Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 280445 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1145 PM CDT WED AUG 27 2014 .UPDATE...
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ISSUED AT 1138 PM CDT WED AUG 27 2014 AFTER SEEING REPORTS OF 3+ INCHES OF RAIN WITHIN THE HEAVY CLUSTER OF STORMS ACROSS NORTH CENTRAL KANSAS...BASED ON TRAJECTORIES OF ONGOING PRECIP AND HRRR/RAP MODELS AS A 2+ PW BULLSEYE MOVES INTO THE AREA...WE DECIDED TO ISSUE A FLASH FLOOD WATCH FOR MUCH OF EAST CENTRAL NEBRASKA AND WESTERN IOWA. THE NEXT ROUND OF RAIN IS EXPECTED TO MOVE OVER MANY OF THE SAME AREAS THAT HAVE EXPERIENCED HEAVY RAINS THE PREVIOUS 2 DAYS.
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&& .SHORT TERM...
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(TONIGHT THROUGH SATURDAY) ISSUED AT 302 PM CDT WED AUG 27 2014 ...HEAVY RAINFALL AND POSSIBLE FLOODING IN THE MAIN CONCERN IN THE SHORT TERM... EARLY AFTERNOON WATER VAPOR IMAGERY INDICATED A POTENT UPPER LEVEL SYSTEM OVER THE CNTRL ROCKIES. THIS SYSTEM AND ASSOCIATED 60 KT H3 JET AND 30-40 M H5 HEIGHT FALLS WILL MOV NEWD OVER THE SHORT TERM BRINGING CONTD PERIODS OF SHOWERS AND THUNDERSTORMS TO THE REGION. PERSISTENT 850-700 MB WAA ACTING THE ON THE ERN EDGE OF THE MID-LEVEL MOISTURE GRADIENT HAS ALLOWED FOR PERSISTENT SHOWERS AND A FEW THUNDERSTORMS THIS AFTN FOR MAINLY ALONG AND E OF THE RIVER. MODELS ARE GENERALLY IN GOOD AGREEMENT THAT THIS AREA OF RAINFALL WILL GENERALLY WEAKEN BY EVENING AS THE BETTER FORCING FOR ASCENT ASSOCIATED WITH THE UPPER LEVEL SYSTEM AND INCREASING LOW-LEVEL JET. THUS WILL INITIALLY FOCUS THE HIGHEST POPS IN THE WRN FA IN THE EVNG. THIS FORCING SHOULD LEAD TO INCREASING SHOWERS AND THUNDERSTORMS OVER CNTRL AND WRN NEB THROUGH THE EVENING. MODELS...ESPECIALLY THE CAMS...INDC THAT AN ORGANIZED MCS WILL TRACK EWD INTO ERN NEB AND WESTERN IOWA...MAINLY AS WE GET TOWARD LATE EVENING AND INTO THE OVERNIGHT HOURS. THERE REMAINS SOME UNCERTAINTY TO THE EXACT TRACK OF SAID SYSTEM AND THUS WHERE THE HEAVIEST RAINFALL WILL FALL WITH MODEL SOLUTION RANGING FROM THE NRN TO SRN CWA. CURRENTLY FEELING IS THAT THE AREA BETWEEN I80 AND HIGHWAY 20 WILL BE THE MOST LIKELY AREA. DESPITE THE UNCERTAINTY IN THE PLACEMENT OF HEAVY RAINFALL THERE IS PRETTY HIGH CONFIDENCE THAT HEAVY RAINFALL WILL OCCUR GIVEN THE 1.8-2.0 IN PWATS AND CLOUD BEARING SW UNIDIRECTIONAL FLOW LEADING TO BACKBUILDING. THUS WILL CONT TO MENTION HEAVY RAINFALL IN THE FORECAST. FF GUIDANCE INDCS THAT DESPITE SPOTTY HEAVY RAINFALL THE LAST TWO NIGHTS THAT MOST AREAS OF THE CWA CAN STILL TAKE A GOOD RAINFALL BEFORE MORE THAN ISO FLOODING WOULD OCCUR. THUS WE