312
FXUS63 KFSD 172323
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
523 PM CST THU JAN 17 2019
SHORT TERM
(THIS EVENING THROUGH FRIDAY)
ISSUED AT 405 PM CST THU JAN 17 2019
WELL, SNOW IS BACK...FOCUS CONTINUES TO BE ON THE WINTER STORM
THAT IS EXPECTED TO IMPACT THE REGION LATE TONIGHT INTO FRIDAY
NIGHT. AN UPPER WAVE DROPPING THROUGH THE NORTHWEST FLOW ALOFT
WILL APPROACH THE AREA, BRINGING MODERATE TO HEAVY SNOW. WHILE
DYNAMICS LARGELY REMAIN SOUTH OF THE REGION WITH A STRONG UPPER
LOW OVER THE SOUTHERN PLAINS, GOOD MID-LEVEL FRONTOGENESIS, STEEP
LAPSE RATES (7-8C/KM) AND THE DIRECT CIRCULATION DUE TO THE UPPER
JET WILL ENHANCE LIFTING AND DYNAMICS ACROSS OUR REGION. HI-RES
MODELS CONTINUE TO SUGGEST A WELL SATURATED DENDRITIC ZONE THROUGH
THE DAY. THIS, ALONG WITH INCREASING THETA-E AND A BROAD AREA OF
295K ISENTROPIC LIFTING, WIDESPREAD SNOW IS LIKELY.
THE LATEST MODEL RUNS BRING A STRONGER SYSTEM WITH WIDESPREAD QPF
FROM 0.30 - 0.60 INCHES. THE TRICKY PART HERE WILL CONTINUE TO BE
SNOW RATIOS. IT IS EXPECTED TO BE AROUND 15:1 DURING MOST OF THE
EVENT; HOWEVER, AS MENTIONED AT PREVIOUS FORECAST, PRECIPITATION
WILL TREND DOWNWARD WITH ANY SMALL DECREASE IN LIQUID QPF. FOR THIS
FORECAST, HAVE GRADUALLY INCREASED SNOW RATIOS THROUGH THE DAY,
AND HAVE BLENDED QPF WITH SUPERBLEND/WPC TO PRODUCE 4 TO 7+
INCHES OF SNOW. WITH THAT SAID, TOTAL SNOWFALL AMOUNTS HAVE
INCREASED ACROSS MUCH OF THE FORECAST AREA. HOWEVER, THERE ARE TWO
AREAS OF CONCERNS WHERE A GRADIENT IN SNOWFALL LOOKS POSSIBLE.
THE FIRST AREA IS ALONG AND NORTH OF HIGHWAY 14, SPECIFICALLY
KINGSBURY, BROOKINGS, LINCOLN/LYON MN COUNTIES. THESE COUNTIES
ARE PLACED ON THE EDGE OF THE SYSTEM. DESPITE STRONG
FRONTOGENESIS, THE EPV* REMAINS LESS UNSTABLE AND DRIER NORTHEAST
FLOW ADVECTING IN AT LOW LEVELS COULD IMPACT/ARRIVE EARLIER. THE
SECOND REGION IS OVER THE MO RIVER VALLEY WHERE ANOTHER TIGHTER
SNOWFALL GRADIENT IS EXPECTED. OVERALL, EXPECT 5 TO 8 INCHES OF
SNOW, ROUGHLY ALONG A LINE FROM HURON, TO SIOUX FALLS TO SPENCER
AND STORM LAKE, IA; 4 TO 6 INCHES ARE EXPECTED ELSEWHERE. LOCALLY
HIGHER AMOUNTS CANNOT BE RULED OUT. WITH THAT SAID, IN
COLLABORATION WITH SURROUNDING OFFICES HAVE UPGRADED THE HEADLINES
INTO WINTER STORM WARNING WHERE 5 TO 8 INCHES ARE EXPECTED.
IN TERMS OF CONFIDENCE LEVELS, THERE IS A HIGH CONFIDENCE 5 TO 6
INCHES OF SNOW OVER MUCH OF THE REGION. UNCERTAINTY REMAINS OVER OUR
FAR NORTHEAST COUNTIES WHERE A TIGHT SNOWFALL GRADIENT WILL LIKELY
OCCUR.
FOR TIMING: DRY AIR AT MID-LEVELS WILL PERSIST UNTIL THE BL
GRADUALLY SATURATES AFTER 06Z FRIDAY FROM WEST TO EAST. THEREFORE,
EXPECT SNOW BEGINNING AFTER MIDNIGHT, PEAKING DURING THE DAYTIME
HOURS. SNOW WILL GRADUALLY TAPER OFF BY LATE FRIDAY EVENING.
