FXUS63 KABR 101617 AAA
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
1017 AM CST THU DEC 10 2009

.UPDATE...
MADE SOME ADJUSTMENTS TO SKY COVER THIS MORNING...WITH MUCH OF THE
AREA CURRENTLY CLOUD FREE. THE EXCEPTIONS ARE RIGHT AROUND THE
WATERTOWN AREA...AND AROUND PIERRE WHERE LAKE/RIVER INDUCED CLOUDS
ARE IN PLACE. THESE CLOUD AREAS HAVE BEEN SHRINKING OVER THE PAST
HOUR OR SO...AND EXPECT THEM TO DISSIPATE COMPLETELY BY EARLY
AFTERNOON. DUE TO THE LACK OF CLOUDS...HAVE REMOVED THE MENTION OF
FLURRIES. TEMPERATURES HAVE RISEN INTO THE SINGLE DIGITS...WITH
WIND CHILL VALUES WELL ABOVE ADVISORY CRITERIA NOW.
THEREFORE...HAVE CANCELLED THE WIND CHILL ADVISORY A COUPLE OF
HOURS EARLY. NO CHANGES MADE TO WINDS OR TEMPERATURES. NEW
AVIATION DISCUSSION BELOW.

&&
.PREV DISCUSSION...
.SHORT TERM...TODAY THROUGH SATURDAY
FORECAST CHALLENGES INCLUDE TEMPERATURES AND THE THREAT OF
FLURRIES TODAY.

CURRENTLY...A SOMEWHAT RELAXED PRESSURE GRADIENT EXISTS ACROSS THE
CWA WITH A SURFACE LOW PRESSURE REFLECTION WORKING THROUGH NORTH
DAKOTA HEADING THIS WAY. THIS SURFACE LOW REFLECTS AN AREA OF LOW
PRESSURE ALOFT THAT IS DIVING SOUTHEASTWARD THROUGH THE BACK-SIDE
OF THE LONGWAVE UPPER TROF IN PLACE OVER THE REGION. LOW LEVEL
WAA/MOISTURE ADVECTION AND CLOUDS/FLURRIES HAVE BEEN ADVECTING
ALONG WITH THIS SURFACE LOW SOUTHEASTWARD THROUGHOUT THE
REGION...AND TEMPERATURES HAVE ACTUALLY BEEN WARMING OVERNIGHT OUT
WEST OVER THE WESTERN DAKOTAS AND PORTIONS OF MONTANA AND WYOMING.
FURTHER EAST...ACROSS PORTIONS OF CENTRAL AND EASTERN SOUTH
DAKOTA /WHERE THE WAA AND MOISTURE ADVECTION IS YET TO REACH/
TEMPERATURES HAVE BEEN STEADILY FALLING...DESPITE SCT-BKN COVERAGE
OF SOME MID AND HIGH CLOUDS. WIND CHILL ADVISORY CRITERIA HAS BEEN
MET SPORADICALLY THROUGHOUT THE CWA THIS MORNING...AND
COLLABORATION YIELDED THE CONTINUANCE OF THE WIND CHILL ADVISORY
RIGHT ON THROUGH MORNING.

THIS DISTURBANCE MOVING ACROSS THE REGION TODAY WILL PRODUCE SOME
SCATTERED COVERAGE OF SNOW FLURRIES OVER THE CWA /PER THE UPSTREAM
SURFACE OBSERVATIONS REPORTING LIGHT SNOW/...AND MOST LIKELY
EXTENDING FOR A TIME INTO THE OVERNIGHT HOURS TONIGHT. LOW LEVEL
THERMAL ADVECTION PROGS IN THE NAM/GFS AND ECMWF ALL POINT TO A
WARMING TREND FROM TODAY THROUGH SATURDAY...AS 925HPA TEMPERATURES
WARM FROM APPX -20C TO MORE LIKE -5C TO -10C HEADING INTO THE
FIRST HALF OF THE WEEKEND. OTHER THAN THESE FLURRIES
TODAY/TONIGHT...THERE REALLY IS NOT ANY OTHER CHANCES FOR
PRECIPITATION FRIDAY OR SATURDAY AS THE FLOW PATTERN ALOFT
TRANSITIONS FROM THIS DEEP POLAR COLD NORTHERLY FLOW TO MORE OF A
WEST-NORTHWESTERLY QUASI-ZONAL FLOW ALOFT.

.LONG TERM...SATURDAY NIGHT THROUGH MONDAY NIGHT

MODEL AGREEMENT STILL LEAVES SOMETHING TO BE DESIRED IN THE MID
RANGE. BIGGEST CHALLENGE IS A H7 SHORTWAVE MOVING OVER THE REGION
SUNDAY NIGHT AND A TRAILING COLD FRONT ASSOCIATED WITH A STRONG
LOW OVER NORTHERN CANADA. MODELS CANNOT AGREE ON TIMING OR
STRENGTH OF THESE FEATURES. NOT TO BEAT A DEAD HORSE...BUT MODELS
ARE HAVING TROUBLE THIS SEASON COPING WITH THE SPLIT FLOW JET.
GENERALLY SPEAKING ANY NORTHERN JET SYSTEMS HAVE THREATENED SD
WITH SOME SNOW AND THEN RETREAT BECAUSE OF LACK OF MOISTURE. THIS
TIME THERE IS A CATCH IN THE FORM OF A WEAK SFC LOW THAT WILL MOVE
SOUTHEAST OF THE REGION SUNDAY/SUNDAY NIGHT. IT MAY LET ENOUGH
MOISTURE CREEP NORTHWARD TO LET THE CWA SEE A LITTLE MORE SNOW.
THEREFORE HAVE LEFT SLIGHT CHANCES IN THE GRIDS.

THE EVOLUTION OF THE PRECIP IS ALSO AFFECTING THE TEMPERATURE
FORECAST. ALL MODELS ARE INDICATING A WARMING TREND FOR THE PERIOD
WITH SOUTHERLY SFC FLOW AND WESTERLIES ALOFT. THE INTENSITY OF THE
WARMING IS STILL IN QUESTION SO FOR NOW HAVE NOT GONE HIGHER THAN
TEENS FOR FORECAST HIGHS.

&&

.AVIATION...
VFR CONDITIONS ARE EXPECTED AT ALL TAF SITES THROUGH THE DAY.

&&

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

$$
UPDATE...PARKIN
SHORT TERM...DORN
LONG TERM...WISE
AVIATION...SD

WEATHER.GOV/ABERDEEN