Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 170845
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
345 AM CDT FRI APR 17 2015

.SHORT TERM...(TODAY THROUGH SUNDAY AFTERNOON)
ISSUED AT 342 AM CDT FRI APR 17 2015

AN UPPER LEVEL TROUGH OF LOW PRESSURE CURRENTLY OVER THE FOUR
CORNERS REGION WILL SLOWLY CROSS THE CENTRAL PLAINS ON SATURDAY.
THIS SYSTEM WILL SLOWLY SPREAD SHOWERS INTO SOUTHERN SOUTH DAKOTA
LATE THIS AFTERNOON...OR MORE LIKELY AFTER 0Z SATURDAY. A DRY AIR
MASS OVER MOST OF THIS CWA TODAY WITH DEW POINTS LIKELY FALLING
INTO THE LOWER 20S SHOULD KEEP PCPN CHANCES CONFINED TO THE I-90
CORRIDOR AT BEST.

INCREASING LLM...THANKS TO DECENT ISOTROPIC FORCING...WILL SURGE
NORTHWARD ON SATURDAY. PWATS INCREASE CONSIDERABLY ON SATURDAY
AFTERNOON...PEAKING AOA AN INCH OVER MUCH OF THIS CWA. PWAT VALUES
OVER AN INCH IS CONSIDERED TWO STANDARD DEVIATION ABOVE NORMAL FOR
THIS TIME OF YEAR. SATURDAY AND SATURDAY NIGHT CERTAINLY LOOKS
GOOD FOR DECENT RAINFALL AMOUNTS...ESPECIALLY IN EASTERN SOUTH
DAKOTA WHERE ISOLATED THUNDERSTORMS ARE POSSIBLE. RAINFALL AMOUNTS
OF A HALF INCH TO ONE INCH SEEMS POSSIBLE WITH THIS EVENT.

THIS SYSTEM SHOULD PUSH EAST OF THE REGION ON SUNDAY WHICH WILL
ALLOW STRONG NORTHWESTERLY WINDS TO DEVELOP...ALONG WITH
INSTABILITY SHOWERS. SUSTAINED WINDS OF 25 TO 30 MPH WITH GUSTS
AROUND 45 MPH WILL BE POSSIBLE.

.LONG TERM...(SUNDAY EVENING THROUGH THURSDAY)
ISSUED AT 342 AM CDT FRI APR 17 2015

THE LONGER RANGE MODELS ARE STILL DOING A PRETTY GOOD JOB FINDING
CONSENSUS/AGREEMENT IN THE OUT PERIOD THROUGH ABOUT TUESDAY
NIGHT/WEDNESDAY MORNING. THEN...THE GFS STARTS RACING OUT AHEAD
OF THE OTHER MODELS /TYPCIAL/ IN TERMS OF FLATTER UPPER FLOW
PROGRESSION WITH FASTER S/W TROF MOVEMENT. THE SOMEWHAT SLOWER
GEM/ECMWF LONGWAVE PATTERN EVOLUTION SHOWCASES GREATER
AMPLIFICATION OF THE RIDGE WEST/TROF EAST PATTERN AND KEEPS THINGS
DRIER AND SLIGHTLY COOLER FOR LONGER OVER THIS REGION /COMPARED TO
THE GFS/...WITH NOTABLE NORTH-NORTHEASTERLY LOW-LEVEL "FETCH" OF
DRY AND COOL AIR OUT OF CENTRAL AND SOUTH CENTRAL CANADA FROM MID
TO LATE WEEK NEXT WEEK.

AS THE PERIOD OPENS...A LONGWAVE TROF DIPPING SOUTHEAST INTO THE
NORTHERN PLAINS IS PICKING UP THE LOW PRESSURE SYSTEM THAT IS
OPENING UP AND LIFTING NORTHEASTWARD INTO THE NORTHERN
PLAINS/WESTERN GREAT LAKES REGION. PRECIPITATION CHANCES LINGER
FROM SUNDAY NIGHT THROUGH MONDAY NIGHT MAINLY ACROSS THE EASTERN
HALF OF THE CWA. WORTH NOTING...0.5KM LOW LEVEL WIND SPEEDS ARE
PROGGED TO ACTUALLY BE STRONGER ON MONDAY THAN ON SUNDAY...BUT FOR
NOW...SIMPLY ACCEPTED SLOWER WIND SPEEDS GIVEN BY SUPERBLEND AND
WILL ALLOW FOR NEXT COUPLE OF SHIFTS TO REALLY BEGIN RAMPING UP
WHAT APPEARS TO BE SOLID TO HIGH END WIND ADVISORY STRENGTH WIND
SPEEDS /PER BUFKIT/ ON MONDAY IN CAA. THE OTHER TIDBIT WORTH
NOTING IS AMID UNI-DIRECTIONAL FLOW OUT OF THE NORTH-NORTHWEST ON
MONDAY...STEEP LOW TO MID LEVEL LAPSE RATES AND APPX 50 TO 150
J/KG OF CAPE ON MONDAY...PRECIPITATION DEVELOPING COULD BE OF A
COLD AIR INSTABILITY NATURE. THE LOWEST ROUGHLY 250 TO 500 METERS
OF THE ATMOSPHERE MAY BE ABOVE FREEZING...BUT ABOVE THAT
TEMPERATURES ACTUALLY COOL INTO THE DENDRITIC GROWTH ZONE. THAT`S
HOW COLD IT WILL BE ALOFT IN AND AT THE TOP OF CLOUDS ON MONDAY.
SO...COULD THERE BE SOME GRAUPEL OR MELTING SNOW FLAKES TO BE HAD
ON MONDAY IN ADDITION TO RAIN? CERTAINLY NOT OUT OF THE QUESTION.
FOR NOW...JUST LEFT THE P-TYPE ON MONDAY AS RAIN SHOWER MENTION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1250 AM CDT FRI APR 17 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE TAF FORECAST PERIOD WITH
LIGHT NORTH TO NORTHEAST WINDS. LATE IN THE TAF PERIOD...RAIN
CHANCES WILL BEGIN TO INCREASE IN AND AROUND THE KPIR TERMINAL.

&&

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

$$

SHORT TERM...SD
LONG TERM...DORN
AVIATION...DORN





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