Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 231603
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
1103 AM CDT THU APR 23 2015

.UPDATE...
ISSUED AT 1102 AM CDT THU APR 23 2015

THE CURRENT FORECAST LOOKS GOOD OVERALL. NO MAJOR CHANGES PLANNED
AT THIS TIME.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY AFTERNOON)
ISSUED AT 327 AM CDT THU APR 23 2015

A HIGH PRESSURE RIDGE CURRENTLY EXTENDS ACROSS THE EASTERN
CWA...WITH RETURN FLOW WINDS SETTING UP ACROSS WESTERN AND CENTRAL
SOUTH DAKOTA. WHILE SOME MOISTURE RETURN IS EXPECTED ACROSS THE
WESTERN CWA THIS AFTERNOON...VERY DRY CONDITIONS WILL PERSIST
ACROSS THE EASTERN CWA. LUCKILY WINDS ACROSS THE EAST SHOULD BE
FAIRLY LIGHT TODAY...WHILE THE SOUTHEASTERLY WINDS ACROSS THE
WESTERN CWA BECOME GUSTY LATER THIS AFTERNOON. SO...FOR FIRE
WEATHER CONCERNS...IT DOESNT SEEM LIKE THE DRY AIR AND WINDS EVER
COUPLE AND NO HEADLINES ARE NECESSARY.

LATER TODAY/TONIGHT...THE LONG WAVE UPPER TROUGH OVER THE
SOUTHWEST CONUS SHIFTS EAST...AND THE UPPER LEVEL PATTERN ACROSS
THE NORTHERN PLAINS TRANSITIONS FROM THE NORTHWEST TO A WEAK
SOUTHWESTERLY FLOW. WEAK ENERGY IS EXPECTED TO MOVE THROUGH THE
UPPER PATTERN...BUT THE LOW LEVEL JET AND AND STRONG WARM AIR
ADVECTION WILL BE THE MAIN SOURCES OF LIFT. TEMPERATURES WILL
LIKELY BE PRETTY STEADY OR SLOWLY RISING THROUGH THE
NIGHT. HOW QUICKLY THE COLUMN CAN SATURATE IS STILL A BIG
QUESTION. BUFKIT SOUNDINGS OFF BOTH THE NAM AND GFS SUGGEST THE
WATERTOWN REGION WILL NOT SATURATE UNTIL 6Z OR LATER...SO TRENDED
POPS TOWARD THIS TIMING. IT IS NOTED THAT THIS TIMING IS SLOWER
THAN MOST HI RES MODEL DEPICTIONS. MU CAPE VALUES ARE IN THE
200-400 J/KG RANGE ACROSS MOST OF THE CWA TONIGHT...SO WENT AHEAD
AND ADDED A THUNDER MENTION INTO THE FORECAST. OVERALL THE BEST
CHANCES FOR SHOWERS AND THUNDERSTORMS DO APPEAR TO BE ACROSS THE
EASTERN CWA TONIGHT THROUGH THE DAY FRIDAY...HOWEVER IF SURFACE
BASED CONVECTION COULD DEVELOP ACROSS THE SOUTHWEST CWA FRIDAY
AFTERNOON...SOME MODELS SUGGEST MLCAPE VALUES COULD BE AS HIGH AS
700 J/KG.

PRECIP CHANCES FOR FRIDAY NIGHT INTO SATURDAY ARE PRETTY
UNCERTAIN...WITH THE WEAK UPPER PATTERN IT IS HARD TO PINPOINT
ANY SIGNIFICANT WAVES OF ENERGY AND THE MAIN SURFACE LOW LOOKS TO
TRACK WELL SOUTH OF OUR CWA. KEPT THE SLIGHT CHANCE POPS FROM THE
CONSALL SOLUTION...BUT NO REAL CONFIDENCE.

.LONG TERM...(SATURDAY EVENING THROUGH WEDNESDAY)
ISSUED AT 327 AM CDT THU APR 23 2015

THE HIGHLY MERIDIONAL THEME CONTINUES IN THE OUT PERIODS. OVER
THIS REGION...WEAK UPPER LEVEL RIDGING IS DOING THE BEST IT CAN TO
CALL THE DAKOTAS HOME AMID A VERY "STOPPED UP" AND BLOCKY PATTERN
COMPLETE WITH UPPER LEVEL TROFS BOOK-ENDING THE CONUS AT THE START
OF THE PERIOD. UNDOUBTEDLY...THERE ARE SEVERAL LITTLE S/WS
EMBEDDED WITHIN THIS DIFFUSE/WEAK STEERING FLOW PATTERN ALOFT THAT
COULD BE POTENTIALLY INFLUENCING THE CWA WITH PRECIP CHANCES
BETWEEN SATURDAY NIGHT AND MONDAY. HOWEVER...BY MONDAY THE
GFS/CANADIAN/ECMWF MODELS ALL SUPPORT THE FORMATION OF A MUCH
STRONGER UPPER LEVEL LONGWAVE RIDGE OVER THE WESTERN CONUS. THAT
WOULD CREATE A NORTHWEST FLOW PATTERN OVER THIS REGION. THE
STRENGTH/TRAJECTORY OF THAT NORTHWEST FLOW STILL LOOKS TO PLAY A
LARGE ROLE IN WHETHER THE CWA IS DRY AND WARM OR DRY AND COLD. FOR
NOW...THE SUPERBLEND OUTPUT THIS MORNING HAS PRETTY MUCH ALL THE
20 TO 30 PERCENT POPS RELEGATED TO THE FIRST FEW FORECAST PERIODS
IN THE EXTENDED...TIMING/MARCHING PRECIP CHANCES FROM WEST TO
EAST THROUGH MONDAY NIGHT BEFORE BASICALLY DRYING THINGS OUT FOR
TUESDAY/WEDNESDAY. IT IS ALSO LEANING MORE TOWARD A SLOW WARMING
TREND TO ABOVE NORMAL TEMPS HEADING INTO THE FIRST OF MAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 643 AM CDT THU APR 23 2015

VFR CONDITIONS WILL PREVAIL ACROSS THE AREA TODAY AND TONIGHT...AS
SOUTHEASTERLY BREEZES DEVELOP. THERE IS THE SLIMMEST OF CHANCES
THAT AN ISOLATED SHOWER OR THUNDERSTORM COULD DEVELOP BY LATE THIS
AFTERNOON...WITH LOW END CONVECTION CHANCES CONTINUING OVERNIGHT.
PRESENTLY...THE ONLY TERMINAL WORTH A VICINITY THUNDER MENTION
LATER THIS EVENING IS THE KPIR TERMINAL.

&&

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

$$

UPDATE...SD
SHORT TERM...SERR
LONG TERM...DORN
AVIATION...DORN




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