429
FXUS63 KFSD 180847
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
247 AM CST MON NOV 18 2024
KEY MESSAGES
- RAIN (90%-100% CHANCE) WILL MOVE IN FROM THE SOUTH FROM LATE THIS
MORNING INTO THE AFTERNOON, THEN COME TO AN END FROM SOUTH TO
NORTH THROUGH TUESDAY MORNING. RAIN RATES UP TO 0.25"
INCHES/HR AS WELL AS SOME HIGHER RATES IN LATE AFTERNOON AND
EVENING CONVECTION COULD LEAD TO ACCUMULATIONS OF 1-2" INCHES
IN AREAS NEAR AND EAST OF HIGHWAY 81.
- LIGHT SNOW WILL BE POSSIBLE NEAR AND NORTH OF I-90 FROM
TUESDAY NIGHT TO WEDNESDAY. HOWEVER, UNCERTAINTY STILL REMAINS
IN EXACT AMOUNTS.
- STRONG NORTHWESTERLY WINDS ARE EXPECTED ON TUESDAY AND
WEDNESDAY WITH WIND GUSTS BETWEEN 45 TO 55 MPH POSSIBLE. THE
STRONGEST WINDS ARE MOST LIKELY ON WEDNESDAY.
- COLD WIND CHILLS IN SINGLE DIGITS TO TEENS ARE LIKELY TUESDAY
NIGHT INTO THURSDAY MORNING.
DISCUSSION
ISSUED AT 246 AM CST MON NOV 18 2024
RAIN POTENTIAL TODAY INTO TUESDAY MORNING:
VERY FEW CHANGES TO THE FORECAST IN REGARDS TO TIMING AND AMOUNTS OF
RAINFALL FROM LATE MORNING TODAY THROUGH TUESDAY MORNING. LOW
PRESSURE DEEPENS TO THE SOUTH TODAY AND BRINGS A SWATH OF MOISTURE
NORTHWARD. RAIN SHOULD BEGIN TO MOVE INTO THE MISSOURI RIVER VALLEY
NEAR NEBRASKA BY LATE MORNING, THEN SPREAD NORTH TOWARDS HIGHWAY 14
BY MID TO LATE AFTERNOON. AS THE DRY SLOT AND VORTICITY MAXIMUM MOVE
TOWARDS SIOUX CITY FROM ABOUT 5PM TO 9PM, ISOLATED THUNDERSTORMS
WILL BE POSSIBLE WITH SOME LOCALLY HEAVIER RAIN THE MAIN THREAT.
STILL VERY HIGH CHANCES (70-100%) FOR A HALF AN INCH OR MORE OF
RAINFALL EAST OF THE JAMES RIVER, WITH A 50-80% CHANCE FOR AN INCH
OR MORE NEAR AND EAST OF I-29. CENTRAL SD, NEAR GREGORY AND
CHAMBERLAIN, ARE STILL EXPECTED TO SEE THE LOWEST RAINFALL TOTALS.
IN FACT THE LATEST EC ENSEMBLE AND GEFS RUNNING JUST 20-40 PERCENT
CHANCE FOR A TENTH OF AN INCH OR MORE.
