FXUS63 KFSD 242138
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
335 PM CST THU DEC 24 2009
.DISCUSSION...
STORM WELL ON TRACK TO PRODUCE WIDESPREAD SNOW TONIGHT. CURRENT
RADAR AND WATER VAPOR SHOWING AN ABUNDANCE OF MOISTURE STREAMING N
AHEAD OF AN UPPER LEVEL LOW. DEEP STRONG THETAE ADVECTION...COUPLED
WITH NEG DIVQ ALOFT SETS THE STAGE FOR SNOW TO SPREAD WEST ACROSS
THE CWA THE REMAINDER OF THIS AFTERNOON AND THIS EVENING. THIS ALSO
SETS THE STAGE FOR SNOW TO BE HEAVY AT TIMES...WITH RATES AS HIGH AS
1 INCH PER HR. GRADIENT WINDS WILL SLOWLY INCREASE ACROSS THE
AREA...AS SFC LOW DEVELOPS OVER MO AND LIFTS N INTO IA. WINDS WILL
INCEASE OUT OF THE NW TO 25 TO 35 MPH...WITH GUST OVER 40 MPH ACROSS
MUCH OF SE SD TONIGHT AND THROUGH TOMORROW. A BLIZZARD WARNING HAS
BEEN ISSUE...BEGINING AT MIDNIGHT TOINGHT FOR SE SD. A WINTER STORM
WARNING REMAINS IN EFFECT FOR SW MN AND NW IA TONIGHT. CONDITONS
WILL MAKE TRAVEL EXTEREMLY DIFFICULT TONIGHT ACROSS THE AREA...
REGARDLESS OF THE TYPE OF WARNING. THE COMBINATION OF STRONG WINDS
AND FALLING SNOW WILL BE SIGIFICANTLY REDUCE VISIBILITIES...
PRODUCING WHITEOUT CONDITIONS OVER MUCH OF THE AREA TONIGHT.
UPPER LOW WILL CONT TO MEANDER AND LIFT NWD THRU IA FRI INTO FRI
NIGHT WITH SFC LOW RETROGRADING NWWD INTO NW IA BY 18Z FRI. THIS
WRAP PLENTY ON MOIST AIR ALOFT WWD ACRS CWA THRU FRI NIGHT AND WITH
SOUNDINGS INDICATING PRECIP WL BE ALL SNOW...SHUD ACCUM QUITE HEAVY
ACRS THE CWA WITH THE HEAVIEST AMOUNTS ALONG AND E IF I29. STRONG NW
WINDS WL ALSO PERSIST ACRS AREAS W OF I29 THRU FRI NITE...AND WL
ACTUALLY DECREASE DURING THE DAY E OF I29 AS SFC LOW RETROGRADES AND
TIGHEST SFC GRAD SHIFTS TO AREAS W OF I29. SO THEREFORE WL CONT WS
WARN E OF I29 WITH BLIZZARD WARNING TO THE WEST. BY THE TIME THE
SNOW TAPERS OFF LATER FRI NIGHT...12+ INCHES OF SNOW WL OCCUR ACRS A
LARGE PART OF THE CWA WITH PSBLY FAR WRN CWA REMAINING BLO 12
INCHES. WITH RETROGRADING SFC LOW AND WARMER AIR ALOFT WRAPPING
WWD...TEMPS WILL ACTUALLY BE WARMER ACRS THE W ON FRI WITH HIGHS
NEAR 30 ACRS THE FAR E. THIS WL BE A VERY WET SNOW WITH RATIOS
CLOSER TO 10:1.
WL NEED TO LINGER LIGHT SNOW ACRS THE CWA ON SAT AS UPPER LOW
MEANDERS ACRS THE WRN GREAT LAKES REGION. THIS WL KEEP WNDS UP ACRS
THE CWA THRU SAT NIGHT. ANY SNOW ACCUM ON SAT SHUD GENLY BE AN INCH
OR LESS.
WL ADD MENTION OF FLURRIES FOR SUN AS WRAP AROUND CONTS. DID NOT
CHANGE EXTENDED FCST MUCH WITH TEMPS BLO NORM WITH ALL THE FRESH
SNOW COVER. CUD SEE A LTL LIGHT SNOW WED OR THU WITH WEAK S/W BUT
MODELS DIFFER ON TIMING AND FOR NOW WL LEAVE DRY UNTIL MODELS GET A
BETTER HANDLE.
&&
.AVIATION...
SNOW WILL SPREAD FROM SW MN AND NW IA THIS AFTERNOON...ACROSS SD
THIS EVENING. FALLING SNOW COMBINDED WITH STRONG NW WINDS OF 25 TO
40 MPH WILL PRODUCE IFR CIGS AND VISBYS TONIGHT AND TOMORROW. VISBYS
WILL BE NEAR ZERO AT TIMES.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WARNING UNTIL NOON CST SATURDAY FOR IAZ001>003-
012>014-020>022-031-032.
MN...WINTER STORM WARNING UNTIL NOON CST SATURDAY FOR MNZ071-072-080-
081-089-090-097-098.
NE...WINTER STORM WARNING UNTIL MIDNIGHT CST TONIGHT FOR NEZ013-014.
BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO NOON CST SATURDAY FOR
NEZ013-014.
SD...WINTER STORM WARNING UNTIL MIDNIGHT CST TONIGHT FOR SDZ038>040-
050-052>071.
BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO NOON CST SATURDAY FOR
SDZ038>040-050-052>071.
&&
$$
