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000
FXUS63 KFSD 012119
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
319 PM CST SUN MAR 1 2015

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 318 PM CST SUN MAR 1 2015

UPPER TROUGH ACROSS NORTHERN SOUTH DAKOTA WILL STEAM EASTWARD THIS
EVENING. STRATOCUMULUS FIELD AS A RESULT OF SURFACE BASED MIXING
WILL QUICKLY DISSIPATE THIS EVENING...AS WILL THE FEW SCATTERED
FLURRIES WHICH WILL GLANCE THE NORTHERN/NORTHEASTERN CWA LATE
AFTERNOON...AND THE GUSTY WESTERLY WINDS AS SURFACE RIDGE BUILDS
ACROSS THE CWA TONIGHT. DIFFERENCE IN SURFACE CONDITIONS SHOULD
AGAIN BE EVIDENT OVERNIGHT...AND WHERE RIDGE AXIS AND CLEARING
COINCIDE WITH MINOR SNOW COVER...WOULD NOT BE SURPRISED TO FIND LOWS
PLAYING WITH NEAR ZERO READINGS ONCE AGAIN...WHILE SNOW FREE AREAS
STAY CLOSER TO 10 ABOVE.

CLOUDS WILL START TO INFRINGE ON THE SOUTHWESTERN CWA DURING THE
EARLY MORNING...WITH BUILDING HEIGHTS/WARM AIR ADVECTION INCREASING
THROUGH THE DAY. PROSPECT OF GETTING MUCH TO REACH THE GROUND IN THE
INITIAL WARM ADVECTIVE PULSE IS FAIRLY LOW INITIALLY WITH DRY AIR AT
LOWER LEVEL. GRADUALLY...SHOULD SEE SOME LOWER CHANCES FOR
PRECIPITATION DEVELOPMENT AS THE BAND LIFTS NORTHEAST THROUGH THE
DAY.  A BIT OF DISCONNECT BETWEEN THE SURGING MID LEVEL LIFT AND
MOISTURE...AND LAGGING LOWER LEVEL MOISTURE COMING UP LATER IN THE
DAY. WILL LIKELY HAVE A GREATER STRATUS DEVELOPMENT GOING THROUGH
THE AFTERNOON COMING OUT OF EASTERN NEBRASKA ON LOW LEVEL JET.
SURFACE WINDS WILL BE QUITE BRISK FROM THE SOUTH...AND SHOULD SEE
SOME WINDS APPROACHING ADVISORY CRITERIA OVER THE WESTERN CWA.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 318 PM CST SUN MAR 1 2015

THE MAIN STORY CONTINUES TO BE THE SYSTEM PROJECTED FOR MONDAY NIGHT
INTO TUESDAY. SOME FAIRLY SIGNIFICANT CHANGES IN THE MODELS TODAY.
THE TREND BEGAN LAST NIGHT AND HAS BEEN REINFORCED WITH THE 12Z
RUNS...MAINLY ON SHIFTING THE FORCING FARTHER NORTH. THE FAR
SOUTHERN CWA NOW CLOSER TO AN ELEVATED DRY SLOT AND ALSO TO THE
DEEPER LOW LEVEL MOISTURE THUS SOUNDING ANALYSIS INDICATING THAT
FREEZING DRIZZLE SHOULD BE MORE OF A THREAT THAN WAS PREVIOUSLY
EXPECTED. BETWEEN ABOUT 9Z AND 15Z...THE BETTER CHANCE FOR FREEZING
DRIZZLE...THERE IS A LITTLE ELEVATED INSTABILITY SO WITH WET BULB
TEMPERATURES SUPPORTING SNOW IF SNOW SHOWERS CAN DEVELOP NOT AN EASY
SOLUTION TO GO JUST FREEZING DRIZZLE. AND WITH A SURGE OF WARM/MOIST
ADVECTION DURING THE EVENING DO EXPECT SOME SNOW SHOWERS TO PUSH
INTO THE EASTERN CWA BUT SHOULD REMAIN MOSTLY DISORGANIZED. THE MAIN
WAVE COMES OUT AND CONVERGENCE ON THE MID LEVEL BAND INCREASES IN
THE SOUTHWEST CWA AROUND MIDNIGHT...THEN SHOULD QUICKLY COLLAPSE
EASTWARD OVERNIGHT. STILL EXPECTING PRETTY MUCH ALL SNOW. THIS BROAD
BAND SHOULD START TO THEN COLLAPSE SOUTHEAST AND PRETTY MUCH BE
SOUTH OF THE CWA BETWEEN 18Z AND 21Z TUESDAY. THE CONCERN THEN TURNS
TOWARDS NORTH WINDS OF 25 TO 40 MPH ON TUESDAY LATE MORNING INTO THE
AFTERNOON WHICH WILL LIKELY CAUSE SOME DECENT BLOWING SNOW. FOR NOW
BELIEVE THIS EVENT WILL REMAIN BELOW WARNING CRITERIA SO NO WATCH
PLANNED. SINCE IT ALSO IS MOSTLY A 4TH PERIOD ISSUE WILL HOLD OFF ON
ANY ADVISORIES AND TRY TO IRON OUT WHETHER OR NOT THIS NORTHWARD
SHIFT IS CORRECT.