WIND (TUESDAY AND WEDNESDAY) AND SNOW POTENTIAL (LATE TUESDAY NIGHT
INTO WEDNESDAY):
ATTENTION STILL ON WEDNESDAY AS THE EC AND GEFS CONTINUE TO SHOW
DISAGREEMENT. THE GEFS CONTINUES TO LEAN TOWARDS MUCH LOWER AMOUNTS
OF SNOW NORTH OF I-90, NEED TO GET TO THE 90TH PERCENTILE TO SHOW 1-
2" OF POTENTIAL. THE LATEST RUN OF THE NAM IS ALSO LEANING ON THE
DRIER SIDE WITH ONLY A COUPLE OF TENTHS OF AN INCH OF POTENTIAL NEAR
HIGHWAY 14. BOTH THE GEFS AND EC ENSEMBLE HAVE THE HIGHER CHANCES OF
SNOW ACROSS SLIGHTLY HIGHER ELEVATIONS OF EASTERN BRULE AND
KINGSBURY COUNTIES. THE LATEST EC ENSEMBLE HAS ALSO BACKED OFF ON
THE HIGHER AMOUNTS WITH ONLY A 20-30 PERCENT CHANCE TO GET ABOUT 1"
OR MORE OF SNOW NEAR HIGHWAY 14. THE EC ENSEMBLE IS ALSO SHOWING
NEEDING TO GET TO THE 75-90TH PERCENTILE TO GET CLOSER TO AN INCH OR
TWO OF SNOW, WHICH IS DOWN FROM PREVIOUS RUNS SO IT IS NOW MORE IN
LINE WITH THE LOWER AMOUNTS FROM THE GEFS.
DYNAMICALLY, THE MODELS ARE INDICATING A DEEPENING LOW ACROSS
NORTHERN MN WHICH TRIES TO SWING A WEAK MID LEVEL WAVE IN THE
NORTHWEST FLOW ON THE BACKSIDE INTO THE AREA LATER TUESDAY NIGHT
INTO WEDNESDAY. BOTH THE GFS AND NAM MODEL SOUNDINGS SHOWING
SATURATION FROM ABOUT 800-500 MB WHICH IS WHERE THE DENDRITIC ZONE
LIES. THIS SHOULD AID IN PRODUCING AT LEAST SOME LIGHT SNOW.
INCREASED CHANCES A BIT AND BROUGHT THE THREAT FOR A COUPLE OF
TENTHS OF AN INCH TO I-90.
WHAT APPEARS TO BE MOST LIKELY ARE WIND GUSTS OF 45 TO 55 MPH ON
WEDNESDAY WHICH IS WHY AN INCH OR TWO OF SNOW IS SUCH A BIG DEAL. A
COUPLE OF TENTHS NOT MANY PROBLEMS, A COUPLE OF INCHES WITH THIS
KIND OF WIND COULD LEAD TO SHORT TERM BLIZZARD CONDITIONS. RIGHT NOW
THIS THREAT, WHILE LOW (10-20%), IS RELEGATED TO LOCATIONS NEAR
HIGHWAY 14.
FROM THURSDAY INTO THE WEEKEND BELOW NORMAL TEMPERATURES AND DRY
CONDITIONS ARE EXPECTED. GENERALLY HIGHS IN THE 30S AND LOWS IN THE
TEENS AND 20S.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1102 PM CST SUN NOV 17 2024
VFR CONDITIONS AND RELATIVELY LIGHT WINDS WILL PREVAIL THROUGH
THE NIGHTTIME HOURS AND INTO EARLY MORNING MONDAY.
AFTER 14Z-15Z, RAIN WILL QUICKLY SPREAD NORTH ACROSS MUCH OF THE
FORECAST AREA, BRINGING A RAPID DETERIORATION IN CEILINGS, AND
TO A LESSER EXTENT VISIBILITY. BY LATE AFTERNOON MONDAY, IFR TO
LIFR CEILINGS WILL BE WIDESPREAD, PERHAPS NOT REACHING KHON BY
19/02Z. WITH LIGHT TO MODERATE RAIN EXPECTED, MVFR TO LOCALLY
IFR VISIBILITY IS ALSO LIKELY.
EAST WINDS WILL INCREASE AFTER DAYBREAK, AND ESPECIALLY AFTER
18Z, WITH GUSTS 20-25KT PREVALENT EAST OF THE JAMES RIVER VALLEY
THROUGH THE AFTERNOON. GUSTY WINDS SWING AROUND TO THE NORTH IN
SOME LOCATIONS THROUGH MONDAY EVENING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...08
AVIATION...JH
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