352
FXUS63 KFSD 281106
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
506 AM CST MON NOV 28 2022
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 358 AM CST MON NOV 28 2022
THE CALM BEFORE THE STORM, WITH A RELATIVELY MILD DAY IN STORE
ACROSS THE AREA. CURRENT MESOANALYSIS INDICATES A SURFACE LOW
SLIDING EASTWARD ACROSS THE CANADIAN PRAIRIE PROVINCE, WITH A COLD
FRONT EXTENDING SOUTHWARD INTO WESTERN SD. OUT AHEAD OF THIS
FEATURE, A STRENGTHENING SURFACE PRESSURE GRADIENT IS PRODUCING A
GRADUAL INCREASE IN SOUTHERLY WINDS ACROSS OUR AREA. WITH THAT,
TEMPERATURES HAVE BEEN SLOWLY RISING FROM WEST TO EAST OVERNIGHT.
THIS TREND WILL CONTINUE THROUGH THE MORNING HOURS, WITH
TEMPERATURES EVENTUALLY RISING INTO THE LOWER 40S TO LOWER 50S BY
AFTERNOON. THE AFOREMENTIONED COLD FRONT WILL WORK SLOWLY ACROSS THE
AREA DURING THE DAY, THOUGH NOT FULLY MAKING IT OUT OF OUR AREA
UNTIL TONIGHT. WINDS WILL ACTUALLY DROP OFF DURING THE AFTERNOON AS
THE FRONT SLIDES IN AND THE SPG DECREASES.
BY TONIGHT, A DEEPENING SURFACE LOW OVER CO BEGINS TO MOVE TO THE
NORTHEAST, BEING CENTERED OVER NORTHEASTERN KS BY TUESDAY MORNING.
AT THE SAME TIME, AN UPPER LEVEL TROUGH OVER THE ROCKIES BEGINS TO
DRIFT EASTWARD INTO THE PLAINS. BY LATER TONIGHT, FRONTOGENESIS WILL
BEGIN TO INTENSIFY FROM AROUND 800-700 MB ORIENTED APPROXIMATELY
FROM SOUTH CENTRAL SD/CENTRAL MO RIVER CORRIDOR INTO SOUTHWESTERN
MN. WITH THAT, LIGHT SNOW WILL DEVELOP IN THAT VICINITY (WITH SOME
SLIGHT VARIATION AMONG CAMS) AS UPPER LEVEL LIFT INCREASES PER 300-
500 MB DIV Q. SNOWFALL AMOUNTS PRIOR TO 12Z ON TUESDAY WILL BE LIGHT
- GENERALLY LESS THAN HALF AN INCH. LOW TEMPERATURES OVERNIGHT WILL
RANGE FROM NEAR 20 OUR WESTERN AND NORTHERN AREAS TO UPPER 20S OVER
NORTHWESTERN IA.
LONG TERM
(TUESDAY THROUGH SUNDAY)
ISSUED AT 358 AM CST MON NOV 28 2022
BY TUESDAY MORNING, FRONTOGENESIS CONTINUES TO INTENSIFY WITH UPPER
LEVEL DIVERGENCE INCREASING IN THE LEFT EXIT REGION OF AN UPPER
LEVEL JET STREAMING NORTHWARD THROUGH EASTERN NE INTO IA. THERE ARE
SOME INDICATIONS THAT THERE MAY BE A BIT OF INSTABILITY ABOVE THE
FRONTAL CIRCULATION FOR A BRIEF TIME BETWEEN 12Z TO 15Z, AND WITH
THAT WE WILL SEE SNOWFALL PICK UP IN A BAND GENERALLY LOCATED IN A
LINE ROUGHLY FROM YANKTON TO LUVERNE TO WINDOM. OBVIOUSLY THE
HEAVIER BAND MAY SHIFT SLIGHTLY IN FUTURE MODEL RUNS, BUT PRESENTLY
CAMS AND GLOBAL MODELS ARE IN DECENT AGREEMENT ON THE GENERAL
LOCATION OF THE BAND. SOUNDINGS ARE INDICATING THAT THERE COULD BE A
BRIEF PERIOD OF FREEZING RAIN/DRIZZLE OVER NORTHWESTERN IA AT THE
ONSET OF PRECIPITATION PRIOR TO 18Z WITH LACK OF SATURATION IN THE
DENDRITIC LAYER, THOUGH ANY ICE ACCUMULATION IS EXPECTED TO BE
MINIMAL DUE TO THE SHORT DURATION. BY AFTERNOON, FRONTOGENESIS
BEGINS WEAKEN AND SHIFT TO THE SOUTHEAST WITH NO INSTABILITY NOTED
ABOVE THE FRONT. IN RESPONSE, SNOWFALL AMOUNTS WILL TREND DOWNWARD
THROUGH 00Z. OVERALL, ENSEMBLE PLUMES CONTINUE TO SHOW SOME
CLUSTERING IN THE VICINITY OF THE HEAVIER BAND AT THE RANGE OF
APPROXIMATELY 2 TO 4 INCHES - WITH LIGHTER AMOUNTS ON EITHER SIDE OF
THIS BAND.
