Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS63 KOAX 200811 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 311 AM CDT SAT SEP 20 2014 .SHORT TERM...(TODAY THROUGH MONDAY) ISSUED AT 311 AM CDT SAT SEP 20 2014 ...PRIMARY FORECAST CONCERNS ARE POPS THIS MORNING... AREA OF SCATTERED THUNDERSTORMS CONTINUES TO BE ACTIVE OVER EASTERN NEBRASKA AND SOUTHWEST IOWA...CONFINED MAINLY NORTH OF INTERSTATE 80 THUS FAR. OVERALL THIS AREA HAS SLOWLY SHIFTED SOUTH DURING THE EARLY MORNING HOURS AND HAS MAINTAINED MOSTLY WEAK UPDRAFTS. AIRMASS AHEAD OF THE CONVECTION...OVER SOUTHEAST NEBRASKA AND SOUTHWEST IOWA...REMAINS SOMEWHAT UNSTABLE WITH DEWPOINTS IN THE MID TO UPPER 60S. MOST UNSTABLE CAPE IS AROUND 1000 J/KG ALTHOUGH LIFTED PARCEL LEVELS ARE AROUND 2000 METERS. LOW LEVEL JET IS AROUND 50 KNOTS ON KOAX VWP BUT HAS VEERED TO THE WSW. ALL OF THIS POINTS TO CONTINUED SUPPORT OF CONVECTION FOR THE NEXT FEW HOURS BUT REMAINING WELL BELOW SEVERE LEVELS...AND MOSTLY ELEVATED. HOW LONG IT WILL LINGER...AND SPECIFICALLY WHERE...SEEMS TO BE TIED TO THE VERTICAL MOTION CAUSING IT. THE VERTICAL MOTION IS MOSTLY BEING ATTRIBUTED TO MODERATELY STRONG FRONTOGENESIS IN THE MID LEVELS THAT IS OCCURRING ABOVE THE SURFACE COLD FRONT THAT WAS ANALYZED AT 07Z EXTENDING FROM NORTHWEST IOWA INTO CENTRAL NEBRASKA. THIS IS FORECAST BY MOST SHORT TERM MODELS TO EXIT THE FORECAST AREA BY EARLY AFTERNOON. HAVE TAPERED POPS FROM NORTH TO SOUTH THROUGH THE MORNING AND HAVE ALL AREAS DRY BY 22Z. GENERALLY EXPECT AREAS FROM INTERSTATE 80 NORTH TO BE DRY BY LATE MORNING... BUT KEPT A SMALL CHANCE IN THE FAR SOUTHEAST CORNER OF NEBRASKA AND SOUTHWEST IOWA DURING EARLY AFTERNOON BASED ON PROXIMITY TO DECELERATING SURFACE COLD FRONT AND OUTFLOW BOUNDARY FROM ON- GOING CONVECTION THAT IS EXPECTED TO SETTLE IN THAT AREA. COOLER AND DRIER AIRMASS MOVES INTO THE FORECAST AREA TONIGHT WITH SURFACE HIGH BUILDING INTO THE PLAINS SUNDAY. PLEASANT WEATHER WITH LIGHT WINDS EXPECTED SUNDAY. MONDAY WILL BE NICE AS WELL... ALTHOUGH THE SURFACE HIGH SHOULD MOVE TO THE MISSISSIPPI RIVER VALLEY MONDAY AFTERNOON WITH A RETURN FLOW OF SOUTH WINDS SETTING UP MONDAY. .LONG TERM...(MONDAY NIGHT THROUGH FRIDAY) ISSUED AT 311 AM CDT SAT SEP 20 2014 ...MAIN CHALLENGE IS POPS MONDAY NIGHT INTO THURSDAY... THE MODELS ARE IN GOOD AGREEMENT WITH AN UPPER RIDGE OVER THE PLAINS MONDAY...AND A PRONOUNCED UPPER LEVEL LOW MOVING THROUGH THE WESTERN US. REMARKABLE SIMILARITY BETWEEN MODEL SOLUTIONS AT 12Z TUESDAY WITH UPPER LOW CIRCULATION NEAR THE BLACK HILLS AND STRONG SOUTHERLY LOW LEVEL FLOW OVER NEBRASKA BRINGING A RETURN OF LOW LEVEL MOISTURE. MAJORITY OF DETERMINISTIC MODELS AND ENSEMBLE MEMBERS SHOW RAIN OVER SOUTH DAKOTA...NEBRASKA...AND KANSAS AT 12Z TUE...THEN THE FEATURES AND ASSOCIATED RAIN MOVES EAST OVER THE FORECAST AREA BETWEEN 12Z TUESDAY AND 18Z WEDNESDAY. WE CONTINUED THE CHANCE POPS DURING THAT PERIOD...WITH LIKELY POPS TUESDAY FOR PARTS OF THE AREA. MODEL SOLUTIONS DIVERGE DRASTICALLY FROM WEDNESDAY NIGHT INTO FRIDAY...THEREFORE CONFIDENCE DROPS CONSIDERABLY. THE GFS SUGGESTS A CONTINUATION OF THE WET PATTERN BY DROPPING THE UPPER LOW INTO NEBRASKA...WHEREAS THE ECMWF ALLOWS THE LOW TO BE SHEARED OFF TO THE EAST BY THE BROADER SCALE UPPER RIDGE FLOW...WHICH LOOKS MORE REALISTIC. KEPT THE CHANCE POPS WEDNESDAY NIGHT BUT WENT DRY FOR THURSDAY AND FRIDAY BASED ON THE ECMWF. && .AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1145 PM CDT FRI SEP 19 2014 TSTMS ACROSS NERN NE SHOULD CONTINUE TO DEVELOP SOUTHWARD WITH TIME TOWARD KOMA AND KLNK. THESE MAY HAVE MVFR CEILINGS AND VSBYS UNTIL AT LEAST MID MORNING. IFR CONDITIONS ARE POSSIBLE BUT DID NOT HAVE ENOUGH CONFIDENCE TO PUT THESE INTO TAFS ATTM. WINDS WILL GRADUALLY SHIFT TO THE NORTH AND BE A BIT GUSTY SATURDAY AFTN. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...NIETFELD LONG TERM...NIETFELD AVIATION...MILLER

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.