Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 021124 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 624 AM CDT SAT MAY 2 2015 .SHORT TERM...(TODAY) ISSUED AT 334 AM CDT SAT MAY 2 2015 PRIMARY FORECAST CONCERNS FOR TODAY ARE PCPN CHANCES/COVERAGE AND HIGH TEMPERATURES. SCATTERED TO ISOLATED SHOWERS/THUNDERSTORMS WILL CONTINUE TO LIFT EAST/NORTHEAST ACROSS THE AREA THIS MORNING...AND MAY LINGER THIS AFTERNOON. MAIN FORCING MECHANISMS THIS MORNING ARE WARM/MOIST LOW/MID LEVEL ADVECTION WITH ISENTROPIC UPGLIDE IN THE 300-305K LAYER. THERE IS ALSO A LOW LEVEL JET OF AROUND 40 KNOTS AT 1 KM AGL THAT EXTENDS FROM THE TX PANHANDLE UP INTO SERN NE. THIS SHOULD GRADUALLY MOVE NORTHEAST AND WEAKEN LATER TODAY. HIGHS IN ERN NE ARE EXPECTED TO REACH THE UPPER 70S AND LOWER 80S...WITH HIGHS MAINLY 75 TO 80 IN SWRN IA. HIGHS IN IOWA COULD BE SLIGHTLY LOWER IF CLOUDS DO NOT DECREASE AS EXPECTED. .LONG TERM...(TONIGHT THROUGH FRIDAY) ISSUED AT 334 AM CDT SAT MAY 2 2015 BEHIND EASTWARD DRIFTING AFTERNOON CONVECTION...ATTENTION THEN TURNS TO COLD FRONT APPROACHING OUR AREA SUNDAY AFTERNOON AND EVENING. SOUTHWEST LOW LEVEL JET SHOULD KEEP LAYER MOISTURE RELATIVELY DRY OVERNIGHT BEFORE INCREASING DURING THE DAY SUNDAY. THUS WILL KEEP A DRY FORECAST GOING THROUGH SUNDAY MORNING. PERSISTENT SOUTHERLY SURFACE FLOW WILL DRIVE DEW POINTS INTO THE MIDDLE 50S AHEAD OF FRONT...AND COMPRESSIONAL WARMING SHOULD PUSH HIGHS WELL INTO THE 80S. THIS COMBINATION WILL YIELD SURFACE-BASED CAPE VALUES APPROACHING 2000 J/KG AS PER GFS...BUT RELATIVELY WARM MID LEVEL TEMPS MAY HOLD CONVECTION OFF UNTIL CLOSER TO EVENING. FRONTAL BOUNDARY SHOULD BE INTO NORTHEAST NEBRASKA BY 00Z...SO WILL INITIATE THUNDERSTORM CHANCES THERE LATE SUNDAY AFTERNOON...WITH INCREASING CHANCES IN THE EVENING AS THE FRONT SETTLES SOUTH AND MID LEVELS COOL. BULK SHEAR VALUES ARE HIGHEST BEHIND FRONTAL ZONE...SO ORGANIZED STORMS ALONG AND AHEAD OF FRONT LOOK TO BE WIDELY SCATTERED. HOWEVER STILL COULD SEE HAIL AND WINDS WITH THE STRONGEST. CONTINUED DEVELOPMENT OF CONVECTION IS EXPECTED OVERNIGHT AS FRONT SETTLES INTO SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. LOW LEVEL JET IS NOT STRONG AND PARALLELS FRONT...SO SEVERE RISK SHOULD DIMINISH BUT OCCASIONAL RAIN/THUNDER WILL PERSIST. COULD SEE SOME LOCALLY HEAVY RAINS WHERE TRAINING OF STORMS OCCURS. ON MONDAY...A MAJORITY OF SYNOPTIC SCALE MODELS INDICATE A SHORTWAVE WILL EJECT INTO THE PLAINS...DRAWING MOISTURE/INSTABILITY OVER TOP OF STALLED FRONT ALONG THE KANSAS BORDER. VARYING DEGREES OF THIS MOISTURE RETURN ARE NOTED...BUT ALL KEEP FAIRLY HIGH RAIN CHANCES IN PLACE DURING THE DAY. WE COULD SEE A LULL IN ACTIVITY MONDAY MORNING BEFORE SHOWERS/STORMS INCREASE FROM WEST TO EAST THROUGH THE MORNING. WHILE SEVERE THREAT IS MINIMAL...STORMS NEAR THE KANSAS BORDER NEARER FRONTAL BOUNDARY AND HIGHER INSTABILITY COULD BE STRONG. THE SEVERE POTENTIAL WILL INCREASE SOMEWHAT MONDAY NIGHT WHEN MID LEVEL FLOW TURNS MORE SOUTHWESTERLY AS TROUGH SWINGS INTO THE SOUTHERN ROCKIES. FRONT ALONG KANSAS BORDER WILL LIFT NORTH OVERNIGHT AS DIFFLUENT FLOW ALOFT IN AREA OF COUPLED JET STRUCTURE INDUCES INCREASE IN LOW LEVEL JET AND THUS STRONG THETA-E ADVECTION. THIS REGIME WILL CONTINUE LIFTING NORTHEAST TUESDAY MORNING...AND WOULD EXPECT A LULL IN CONVECTION ACROSS ALL OF THE CWA TUESDAY AFTERNOON AND EVENING BEFORE MID LEVEL TROUGH ENTERS THE PLAINS LATER TUESDAY NIGHT AND WEDNESDAY. WILL SEE OFF AND ON THUNDERSTORM CHANCES WEDNESDAY AND THURSDAY AS THAT TROUGH LIFTS THROUGH THE PLAINS. EXACT LOCATION/TIMING OF STRONGEST STORMS WILL HAVE TO BE WORKED OUT WITH TIME...BUT MUCH OF OUR AREA WILL BE IN FAVORABLE SHEAR AND INSTABILITY PROFILES WEDNESDAY AFTERNOON THROUGH THURSDAY EVENING FOR POTENTIALLY SEVERE STORMS. SHOULD SEE A LOWER POTENTIAL FOR STORMS ON FRIDAY WITH INITIAL TROUGH EXITING TO OUR NORTHEAST. && .AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 625 AM CDT SAT MAY 2 2015 EXPECT MAINLY VFR CEILINGS AT THE TAF SITES THE NEXT 24 HOURS. THERE WILL BE SOME SPOTTY MVFR CEILINGS AND SOME VSBYS LESS THAN 3 MILES IN THE HEAVIER SHRA/TSRA BUT CHANCES SEEM TOO LOW TO MENTION IN THE TAFS AT THIS POINT. WILL AMEND AS NEEDED. SOUTHERLY WINDS WILL INCREASE LATER TODAY WITH SOME GUSTS MAINLY IN THE AFTERNOON. WINDS WILL DECREASE BY EARLY EVENING. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...MILLER LONG TERM...DERGAN AVIATION...MILLER

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