FXUS63 KABR 051002
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
402 AM CST SAT DEC 5 2009

.SHORT TERM...TODAY THROUGH MONDAY
AS THE PREVIOUS AFD MENTIONED...TEMPERATURES THROUGHOUT THE SHORT
TERM WILL BE PROBLEMATIC BASED ON WHETHER OR NOT MODELS ARE
INGESTING SNOW COVER. THE NESDIS SNOW COVER WED SITE DOES DEPICT
THE ENTIRE CWA AS HAVING SNOW ON THE GROUND. BASED ON COOP
REPORTS...IT APPEARS AS THOUGH SNOW DEPTHS ARE AN INCH OR LESS
ACROSS MUCH OF THE AREA WITH THE EXCEPTION TO THE HIGHER TERRAIN
OF THE SISSETON HILLS. ADJMAV IS VIRTUALLY UNCHANGED FROM
YESTERDAY'S 0Z RUN...HOWEVER THE ADJMET HAS TRENDED SEVERAL DEGREES
COOLER. FOR A BRIEF COMPARISON...HAVE MIXED DOWN H925 TEMPERATURES
USING A LAPSE RATE BETWEEN THE DRY AND MOIST ADIABATIC LAPSE RATES
AT 18 AND 21Z. THIS PROCESS DID YIELD TEMPS SIMILAR TO THE
NUMERICAL GUIDANCE FOR TODAY...AND ONE TO FOUR DEGREES WARMER FOR
SUNDAY. THIS TECHNIQUE WAS NOT USED ON MONDAY AS MODELS DISAGREE
WITH THE STRENGTH AND SOUTHERN PLUNGE OF A COLD CANADIAN AIR MASS.
THE GFS IS THE COLDEST MODEL WITH TEMPS AT H925 IN THE MID TEEN
BELOW ZERO BY 18Z MONDAY. BOTH THE NAM/ECMWF ARE THREE TO FOUR
DEGREES WARMER FOR THE SAME TIME PERIOD.

PRECIPITATION CHANCES THROUGHOUT THE SHORT TERM APPEARS TO BE
FAIRLY MINIMAL. THE BEST LOCATION FOR MEASURABLE PRECIPITATION
WILL BE THE WESTERN HALF OF THE CWA. A STORM SYSTEM DROPPING INTO
THE NORTHERN ROCKIES MAY PROVIDE FOR A SLIGHT CHANCE FOR SNOW
LATER THIS AFTERNOON...WITH CHANCES CONTINUING THROUGHOUT MUCH OF
THE SHORT TERM. OVERALL LIFT AND MOISTURE IS UNIMPRESSIVE WITH
THIS SYSTEM...HOWEVER HAVE LITTLE CONFIDENCE TO REMOVE POPS/WX.

.LONG TERM...MONDAY NIGHT THROUGH WEDNESDAY NIGHT

THE PERIOD OPENS WITH AN UPPER TROF OVER THE CASCADES AND A DEEP
SFC LOW OVER THE SW. AS BOTH OF THESE FEATURES MOVE EAST ON
TUESDAY THERE IS THE CHANCE OF SOME WRAP AROUND SNOW TO AFFECT SD
FROM MON NIGHT THROUGH TUE NIGHT. AS MENTIONED IN PREVIOUS
DISCUSSIONS THE MODELS HAVE HAD A HISTORY THIS SEASON OF ONLY
GRADUALLY PROGRESSING THESE SYSTEMS FARTHER SOUTH OF OUR AREA BEFORE
SHOOTING THEM TOWARD THE GREAT LAKES. SO CONFIDENCE IS LOW THAT
MUCH OF THE MOISTURE AND RESULTING PRECIP WILL MAKE IT TO THIS
CWA. THERE IS LITTLE REASON THE DOMINANT SOUTHERN JET WILL WEAKEN
ENOUGH OVER THE NEXT FEW DAYS TO RESULT IN THE SYSTEM SQUEAKING NORTHWARD.

EITHER WAY...WITH SD SANDWICHED BETWEEN THE SFC HIGH OVER MT AND
THE LOW OVER THE CENTRAL PLAINS ON TUE WINDS WILL INCREASE OUT OF
THE NORTH AND NORTHWEST. EXPECT COLD TEMPERATURES TO CONTINUE THROUGH THE
PERIOD WITH HIGHS IN THE TEENS AND LOWS DROPPING DOWN INTO THE
NEGATIVE SINGLE DIGITS.

&&

.AVIATION...
VFR CONDITIONS EXPECTED THROUGH THIS AFTERNOON AT ALL TAF SITES.
THIS EVENING EXPECT SOME MVFR CIGS TO MOVE ACROSS THE REGION AND
LINGER INTO SUNDAY.

&&

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

$$
SHORT TERM...SD
LONG TERM...WISE
AVIATION...WISE

WEATHER.GOV/ABERDEEN