000
FXUS63 KABR 170843
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
343 AM CDT FRI MAY 17 2013

.SHORT TERM...TODAY THROUGH SUNDAY
THE THREAT OF SEVERE STORMS TODAY AND AGAIN SATURDAY WILL BE THE
MAIN FORECAST CHALLENGE.

THE UPPER LEVEL FLOW PATTERN CONSISTS OF A RIDGE ACROSS THE CENTRAL
CONUS...WITH A TROUGH OVER SOUTHERN CALIFORNIA. THIS TROUGH WILL
CONTINUE TO TRACK TOWARDS THE FOUR CORNERS REGION OVER THE NEXT
36 HOURS. THIS UPPER LEVEL FEATURE...ALONG WITH INCREASING LLM
FROM THE GULF WILL PRODUCE TWO PERIODS OF SEVERE STORMS ACROSS THE
CWA.

THE FIRST CHANCE OF SEVERE WEATHER WILL BE LATER THIS EVENING
FOR AREAS ACROSS THE SOUTHWEST PORTION OF THE CWA. SURFACE DEW
POINTS ALONG A WARM FRONT DRAPED EAST/WEST ACROSS SOUTHERN SOUTH
DAKOTA WILL BE THE FOCUS MECHANISM FOR CONVECTION. SURFACE LOW
PRESSURE OVER NW NEBRASKA WILL PRODUCE MOISTURE ADVECTION INTO THE
BLACK HILLS REGION. THUNDERSTORMS DURING THE AFTERNOON HOURS WILL
LIKELY TRACK EAST SOUTHEAST ALONG THE WARM FRONT/INSTABILITY AXIS
THIS EVENING...REACHING KPIR/K9V9 BETWEEN 3-6Z. A FEW STORMS MAY
PRODUCE GUSTY WINDS AND SMALL HAIL. WHILE THE SEVERE POTENTIAL
SEEMS TO WANE AFTER 3Z...THUNDERSTORMS SHOULD CONTINUE TO TRACK
ACROSS THE REST OF THE CWA DUE TO AN INCREASING LLJ.

SOUTHWEST FLOW ALOFT WILL CONTINUE THROUGH THE DAY ON
SATURDAY...WHICH WILL DRAW MID 60S SURFACE DEW POINTS INTO THE CWA.
HIGH TEMPERATURES SHOULD QUICKLY WARM ACROSS EASTERN SOUTH
DAKOTA...WITH THE MID LEVEL CAPPING BEING OVER COME DURING THE MID
AFTERNOON HOURS. HI-RES MODELS GENERALLY SUPPORT THE IDEA OF
CONVECTION DEVELOPING MUCH SOONER THAN ORIGINALLY EXPECTED...OR
BETWEEN 18-21Z. WHILE EARLIER INITIATION MAY LIMIT THE OVERALL
SEVERE THREAT...DISCRETE SUPERCELLS WILL STILL BE POSSIBLE. LARGE
HAIL AND ISOLATED TORNADOES ARE POSSIBLE DURING THE ONSET OF
CONVECTION.

AN ADDITIONAL THREAT FOR SEVERE STORMS WILL BE POSSIBLE ON SUNDAY
AS A STRONG COLD FRONT MOVES ACROSS THE REGION. THE BEST
INSTABILITY AXIS BY 0Z MONDAY CURRENTLY LIES ALONG THE I-29
CORRIDOR. THANKFULLY 0-6KM BULK SHEAR VALUES ARE VERY WEAK ALONG
THE INSTABILITY AXIS WHICH MAY LIMIT THE OVERALL SEVERE THREAT.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY

STILL GOOD AGREEMENT AMONG THE MODELS IN THE LONG TERM FOR A WET
START TO THE EXTENDED PERIOD. A SFC LOW WILL OCCLUDE OVER THE
NORTHERN PLAINS SUNDAY NIGHT AND MONDAY WHILE THE UPPER LOW
CATCHES UP TO IT. PRECIP WILL REINTENSIFY WITH THE ADDITION OF THE
UPPER TROF AND CAA. IF THE GFS IS CORRECT WILL LIKELY NEED TO
INCREASE THE WINDS WITH THIS SYSTEM ON MONDAY. AT THE MOMENT MAIN
IMPACTS AT THE SFC WILL BE CONTINUED RAIN WITH SOME TSTORMS ONLY
SLOWLY EXITING TO THE EAST ON WEDNESDAY AND MUCH COOLER TEMPS
BEHIND THE LOW. TEMPS WILL FALL BACK INTO THE 60S FOR HIGHS EVEN
AS AN UPPER RIDGE BUILDS INTO THE PLAINS TOWARD THE END OF THE WEEK.

&&

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

GENERALLY SPEAKING VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT.
HOWEVER SOME MODEL DATA INDICATES THE POTENTIAL FOR MVFR/IFR CIGS
LATE TNT ACROSS PARTS OF THE REGION. FORECASTER CONFIDENCE IN THE
DEVELOPMENT OF THE LOWER CIGS IS LOW THUS ONLY A MEAGER MENTION
FOR NOW IN THE TAFS.

&&

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

$$
SHORT TERM...SD
LONG TERM...WISE
AVIATION...WISE

WEATHER.GOV/ABERDEEN