Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 010840 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 340 AM CDT SAT AUG 1 2015 .SHORT TERM...(TODAY THROUGH MONDAY) ISSUED AT 335 AM CDT SAT AUG 1 2015 CHANCE FOR SEVERE THUNDERSTORMS TODAY AND TONIGHT...THEN WARM TEMPERATURES SUNDAY...ARE THE PRIMARY FORECAST CONCERNS. CONVECTION TIED TO SOUTHWARD-ADVANCING SURFACE FRONT HAD CLEARED THE SOUTHERN NEBRASKA AND IOWA BORDERS LATE LAST EVENING. THAT BOUNDARY IS EXPECTED TO RETREAT NORTHWARD TODAY AS A WARM FRONT IN RESPONSE TO LOWERING PRESSURES TO OUR NORTHWEST IN ADVANCE OF MID LEVEL SHORTWAVE DIVING FROM THE NORTHERN ROCKIES INTO SOUTH DAKOTA THIS AFTERNOON. STRONG MOISTURE ADVECTION WILL FOLLOW WARM FRONT IN SOUTHERLY LOW LEVEL FLOW...AND WHEN COMBINED WITH POTENT AFTERNOON HEATING...WILL PRODUCE MOST-UNSTABLE CAPES WELL OVER 2500 J/KG. ENHANCED NORTHWESTERLY MID LEVEL FLOW ATTENDANT TO APPROACHING SHORTWAVE WILL INDUCE STRONG 0-6KM BULK SHEAR ON THE ORDER OF 40KT AS SOUTH TO SOUTHWEST SURFACE FLOW INCREASES. VEERING WIND PROFILES WITH MAGNITUDE OF SHEAR VECTORS WILL BE SUPPORTIVE OF ROTATING STORMS SUGGESTING ALL MODES OF SEVERE WILL BE POSSIBLE THIS AFTERNOON...WITH TORNADO POTENTIAL HIGHEST NEAR WARM FRONT IN NORTHEAST NEBRASKA AND SOUTHEAST SOUTH DAKOTA...AND ESPECIALLY NEAR TRIPLE POINT WHERE SOUTHEASTERLY-ADVANCING TROUGH/DRYLINE INTERSECTS WARM FRONT. EXPECT STORMS CURRENTLY FIRING IN SOUTH CENTRAL SOUTH DAKOTA INTO CENTRAL NEBRASKA TO GRADUALLY WORK EAST AND SOUTHEAST THIS MORNING...WITH ISOLATED TO SCATTERED STORMS REACHING OUR WESTERN CWA. BETTER CONVECTIVE CHANCES COME THIS AFTERNOON WHEN INSTABILITY IS MAXIMIZED...WITH FOCUS GEARED TOWARD LOW LEVEL CONVERGENCE ALONG WARM FRONT...WHICH SHOULD LIE ACROSS NORTHEAST NEBRASKA INTO WEST CENTRAL IOWA. INCREASING LOW LEVEL JET DURING THE EVENING WILL SUPPORT CONTINUED DEVELOPMENT OF CONVECTION WITH PROPAGATION VECTORS SHOWING A SOUTHEAST PROGRESSION ACROSS PARTS OF EASTERN NEBRASKA AND WESTERN IOWA. EXPECT MOST CONVECTION TO BE WELL EAST OF WESTERN IOWA BY SUNRISE SUNDAY...BUT SOME LINGERING INSTABILITY/STORMS ARE POSSIBLE IN THE MORNING IN SOUTHWEST IOWA. MOST OF SUNDAY IS EXPECTED TO BE DRY AS WESTERLY LOW LEVEL FLOW PREVAILS ACROSS MUCH OF OUR CWA DURING THE MORNING. HOWEVER LOW LEVEL MOISTURE WILL TAKE SOME TIME BEFORE BEING SWEPT SOUTH. A COLD FRONT IS FORECAST TO FOLLOW EXITING SHORTWAVE...REACHING INTERSTATE 80 BY EARLY AFTERNOON THEN CLEARING OUR SOUTHERN BORDER BY LATE SUNDAY AFTERNOON. WESTERLY WIND COMPONENT POINTS TO TEMPERATURES WELL INTO THE 90S OVER THE SOUTHERN HALF OF OUR CWA...BUT NORTHERLY WINDS BEHIND THE FRONT SUGGEST HIGHS CLOSER TO 90 IN OUR NORTH. AND WITH LOW LEVEL MOISTURE...DEW POINTS IN THE MID 