Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 010453 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1153 PM CDT THU APR 30 2015 .SHORT TERM...(TONIGHT THROUGH SUNDAY) ISSUED AT 319 PM CDT THU APR 30 2015 RAIN CHANCES BEGINNING LATER TONIGHT INTO FRIDAY...AND WHEN BEST CHANCES ARE OVER THE WEEKEND...REMAIN THE PRIMARY FORECAST CONCERNS. MID LEVEL SHORTWAVE EXTENDING FROM EASTERN SASKATCHEWAN INTO MONTANA WILL CONTINUE ITS TREK EASTWARD THIS AFTERNOON AND WEAKEN LATER TONIGHT AS IT MOVES TOWARD THE GREAT LAKES. ATTENDANT COLD FRONT NOW IN THE HIGH PLAINS OF THE DAKOTAS WILL BE PUSHED SOUTHEAST INTO NORTHEAST NEBRASKA AFTER MIDNIGHT...BUT WILL ONLY LIMP FARTHER SOUTHEAST AS UPPER SUPPORT WEAKENS. CURRENT AND FORECAST MOISTURE PROFILES ARE RELATIVELY DRY...ALONG WITH LIMITED UPPER SUPPORT. SO WHILE AM EXPECTING SHOWERS AND ISOLATED THUNDER TO OCCUR ALONG FRONTAL BOUNDARY...COVERAGE SHOULD BE WIDELY SCATTERED IN NATURE. WILL INTRODUCE PRECIP ALONG FRONT BEGINNING IN NORTHEAST NEBRASKA AFTER 06Z...THEN APPROACHING INTERSTATE 80 BY MID FRIDAY MORNING. GIVEN LESSENING AFFECTS OF FORCING ALOFT AND ALONG FRONTAL ZONE...HAVE GRADUALLY DECREASING CHANCES FOR PRECIPITATION FRIDAY AFTERNOON AND EVENING. FOR SATURDAY...ISOLATED SHOWERS COULD LINGER IN SOUTHWEST IOWA OR SOUTHEAST NEBRASKA IN THE MORNING...BUT MOST OF THE REST OF THE DAY SHOULD BE DRY. MODEL OUTPUT IS BASICALLY DRY SATURDAY AFTERNOON...AND CAN NOT REALLY PIN DOWN RESIDUAL FRONTAL BOUNDARY...AND UPPER SUPPORT IS NON EXISTENT. HOWEVER GFS IS PAINTING AN AREA OF 1000-1500 J/KG OF SURFACE-BASED CAPE SATURDAY AFTERNOON IN EASTERN NEBRASKA WITH LIMITED CINH. SO CAN NOT RULE OUT AN ISOLATED STORM FIRING AT SOME POINT...BUT AREAL COVERAGE LOOKS MINIMAL. THEN ATTENTION TURNS TO WARMER TEMPERATURES SUNDAY AHEAD OF ANOTHER APPROACHING COLD FRONT. MID LEVEL WAVE TRACKING ACROSS SOUTHERN CANADA AND THE NORTHERN PLAINS WILL AGAIN PUSH A COLD FRONT INTO NORTHEAST NEBRASKA LATER SUNDAY AFTERNOON. WARM MID LEVEL TEMPERATURES SHOULD CAP MOST CONVECTION AT THAT TIME...AND WILL ALSO ALLOW TEMPERATURES AHEAD OF THE FRONT TO WARM WELL INTO THE 80S. THERMAL TROUGH AT 850MB POINTS DIRECTLY INTO NORTHEAST NEBRASKA WHERE HIGHS IN THE MID 80S OR HIGHER SHOULD OCCUR...WITH AT LEAST LOWER 80S ACROSS THE REST OF EASTERN NEBRASKA AND SOUTHWEST IOWA. .LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY) ISSUED AT 319 PM CDT THU APR 30 2015 BETTER SHOWER/THUNDER CHANCES ARE IN THE OFFING FOR MUCH OF THE WEEK AS SUNDAY COLD FRONT SLIPS INTO THE CWA AND REMAINS CLOSE TO OUR AREA UNTIL LATER IN THE WEEK AS AN UPPER LOW/TROUGH APPROACHES. INSTABILITY SHOULD BE AT LEAST MODERATELY HIGH SUNDAY EVENING GIVEN WARM AFTERNOON TEMPERATURES AND INCREASING LOW LEVEL MOISTURE. AS ATMOSPHERE COOLS IN THE EVENING...EXPECT SCATTERED STORMS ALONG COLD FRONT AS IT MOVES TOWARD INTERSTATE 80 AND BEYOND. SOME HAIL POTENTIAL GIVEN DEGREE OF INSTABILITY...BUT SHEAR IS RATHER WEAK AT THIS TIME. THERE IS SOME MODEL CONSISTENCY IN STALLING FRONT IN SOUTHEAST NEBRASKA ON MONDAY...THE SHOVING IT BACK NORTH INTO NORTHEAST NEBRASKA ON TUESDAY. THE POTENTIAL WILL EXIST FOR STORMS ALONG THIS BOUNDARY BOTH DAYS...AND THE EXACT LOCATION WILL BE TOUGH TO NAIL DOWN RIGHT NOW. HOWEVER IT SEEMS LOGICAL THAT AFTERNOON HEATING WILL PLAY A ROLE IN TIMING OF HIGHEST PRECIP CHANCES...FAVORING THE AFTERNOON AND EVENING BOTH MONDAY AND TUESDAY. BY WEDNESDAY...UPPER TROUGH WILL BE ROTATING INTO THE PLAINS...BRINGING COOLER MID LEVEL TEMPERATURES OVER GRADUALLY MOISTENING LOW LEVELS. THUS INSTABILITY AND POTENTIAL FOR SEVERE ARE FORECAST TO INCREASE BOTH WEDNESDAY AND THURSDAY...WITH GFS SUGGESTING 3000 J/KG OF SURFACE-BASED CAPE THURSDAY AFTERNOON. && .AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1144 PM CDT THU APR 30 2015 FORECAST REASONING REMAINS FROM PREVIOUS TAF CYCLE. VFR CONDITIONS ARE EXPECTED TO CONTINUE. ISOLATED TO SCATTERED SHOWERS AND A POSSIBLE RUMBLE OF THUNDER SHOULD MOVE INTO THE AREA FROM LATE OVERNIGHT/EARLY MORNING THROUGH THE AFTERNOON...BUT COVERAGE CONCERNS PRECLUDES MENTION AT THIS TIME. SOUTHEAST WINDS WILL BECOME SOUTHWESTERLY...WITH SPEEDS AT OR BELOW 10KT. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...MAYES

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