972
FXUS63 KFSD 201137
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
537 AM CST WED FEB 20 2019
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 413 AM CST WED FEB 20 2019
HEAVIEST SNOW MOVING THROUGH SIOUX FALLS AT THIS TIME, AND SNOWFALL
RATES WITHIN THIS AREA ARE QUITE IMPRESSIVE, WITH A DISTINCT CHANGE
IN SNOW CHARACTER AS THE STRONGEST LIFT IN THE DENDRITIC GROWTH ZONE
MOVES OVER THE AREA. PRIOR TO 2 AM SNOW-LIQUID RATIOS WERE AVERAGING
RIGHT AROUND 10:1, BUT THE DENDRITIC SNOWS BROUGHT A QUICK 2.3 IN/HR
WITH ONLY 0.08" LIQUID, OR NEARLY 30:1 RATIO!
THIS STRONGEST LIFT SHIFTS INTO THE FAR NORTHEAST CORNER OF THE
FORECAST AREA/MINNESOTA RIVER VALLEY BY 12Z, SO EXPECT RATES TO DROP
BACK QUICKLY DURING THE REMAINING PRE-DAWN HOURS. HOWEVER, BECAUSE
OF THE RAPID ACCUMULATION IN THAT HEAVIEST AREA, OPTED TO EXPAND THE
WINTER STORM WARNING WESTWARD INTO THE I-29 CORRIDOR. BASED ON WHERE
THE HEAVIER RETURNS ARE ON RADAR, ALONG WITH VISIBILITY ON WEB CAMS
AND AIRPORT OBSERVATIONS, HAVE LEFT THE WESTERN EDGE OF THE ADVISORY
ALONE, THOUGH WOULD NOT BE SURPRISED TO SEE ISOLATED AMOUNTS AROUND
OR JUST A LITTLE HIGHER THAN 3 INCHES INTO THE JAMES RIVER VALLEY.
ALSO ADJUSTED THE END TIME OF THE HEADLINES ALONG AND SOUTH OF A
LINE FROM SIOUX FALLS TO STORM LAKE TO NOON INSTEAD OF 3 PM, AS ONLY
MINIMAL ADDITIONAL SNOW IS EXPECTED AFTER NOON IN THESE AREAS.
AS FAR AS WHEN IT WILL END, PRETTY GOOD MODEL CONSENSUS DEPICTING A
WELL-DEFINED BACK EDGE LIFTING NORTHEAST AS SURFACE BOUNDARY SWINGS
WINDS AROUND TO THE SOUTHWEST AND WEST, AND THIS SHOULD REACH THE
MISSOURI RIVER VALLY BY MID MORNING, KHON-KFSD_KSLB BY NOON, AND
EXIT THE NORTHEAST CWA BY 3 PM. STILL NOT LOOKING AT MUCH WIND,
RELATIVELY SPEAKING, BUT COULD SEE SOME WESTERLY GUSTS UP TO AROUND
15-25 MPH ALONG AND SOUTH OF I-90 THIS AFTERNOON, SO SOME DRIFTING
OF THIS POWDER IS CERTAINLY POSSIBLE.
TONIGHT INTO THURSDAY SHOULD BE RATHER TRANQUIL, A BRIEF CALM BEFORE
THE NEXT ACTIVE PERIOD WHICH ARRIVES IN OUR FAR WEST LATE THURSDAY
AFTERNOON. AS WINDS DROP OFF OVER THE FRESH SNOW TONIGHT, SHOULD SEE
LOWS IN THE ZERO TO 5 ABOVE RANGE FOR MOST AREAS, WITH LOCALIZED SUB-
ZERO READINGS POSSIBLE. HIGHS THURSDAY GENERALLY IN THE UPPER TEENS
TO MID 20S.
LONG TERM
(THURSDAY THROUGH TUESDAY)
ISSUED AT 413 AM CST WED FEB 20 2019
WITH ONGOING WEATHER, DID NOT HAVE A LOT OF EXTRA TIME TO DEVOTE TO
DEEP INTERROGATION OF THE MID-LONG RANGE. HOWEVER, CONTINUES TO LOOK
LIKE AN ACTIVE PATTERN, WITH A PROLONGED PERIOD OF SNOWFALL POSSIBLE
THURSDAY NIGHT INTO SATURDAY NIGHT AS ELONGATED TROUGH SLIDING OUT
OF THE ROCKIES BY FRIDAY, BEGINS TO INTENSIFY AS IT LIFTS NORTHEAST
TOWARD THE MID-MISSISSIPPI VALLEY THIS WEEKEND. COULD BE SOME PRECIP
TYPE ISSUES IN OUR FAR SOUTHEAST AS WARMER AIR ALOFT IS WRAPPED INTO
NORTHERN IOWA, BUT OTHERWISE GENERALLY LOOKS LIKE SNOW FOR MOST OF
US. STILL FAR TOO EARLY TO HAVE ANY KIND OF HANDLE ON POTENTIAL
AMOUNTS AT THIS TIME, AS TRACK AND INTENSITY ARE STILL QUITE
VARIABLE AMONG THE MODELS. UNFORTUNATELY, STRONGER WINDS LOOK TO
ACCOMPANY THIS SYSTEM, SO WILL ALSO HAVE TO CONTEND WITH SOME
BLOWING AND DRIFTING SNOW AS WELL.
ONLY A BRIEF REPRIEVE EARLY NEXT WEEK, AS BROAD CONSENSUS SHOWS
ANOTHER, MUCH WEAKER, WAVE SLIDING ACROSS THE REGION DURING THE
MONDAY-TUESDAY TIME FRAME.
AS FAR AS TEMPERATURES, SHOULD SEE A BRIEF WARM-UP AHEAD OF THE
LATE WEEK SYSTEM, WHICH COULD BRING HIGHS CLOSE TO OR EVEN A LITTLE
ABOVE FREEZING FOR SOME SOUTH OF I-90 FRIDAY/SATURDAY. OTHERWISE
READINGS REMAIN BELOW NORMAL, WITH ANOTHER SHOT OF WELL-BELOW NORMAL
AIR RETURNING EARLY NEXT WEEK, WITH HIGHS 5 TO 15 AND LOWS A FEW
DEGREES EITHER SIDE OF ZERO.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 537 AM CST WED FEB 20 2019
IFR-VLIFR VISIBILITY IN SNOW ACROSS THE REGION TO START THE TAF
PERIOD, WITH GRADUAL IMPROVEMENT EXPECTED SOUTHWEST TO NORTHEAST
THROUGH 15Z TO 21Z AS SYSTEM LIFTS OUT OF THE REGION. EXPECT VFR
CONDITIONS TO PREVAIL THROUGH THE LATTER HALF OF THE FORECAST
PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR SDZ060-061-065-
068-069.
WINTER STORM WARNING UNTIL NOON CST TODAY FOR SDZ062-066-067-070-
071.
WINTER STORM WARNING UNTIL 3 PM CST THIS AFTERNOON FOR SDZ040-
055-056.
WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR SDZ039-
054.
MN...WINTER STORM WARNING UNTIL 3 PM CST THIS AFTERNOON FOR MNZ071-
072-080-081-089-090-097-098.
IA...WINTER STORM WARNING UNTIL NOON CST TODAY FOR IAZ001-012-013-
020>022-031-032.
WINTER STORM WARNING UNTIL 3 PM CST THIS AFTERNOON FOR IAZ002-
003-014.
NE...WINTER STORM WARNING UNTIL NOON CST TODAY FOR NEZ013-014.
SHORT TERM...JH
LONG TERM...JH
AVIATION...JH
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