60S...REMAINING OVER SOUTHEAST NEBRASKA AND SOUTHWEST IOWA SUNDAY AFTERNOON...MUCAPES WILL AGAIN TOP 2500 J/KG AS FRONT INVADES. THUS WILL INTRODUCE SOME SMALL THUNDERSTORM CHANCES IN OUR SOUTH THEN. MONDAY MAY BRING A SIMILAR SCENARIO TO TODAY AS SUNDAY COLD FRONT STALLS IN NORTHERN KANSAS SUNDAY NIGHT THEN RETREATS BACK NORTH INTO EASTERN NEBRASKA AND WESTERN IOWA MONDAY. SHORTWAVE IN NORTHWEST FLOW ALOFT WILL AGAIN LOWER PRESSURES IN THE HIGH PLAINS...INDUCING SOUTHERLY LOW LEVEL FLOW AND MOISTURE RETURN INTO OUR AREA. WE SHOULD AGAIN SEE CONVECTION FIRING NEAR AND NORTH OF THE WARM FRONT. EXACT PLACEMENT OF THAT FRONT WILL NEED TO BE REFINED LATER...BUT WILL HAVE AT LEAST A SLIGHT CHANCE FOR STORMS OVER MOST OF THE CWA...WITH HIGHER CHANCES NEAR AND NORTH OF A COLUMBUS TO NEBRASKA CITY AND CLARINDA LINE. SUFFICIENT INSTABILITY AND SHEAR...30- 40KT...AGAIN SUGGEST SOME SEVERE STORMS WILL BE POSSIBLE. .LONG TERM...(MONDAY NIGHT THROUGH FRIDAY) ISSUED AT 335 AM CDT SAT AUG 1 2015 THERE WILL BE A CHANCE FOR THUNDERSTORMS MUCH OF NEXT WEEK AS NORTHWEST FLOW ALOFT CONTINUES TO EJECT SHORTWAVES INTO THE NORTHERN AND CENTRAL PLAINS. THERE IS SOME INDICATION UPPER RIDGE AXIS WILL SHIFT INTO THE PLAINS FOR A SHORT TIME WEDNESDAY NIGHT...KEEPING THAT PERIOD DRY...BUT WE QUICKLY GET BACK INTO THE UNSETTLED NORTHWEST FLOW PATTERN LATE IN THE WEEK. MONDAY FRONTAL BOUNDARY IS EXPECTED TO REMAIN IN OR NEAR OUR CWA MONDAY NIGHT INTO TUESDAY BEFORE MORE DEFINED MID LEVEL WAVE SWEEPS FRONT/MOISTURE TO OUR SOUTHEAST LATER TUESDAY NIGHT OR WEDNESDAY. GFS SHOWS OUR AREA ON COOL SIDE OF FRONTAL SYSTEM ON TUESDAY...SO SEVERE THREAT LOOKS MINIMAL. HOWEVER SEVERE POTENTIAL RETURNS BY THURSDAY AFTERNOON WHEN MAIN STORM TRACK SHIFTS BACK TO THE NORTH BRINGING LOW LEVEL MOISTURE AND SUPPORTIVE SHEAR PATTERN BACK INTO OUR AREA. TEMPERATURES THROUGH THE WEEK LOOK COOLER...AVERAGING THE LOWER 80S MOST AREAS...AS CLOUDS/PRECIP/THERMAL PROFILE KEEP A LID ON WARMING. && .AVIATION...(06Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1145 PM CDT FRI JUL 31 2015 WILL GENERALLY FOLLOW TRENDS FROM MOST RECENT HRRR MODEL RUNS. SOME PATCHY FOG APPEARS POSSIBLE ESPECIALLY AFTER 09Z AND MAINLY AROUND KOMA. BY MID TO LATE MORNING...SOUTH/SOUTHWEST WINDS SHOULD INCREASE TO AROUND 10 KNOTS OR SO. THERE APPEARS TO BE A DECENT CHANCE THAT A TSTM COMPLEX WILL DROP SOUTHEAST INTO NORTHEAST NEBRASKA BY MID TO LATE MORNING AND THEN DEVELOP/MOVE SOUTHEAST. ATTEMPTED TO TIME THIS WITH PROB30 GROUPS FOR NOW. MENTIONED SOME VARIABLE GUSTY WINDS AT KOFK WHERE CONFIDENCE IS HIGHEST AND ACTIVITY WILL LIKELY AFFECT THAT LOCATION FIRST. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...MILLER

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