Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 251741 AAC
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
1141 AM CST TUE NOV 25 2014

.UPDATE...

UPDATED AVIATION DISCUSSION BELOW FOR 18Z TAFS.

OVERALL THE FORECAST FOR TODAY IS IN PRETTY GOOD SHAPE AND ONLY
MINOR TIMING CHANGES WERE ADDRESSED FOR THE ONSET OF SNOWFALL
EXPECTED THROUGH THE DAY. THE FAR NORTHWEST CWA HAS STARTED
SNOWING...AS EVIDENCED BY LEMMON WEB CAM AND RADAR RETURNS. WILL
CONTINUE TO SEE SNOW SPREAD ACROSS THE AREA THROUGH THE
DAY...EVENTUALLY REACHING THE JAMES VALLEY BY LATE AFTERNOON AND
THE FAR EASTERN CWA THIS EVENING. TEMPERATURES OVER THE
WEST/SOUTHWEST CWA STILL APPEAR TO GET WARM ENOUGH THIS AFTERNOON
TO INTRODUCE SOME RAINFALL MENTION OR A RAIN/SNOW MIX. NO CHANGES
TO HEADLINES OR SNOW AMOUNT FORECAST AT THIS TIME AND WILL ADDRESS
THIS LATER THIS AFTERNOON...IF NECESSARY.

&&

.PREVIOUS DISCUSSION...

.SHORT TERM...TODAY THROUGH THURSDAY

THE MAIN FORECAST CHALLENGE WILL CENTER AROUND A CLIPPER SYSTEM
PASSING ACROSS THE REGION LATER THIS AFTERNOON THROUGH WEDNESDAY
MORNING. THERE IS A REASONABLE AGREEMENT AMONG MODELS WITH THE
OVERALL TRACK OF THIS SYSTEM WHICH LEADS TO HIGH FORECASTER
CONFIDENCE. THE MAIN QUESTION LEFT UNANSWERED IS WHETHER OR NOT
CENTRAL SD SEES ANY ACCUMULATING SNOWFALL.

A CLIPPER SYSTEM...CURRENTLY OVER SW SASKATCHEWAN...WILL TRACK
SOUTHEASTWARD ACROSS THE NORTHERN PLAINS LATER THIS AFTERNOON AND
TONIGHT. MODELS HAVE SLOWED DOWN THE OVERALL PROGRESSION OF THIS
SYSTEM WITH PCPN LIKELY NOT REACHING THE JAMES RIVER VALLEY UNTIL
AFTER 21Z. BASED ON THE AMOUNT OF WARM AIR AHEAD OF THIS
SYSTEM...PCPN COULD BEGIN AS RAIN...ESPECIALLY AROUND THE PIERRE
AREA. HOWEVER DECENT CAA DEVELOPS BEHIND THE SURFACE LOW WITH RAIN
CHANGING OVER TO ALL SNOW BY LATER THIS EVENING. BASED ON THE
CURRENT LOW TRACK...THE NE PORTION OF THE CWA WILL LIKELY SEE ALL
SNOW WITH THE POTENTIAL FOR TWO TO FOUR INCHES BY WEDNESDAY
MORNING. THE SURFACE LOW DOES TAKE A NEGATIVE TILT ON WEDNESDAY
WITH THE POTENTIAL FOR ADDITIONAL SNOWFALL ON THE EASTERN SIDE OF
THE PRAIRIE COTEAU.

STRONG NORTHERLY WINDS WILL DEVELOP BEHIND THIS SYSTEM WITH THE
HIGHEST SUSTAINED WINDS OCCURRING ALONG THE MISSOURI RIVER. WINDS
SHOULD EASILY EXCEED WIND ADVISORY LEVELS AFTER 0Z TONIGHT. THOUGHT
ABOUT ISSUING A WIND ADVISORY FOR THIS AREA...HOWEVER AM UNCERTAIN
ON SNOWFALL AMOUNTS. IF THE MISSOURI RIVER SEES ACCUMULATING
SNOWFALL...THEN A WINTER WX ADVISORY MAYBE NEEDED INSTEAD.

