Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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909 FXUS63 KOAX 171747 AAD AFDOAX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1247 PM CDT SUN MAY 17 2015 .SHORT TERM...(TODAY THROUGH TUESDAY) ISSUED AT 326 AM CDT SUN MAY 17 2015 AFTERNOON THUNDERSTORM CHANCES TODAY...THEN COOLER TEMPERATURES FOR THE FIRST PART OF THE WEEK...ARE THE PRIMARY FORECAST CONCERNS. UPPER LOW LIFTING NORTH-NORTHEAST THROUGH WESTERN NEBRASKA IS FORECAST TO DRIFT FROM SOUTH CENTRAL TO NORTHEAST SOUTH DAKOTA DURING THE DAY. ATTENDANT SURFACE LOW WILL TAKE A SIMILAR PATH...WITH COLD FRONT ROTATING SOUTHEAST ON BACK SIDE OF SYSTEM ENTERING NORTHEAST NEBRASKA LATER THIS MORNING AND TO INTERSTATE 80 LATE IN THE DAY. SOUTHWEST SURFACE FLOW AHEAD OF THE FRONT WILL TEND TO DRY LOW LEVELS AND PROVIDE DECENT COMPRESSIONAL WARMING COMPONENT TO DRIVE TEMPERATURES CLOSE TO 80 FOR MUCH OF THE SOUTHERN HALF OF OUR CWA. MORE OF A NORTHWESTERLY COMPONENT IN THE NORTH WILL DO THE SAME THING...BUT TEMPERATURES THERE WILL BE AFFECTED BY COOL ADVECTION AND MORE CLOUD COVER. HOWEVER RELATIVELY STEEP LAPSE RATES WILL STILL BE REALIZED IN OUR NORTH GIVEN PROXIMITY TO UPPER LOW/COLD POOL. AND MODELS SUGGEST SURFACE BASED CAPES WILL TOP 1000 J/KG AT 21Z WHEN DEW POINTS IN THE LOWER TO MID 50S WILL BE PRESENT ALONG FRONTAL ZONE. PLENTY OF 0-6KM BULK SHEAR IN THE NEIGHBORHOOD OF 40KT WILL BE PRESENT AS WELL. ALTHOUGH MOISTURE PROFILES WILL BE BECOMING LESS CONDUCIVE FOR CONVECTION...STILL THINK AT LEAST ISOLATED STORMS COULD FIRE NEAR COLD FRONT LATER TODAY...GENERALLY NEAR OR NORTH OF INTERSTATE 80. AND GIVEN SHEAR/INSTABILITY COMBINATION...A SNEAKY STRONG STORM IS CERTAINLY POSSIBLE. ANY CONVECTION THAT MANAGES TO FIRE TODAY WILL DIE DOWN QUICKLY THIS EVENING WITH LOSS OF HEATING. THEN CONTINUED COOL ADVECTION WILL PERSIST FOR THE NEXT COUPLE OF DAYS. 850 TEMPERATURES ACTUALLY DROP BELOW 0C IN NORTHEAST NEBRASKA FOR A TIME MONDAY MORNING BEFORE SOME REBOUND AS CORE OF UPPER LOW SLIDES NORTHEAST. STILL RELATIVELY COOL AIRMASS WILL REMAIN IN PLACE THROUGH TUESDAY AS NORTH TO NORTHEAST LOW LEVEL FLOW CONTINUES. SOME WIND SUNDAY NIGHT SHOULD KEEP TEMPERATURES IN THE 40S OR LOWER 50S...WITH SUNSHINE HELPING TO WARM TEMPS INTO THE 60S DURING THE DAY MONDAY. CLEAR SKIES AND LIGHT WINDS UNDER SURFACE RIDGE SHOULD ALLOW SOME TEMPS TO DROP INTO THE 30S IN OUR NORTH TUESDAY MORNING...WITH SOME PATCHY FROST NOT OUT OF THE QUESTION. INCREASING CLOUDS LATER IN THE DAY SHOULD HOLD HIGHS TO THE LOWER 60S AGAIN. .LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY) ISSUED AT 326 AM CDT SUN MAY 17 2015 UPPER LOW/TROUGH SETTLING INTO THE SOUTHWEST STATES EARLY IN THE WEEK IS FORECAST TO EJECT INTO THE PLAINS AS AN OPEN WAVE EARLY IN THE LONGER TERM PERIOD. THEN TROUGH RELOADS IN THE WEST...PROVIDING SOUTHWEST FLOW ALOFT IN THE PLAINS...WITH WEAK RIDGING NOTED ON MAJORITY OF LONGER TERM MODELS MOVING INTO THE PLAINS TO END THE WEEK. WILL CONTINUE WITH RELATIVELY HIGH RAIN CHANCES TUESDAY NIGHT THROUGH WEDNESDAY NIGHT AS INITIAL WAVE TRACKS THROUGH THE AREA. MOISTURE RETURN LOOKS TO BE MINIMAL...THUS INSTABILITY PROGS SUGGEST ONLY A SMALL CHANCE FOR THUNDER. WEDNESDAY WILL BE RATHER COOL AS WELL GIVEN EXPECTED RAIN/CLOUDS...WITH HIGHS GENERALLY ONLY IN THE 50S. A SLIGHT WARMING TREND SHOULD COMMENCE THURSDAY AND FRIDAY WITH RISING MID LEVEL HEIGHTS AND RETURNING SOUTHEAST LOW LEVEL FLOW. HOWEVER HIGHS WILL LIKELY BE TEMPERED ON FRIDAY AS MID/HIGH LEVEL MOISTURE/CLOUDS SPREAD INTO THE REGION AHEAD OF NEXT SOUTHWEST TROUGH PROGRESSING THROUGH THE ROCKIES. WILL SEE INCREASING RAIN CHANCES AGAIN FRIDAY NIGHT INTO SATURDAY AS THIS SYSTEM APPROACHES. && .AVIATION...
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(18Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1232 PM CDT SUN MAY 17 2015 SOMEWHAT STACKED LOW PRESSURE SYSTEM WAS LOCATED OVER CENTRAL AND EASTERN SOUTH DAKOTA. LAPSE RATES AND INSTABILITY SUPPORTS CONTINUED SHOWERS AND ISOLATED THUNDERSTORMS THROUGH 00Z. BETTER CHANCES OF THUNDER AT KOFK AND KOMA. DUE TO VERY ISOLATED IN NATURE...HAVE VCSH IN KOFK AND KOMA AND HAVE NOT INCLUDED IT IN THE KLNK TAF. OTHERWISE MAJORITY OF THE TIME ALL THREE TAF SITES WILL BE VFR AND ONLY DIPPING INTO MVFR WHEN...IF -TSRA MOVES ACROSS TAF SITE. WINDS EITHER HAVE ALREADY BECOME...OR SHORTLY WILL BECOME...SOUTHWEST AND GUSTY IN ADVANCE OF APPROACHING COLD FRONT FROM THE WEST. WINDS WILL SWITCH TO WEST AND NORTHWEST BETWEEN 20Z AND 23Z AT ALL THREE TAF SITES AND REMAIN GUSTY.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...MEYER

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