WILL HOLD OFF ON A FLASH FLOOD WATCH ATTM. OF COURSE THERE ARE A COUPLE OF NARROW CORRIDORS OF THE CWA THAT ARE MORE SUSCEPTIBLE TO FLOODING DUE TO RECENT RAINS...AND THESE WILL HAVE TO BE MONITORED CLOSELY. ONCE CONFIDENCE IN THE EVENTUAL TRACK OF THE MCS INCREASES A WATCH MAY BE ISSUED LATER. CONVECTION SHOULD CONT INTO THU MORNING WITH THE WRN EDGE OF THE MCS LIKELY ALONG AND JUST WEST OF THE RIVER AT THAT TIME. BY MID TO LATE MORNING THE SYSTEM SHOULD MOVE OFF TO THE EAST. THE UPPER LEVEL SYSTEM WILL BE OPENING UP ON THU WITH A WEAK BOUNDARY IN THE AREA. GIVEN THE LACK OF A CAPPING INVERSION...FAVORABLE LARGE- SCALE FORCING FOR ASCENT...AND THE BOUNDARY IN THE AREA WE SHOULD SEE STORMS REDEVELOP ON THU AFTN...ESPECIALLY OVER THE CTNRL AND ERN FA. THESE WILL LIKELY CONT INTO THU NIGHT BUT BY THIS TIME THE THREAT OF MORE WIDESPREAD HEAVY RAINFALL WILL LIKELY BE EAST OF OUR AREA BY THEN. THIS PATTERN MAY AGAIN DEVELOP ON FRI AFTERNOON BEFORE THE SYSTEM MOVES OFF TO THE EAST AND DRY WEATHER DEVELOPS FOR SAT. .LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY) ISSUED AT 302 PM CDT WED AUG 27 2014 ONLY A QUICK BREAK IN ACTIVE WEATHER IS EXPECTED BEFORE THE NEXT TROUGH AND ASSOCIATED SFC LOW/CDFNT WILL QUICKLY MOV INTO THE REGION FOR SUNDAY. THIS SYSTEM APPEARS PRETTY DYNAMIC AND MAY LEAD TO SOME SVR WX FOR SUN ACRS THE CWA AS HIGHLIGHTED IN THE SPC OUTLOOKS. OTHERWISE ONCE THIS FRONT MOVES THROUGH WED SHOULD SEE DRY WEATHER AND SEASONABLE TEMPERATURES FOR MON NIGHT THRU THU.
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&& .AVIATION...
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(06Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1138 PM CDT WED AUG 27 2014 VERY MESSY AND COMPLICATED TAF FORECAST SETTING UP WITH IFR CONDITIONS...SCATTERED SHOWERS...AND EVENTUALLY THUNDERSTORMS WITH HEAVY RAIN OVER THE NEXT SEVERAL HOURS. TRIED TO TIME THE STORMS AT ANY LOCATION TO A 4 HOUR WINDOW...08-12Z AT KLNK/KOMA AND 10-14Z AT KOMA. CONDITIONS MAY IMPROVE BACK TO VFR LATER IN THE MORNING AND AFTERNOON. COULD SEE ADDITIONAL THUNDERSTORM DEVELOPMENT AT KLNK/KOMA BY 20-24Z DURING PEAK HEATING.
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&& .OAX WATCHES/WARNINGS/ADVISORIES...
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NE...FLASH FLOOD WATCH THROUGH THURSDAY MORNING FOR NEZ015-017-018- 030>034-042>045-050>053-065>068-078. IA...FLASH FLOOD WATCH THROUGH THURSDAY MORNING FOR IAZ043-055-056- 069-079-080-090-091.
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&& $$ UPDATE...DEWALD SHORT TERM...BOUSTEAD LONG TERM...BOUSTEAD AVIATION...DEWALD

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