Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 220919
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
419 AM CDT FRI AUG 22 2014

.SHORT TERM...TODAY THROUGH SUNDAY

SHOWERS AND THUNDERSTORMS MOVING ACROSS WESTERN AND CENTRAL SD
EARLY THIS MORNING WHERE WEAK LOW LEVEL JET AND LEFT EXIT REGION
OF THE UPPER LEVEL JET RESIDE. NOT MUCH TO SUPPORT SIGNIFICANT
EASTWARD MOVEMENT INTO THE CWA...BUT LATEST RADAR TRENDS INDICATE
ACTIVITY COULD MAKE IT AS FAR EAST AS THE JAMES VALLEY OVER THE
NEXT FEW HOURS.

ALSO WATCHING FOG DEVELOPMENT THIS MORNING. EXTENSIVE AREA OF
DENSE FOG JUST TO OUR EAST OVER MN...BUT IS TRYING TO CREEP
TOWARDS THE SD/MN BORDER AND OVER BIG STONE/TRAVERSE COUNTIES.
WHEATON HAS BEEN DOWN TO A QUARTER MILE FOR SOME TIME BUT
ORTONVILLE STILL AT 5SM. ALSO SEEING SOME DENSE FOG ALONG THE
SPINE OF THE COTEAU AND ON THE LEE SIDE...BUT DOES NOT APPEAR TO
EXTEND MUCH FURTHER FROM THAT BASED ON FOG SATELLITE. DEBATED ON
DENSE FOG ADVISORY BUT JUST DOES NOT APPEAR TO BE WIDESPREAD
ENOUGH YET IN OUR CWA TO WARRANT ONE...SO WILL CONTINUE TO MONITOR
AND JUST INSERT DENSE FOG MENTION IN THE FORECAST/GRIDS.

MAIN STORY IN THE SHORT TERM IS THE POTENT LOW PRESSURE SYSTEM
THAT WILL MOVE NORTHWARD ACROSS THE REGION. WIDESPREAD MODERATE TO
HEAVY RAINFALL SHOULD SPREAD NORTHWARD OVER THE AREA LATE TONIGHT
AND THROUGH THE DAY SATURDAY. WHATS MORE UNCLEAR IS THE SEVERE
STORM POTENTIAL. MODELS STILL NOT AGREEING ON A LOW PRESSURE
TRACK. 06Z NAM IS ACTUALLY A BIT FURTHER WEST AND PLACES THE QPF
BULLS EYE OVER WESTERN AND CENTRAL SD AND ACTUALLY DRY SLOTS THE
EAST A BIT. IN THIS CASE...MUCH MORE INSTABILITY SURGES NORTHWARD
OVER THE EASTERN CWA WITH VERY IMPRESSIVE SHEAR VALUES. GFS AND EC
THOUGH ARE FURTHER EAST WITH ITS LOW AND QPF TRACKS...THUS KEEPING
MOST THE AREA IN CLOUD COVER AND MORE STRATIFORM MODERATE TO HEAVY
RAIN. THIS WOULD LIMIT SEVERE CHANCES QUITE A BIT. LEFT HEAVY RAIN
MENTION IN THE GRIDS...BUT TRIMMED THE TIMING DOWN JUST A BIT TO
MATCH UP TO WHEN THE MODELS HAVE THE HEAVIEST RAIN MOVING THROUGH.
MORE REFINEMENTS WILL HAVE TO BE MADE WHEN 12Z DATA STARTS ROLLING
IN LATER TODAY.

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY

AS THE PERIOD OPENS...THE CWA IS STILL UNDER SOUTHWEST FLOW
ALOFT...ALTHOUGH THERMODYNAMICS AT AND BELOW 850HPA SHOW
DRYING/STABILIZING CONDITIONS. ARGUABLY...THERE COULD BE SOME
PRECIPITATION DEVELOPING/LIFTING NEWD MAINLY ACROSS THE EASTERN
CWA MONDAY NIGHT INTO TUESDAY MORNING FROM A MID-LEVEL BAROCLINIC
ZONE PROGGED TO BE IN PLACE OVER PARTS OF THE CENTRAL PLAINS/UPPER
MIDWEST. AS THE PRIMARY ENERGY EMBEDDED WITHIN THE WESTERN CONUS
LONGWAVE TROF WORKS ACROSS THE REGION ON WEDNESDAY /500HPA COOL
AIR POCKET/...THERE COULD BE SOME HEAT OF THE DAY "INSTABILITY
SHOWERS" TO CONTEND WITH. OTHERWISE...IT`S LOOKING MORE LIKE MUCH
OF THE EXTENDED WILL PROBABLY BE DRY. NORTHWEST FLOW WILL BE
TAKING OVER UPPER LEVEL STEERING FLOW BY THE END OF THE DAY
WEDNESDAY...PERSISTING THROUGH THE END OF THE PERIOD. BY THURSDAY
NIGHT...MODELS ARE SUGGESTING SOME WAA/ACCAS-TYPE CONVECTION COULD
BE GETTING GOING ACROSS THE FAR WESTERN ZONES.

ALSO WORTH NOTING...SOME OF THE LONG RANGE MOS GUIDANCE COMING IN
THIS MORNING /ECMWF/ SUGGESTS HIGH TEMPERATURES MONDAY AND TUESDAY
WILL ONLY ACHIEVE MID TO UPPER 60S.

&&

.AVIATION...

06Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS

A FEW SHOWERS AND THUNDERSTORMS MAY TRACK ACROSS PARTS OF THE
WESTERN CWA DURING THE OVERNIGHT HOURS. NO SEVERE WEATHER IS
EXPECTED. OTHER THAN THE POTENTIAL FOR SOME MVFR VSBYS IN FOG
ACROSS THE EASTERN CWA DURING THE EARLY MORNING HOURS...VFR
CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. ANOTHER AREA OF
SHOWERS AND THUNDERSTORMS MAY JUST BE APPROACHING THE WESTERN PART
OF THE CWA LATE FRIDAY EVENING. HAVE OPTED TO NOT MENTION THEM IN
THE TAFS AT THIS TIME DUE TO TIMING UNCERTAINTY.

&&

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

$$
SHORT TERM...TMT
LONG TERM...DORN
AVIATION...DORN

WEATHER.GOV/ABERDEEN




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