Issued by NWS Aberdeen, SD
000
FXUS63 KABR 070121
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
721 PM CST THU NOV 6 2008
.UPDATE...
UPGRADED PART OF NORTHEAST SD WINTER WEATHER ADVISORY TO A WINTER
STORM WARNING DUE TO THE PRESENT ACCUMULATIONS IN THE AREA OF 2 TO
3 INCHES AND SNOW CONTINUING FOR SEVERAL HOURS YET.
OTHERWISE...REST OF FORECAST WILL NOT CHANGE AS SNOW CONTINUES TO
WRAP AROUND UPPER LOW AND WINDS CONTINUE VERY STRONG CREATING
WIDESPREAD BLOWING SNOW AND LOW VISIBILITIES.
&&
.PREV DISCUSSION...
.SHORT TERM...TONIGHT THROUGH SATURDAY
FORECAST FOCUS ON BLIZZARD CONDITIONS THIS EVENING AND TONIGHT.
AFTER MUCH HOOPLA...WELL ADVERTISED WINTER STORM FINALLY TAKEN
SHAPE OVER NORTH-CENTRAL AND NORTHEASTERN SOUTH DAKOTA. CURRENT
WATER VAPOR IMAGERY SHOWING WELL DEFINED UPPER LOW CENTERED NEAR
SIOUX FALLS...WITH DRY SLOT CURRENTLY WRAPPING N/NWWD INTO SRN MN.
MSAS SURFACE ANALYSIS SHOWING PRIMARY LOW PRESSURE CENTER NOW
CONSOLIDATING OVER SRN MN AS IMPRESSIVE 130M HEIGHT FALLS AT H5
OVERSPREAD THE AREA. AS SUCH...VERY TIGHT PRESSURE GRADIENT
RESIDING OVER THE DAKOTAS WITH CURRENT WIND GUSTS IN THE 30 TO 50
MPH OVER THE WESTERN HALF OF SD WHERE BLIZZARD CONDITIONS
CONTINUE. CLOSER TO HOME...AREA RADARS CURRENTLY SHOWING A
PRONOUNCED INCREASE IN PRECIP COVERAGE AS NEXT SLUG OF MOISTURE
ASSOCIATED WITH WARM CONVEYOR BELT ROTATES INTO THE AREA FROM THE
E/NE.
INITIAL FORECAST PROBLEM THIS EVENING WILL BE TIMING DEVELOPMENT
AND/OR CHANGEOVER TO SNOW. NAM/GFS/RUC THERMAL PROGS AND SOUNDINGS
INDICATE THAT AREAS WEST OF THE JAMES VALLEY WILL SEE A QUICKER
CHANGEOVER TO SNOW DUE TO COLDER SFC TEMPS /LIKELY BY 4PM CST/.
FURTHER EAST...18Z SOUNDING AT KABR SHOWED WARMER BOUNDARY LAYER
TEMPS WHICH WILL TAKE SOME TIME TO DIABATICALLY COOL...PROBABLY
DELAYING ONSET OF ACCUMULATING SNOW TO AROUND 4 OR 5PM AT
ABERDEEN...AND POSSIBILITY AS LATE AS 6PM ALONG I-29 NEAR
SISSETON.
ONCE SNOW BEGINS...BELIEVE WE WILL SEE SOME RATHER IMPRESSIVE
SNOWFALL RATES AND REDUCTIONS IN VISIBILITY DUE TO COMBINATION OF
PLENTIFUL MOISTURE /4 TO 5 G/KG/...STRONG LIFT THROUGH THE
DENDRITIC ZONE...AND LOW STATIC STABILITY. SNOWFALL RATES OF AN
INCH OR TWO PER HOUR WILL BE POSSIBLE IN HEAVIER BANDS.
VISIBILITIES ARE STILL FORECAST TO DROP BELOW 1/4 MILE AT TIMES
DUE TO FALLING/BLOWING SNOW...RESULTING IN OCCASIONAL BLIZZARD
CONDITIONS.
GFS/NAM AND LOCAL HIRES WRF-ARW MODELS INDICATE THAT THE HEAVIEST SNOW
SHOULD GENERALLY FALL BETWEEN 00Z AND 09Z...WITH A GRADUALLY
DECREASE IN THE PRECIP INTENSITY/COVERAGE BY FRIDAY MORNING AS
ANOTHER SURGE OF DRY AIR WRAPS INTO THE AREA. TOTAL SNOWFALL
AMOUNTS REMAIN SOMEWHAT PROBLEMATIC DUE TO BANDING
POTENTIAL...BUT BELIEVE A FEW LOCATIONS COULD SEE 4 TO 8 INCHES BY
FRIDAY AFTERNOON...WITH LOCALLY HIGHER AMOUNTS WITHIN M0RE
PERSISTENT BANDS. OF COURSE WITH 40+ MPH WINDS...MEASURING SNOW
WITH ANY ACCURACY IS ALWAYS A TREAT. COULD ALSO SEE ANOTHER
PERIOD OF LIGHT FREEZING RAIN/DRIZZLE ON FRIDAY AS MODEL SOUNDINGS
SHOW A LOSS OF ICE IN THE CLOUDS.
LOW PRESSURE SYSTEM WILL GRADUALLY SLIDE OFF THE EAST ON FRIDAY
NIGHT AND SATURDAY ENDING ANY AND ALL PRECIP. WITH EXPECTED
SNOWCOVER...BELIEVE TEMPS WILL BE RATHER CHILLY FRIDAY NIGHT /20S
OR TEENS/ AND SATURDAY /LOW 30S/.
.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY
FAIR AGREEMENT BETWEEN MEDIUM RANGE MODELS. HPC GUIDANCE AND
MODELS CONTINUE TO POINT TO A DRY PERIOD THROUGH THE EXTENDED
PERIOD. STAYED WITH THE IDEA OF TEMPERATURES BELOW CLIMATOLOGICAL
NORMALS EXPECTING AFFECTS OF NEW SNOW FIELD TO HOLD VALUES LOW.
OTHERWISE MADE FEW ADJUSTMENTS TO GOING GRIDS THAT APPEAR TO BE IN
GOOD SHAPE.
&&
.AVIATION...
SNOW AND BLOWING SNOW ALONG WITH MVFR/IFR CEILINGS AND
VISIBILITIES WILL CONTINUE THROUGH THE NIGHT AT ALL TAF SITES.
EXPECT IMPROVEMENT IN VISIBILITIES AND CEILINGS ON FRIDAY AS THE
SNOW DECREASES AND WINDS DECREASE.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...BLIZZARD WARNING UNTIL 12 PM CST /11 AM MST/ FRIDAY FOR BROWN-
BUFFALO-CAMPBELL-CLARK-CORSON-DAY-DEWEY-EDMUNDS-FAULK-HAND-
HUGHES-HYDE-JONES-LYMAN-MARSHALL-MCPHERSON-POTTER-SPINK-
STANLEY-SULLY-WALWORTH.
WINTER WEATHER ADVISORY UNTIL 12 PM CST FRIDAY FOR ROBERTS.
WINTER STORM WARNING UNTIL 12 PM CST FRIDAY FOR CODINGTON-DEUEL-
GRANT-HAMLIN.
MN...WINTER WEATHER ADVISORY UNTIL 12 PM CST FRIDAY FOR BIG STONE-
TRAVERSE.
&&
$$
UPDATE...MOHR
SHORT TERM...FOWLE
LONG TERM...KEEFE
AVIATION...MOHR
WEATHER.GOV/ABERDEEN
