Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 270828 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 328 AM CDT SAT JUN 27 2015 .SHORT TERM...
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(TODAY THROUGH MONDAY) ISSUED AT 254 AM CDT SAT JUN 27 2015 SMALL RAIN CHANCE LATER TONIGHT INTO SUNDAY MORNING IS THE PRIMARY FORECAST CONCERN. OTHERWISE A DRY FORECAST IS EXPECTED. UPPER FLOW PATTERN WILL CHANGE VERY LITTLE THE NEXT SEVERAL DAYS AS LONGWAVE RIDGE IN THE WESTERN STATES AND MEAN TROUGH FROM THE GREAT LAKES TO THE GULF COAST BOTH REMAIN LOCKED IN POSITION AT LEAST THROUGH MONDAY. THIS LEAVES EASTERN NEBRASKA AND WESTERN IOWA UNDER NORTH-NORTHWEST MID LEVEL FLOW REGIME. WHILE RIPPLES IN THAT FLOW COULD BRING A STRAY SHOWER TO OUR AREA...THE TENDENCY TOWARD A MAINLY DRY FORECAST IS STRONG. LATER TONIGHT INTO SUNDAY MAY BE THE EXCEPTION AS A STRONGER SHORTWAVE IS SCHEDULED TO PLUNGE INTO THE PLAINS THEN. CURRENT SURFACE SITUATION SHOWS RIDGE IN PLACE FROM NORTHERN WISCONSIN INTO NORTHWEST KANSAS. NORTHERLY LOW LEVEL FLOW FROM FRIDAY SHUNTED FRONTAL BOUNDARY AND MOISTURE WELL TO OUR SOUTH INTO OKLAHOMA AND ARKANSAS...AND MOISTURE WILL BE SLOW TO RETURN GIVEN UPPER FLOW PATTERN. WEAK INSTABILITY IS FORECAST ACROSS OUR AREA EACH OF THE NEXT SEVERAL AFTERNOONS AS TEMPERATURES RISE WELL INTO THE 80S EACH DAY...PROVIDING SCATTERED AFTERNOON CUMULUS BUT NOT MUCH ELSE SAVE FOR PASSING MID LEVEL CLOUDS ASSOCIATED WITH WEAK SHORTWAVES. THE BEST CHANCE FOR PRECIPITATION THROUGH MONDAY WILL COME TONIGHT INTO SUNDAY MORNING AS STRONG SHORTWAVE CURRENTLY TAKING SHAPE IN NORTHERN MANITOBA AND SASKATCHEWAN DIVES INTO NORTHERN MINNESOTA LATER TONIGHT...THEN TRACKS ALONG THE MISSISSIPPI RIVER INTO SUNDAY NIGHT. POTENT MID LEVEL WARM ADVECTION WILL BE MAXIMIZED WELL TO OUR EAST...CLOSER TO SHORTWAVE TRACK. HOWEVER SHEARED VORTICITY EXTENDING TO THE WEST MAY CLIP OUR FAR EASTERN CWA WITH A FEW SHOWERS OR STORMS LATE TONIGHT AND SUNDAY. WILL MAINTAIN SMALL PRECIPITATION CHANCES FOR PARTS OF WESTERN IOWA TO ACCOUNT FOR THIS AS MODELS HAVE BEEN RELATIVELY PERSISTENT IN SHOWING QPF THERE. .LONG TERM...(MONDAY NIGHT THROUGH FRIDAY) ISSUED AT 254 AM CDT SAT JUN 27 2015 NORTHWEST FLOW ALOFT WILL BRING OCCASIONAL THUNDERSTORM CHANCES TO THE AREA NEXT WEEK...BUT NAILING DOWN BEST RAIN CHANCES IS THE MAIN LONGER TERM FORECAST CONCERN. MAIN MID LEVEL FLOW PATTERN WILL TREND TOWARD A LITTLE LESS AMPLIFICATION WITH EASTERN TROUGH AND WESTERN RIDGE NEXT WEEK...LEAVING NEBRASKA AND IOWA UNDER NORTHWEST FLOW. AS IS THE CASE THIS WEEKEND...SEVERAL POTENTIAL IMPULSES ROLLING THROUGH THE FLOW COULD BRING STRAY SHOWERS FROM TIME TO TIME. HOWEVER THERE IS SOME AGREEMENT BETWEEN MODEL FORECASTS...ESPECIALLY GFS AND ECMWF...IN SHOWING MORE SIGNIFICANT SHORTWAVES AFFECTING OUR AREA IN THE TUESDAY NIGHT/WEDNESDAY AND THURSDAY NIGHT/FRIDAY TIMEFRAMES. MOISTURE RETURN WILL BEGIN TUESDAY AS MID LEVEL WAVE APPROACHES AND INDUCES SOUTHERLY FLOW IN THE PLAINS. STRONG BAROCLINIC ZONE WILL RESULT...TAKING A NORTHWEST TO SOUTHEAST ORIENTATION WITH TIME BY TUESDAY NIGHT. EXPECT ECMWF IS PROBABLY MORE ACCURATE IN SHOWING TIGHTEST GRADIENT TO OUR SOUTHWEST...SUGGESTING ISENTROPIC UPGLIDE WILL RESULT IN BEST LIFT/SATURATION OVER EASTERN NEBRASKA AND SOUTHWEST IOWA AS LOW LEVEL JET INTENSIFIES. GIVEN RELATIVE MODEL AGREEMENT AND PERSISTENCE...WILL BEGIN TO INCREASE THUNDER CHANCES FOR TUESDAY NIGHT INTO WEDNESDAY. WOULD THINK WEDNESDAY NIGHT AND THURSDAY WILL BE MAINLY DRY IN WAKE OF SHORTWAVE...BUT WILL MAINTAIN SMALL POPS IN CASE TIMING IS OFF A BIT. THEN AN INCREASE IN PRECIP CHANCES IS AGAIN IN ORDER AS NEXT WAVE APPROACHES THURSDAY NIGHT AND FRIDAY.
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&& .AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1145 PM CDT FRI JUN 26 2015 SOME PATCHY FOG WITH MVFR VSBYS MAY OCCUR TOWARD MORNING. WINDS WILL REMAIN FAIRLY LIGHT OVERNIGHT INTO SATURDAY. VFR CONDITIONS SHOULD PREVAIL AFTER MID MORNING SATURDAY. ISOLD -SHRA/-TSRA WILL BE POSSIBLE AFTER SATURDAY AFTN...BUT PCPN CHANCES SEEM TOO SMALL TO PUT ANYTHING IN THE TAFS FOR NOW. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...MILLER

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