UNFORTUNATELY, WITH THE SPG STRENGTHENING IN RESPONSE TO THE
AFOREMENTIONED SURFACE LOW TRACKING THROUGH IA DURING THE DAY,
NORTHERLY WINDS WILL CRANK UP BY THE AFTERNOON, GUSTING 30 TO 35 MPH
INTO THE EVENING. AS A RESULT, PATCHY BLOWING SNOW WILL BE POSSIBLE
IN AREAS THAT RECEIVE HEAVIER SNOWFALL. BASED ON ALL OF THE ABOVE,
WENT AHEAD AN ISSUED A WINTER WEATHER ADVISORY FOR PORTIONS OF
SOUTHEASTERN SD, NORTHEASTERN NE, NORTHWESTERN IA, AND SOUTHWESTERN
MN FOR TUESDAY.
SNOW ENDS EARLY ON TUESDAY NIGHT AS THE SURFACE LOW MOVES INTO THE
GREAT LAKES REGION. THE UPPER LEVEL TROUGH MOVES INTO THE
MISSISSIPPI VALLEY ON TUESDAY NIGHT, THEN TO THE EASTERN SEABOARD BY
EARLY THURSDAY. THIS PUTS OUR AREA IN A NORTHWESTERLY UPPER FLOW
DURING THE PERIOD, AND VERY COLD AIR WILL FUNNEL INTO OUR AREA FOR
TUESDAY NIGHT INTO WEDNESDAY NIGHT. BOTH THE NAEFS AND ECMWF
ENSEMBLES SHOW 850 MB TEMPERATURES IN THE BOTTOM 10TH PERCENTILE OR
LOWER WITH RESPECT TO CLIMATOLOGY, AND WE ARE LOOKING AT LOWS MAINLY
IN THE SINGLE DIGITS FOR BOTH TUESDAY NIGHT AND WEDNESDAY NIGHT,
WITH HIGHS ON WEDNESDAY IN THE UPPER TEENS AND 20S. WITH THE COLD
AIR ADVECTION, A STRONG SURFACE PRESSURE GRADIENT, AND WINDS RUNNING
AROUND 25 TO 30 KTS AT THE TOP OF THE MIXED LAYER, THE COLD WILL BE
FURTHER AGGRAVATED BY THE STRONG NORTHWESTERLY WINDS THROUGH THAT
PERIOD - WITH WIND CHILLS BELOW ZERO ON TUESDAY NIGHT INTO EARLY
WEDNESDAY.
A FAIRLY RAPID RECOVERY OCCURS FOR THURSDAY AND FRIDAY AS THE UPPER
LEVEL FLOW TAKES ON A MORE SOUTHWESTERLY COMPONENT, WITH A SOUTHERLY
FLOW AT THE SURFACE AS HIGH PRESSURE EXITS TO THE EAST AND A SURFACE
TROUGH APPROACHES FROM THE WEST. THIS WILL THROW HIGHS BACK INTO THE
30S AND 40S ON THURSDAY AND FRIDAY, AND IT AGAIN LOOKS TO BE A
BREEZY TO WINDY PERIOD. A COLD FRONT SWINGS THROUGH THE REGION LATER
ON FRIDAY, BRINGING A COOL DOWN FOR THE EARLY PART OF NEXT WEEKEND,
BEFORE WARMING AGAIN ON SUNDAY AS THE UPPER LEVEL FLOW BECOMES MORE
ZONAL. OUTSIDE OF THE POTENTIAL FOR LIGHT PRECIPITATION ON FRIDAY
NIGHT, IT APPEARS TO BY DRY FOR THE END OF THE WEEK INTO THE
WEEKEND.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 458 AM CST MON NOV 28 2022
WITH A LOW LEVEL JET OVERHEAD, THERE WILL BE A PERIOD OF LOW LEVEL
WIND SHEAR AT KSUX THIS MORNING. OTHERWISE, GUSTY SOUTHERLY WINDS
EARLY IN THE DAY WILL DIMINISH IN THE AFTERNOON, TRANSITIONING TO
WEST/NORTHWESTERLY AS A FRONTAL BOUNDARY SLIDES ACROSS THE REGION
INTO TONIGHT. LIGHT SNOW WILL DEVELOP THROUGH SOUTH CENTRAL SD
EARLY TONIGHT, THEN EXPAND TO THE NORTH AND EAST THROUGH THE
REMAINDER OF THE TAF PERIOD - AFFECTING KFSD TOWARD THE END OF THE
PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...WINTER WEATHER ADVISORY FROM 6 AM TO 6 PM CST TUESDAY FOR SDZ062-
066>071.
MN...WINTER WEATHER ADVISORY FROM 6 AM TO 6 PM CST TUESDAY FOR MNZ080-
081-089-090-097-098.
IA...WINTER WEATHER ADVISORY FROM 6 AM TO 6 PM CST TUESDAY FOR
IAZ001>003-012>014-020.
NE...WINTER WEATHER ADVISORY FROM 6 AM TO 6 PM CST TUESDAY FOR NEZ013.
SHORT TERM...JM
LONG TERM...JM
AVIATION...JM
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