AN ARCTIC HIGH PRESSURE DRIFTING ACROSS THE REGION BEYOND
WEDNESDAY AFTERNOON WILL BRING MOSTLY DRY CONDITIONS TO THE AREA.
UNFORTUNATELY THIS HIGH PRESSURE WILL ALSO BRING MORE SIGNIFICANT
BELOW NORMAL TEMPERATURES THROUGH THANKSGIVING.

.LONG TERM...THURSDAY NIGHT THROUGH MONDAY

UPPER LEVEL NORTHWEST FLOW WILL BE IN PLACE WHEN THE EXTENDED
PERIOD STARTS...WITH A SHORTWAVE SET TO TRACK ACROSS THE STATE
OVERNIGHT. A MORE ZONAL PATTERN THEN SETS UP...WITH JUST A SLIGHT
SHIFT TO SOUTHWESTERLY FLOW ON MONDAY.

AT THE SURFACE...HIGH PRESSURE WILL BE EAST OF THE REGION WITH A
LOW PRESSURE SYSTEM EXTENDING FROM THE PACIFIC NORTHWEST TO
MONTANA TO THE LEE OF ROCKIES. THE MODELS AGREE THAT MUCH OF THE
PRECIPITATION WITH THIS SYSTEM WILL STAY NORTH OF THE CWA...BUT
THAT THE NORTHEAST MAY GET CLIPPED...SO WILL LEAVE A SMALL POP IN
THAT AREA. MAY SEE A LITTLE LIGHT SNOW ACROSS THE WESTERN CWA ON
SATURDAY BEFORE HIGH PRESSURE DROPS IN AND BECOMES DOMINANT
THROUGH THE DAY MONDAY. OTHERWISE...THE REST OF THE EXTENDED
PERIOD LOOKS TO BE DRY.

WILL SEE WAA OVER THE AREA ON FRIDAY AS H85 TEMPS RISE INTO THE +2
TO +10 DEGREE RANGE. HIGHS WILL GENERALLY BE IN THE 30S AND
40S...WITH A FEW AREAS POSSIBLE HITTING 50 DEGREES SOUTH OF
INTERSTATE 90. THE WARMER AIR WILL BE SHORT LIVED AS ANOTHER COLD
PUNCH BEGINS ON SATURDAY AND CONTINUES THROUGH THE END OF THE
PERIOD. HIGHS ON SATURDAY WILL BE IN THE 20S TO LOWER 30S...THEN
MOST AREAS WILL SEE HIGHS MAINLY IN THE TEENS AND 20S SUNDAY AND
MONDAY.

&&

.AVIATION...

18Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS

CIGS WILL LOWER THROUGH THE DAY FROM WEST TO EAST AS STORM SYSTEM
MOVES IN. -SN/SN WILL ALSO SPREAD FROM WEST TO EAST THROUGH THE
DAY...FIRST ARRIVING IN KMBG AROUND 18Z...THEN KABR AROUND 21Z.
-SN/SN WILL MAKE IT INTO KATY NEAR 00Z THIS EVENING. OVER
KPIR...WARMER TEMPS WILL ALLOW FOR -RA INITIALLY...WITH -RASN MIX
THIS EVENING. AS FOR THE CIGS THEMSELVES...WILL SEE THEM LOWER
INTO MVFR AS THE -SN/SN MOVES IN...WITH POSSIBLE IFR AT TIMES.
VSBY MAY DROP TO BELOW 1SM WITHIN ANY HEAVIER SN AND BLSN ONCE THE
GUSTY NORTHERLY WINDS DEVELOP LATER TONIGHT. KABR AND KATY WILL BE
AFFECTED MOST BY LOWER VSBY DUE TO THE COMBINATION OF SNOWFALL AND
BLSN AT TIMES.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...

SD...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 9 AM CST
     WEDNESDAY FOR BROWN-CLARK-CODINGTON-DAY-DEUEL-EDMUNDS-FAULK-
     GRANT-HAMLIN-MARSHALL-MCPHERSON-ROBERTS-SPINK.

MN...NONE.
&&

$$
UPDATE...TMT
SHORT TERM...SD
LONG TERM...PARKIN
AVIATION...TMT

WEATHER.GOV/ABERDEEN





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