Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 051114 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 614 AM CDT SAT SEP 5 2015 .SHORT TERM...(TODAY THROUGH MONDAY) ISSUED AT 352 AM CDT SAT SEP 5 2015 CHANCES FOR THUNDERSTORMS THROUGH MONDAY...WITH A SEVERE POTENTIAL SUNDAY...ARE THE MAIN FORECAST PROBLEMS. SOUTHWEST FLOW ALOFT CONTINUED THIS MORNING FROM THE BASE OF AN UPPER TROUGH ALONG THE WEST COAST INTO THE NORTHERN PLAINS. MID LEVEL RIDGING WAS NOTED FROM THE SOUTHERN PLAINS INTO EASTERN KANSAS. WARM MID LEVEL TEMPERATURES UNDER RIDGE AXIS WAS SQUASHING ATTEMPTS AT CONVECTION IN EASTERN NEBRASKA AND SOUTHWEST IOWA...BUT PERSISTENT 45KT LOW LEVEL JET FINALLY LEAD TO A FEW STORMS IN WEST CENTRAL IOWA. WE MAY SEE A FEW MORE OF THESE EARLY THIS MORNING...BUT MOST SHOULD BE OUT OF OUR AREA SHORTLY AFTER SUNRISE. OTHERWISE MAIN STORM TRACK WILL REMAIN MOSTLY TO OUR WEST AND NORTHWEST MUCH OF TODAY BEFORE UPPER LOW IN THE PACIFIC NORTHWEST BEGINS TO EJECT INTO THE NORTHERN ROCKIES. MID LEVEL THETA-E AXIS WILL NUDGE EAST AS THIS OCCURS...PUTTING PARTS OF NORTHEAST NEBRASKA IN AREA OF SMALL PRECIPITATION POTENTIAL BEFORE SUNSET. THAT POTENTIAL GRADUALLY INCREASES TONIGHT AND SHIFTS EAST AS UPPER LOW CONTINUES LIFTING INTO SOUTHERN CANADA AND HEIGHTS ARE SUPPRESSED SOUTHEAST IN THE PLAINS. ATTENDANT INCREASE IN WIND FIELDS COMBINED WITH SOUTHEAST SHIFT IN THETA-E AXIS WILL RESULT IN SCATTERED ELEVATED CONVECTION FIRING IN NORTHEAST NEBRASKA DURING THE EVENING AND SPREADING TOWARD INTERSTATE 80 BY LATE TONIGHT. WILL LIKELY SEE A DECREASE IN ACTIVITY SUNDAY MORNING AS LOW LEVEL JET SUBSIDES FOR A TIME. THEN BY LATER SUNDAY MORNING...COLD FRONT BEING DRIVEN EAST AND SOUTHEAST BY NORTHERN PLAINS TROUGH WILL ENTER NORTHEAST NEBRASKA. QUALITY OF ATMOSPHERE AHEAD OF THIS FRONT IS STILL IN QUESTION GIVEN POTENTIAL FOR MORNING CLOUDS/CONVECTION. HOWEVER MODEL FORECASTS ARE HONING IN ON A RIBBON OF SIGNIFICANT INSTABILITY ON THE ORDER OF 2000 J/KG OR GREATER JUST AHEAD OF WIND SHIFT SUNDAY AFTERNOON. 0-6KM BULK SHEAR OF 35KT IS FORECAST AS WELL...STARTING OUT NEARLY PERPENDICULAR TO LINE OF CONVECTION SUGGESTING SUPERCELL STORMS ARE POSSIBLE DURING EARLY STORM DEVELOPMENT PHASE. SHEAR VECTORS BECOME MORE PARALLEL TO FRONT/CONVECTION WITH TIME DURING THE EVENING...LEADING TO MORE LINEAR STORM STRUCTURES AND A POTENTIAL FOR TRAINING OF STORMS AS FRONT BEGINS TO STALL OUT IN SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. SIGNIFICANT QPF IS NOTED FROM GFS IN 00Z-06Z MONDAY TIMEFRAME WHEN 2 TO 4 INCHES OF RAIN IS PAINTED ACROSS SOUTHWEST IOWA. FRONT IS EXPECTED TO ONLY SLOWLY DRIFT SOUTH LATER SUNDAY NIGHT INTO MONDAY MORNING...BASICALLY STALLING OUT NEAR THE KANSAS BORDER. SHOULD SEE GENERAL DECREASE IN STORMS TOWARD MONDAY MORNING WITH UPPER SUPPORT WANING AND LOW LEVEL JET DECREASING. HOWEVER WILL SEE AN INCREASE IN ACTIVITY THROUGH THE DAY WHEN MID LEVEL SHORTWAVE/JET ROTATE THROUGH BROAD TROUGH IN THE PLAINS...LEADING TO STRONG ISENTROPIC UPGLIDE OVER FRONT MONDAY AFTERNOON. IN FACT...GFS SHOWS MORE INSTABILITY MONDAY AFTERNOON THAN SUNDAY DESPITE NORTHERLY SURFACE WINDS. WE COULD AGAIN SEE SIGNIFICANT RAINFALL IN PARTS OF EASTERN NEBRASKA AND SOUTHWEST IOWA WITH TRAINING OF STORMS. TEMPERATURES SHOULD CLIMB INTO THE 90S OVER MOST OF THE CWA TODAY BEFORE COOLING BEGINS SUNDAY BEHIND COLD FRONT. WILL LIKELY SEE SOME 90S AHEAD OF THE FRONT SUNDAY AFTERNOON IN SOUTHEAST NEBRASKA AND SOUTHWEST IOWA...BUT ONLY MID 80S IN OUR NORTH. LOW TO MID 80S ARE FORECAST MONDAY BEHIND THE FRONT AND UNDER CLOUDS/PRECIP. .LONG TERM...(MONDAY NIGHT THROUGH FRIDAY) ISSUED AT 352 AM CDT SAT SEP 5 2015 MUCH COOLER WEATHER IS FORECAST THROUGH THE BALANCE OF THE WEEK AS A BROAD TROUGH REMAINS OVER THE MIDDLE OF THE COUNTRY. A COUPLE OF SHORTWAVES MOVING THROUGH THE MAIN FLOW WILL BRING A CHANCE FOR SHOWERS AND THUNDERSTORMS TUESDAY AND THEN AGAIN THURSDAY. RELATIVELY STABLE BOUNDARY LEVEL AIR SUGGESTS SEVERE POTENTIAL IS LOW DURING THIS TIME. AND A STRONG COLD FRONT ACCOMPANYING THURSDAY WAVE WILL LEAD TO EVEN COOLER TEMPERATURES ON FRIDAY. LOOK FOR HIGHS CLOSE TO 80 TUESDAY AND WEDNESDAY BEFORE COOLING INTO THE 70S THURSDAY...AND PERHAPS 60S FOR FRIDAY. && .AVIATION...
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(12Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 614 AM CDT SAT SEP 5 2015 MAINLY VFR CONDITIONS ARE EXPECTED THROUGHOUT THE PERIOD. LLWS WILL BE POSSIBLE THIS MORNING BEFORE DIMINISHING AS SURFACE WINDS INCREASE TODAY. A FEW SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ACROSS THE REGION TONIGHT...HOWEVER WILL NOT MENTION IN THE TAFS AT THIS TIME DUE TO LOW CONFIDENCE IN TIMING AND LOCATION OF STORM DEVELOPMENT.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...KG

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