Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 181750 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1250 PM CDT SAT APR 18 2015 .UPDATE... ISSUED AT 1244 PM CDT SAT APR 18 2015 HAVE MADE A FEW ADJUSTMENTS TO POPS AND AREAL COVERAGE THROUGH THE DAY. RAIN WILL CONTINUE ALONG/EAST OF THE MISSOURI RIVER INTO THE AFTERNOON. BEST THREAT FOR THUNDER APPEARS TO REMAIN ACROSS WESTERN IOWA. AS YOU GO FURTHER WEST THROUGH THE FORECAST AREA...RAIN CHANCES DIMINISH...WITH AREAS FROM NORFOLK SOUTHWARD TO FAIRBURY MAY NOT SEE ANY ADDITIONAL RAINFALL. SPC ALSO PULLED SLIGHT RISK OF SEVERE STORMS FURTHER WEST OUT OF THE FORECAST AREA. APPEARS THAT ANY STRONGER STORMS WILL FIRE WEST OF THE FORECAST AREA THIS EVENING AND LIKELY NOT REMAIN STRONG ENOUGH IF THEY PUSH FURTHER EAST. ALSO LOWERED HIGHS A BIT WHERE RAIN AND CLOUDS WILL REMAIN THIS AFTERNOON...ALONG/EAST OF THE MISSOURI RIVER. && .SHORT TERM...(TODAY THROUGH MONDAY) ISSUED AT 351 AM CDT SAT APR 18 2015 THE CHANCE FOR SHOWERS AND THUNDERSTORMS THROUGH SUNDAY IS THE PRIMARY FORECAST CONCERN. UPPER LOW CONTINUED TO SPIN ACROSS SOUTHERN COLORADO THIS MORNING... AND WAS MAKING ONLY SLOW PROGRESS TO THE EAST. MODELS ARE RELATIVELY SIMILAR IN MOVING LOW INTO THE HIGH PLAINS OF KANSAS THIS EVENING BEFORE IT OPENS UP AND SWINGS THROUGH KANSAS ON SUNDAY AS KICKER LOW DROPS SOUTHEAST INTO SOUTHERN MANITOBA. AHEAD OF THE LOW THIS MORNING...PLUME OF MID LEVEL MOISTURE AGITATED BY SHEARED VORTICITY IN WARM ADVECTION WING WAS LEADING TO SCATTERED SHOWERS AND THUNDERSTORMS FROM CENTRAL KANSAS INTO CENTRAL AND WESTERN NEBRASKA. A FEW ISOLATED SHOWERS WERE NOTED FARTHER EAST OVER OUR AREA. ALL ACTIVITY WAS GENERALLY LIFTING NORTH OR NORTHWEST...WITH NO REAL PUSH INTO EASTERN NEBRASKA AS OF YET. COMBINATION OF RADAR AND SATELLITE TRENDS...ALONG WITH A BLEND OF SHORT-RANGE MESOSCALE MODELS...SUGGESTS MID LEVEL MOISTURE PLUME AND ASSOCIATED CONVECTION WILL ROTATE NORTH AND NORTHEAST THIS MORNING...SWEEPING THROUGH EASTERN NEBRASKA AND WESTERN IOWA. BEST COVERAGE OF STORMS WILL OCCUR IN NORTHEAST NEBRASKA WITH A MORE SCATTERED LOOK TO SHOWERS AND ISOLATED STORMS AS WE MOVE SOUTHEAST OF THERE. MOST OF THIS ACTIVITY SHOULD BE MOVING NORTHEAST OF OUR AREA IN THE EARLY AFTERNOON WHEN FOCUS OF ADDITIONAL DEVELOPMENT MOVES WEST WITH APPROACHING MID LEVEL LOW AND DEVELOPING SURFACE SURFACE LOW. THAT ADDITIONAL DEVELOPMENT WILL BE CONDITIONAL ON AMOUNT OF CLEARING AND SUBSEQUENT INSTABILITY SEEN IN CENTRAL SECTIONS OF NEBRASKA AND KANSAS. NAM IS MOST AGGRESSIVE IN THIS REGARD AND IS THE ODD MODEL OUT IN DEVELOPING CONVECTION IN CENTRAL NEBRASKA NEAR SURFACE CIRCULATION AND ALONG WARM FRONT EXTENDING INTO OUR WESTERN CWA. GFS/ECMWF AND CONVECTION-ALLOWING MESOSCALE MODELS SUGGEST CAPPING WILL HOLD IN MOST OF NEBRASKA...AND INSTEAD DEVELOPING STORMS ALONG DRYLINE IN KANSAS. EXPECT THIS TO BE THE THE LIKELY SCENARIO...BUT IF STORMS DO FIRE AS NAM