THE WEST AND SOUTHWEST COMPONENT AND BIAS TOWARD COLD
READINGS ON THIS WIND DIRECTION...BOOSTED SOME READINGS 3-5
DEGREES FROM INITIAL GUIDANCE.

CLIPPER SYSTEM DIVES WELL NORTHEAST OF THE AREA ON THURSDAY NIGHT
AND FRIDAY...AND WILL SET UP A WINDY DAY ON FRIDAY...AND WENT
NEAR A 925 HPA BLEND FOR HIGHS...MID 40S NORTHEAST TO LOWER TO MID
50S MISSOURI RIVER VALLEY. COLD ADVECTION AND MORE CLOUDS FOR THE
WEEKEND. SATURDAY INTO SAT NIGHT...ANOTHER CLIPPER WAVE...THIS ONE
DIGGING IN A BIT MORE TO THE SOUTHWEST AND THERMAL GRADIENT OVER
THE SOUTHWEST CWA...COULD YIELD A LITTLE SNOW...OR RAIN. GFS
SUGGESTS A BIT MORE STRENGTH TO SYSTEM...AND PERHAPS A LITTLE MORE
SNOW THAN RAIN CHANCE...DEPENDING ON DIURNAL IMPACT ON SURFACE
LAYER TEMPS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY EVENING)
ISSUED AT 954 PM CDT SUN MAR 9 2014

VFR THROUGH THE PERIOD. AT THIS TIME PRECIPITATION SHOULD REMAIN
NORTH AND WEST OF THE AREA THROUGH 6Z MONDAY.

&&

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

$$

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