STRONG WINDS AND PATCHY DRIFTING SNOW WILL CONTINUE INTO TUESDAY
NIGHT AND WEDNESDAY MORNING AND WITH TEMPERATURES LIKELY BELOW ZERO
IN MANY LOCATIONS WIND CHILLS WILL DROP TO ABOUT 15 BELOW TO 25
BELOW.

WEDNESDAY WILL BE JUST PLAIN COLD WITH GRADUALLY DIMINISHING
NORTHWEST WINDS AND HIGHS MAINLY IN THE SINGLE DIGITS. A LITTLE
WARMER ALONG THE MISSOURI RIVER WITH TEMPERATURES IN THE TEENS.

DID GO AHEAD AND LOWER LOWS A BIT WEDNESDAY NIGHT WITH EXPECTATION
OF FRESH SNOW COVER AND A RIDGE OF HIGH PRESSURE PASSING THROUGH.
THE COLDEST TEMPERATURES SHOULD BE FROM THE BIG SIOUX RIVER VALLEY
EAST WHERE WINDS WILL BE LIGHTEST TOWARDS SUNRISE THURSDAY MORNING.

IN THE OUTER PERIODS(THURSDAY THROUGH SUNDAY)...STILL VERY MUCH ON
TRACK FOR A WARM UP...ESPECIALLY ALOFT...WITH THE MAIN CHALLENGE
FIGURING OUT HOW MUCH OF THIS TRANSLATES TO THE SURFACE GIVEN THE
EXPECTED FRESH SNOW COVER. FOR NOW WITH THE EXPECTATION BEING A BAND
OF 2 TO 4 INCHES DO NOT FEEL IT WILL COMPLETELY WIPE OUT THE WARM UP
BUT WILL TEMPER HIGHS AND LOWS A BIT INTO THE WEEKEND. REGARDLESS
STILL LOOKING AT HIGHS IN THE 40S SOUTH AND WEST AND 30S NORTH AND
EAST. THE WEAK SYSTEM ON SATURDAY HAS BEEN AVERAGED OUT BETWEEN
YESTERDAYS VERY COLD GFS AND YESTERDAY VERY WARM ECMWF TO SOMETHING
MORE BELIEVABLE TODAY WITH JUST A BRIEF SHOT OF COOL AIR. NO PLANS
ON ANY PRECIPITATION DURING THIS TIME FRAME.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1148 AM CST SUN MAR 1 2015

WHILE VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD...THERE
IS A LESS THAN MENTIONABLE THREAT FOR A BRIEF PERIOD OF MVFR
VISIBILITY LATE NIGHT AND EARLY MORNING AT EACH SITE...BUT MORE
LIKELY TO BE SHALLOW FOG IF ANY DEVELOPS. WINDS WILL INCREASE ON
MONDAY...AND COULD SEE A FEW SURFACE GUSTS TO AROUND 25 KNOTS
STARTING LATE MORNING AT KHON.

&&

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

$$

SHORT TERM...CHAPMAN
LONG TERM...08
AVIATION...CHAPMAN