FXUS63 KABR 080327
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
927 PM CST MON DEC 7 2009

.UPDATE...
OVERALL NO MAJOR CHANGES IN FORECAST THINKING THIS EVENING. 00Z UA
ANALYSIS AND WV IMAGERY CONTINUE TO DEPICT A POWERFUL STORM
SYSTEM CHURNING SLOWLY EWD THROUGH THE DESERT SOUTHWEST. THIS
SYSTEM STILL EXPECTED TO SLIDE EWD OVERNIGHT...INDUCING A STRONG
SFC LOW OVER THE SRN PLAINS DURING THE DAY ON TUESDAY. THE VARIOUS OPERATIONAL
MODELS REMAIN IN FAIRLY GOOD AGREEMENT WITH THE TRACK OF THE UPPER
LEVEL CIRCULATION AND ATTENDANT SFC LOW. THUS...STILL EXPECTING
OUR FORECAST AREA TO REMAIN ON THE NORTHERN FRINGE OF THE SYSTEM. 

AS SUCH...STILL THINK THE HEAVIEST SNOW WILL FALL ALONG THE FAR SRN
PORTIONS OF THE CWA...GENERALLY ALONG AND SOUTH OF A LINE FROM
SISSETON TO PIERRE...WHERE 2 TO 4 INCHES OF SNOW APPEAR LIKELY.
NORTH OF THIS LINE EXPECTING 2 INCHES OR LESS.

A COUPLE TIDBITS TO NOTE:

THE NAM CONTINUES TO TRACK THE LOW THE FARTHEST NORTH OF THE
OPERATIONAL MODELS...WHICH IF CORRECT WOULD BRING SLIGHTLY HIGHER
SNOW TOTALS TO THE AREA. AT THIS POINT THE NATIONAL CENTERS PREFER
THE MORE SLY TRACK.

LOCALLY RUN HIGH RESOLUTION MODELS /4KM/ DEPICT THE POTENTIAL FOR
SLIGHTLY HIGHER PRECIP TOTALS ON THE SISSETON HILLS/COTEAU
REGION...DUE TO ENHANCED CONVERGENCE ASSOCIATED WITH THE NELY FLOW.

WITH THE VERY COLD SFC TEMPS...EVEN LIGHT SNOW MAY CREATE TRAVEL
PROBLEMS ON HIGHWAYS. BECAUSE OF THIS...FUTURE SHIFTS MAY WANT TO
CONSIDER A WINTER WX ADVISORY...DUE TO POTENTIAL IMPACT.

UPDATED AVIATION DISCUSSION ALSO BELOW.

FOWLE

&&
.PREV DISCUSSION...
.SHORT TERM...THROUGH THURSDAY AM

THANKFULLY GUIDANCE TRENDS AND TRACK HAVE GOOD CONTINUITY WITH
UPCOMING STORM...THE ONLY CAVEAT IS FOR SOMEWHAT LATER ARRIVAL
TIMING ON SNOWFALL. CONDITIONS AHEAD OF THIS SYSTEM...MAINLY LOW
LEVEL LAPSE RATES AND TEMPERATURES...CONTINUE TO BE CONDUCIVE FOR
FLURRY ACTIVITY...SO SHOULD BE AN EASY TRANSITION TO LIGHT SNOW
WITH SEEDER FEEDER. MORE SIGNIFICANT SNOWFALL WILL OCCUR WITH
STRONGEST ISENTROPIC FORCING SOUTH OF I90. EXPECT VERY HIGH SNOW
TO LIQUID RATIOS UNDER PRESENCE OF ARCTIC AIRMASS. POPS WILL DROP
OFF RAPIDLY EARLY WEDNESDAY MORNING...HOWEVER WITHOUT SIGNIFICANT
SURFACE HIGH TO CLEAR OUT REGION...COMBINED WITH LOW LEVEL
TEMPERATURES IN THAT FAVORABLE DENDRITIC GROWTH ZONE...PERSISTENT
CLOUD COVER AND FLURRIES COULD CONTINUE INTO THURSDAY. AS FOR
WINDS...GIVEN LACK OF SIGNIFICANT FOLLOW ON HIGH PRESSURE...MODEST
PRESSURE GRADIENT WILL LEAD TO ONLY 1 TO 2 MB/6HR PRESSURE RISES.
BUFKIT HAS 30KTS AT H85 TRANSLATE DOWN TO 20-25KTS..AND GIVEN A
NEARLY -20C AIRMASS THROUGH H925...WIND CHILL READINGS WILL BE
DOWN TO -30F IN SPOTS WEDNESDAY AM.

