Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 181743 AAB
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
1243 PM CDT SAT APR 18 2015

.UPDATE...
ISSUED AT 1030 AM CDT SAT APR 18 2015

WITH DRY AIR IN PLACE...ERODING NORTHERN EXTENT OF SHOWER
ACTIVITY...REDUCED POPS/QPF NORTH OF THE MAIN BAND OF
PRECIPITATION FOR THE AFTERNOON IN LINE WITH LATEST HRRR AND RUC
GUIDANCE. LATEST NAM IS IN LINE WITH CURRENT FORECAST AFTER 00Z.
HRRR COLUMN MAX REF DOES LOOK LIKE A WEAK FEW CONVECTIVE CELLS
FORM OVER THE CWA TODAY SO WILL LEAVE MENTION OF THUNDER IN.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 327 AM CDT SAT APR 18 2015

PRECIPITATION CHANCES OVER THE NEXT 24 HOURS...AND WINDS SUNDAY
AND MONDAY WILL BE THE FORECAST CHALLENGES.

A FAIRLY DRY AIR MASS REMAINS IN PLACE ACROSS MOST OF THE CWA THIS
MORNING WITH DEW POINTS MAINLY IN THE UPPER 20S. HIGHER DEW
POINTS ARE ADVECTING NORTHWESTWARD INTO WESTERN SOUTH DAKOTA WHERE
VALUES IN THE 40S. THESE HIGHER DEW POINTS...ALONG WITH SOME
SHOWERS AND THUNDERSTORMS WILL SLOWLY TRACK NORTHWARD THROUGH THE
DAY AS AN UPPER LEVEL LOW PRESSURE SYSTEM MOVES ACROSS THE CENTRAL
PLAINS. VARIOUS HI-RES MODELS SUGGEST SHOWERS WOULD REACH HIGHWAY
212 AROUND 18Z...AND HIGHWAY 12 BETWEEN 21-0Z THIS AFTERNOON. HAVE
TRIED TO DELAY POPS IN THE NORTHERN AND FAR NORTHEASTERN PORTION
OF THE CWA UNTIL AFTER 21Z. PCPN MAY NOT REACH THE
SISSETON/WHEATON AREA UNTIL AFTER 0Z SUNDAY.

TONIGHT THROUGH SUNDAY MORNING...MODELS SUGGEST THE LOW PRESSURE
SYSTEM WILL MERGE WITH A NORTHERN STREAM TROUGH...WHICH COULD
BRING BETTER CHANCES FOR SHOWERS. THE NORTHERN STREAM WILL LIKELY
BRING GUSTY NORTHWESTERLY WINDS TONIGHT ALONG A SURFACE COLD
FRONT. A FAIRLY DRY AIR MASS WILL FOLLOW THIS COLD FRONT WITH PCPN
LIKELY ENDING FROM WEST TO EAST BY THE MID MORNING HOURS ON
SUNDAY. BY SUNDAY AFTERNOON COLD AIR ADVECTION WILL DEVELOP WITH
GUSTY NORTHWESTERLY WINDS AND INSTABILITY SHOWERS POSSIBLE. WINDS
MAY EXCEED ADVISORY LEVELS...ESPECIALLY IN THE WESTERN HALF OF THE
CWA. A TIGHT PRESSURE GRADIENT OVER THE REGION WILL PROMOTE GUSTY
NORTHWESTERLY WINDS ON MONDAY AS WELL. COLD AIR ALOFT...ALONG WITH
CAPE VALUES AROUND 100 J/KG COULD PRODUCE ISOLATED SHOWERS IN THE
FAR EASTERN PORTION OF THE CWA MONDAY AFTERNOON.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 327 AM CDT SAT APR 18 2015

NOT MUCH CHANGE NOTED IN THE LONGER RANGE MODEL OUTPUT...COMPARED
TO 24 HOURS. PRECIPITATION CHANCES ARE PRETTY MUCH DONE AND GONE
MONDAY NIGHT...WITH A MAINLY DRY FORECAST THERE-AFTER /DRY AND
COOL NORTHWEST FLOW ESTABLISHING OVER THE NORTHERN PLAINS ALOFT/.
BY THURSDAY...THERE IS A RATHER SLIM CHANCE THAT ENERGY TRYING
TO LIFT NORTH-NORTHEAST TOWARD THE NORTHERN PLAINS COULD INTRODUCE
SOME DEFORMATION ZONE-FORCED LIGHT PRECIP POTENTIAL ACROSS THE
SOUTHWESTERN FORECAST ZONES...PRIOR TO EXPERIENCING THE SHEARING
EFFECTS OF NORTHWEST /POLAR JET/ FLOW ALOFT. SUPERBLEND CONTINUES
TO PRODUCE SOME LOW PROBABILITIES FOR PRECIPITATION THURSDAY
NIGHT/FRIDAY THOUGH. UNDER THIS NORTHWEST FLOW ALOFT REGIME...LOW
LEVEL FLOW IS PERSISTENTLY ADVECTING COOL/DRY AIR DOWN OUT OF
CANADA ON NORTHEASTERLY BOUNDARY LAYER MIXING WINDS. TEMPERATURES
DURING THE EXTENDED FORECAST PERIOD SHOULD BE RUNNING NEAR NORMAL
TO PERHAPS A FEW DEGREES BELOW NORMAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1236 PM CDT SAT APR 18 2015

A LOW PRESSURE SYSTEM WILL BRING SOME SHOWERS TO THE REGION THIS
AFTERNOON AND EVENING. VFR CONDITIONS ARE EXPECTED THROUGH THE
PERIOD EXCEPT PERHAPS SOME BRIEF AND TRANSIENT MVFR CIGS IN HEAVIER
SHOWERS NEAR KMBG/KATY THIS EVENING. AS THE LOW EXITS SHOWERS WILL
TAPER OFF BY 9Z AND NORTHWEST WINDS WILL INCREASE TO 15 TO 25 KTS
WITH HIGHER GUSTS.

&&

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

$$

UPDATE...CONNELLY
SHORT TERM...SD
LONG TERM...DORN
AVIATION...WISE







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