INDICATES THERE WILL BE AN INCREASED TORNADO RISK IN AREA OF MAXIMUM LOW LEVEL SHEAR/HELICITY ALONG WARM FRONT. EXPECT STORMS TO FIRE BY LATE AFTERNOON IN SOUTH CENTRAL NEBRASKA AND CENTRAL KANSAS AND LIFT NORTH AND NORTHEAST WITH TIME DURING THE EVENING. AGAIN IT LOOKS LIKE NORTHEAST NEBRASKA WILL SEE THE BRUNT OF ACTIVITY...WITH AT LEAST A SMALL CHANCE FOR SEVERE...WITH MORE HIT AND MISS STORMS ACROSS THE REST OF THE CWA DURING THE EVENING. AFTER MIDNIGHT...COLD FRONT WILL BEGIN PUSHING TOWARD NORTHEAST NEBRASKA...AND IS EXPECTED TO APPROACH INTERSTATE 80 BY SUNRISE BEFORE SWEEPING SOUTHEAST OF THE CWA DURING THE MORNING. THUNDERSTORMS WILL BE POSSIBLE ALONG AND AHEAD OF THE FRONT WITH SHOWERS BEHIND INTO THE AFTERNOON. OTHERWISE DECREASING RAIN CHANCES ARE FORECAST SUNDAY AFTERNOON WITH INCREASING NORTHWEST WINDS. MUCH COOLER AIR SETTLES INTO THE REGION MONDAY AS ECMWF SHOWS SUB- ZERO 850 TEMPERATURES AND BRISK NORTHWEST WINDS. EXPECT HIGHS MONDAY AFTERNOON TO REMAIN IN THE 50S. .LONG TERM...(MONDAY NIGHT THROUGH FRIDAY) ISSUED AT 351 AM CDT SAT APR 18 2015 SOMEWHAT COOL TEMPERATURES ARE EXPECTED DURING THE WEEK...WITH INCREASING CHANCES FOR PRECIPITATION BY LATE WEEK. NORTHWEST MID LEVEL FLOW WILL DOMINATE THE WEATHER ACROSS THE CENTRAL PLAINS THROUGH MID WEEK AS UPPER LOW SLOWLY TRUDGES EAST INTO THE NORTHERN GREAT LAKES. WHILE RIPPLES IN THIS FLOW COULD BRING A SCATTERED SHOWER...THE MAIN WEATHER STORY WILL BE OUR COOLER AIRMASS REMAINING IN PLACE AT LEAST THROUGH WEDNESDAY. SHOULD SEE LOWS IN THE 30S AND HIGHS PERHAPS TOPPING 60 TUESDAY AND WEDNESDAY. A REINFORCING COLD FRONT SETTLING ALONG THE KANSAS BORDER IS FORECAST TO LIFT BACK TO THE NORTH WEDNESDAY NIGHT AND THURSDAY AS SHORTWAVE UPPER RIDGING MOVES INTO THE PLAINS. COULD SEE SCATTERED SHOWERS OR STORMS ALONG THIS FRONT AS IT LIFTS NORTH. HOWEVER BETTER CHANCES FOR STORMS COME FRIDAY AS UPPER LOW EJECTS THROUGH THE ROCKIES INTO THE PLAINS. THERE ARE SURE TO BE TIMING ISSUES WITH THIS SYSTEM...SO PINNING DOWN TIMING/SEVERITY OF CONVECTION RISK WILL HAVE TO BE WORKED OUT WITH TIME. && .AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1244 PM CDT SAT APR 18 2015 SHOWERS WILL CONTINUE TO AFFECT KOMA THROUGH THE REMAINDER OF THE AFTERNOON...WITH VFR/MVFR CONDITIONS. PRECIP CHANCES DIMINISH THERE BY 23-01Z THOUGH. ALSO APPEARS THUNDER MAY REMAIN EAST OF THE KOMA SITE. KLNK MAY SEE A FEW SHOWERS IN THE VICINITY FOR AN HOUR OR TWO. IFR DECK OF CLOUDS AT KLNK SHOULD ALSO LIFT TO VFR BY 19Z. KOFK WILL LIKELY REMAIN DRY EARLY IN THE PERIOD. ADDITIONAL RAIN CHANCES ENTER THE AREA LATER TONIGHT AS A COLD FRONT APPROACHES. NOT CONFIDENT ENOUGH TO FORECAST THUNDER THAT FAR OUT. COLD FRONT ARRIVES AT KOFK BY 10-12Z...AND KLNK/KOMA BY 13-15Z. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ UPDATE...DEWALD SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...DEWALD

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