.LONG TERM...THURSDAY THROUGH MONDAY
NO REAL GREAT CHANCE OF ANY SIGNIFICANT PRECIPITATION DURING THE
EXTENDED...SO MAIN FOCUS WILL BE ON TEMPERATURES. THE PERIOD
STARTS OFF WITH ELONGATED HIGH PRESSURE FROM THE PACIFIC
NORTHWEST TO THE GULF COAST. THIS HIGH SHIFTS EASTWARD
THURSDAY...WITH THE CENTRAL PORTION OF THE HIGH REMAINING OVER THE
NORTHERN PLAINS. H85 TEMPS WILL BE IN THE -15 TO -23 DEGREE
RANGE...WITH THE COLDEST TEMPS ACROSS THE NORTHEASTERN CWA. AS THE
PORTION OF THE HIGH OVER THE UNITED STATES CONTINUES TO PUSH
EASTWARD...AN ARCTIC FRONT APPROACHES FROM THE NORTHWEST FRIDAY
NIGHT...AND LOOKS TO BRING A REINFORCING SHOT OF COLD AIR TO THE
REGION OVER THE WEEKEND. MAY SEE JUST A BRIEF PERIOD OF WARMING
LATE SUNDAY NIGHT INTO EARLY MONDAY...THEN CANADIAN HIGH PRESSURE
DROPS BACK OVER THE NORTHERN AND CENTRAL PLAINS DURING THE DAY
MONDAY AFTERNOON AND MONDAY NIGHT.

&&

.AVIATION...
GENERALLY QUIET CONDITIONS EXPECTED EARLY IN OVERNIGHT
PERIOD /THRU 06Z/...WITH CIGS REMAINING PRIMARILY VFR /8K-10K FEET
AGL/. A STRAY SNOW SHOWER IS POSSIBLE...BUT ANY IMPACTS WOULD BE
BRIEF.

BETWEEN 06Z AND 12Z...CONDITIONS WILL GRADUALLY BEGIN TO
DETERIORATE AS A STRONG LOW PRESSURE SYSTEM EJECTS E/NEWD OUT OF
THE SWRN US. LOOK FOR SNOW TO DEVELOP ACROSS FAR SRN AND SWRN
SD...THEN GRADUALLY SPREAD NORTH AND EAST ACROSS THE AREA DURING
THE MORNING HOURS. THE HEAVIEST SNOW IS STILL EXPECTED TO FALL
ACROSS THE SRN HALF OF SD INCLUDING THE KPIR/KATY
AIRFIELDS...WHERE A COUPLE INCHES OF SNOW IS LIKELY. PREVAILING
IFR CIGS/VSBYS WILL ACCOMPANY THE SNOW...WITH LIFR VSBYS POSSIBLE
IN ANY HEAVIER SNOW BANDS. FARTHER NORTH AT KABR/KMBG...EXPECTING
LIGHTER SNOW AMOUNTS ALTHOUGH IFR CIGS STILL LIKELY. NELY WINDS
WL BECOME NLY BY TUE AFTERNOON AND GUSTY...WHICH MAY RESULT IN
AREAS OF BLOWING SNOW AS WELL.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&

$$
UPDATE...FOWLE
SHORT TERM...CONNELLY
LONG TERM...PARKIN
AVIATION...FOWLE

WEATHER.GOV/ABERDEEN