Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 251130 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 630 AM CDT FRI JUL 25 2014 .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 330 AM CDT FRI JUL 25 2014 TEMPERATURES AND TSTM CHANCES SHOULD AGAIN BE THE PRIMARY FORECAST CONCERNS. WILL KEEP HEAT ADVISORY GOING SOUTHERN ZONES FOR THIS AFTERNOON AND EARLY EVENING. CONVECTION THAT FORMED OVER THE HIGH PLAINS YESTERDAY AFTERNOON AND EVENING CONTINUED TO ROLL EASTWARD OVERNIGHT WITH 40-60 KNOT LOW LEVEL JET AROUND 1 KM AGL. THIS ACTIVITY WAS GENERALLY ROOTED ABOVE THE IMPRESSIVE CAP BELOW 750 MB FROM 00Z KOAX SOUNDING. A FEW THINGS NOTED FROM THAT SOUNDING...700-500 MB LAPSE RATE WAS 7.8 DEGREES C PER KM AND PRECIPITABLE WATER WAS 1.38 INCHES. THIS MORNING WAS A PERFECT EXAMPLE OF HOW WE CAN GET OVERNIGHT CONVECTION EVEN WITH 700 MB TEMPERATURES OF 14-15 DEGREES C. CASES LIKE THIS THOUGH ARE VERY HARD TO PREDICT OVER ABOUT 24 HOURS IN ADVANCE. MAIN FEATURES NOTED FROM 00Z UPPER AIR PLOT AT 500 MB WERE THE CLOSED LOW OVER SOUTHERN ALBERTA AND THE RIDGE THAT STRETCHED FROM SOUTHERN CALIFORNIA INTO THE LOWER MISSISSIPPI RIVER VALLEY. VERY IMPRESSIVE 12 HOUR HEIGHT FALLS...ESTIMATED AT UP TO 140 METERS... WERE NEAR THE ALBERTA/SASKATCHEWAN BORDER. WEAKER HEIGHT FALLS EXTENDED SOUTHWARD INTO WESTERN SOUTH DAKOTA...WESTERN NEBRASKA AND INTO COLORADO. THE CLOSED LOW AT 500 MB WILL MOVE EASTWARD ACROSS SOUTHERN CANADA THROUGH SATURDAY NIGHT...THEN OPEN UP A BIT AND TRACK INTO THE GREAT LAKES REGION AS AN OPEN SHORTWAVE TROUGH. THE 500 MB ANTICYCLONE OVER NEW MEXICO AND TEXAS WILL WOBBLE A BIT THROUGH THE PERIOD. AN EXTENSION OF THAT HIGH THOUGH WILL BUILD UP INTO CENTRAL CANADA THROUGH SUNDAY AS TROUGHS DIG OVER THE NORTHEAST PACIFIC AND OVER THE GREAT LAKES REGION...PUTTING OUR AREA IN MODEST TO STRONG NORTHWEST FLOW. TODAY...CONVECTION SHOULD END BY MID MORNING ACROSS SOUTHEAST NEBRASKA AND SOUTHWEST IOWA AS THE LOW LEVEL JET DECREASES. THIS LEAVES OUR AREA WITH WARM MILD LEVELS AND LITTLE IN THE WAY OF LARGE SCALE FORCING UNTIL LATE AFTERNOON. THE PREVIOUS FORECAST OF TEMPERATURES AND DEWPOINTS WAS NOT CHANGED MUCH. HEAT INDEX VALUES SHOULD PEAK IN THE 105 TO 110 RANGE IN OUR SOUTHERN ZONES THIS AFTERNOON. HAVE SOME CONCERN THAT THERE MAY BE JUST ENOUGH FORCING TO GET SOME ISOLATED STORMS GOING BETWEEN 6 PM AND 10 PM THIS EVENING AS THE WEAK COLD FRONT PUSHES ACROSS SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. OTHERWISE...WE MAY HAVE TO WAIT FOR STORMS TO AGAIN ROLL EASTWARD FROM THE HIGH PLAINS NORTH OF THE FRONT LATE TONIGHT. THAT ACTIVITY WOULD MOSTLY BE CONFINED TO NORTHEAST NEBRASKA PRIOR TO 12Z SATURDAY. NONE OF THE MODELS HAVE BEEN DOING A STELLAR JOB WITH THE CONVECTIVE ACTIVITY THE PAST SEVERAL DAYS...BUT THIS IS TO BE EXPECTED THIS TIME OF YEAR. RECENT SREF MODEL RUNS HAVE SHOWN SOME WEAK 700-500 MB Q VECTOR CONVERGENCE MOVING EASTWARD ALONG THE NEBRASKA/SOUTH DAKOTA BORDER TONIGHT...THEN OVER PORTIONS OF THE AREA ON SATURDAY. NOT OVERLY IMPRESSED WITH ANYTHING...BUT WILL KEEP SOME 20-40 POPS IN NORTHEAST NEBRASKA AND MAINLY 20 PERCENT ELSEWHERE. SPC DAY 2 OTLK DOES HAVE OUR FAR SOUTHERN COUNTIES IN A SLIGHT RISK (I THINK MOSTLY FOR SATURDAY AFTERNOON AND EVENING) AND FOR NOW THAT SEEMS REASONABLE. TEMPERATURES SATURDAY SHOULD NOT BE QUITE AS HOT AS TODAY...GENERALLY 3 TO 6 DEGREES COOLER. BUT COOLER AND DRIER AIR WILL MOVE IN BY SUNDAY AS HIGH PRESSURE AT THE SURFACE BUILDS EAST ACROSS THE NORTHERN AND CENTRAL PLAINS. .LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY) ISSUED AT 330 AM CDT FRI JUL 25 2014 WE STILL LOOK FOR TEMPERATURES AT OR BELOW NORMAL THROUGH THIS PERIOD. PCPN CHANCES GENERALLY LOOK SMALL...WITH ONLY FAIR MODEL AGREEMENT IN REGARDS TO FORCING STRONG ENOUGH TO GET TSTMS GOING. THE 500 MB PATTERN IS EXPECTED TO AMPLIFY A BIT AS THE RIDGE RETROGRADES MID TO LATE NEXT WEEK. && .AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 627 AM CDT FRI JUL 25 2014 VFR CONDITIONS EXPECTED THRU THE FCST PD. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...HEAT ADVISORY FROM NOON TODAY TO 7 PM CDT THIS EVENING FOR NEZ065>068-078-088>093. IA...HEAT ADVISORY FROM NOON TODAY TO 7 PM CDT THIS EVENING FOR IAZ079-080-090-091. && $$ SHORT TERM...MILLER LONG TERM...MILLER AVIATION...DEE

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