FXUS63 KABR 241543 AAA
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
943 AM CST THU DEC 24 2009

.UPDATE...
ADJUSTED THE TEMPERATURE GRIDS TO REFLECT THE COLD FROPA OUT WEST.
EXPECT TEMPS TO REMAIN STEADY OR FALL THROUGH THE DAY. ALSO
ADJUSTED SNOW AMOUNT AND SNOW TOTAL GRIDS BASED ON REPORTS FROM
ACROSS THE REGION THIS MORNING. RATIOS WERE ANYWHERE FROM 9:1 TO
20:1 WITH HIGHEST RATIOS NEAR MOBRIDGE BEHIND THE FROPA. AS THE
WINDS PICK UP TODAY EXPECT RATIOS TO FALL TO AROUND 10:1 ACROSS
THE AREA. OVERALL FORECAST LOOKS TO BE ON TRACK WITH WSW REMAINING
IN EFFECT BUT WILL MOST LIKELY UPGRADE TO A BLIZZARD WARNING FOR THE
WHOLE AREA TONIGHT THROUGH SATURDAY MORNING AS THE SYSTEM INTENSIFIES.

&&
.PREV DISCUSSION...
.SHORT TERM...TODAY THROUGH SATURDAY
FORECAST CHALLENGES REVOLVE AROUND TIMING...SNOWFALL AND IMPACTS
OF THE EVOLVING STORM SYSTEM.

A COLD FRONT IS MAKING ITS WAY ACROSS THE CWA...AND CURRENTLY
EXTENDS ACROSS EASTERN ND...SD...AND NE. A LARGE TEMPERATURE GRADIENT
IS OBVIOUS AS K8D3 AND KATY TEMPS ARE CURRENTLY IN THE LOW 20S
AND KMBG AND KPIR TEMPS IN THE SINGLE DIGITS. RADAR AND OBS ALSO
SHOW LIGHT SNOW FALLING ACROSS THE STATE. WIND SPEEDS HAVE
INCREASED SIGNIFICANTLY BEHIND THE FRONT AND BLOWING SNOW HAS
REDUCED VSBYS AT KMBG...KPIR AND KABR TO AROUND OR LESS THAN 2 MI.

MODEL GUIDANCE WAS NOT QUITE PICKING UP ON STRENGTH OF WINDS
BEHIND THE FRONT THIS MORNING SO WINDS SPEEDS WERE INCREASED IN
THE FORECAST TODAY. ALSO TEMPERATURES WILL BE STEADY TO SLOWLY
FALLING THIS AFTERNOON...SO CAPTURED A NONDIRUNAL TEMP TREND IN
THE GRIDS. WHILE MODELS AND RADAR TRENDS INDICATE A BRIEF LULL IN
SNOWFALL THIS AFTERNOON...BLOWING SNOW WILL CONTINUE TO BE AN
ISSUE THROUGHOUT THE DAY.

FRIDAY AND SATURDAY STILL REMAIN THE BEST DAYS FOR HEAVY SNOW.
BY THIS TIME PERIOD THE SURFACE LOW HAS INTENSIFIED AND THE
POTENT WAVE DROPPING OUT OF NORTHWEST WILL HAVE MERGED WITH THE
MAIN UPPER LOW. IT IS DIFFICULT TO TIME THE NUMEROUS SHORTWAVES
TRAVERSING THROUGH THE PATTERN...HOWEVER MODELS EASILY IMPLY LARGE
SCALE FORCING WILL BE AT ITS MAX DURING THIS PERIOD. GFS SHOWS
DECENT FRONTOGENESIS COUPLED WITH Q VECTOR CONVERGENCE 06Z FRIDAY
THROUGH 00Z SATURDAY. ALSO...ISENTROPIC SURFACES INDICATE UPSLOPE
FORCING FRIDAY AND SATURDAY. THE TIGHT PRESSURE GRADIENT ON THE
BACK SIDE OF THE SYSTEM WILL RESULT IN SUSTAINED WIND SPEEDS OF 25
TO 35 MPH...WITH UPWARDS OF 40 MPH GUSTS.

THE WINTER STORM WARNING WAS EXTENDED UNTIL 18Z SATURDAY TO CAPTURE
WRAP AROUND SNOWFALL AND GUSTY WINDS. ALSO BLIZZARD CONDITIONS ARE
LIKELY TO BE REALIZED LATE THURSDAY THROUGH SATURDAY. LATER SHIFTS
WILL HAVE TO MONITOR THE POTENTIAL FOR AN UPGRADE FROM CURRENT
WINTER STORM WARNING.

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY
THE LARGE UPPER LEVEL LOW PRESSURE AREA TO THE EAST OF THE REGION
COULD STILL BE WRAPPING SOME LIGHT SNOW INTO THE CWA ON SATURDAY
NIGHT. THUS...HAVE IN SOME SLIGHT CHANCE/CHANCE POPS FOR SATURDAY
NIGHT. NORTHWEST WINDS MAY STILL BE ENOUGH TO GENERATE SOME
BLOWING SNOW. OTHERWISE...SEVERAL SURFACE HIGH PRESSURE AREAS WILL
SLIDE IN FROM THE NORTH AND WEST THROUGH THE MIDDLE OF THE WEEK
KEEPING IT DRY AFTER SATURDAY NIGHT. WITH ALL OF THE DEEP SNOW
COVER ACROSS THE CWA ALONG WITH CAA AND NOT MUCH FOR
WINDS...EXPECT TEMPERATURES TO BE BELOW NORMAL THROUGH WEDNESDAY.

&&

.AVIATION...
IFR/MVFR CEILINGS ARE EXPECTED TO REMAIN AT ALL TAF SITES THROUGH
TODAY WITH 2 TO 5SM IN THE LIGHT SNOW. ALL SITES WILL ALSO HAVE
NORTHWEST WINDS IN THE 15 TO 25 KNOT RANGE CAUSING BLOWING SNOW
WITH VSBYS BELOW 1 MILE AT TIMES. AFTER 00Z...WIDESPREAD SNOW
WILL WRAP INTO THE AREA FROM THE EAST WITH VISIBILITIES FALLING
BELOW 1/2SM AT ALL TAF SITES BY 12Z FRIDAY. ALSO...NORTHWEST
WINDS WILL INCREASE SUBSTANTIALLY TONIGHT TO 25 TO 35 KNOTS WITH
HIGHER GUSTS CAUSING WIDESPREAD BLOWING SNOW WITH VISIBILITIES TO
LESS THAN A QUARTER MILE AT TIMES.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER STORM WARNING UNTIL NOON CST /11 AM MST/ SATURDAY FOR 
     BROWN-BUFFALO-CAMPBELL-CLARK-CODINGTON-CORSON-DAY-DEUEL-
     DEWEY-EDMUNDS-FAULK-GRANT-HAMLIN-HAND-HUGHES-HYDE-JONES-
     LYMAN-MARSHALL-MCPHERSON-POTTER-ROBERTS-SPINK-STANLEY-SULLY-
     WALWORTH.

MN...WINTER STORM WARNING UNTIL NOON CST SATURDAY FOR BIG STONE-
     TRAVERSE.

&&

$$
UPDATE...WISE
SHORT TERM...KRAMLICH
LONG TERM...MOHR
AVIATION...TMT

WEATHER.GOV/ABERDEEN