Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 220018 AAA
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
618 PM CST SUN DEC 21 2014

.UPDATE...
THE LOW PRESSURE SYSTEM THAT WILL AFFECT THE REGION THROUGH TUESDAY
IS ONLY SLOWLY COMING TOGETHER THIS EVENING. LEANING TOWARD THE
NEWEST HI-RES MODELS HAVE PUSHED BACK ONSET OF ACCUMULATING PRECIP
UNTIL AROUND 9Z NEAR THE MISSOURI RIVER.

SEE UPDATED AVIATION DISCUSSION BELOW.



&&
.PREVIOUS DISCUSSION...
.SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT

MAIN STORY REMAINS THE LOW PRESSURE SYSTEM SLIDING SOUTHEAST
ACROSS THE DAKOTAS TONIGHT...THEN INTENSIFYING AS IT MOVES EAST.
TONIGHT...MODELS VARY IN QPF BUT ALL HINT AT MOISTURE SURGING
NORTHWARD ACROSS THE I-29 CORRIDOR AND POINTS EAST. GIVEN THE
EXPECTED TEMPS TONIGHT...THIS WILL LIKELY BE A MIX OF
RAIN...FREEZING RAIN...SLEET OR SNOW. FURTHER WEST...THERE IS SOME
QUESTION OVERNIGHT AS TO THE AREAL COVERAGE OF PRECIP THAT MAKES
IT INTO THE WESTERN CWA. INITIALLY...THERE IS A THREAT FOR MIXED
PRECIP...BUT THEN BY MORNING SOUNDINGS APPEAR COLD ENOUGH TO
CHANGE THINGS OVER TO SNOW.

STILL QUITE A BIT OF UNCERTAINTY MONDAY THROUGH TUESDAY IN OVERALL
EVOLUTION OF STORM SYSTEM...ALTHOUGH MODELS ARE IN DECENT
AGREEMENT. THINGS HAVE SLOWED DOWN JUST A BIT...TO WHERE NOW IT
APPEARS THE MAJORITY OF SNOWFALL MAY COME MONDAY NIGHT INTO
TUESDAY. EC AND NAM OFFER UP THIS SOLUTION WHEREAS THE GFS BRINGS
THINGS IN A BIT QUICKER ON MONDAY AFTERNOON. WINDS WILL INCREASE
ACROSS THE WESTERN CWA MONDAY AFTERNOON...BUT NOW IT APPEARS AS IF
THE STRONGER WINDS WILL HOLD OFF ACROSS THE EASTERN COUNTIES UNTIL
TUESDAY. ITS VERY LIKELY THAT THE MORE SIGNIFICANT IMPACTS HOLD
OFF UNTIL MONDAY NIGHT OR TUESDAY ONCE THE WINDS INCREASE. STILL
LOTS TO BE SORTED OUT HERE IN REGARDS TO THIS STORM SO THAT IS WHY
THERE ARE NO HEADLINES CURRENTLY. WILL LET LATER SHIFTS SORT
THROUGH THE 00Z MODEL DATA TO SEE IF IT OFFERS UP MORE CONFIDENCE
IN THE OVERALL OUTCOME OF THE STORM SYSTEM.


.LONG TERM...WEDNESDAY THROUGH SUNDAY
A DEEP UPPER LEVEL TROUGH WILL BE OVER THE MIDDLE PART OF THE
COUNTRY WHEN THE PERIOD STARTS. THE TROUGH PUSHES EAST ON
WEDNESDAY AS ANOTHER WAVE MOVES OVER THE PACIFIC NORTHWEST. THIS
WAVE LOOKS TO TRACK ACROSS EITHER THE NORTHERN OR CENTRAL PLAINS
THURSDAY AFTERNOON/NIGHT...DEPENDING ON THE MODEL...WITH THE GFS
BEING FURTHER NORTH THAN THE ECMWF. THESE SAME DIFFERENCES SHOW UP
IN THE SURFACE PATTERN. AFTER A DAY OF WEAK HIGH PRESSURE ON
WEDNESDAY...A LOW PRESSURE SYSTEM WILL APPROACH THE PLAINS. THE
GFS TRACKS THE LOW ACROSS NORTHERN SOUTH DAKOTA...KEEPING THE
MAJORITY OF THE PRECIPITATION OVER NORTH DAKOTA. THE ECMWF TRACKS
THE LOW ACROSS KANSAS...WITH THE PRECIPITATION OVER SOUTHERN SOUTH
DAKOTA AND NEBRASKA. FOR NOW...WILL STICK WITH THE SUPERBLEND
WHICH SEEMS TO FOLLOW CLOSER TO AN ECMWF SOLUTION. THE REMAINDER
OF THE PERIOD LOOKS TO BE DRY AS HIGH PRESSURE DOMINATES. MODELS
HINTING AT LOW PRESSURE RETURNING LATE IN THE PERIOD...BUT NOT
EVEN CLOSE TO AGREEING ON A SOLUTION...SO WILL JUST LEAVE THE TIME
PERIOD FROM FRIDAY THROUGH SUNDAY DRY.

TEMPERATURES WILL BE RIGHT AROUND NORMAL WEDNESDAY AND THURSDAY
WITH HIGHS MAINLY IN THE 20S TO LOWER 30S. COOLER AIR THEN MOVES
IN BEHIND THE EXITING LOW PRESSURE SYSTEM. HIGHS FRIDAY THROUGH
SUNDAY WILL GENERALLY BE IN THE TEENS TO LOWER 20S...WITH
OVERNIGHT LOWS IN THE SINGLE DIGITS.



&&

.AVIATION...
00Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS

IFR CIGS/VSBY WILL REMAIN OVER THE EASTERN PORTIONS OF THE CWA
THROUGH 12Z. A LOW PRESSURE SYSTEM WILL BRING PRECIPITATION TO THE
AREA LATE TONIGHT AND INTO THE DAY MONDAY...THOUGH NONE OF THIS
PRECIP IS EXPECTED TO NEAR A TAF SITE UNTIL AROUND 9Z. A PERIOD
OF MIXED PRECIPITATION IS POSSIBLE BEFORE IT BECOMES ALL SNOW BY
0Z TUESDAY.


&&

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

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

WEATHER.GOV/ABERDEEN






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