Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 201816 AAA
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
116 PM CDT WED AUG 20 2014

.UPDATE...
18Z AVIATION FORECAST DISCUSSION UPDATED BELOW.

MADE SOME CHANGES TO THE FORECAST FOR THE DAY PERIOD. BASICALLY
BACKED OFF SOME ON POPS AS CANT SEE THE AMOUNT OF COVERAGE OF
SHOWERS/STORMS BEING HIGH ENOUGH TO WARRANT LIKELY POPS...EXCEPT
FOR PERHAPS TOWARD AND IN THE EVENING. ALSO HAVE CONCERNS THAT SKY
COVER ADVECTING EAST AHEAD OF S/W MAY LIMIT DIABATIC HEATING AND
POTENTIALLY ALSO LIMIT AMOUNT OF INSTABILITY. UPDATES ALREADY
ISSUED.

&&
.PREVIOUS DISCUSSION...
.SHORT TERM...TODAY THROUGH THURSDAY

MAIN FOCUS FOR TODAY CENTERS AROUND THUNDERSTORM CHANCES THIS
AFTERNOON/EVENING AND POSSIBLE SEVERITY OF THEM. SVR PARAMETERS
STILL LOOKING GOOD...WITH AMPLE AMOUNTS OF INSTABILITY THIS
AFTERNOON THROUGH THIS EVENING...ALTHOUGH HIGHEST AMOUNTS ARE
ACROSS FSD CWA. NONETHELESS THOUGH...MODERATE INSTABILITY LIES
OVER OUR AREA. BULK SHEAR VALUES STILL OVER 40 KNOTS WITH LOW
LEVEL SHEAR EVEN LOOKING IMPRESSIVE AROUND 00Z. WILL BE WATCHING
CLOUD COVER TRENDS TODAY SINCE THIS WILL DETERMINE JUST HOW MUCH
SUNSHINE WILL BE ABLE TO HEAT THE ATMOSPHERE AND INCREASE THE
INSTABILITY. SPC HAS RAISED HAIL THREATS OVER THE CWA WHICH LOOKS
VERY REASONABLE GIVEN THE PARAMETERS. CANNOT RULE OUT A COUPLE
TORNADOES OVER THE AREA AS WELL GIVEN LOW LEVEL SHEAR PARAMETERS
AND LOW LCLS. CAM SOLUTIONS SHOWING CLUSTERS OF STORMS OR EVEN A
FEW SUPERCELLS OVER THE CWA LATE THIS AFTERNOON INTO THE EVENING.
SEEMS INITIATION WILL BE OVER CENTRAL SD LATE THIS AFTERNOON WITH
ACTIVITY PUSHING EAST INTO THE EVENING...WITH SOME UPSCALE GROWTH
QUITE POSSIBLE. HEAVY RAIN A THREAT WITH SOME OF THE STORMS AS
WELL GIVEN THE HIGH PWATS. INSERTED HEAVY RAIN MENTION INTO THE
GRIDS AS WELL AS T+ FOR SEVERE THREAT. PASSED ON ANY TYPE OF FLASH
FLOOD WATCH AT THIS POINT.

STORM SYSTEM EXITS THE AREA OVERNIGHT...WITH THURSDAY SHAPING UP
TO BE A DRY DAY WITH A WEST TO NORTHWEST BREEZE. STILL RATHER WARM
ALOFT BEHIND THIS SYSTEM...SO STILL FORECASTING RATHER WARM HIGHS
IN THE 80S.


.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY

AN UPPER TROF OVER THE WESTERN CONUS WILL GRADUALLY TRANSITION
INTO THE NORTHERN PLAINS OVER THE COURSE OF THE EXTENDED PERIOD.
WHILE THIS FLOW IS INHERENTLY UNSTABLE...BEST CHANCES FOR
CONVECTION ARE ASSOCIATED WITH A SHORTWAVE FRIDAY/EARLY SATURDAY.
WHILE GREATEST INSTABILITY IS MODELED TO BE SOUTH OF THE
CWA...SPECIFIC HUMIDITY VALUES AT 850HPA TOPS OUT AROUND 14G/KG
AND 2 STANDARD DEVIATIONS ABOVE CLIMO...SO WILL CONTINUE TO SEE A
HEAVY RAIN THREAT GOING INTO THE WEEKEND. A SLOW MOVING FRONT WILL
PASS THROUGH THE REGION SUNDAY...WITH CANADIAN HIGH PRESSURE TO
FOLLOW. THE RESULT IS MUCH COOLER TEMPERATURES FOR NEXT WEEK.
MODELS DO BRING ANOTHER WAVE IN CLOSE TO THE END OF THE EXTENDED
PERIOD...WITH SURPRISINGLY DECENT PARALLELS BETWEEN THE GFS/ECMWF
DETERMINISTIC SOLUTIONS OUT TO 180 HOURS.



&&

.AVIATION...
18Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS
AFTERNOON AND EARLY EVENING AS A WARM FRONT SURGES NORTHWARD IN
ADVANCE OF AN UPPER LEVEL LOW PRESSURE TROUGH. EXPECT ALL OF THE
STATIONS TO BE AFFECTED AT LEAST IN THE VICINITY FOR THUNDER WITH
SHOWERS EXPECTED AT ALL LOCATIONS. SOME OF THE SHOWERS COULD BE
HEAVY. OTHERWISE...THE RAINFALL WILL END THROUGH LATE EVENING
WITH CLOUDS DECREASING WITH WINDS BECOMING LIGHT. EXPECT SOME FOG
AND IFR/MVFR CEILINGS TO FORM AT ABR AND ATY LATE TONIGHT AND
EARLY THURSDAY.



&&

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

$$
UPDATE...MOHR
SHORT TERM...TMT
LONG TERM...CONNELLY
AVIATION...MOHR

WEATHER.GOV/ABERDEEN





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