Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 192136 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE ISSUED BY NATIONAL WEATHER SERVICE SIOUX FALLS SD 436 PM CDT TUE MAY 19 2015 .SHORT TERM...
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(TONIGHT THROUGH FRIDAY) ISSUED AT 434 PM CDT TUE MAY 19 2015 UPPER LEVEL LOW PRESSURE PUSHING ACROSS COLORADO...BUT THE LARGE SCALE SPLIT FLOW BECOMING CONFLUENT ACROSS THE NORTHERN PLAINS WILL BEGIN PROCESS OF SHEARING SYSTEM EASTWARD OVERNIGHT AND EARLY WEDNESDAY. ISENTROPIC LIFT WILL CONTINUE TO INCREASE THIS AFTERNOON... AND AFTER A BATTLE WITH EASTERLY FLOW OF DRIER LOWER TO MID LEVEL AIR...WILL SEE THE COVERAGE OF RAIN BECOME WIDESPREAD ACROSS THE AREA STARTING THIS EVENING WEST OF HIGHWAY 81 NORTH TO HIGHWAY 77 SOUTH...AND SPREADING EASTWARD TONIGHT. SOMEWHAT CONCERNED THAT LONGEVITY OF MORE SIGNIFICANT PRECIP COULD BE IMPACTED BY THE STRONGER SOUTHERN PLAINS CONVECTION...BUT ENOUGH MOISTURE ALREADY IN PLACE IN THE MID LEVELS TO ENSURE RAINFALL FOR ALL. HINT OF ELEVATED INSTABILITY CREEPS NORTHWARD INTO EXTREME SOUTHEASTERN NEBRASKA...AND WILL KEEP A SMALL THREAT FOR THUNDER IN AREA AROUND FALLS CITY. BY LATER WEDNESDAY MORNING...THE MAIN UPPER WAVE FORCING WILL PULL EAST...LEAVING A WEAKENING MID LEVEL BOUNDARY SAGGING SLOWLY SOUTHWARD ACROSS THE AREA. INITIALLY LIKELY TO KEEP A HALF DECENT COVERAGE OF LIGHT PRECIPITATION ACROSS THEN NORTH...BUT AS THE WAVE PULLS EAST AND MID LEVEL DRIES OUT...SHOULD SEE BETTER RAINS COME TO AN END. SOME INDICATION THAT LOWER LEVELS COULD TRY TO BECOME A BIT UNSTABLE AND LEAD TO A FEW SHORT SHOWERS IN THE WAKE...BUT WITH LARGER SCALE FORCING BECOMING INCREASINGLY HOSTILE THROUGH THE AFTERNOON...WOULD NOT EXPECT MUCH. MAINLY HIGHS IN THE 50S WITH CLOUDS ABUNDANT. NORTHERN STREAM BECOMES A BIT MORE DOMINANT INTO THE AREA WEDNESDAY NIGHT INTO THURSDAY...WITH SURFACE RIDGE SLIPPING SOUTH ACROSS THE AREA. WILL SEE GENERAL DECREASE IN CLOUDS WEDNESDAY NIGHT FROM NORTH TO SOUTH...BUT A FEW MORE HIGH CLOUDS MAY SPILL OVER THE WEAKENED RIDGE THROUGH THE SOUTH LATER IN THE NIGHT. HAVE HEDGED TEMPS DOWN JUST A TOUCH GIVEN LIGHT WINDS AND CLEAR SKIES...MAINLY UPPER 30S TO LOWER 40S. A GOOD DOSE OF SUNSHINE WILL LIKELY YIELD A FEW DIURNAL CLOUDS ON THURSDAY...BUT WILL MAKE THE MOST OF LIMITED MIXING UNDER RIDGE AXIS TO RESULT IN MID 60S SOUTH TO NEAR 70 NORTH. WILL SEE WINDS RETURN TO SOUTHERLY ACROSS THE ENTIRE AREA BY LATER THURSDAY NIGHT AND FRIDAY AS RIDGE SHIFTS EAST. LEADING WEAK WAVE ACROSS THE SOUTHWESTERN U.S. WILL EJECT NORTHEAST...LIFTING THROUGH THE DAY INTO THE MEAN UPPER RIDGING. WILL SEE A PULSE OF ISENTROPIC ASCENT WORK NORTHWARD ALONG WITH WAVE...AT SAME TIME SEE THE INITIAL SURGE OF LOWER LEVEL MOISTURE PUSH NORTHWARD ACROSS THE WESTERN PLAINS. A BIT OF MID LEVEL INSTABILITY EXPECTED TO FAVOR SHOWERS AND A FEW THUNDERSTORMS ALONG BAND MOVING TOWARD THE HEART OF THE CWA IN THE AFTERNOON. NOT A GREAT DEAL OF INSTABILITY OR SHEAR TO CONCERN ABOUT ANY SEVERE THREAT. .LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY) ISSUED AT 434 PM CDT TUE MAY 19 2015 MESSY PATTERN THROUGH THE LONG HOLIDAY WEEKEND AS UPPER TROUGH REMAINS ELONGATED FROM THE NORTHERN HIGH PLAINS THROUGH THE SOUTHERN ROCKIES. VARIOUS IMPULSES WILL WORK NORTHWARD AHEAD OF THE TROUGH AXIS...WITH PLENTY OF MOISTURE TO WORK WITH...AND LIKELY SOME PERIODS OF DECENT RAIN CHANCES. QUITE A BIT OF LOWER LEVEL MOISTURE EXPECTED TO CLOG UP THE SYSTEM IN TERMS OF GENERATING GREATER DEGREE OF INSTABILITY. FRONTAL BOUNDARY WILL BE LALLYGAGGING EASTWARD THROUGH THE PERIOD...AND DEPENDING ON LOCATION...SHEAR AND INSTABILITY PARAMETERS SOMEWHAT LACKING...BUT WILL NEED TO BE WATCHED ON SUNDAY WITH A BIT STRONGER MID LEVEL WINDS AND DRYING IN THE MID LEVELS. DIFFERENCES BY TUESDAY IN LOCATIONS OF WEAKER WAVES IN FLOW...SO KEPT DRY FOR THE MOMENT.
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&& .AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 630 AM CDT TUE MAY 19 2015 MVFR CEILINGS HAD MOVED IN AT KOMA AND KOFK A BIT EARLIER AND WILL CONTINUE FOR A WHILE THIS MORNING BEFORE BREAKING UP. MVFR CEILINGS MAY ALSO MOVE IN TO KLNK FOR A FEW HOURS. OTHERWISE LOOK FOR MID CLOUDS TO THICK AND LOWER LATER TODAY. SHOWERS WILL BE ON THE INCREASE WITH MVFR CONDITIONS RETURNING WITH THE PCPN TONIGHT. DID NOT MENTION IFR CONDITIONS AT THIS TIME...BUT CEILINGS AND VSBYS COULD DROP THAT LOW AT SOME POINT...ESPECIALLY AFTER 06Z. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...LONG TERM...CHAPMAN

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