TRAVEL WILL BE IMPACTED NOT ONLY DURING THE MORNING COMMUTE, BUT
ALSO DURING THE EVENING COMMUTE. ROADS ARE EXPECTED TO BECOME
SLIPPERY/SNOW-COVERED AS THE DAY PROGRESSES. ADDITIONALLY, WINDS ARE
NOT EXPECTED TO BE STRONG, BUT 15 TO 25 MPH ARE EXPECTED THROUGH THE
DAY. SNOW AND BREEZY WINDS COULD CAUSE SOME PATCHY BLOWING/DRIFTING
SNOW, AS WELL AS REDUCED VISIBILITIES.
LONG TERM
(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 405 PM CST THU JAN 17 2019
THE WELL ADVERTISED BITTER COLD WEATHER ARRIVES AFTER THE
SNOW. A BURST OF ARCTIC AIRMASS WILL MAKES ITS WAY SOUTHWARD INTO
THE REGION FOR THE WEEKEND. THE FORECAST HIGHS DURING THE PERIOD ARE
EXPECTED TO REACH THE SINGLE DIGITS ABOVE WHILE LOWS ARE EXPECTED TO
DROP INTO THE 10 TO 15 BELOW. WIND CHILL VALUES ARE EXPECTED TO BE
NEAR ADVISORY CRITERIA EARLY IN THE MORNING HOURS WITH READINGS FROM
15 TO 20 BELOW. SURFACE SOUTHERLY AND WAA INCREASES IN THE WAKE OF A
RAPID COMPACT SHORTWAVE MOVES SOUTHWARD INTO THE REGION SATURDAY
NIGHT INTO SUNDAY. THERMAL SOUNDINGS SUGGEST A WELL SATURATED
DENDRITIC LAYER AND LOW TO MID LEVEL MOISTURE. THEREFORE ANOTHER
ROUND OF SNOW WILL BE POSSIBLE WITH BETTER FOCUS ACROSS SOUTHWEST
MINNESOTA AND ALONG AND NORTH OF HIGHWAY 14.
UNSETTLED CONDITIONS CONTINUE TO START OFF THE WEEK. THE NEXT CHANCE
FOR PRECIPITATION RETURNS MONDAY INTO TUESDAY. UPPER FLOW BECOMES
MORE ZONAL AHEAD OF AN UPPER TROUGH SHIFTING EASTWARD INTO THE
DAKOTAS. DYNAMICS/FORCING LOOK MODEST WITH THIS SYSTEM; THEREFORE
ANOTHER ROUND OF SNOW WILL BE POSSIBLE.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 523 PM CST THU JAN 17 2019
MVFR STRATUS ACROSS WESTERN AND FAR SOUTHERN PARTS OF THE CWA TO
START THIS TAF PERIOD, MAY BRIEFLY IMPROVE NEAR/EAST OF I-29 THIS
EVENING BEFORE STRONG WINTER STORM BRINGS DETERIORATING CONDITIONS
TO THE REGION LATE TONIGHT AND FRIDAY. BY MID-LATE MORNING FRIDAY,
EXPECT WIDESPREAD LIFR-VLIFR VISIBILITY IN SNOW TO BLANKET MOST
OF THE FORECAST AREA, WITH SLIGHT IMPROVEMENT FROM THE NORTHWEST
LATE IN THIS TAF PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...WINTER WEATHER ADVISORY FROM 6 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR SDZ068>071.
WINTER STORM WARNING FROM 6 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR SDZ066-067.
WINTER STORM WARNING FROM 3 AM TO 6 PM CST FRIDAY FOR SDZ038-
052>055-057>061-064-065.
WINTER WEATHER ADVISORY FROM 3 AM TO 6 PM CST FRIDAY FOR SDZ039-
040-050-063.
WINTER STORM WARNING FROM 3 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR SDZ056-062.
MN...WINTER STORM WARNING FROM 3 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR MNZ080-081-089-090-097-098.
WINTER WEATHER ADVISORY FROM 3 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR MNZ071-072.
IA...WINTER WEATHER ADVISORY FROM 6 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR IAZ020-031.
WINTER STORM WARNING FROM 6 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR IAZ001>003-012.
WINTER STORM WARNING FROM 9 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR IAZ013-014-021-022-032.
NE...WINTER WEATHER ADVISORY FROM 6 AM FRIDAY TO MIDNIGHT CST FRIDAY
NIGHT FOR NEZ013-014.
SHORT TERM...05
LONG TERM...05
AVIATION...JH
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