Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 312015 AFDOAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 315 PM CDT MON AUG 31 2015 .SHORT TERM...(TONIGHT THROUGH THURSDAY) ISSUED AT 311 PM CDT MON AUG 31 2015 CONTINUED WARM AND MUGGY CONDITIONS WITH SPOTTY RAIN CHANCES THROUGH THURSDAY REMAIN THE FOCUS OF THIS FORECAST. FOG DEVELOPED AGAIN THIS MORNING AND WAS DENSE IN SPOTS. LAX PRESSURE GRADIENT OVERHEAD THIS MORNING WAS TIGHTENING THIS AFTERNOON...WITH STRONGER SOUTHERLY FLOW TAKING OVER. THIS WILL BE THE TREND OVERNIGHT AS WELL...SO FOG IS NOT EXPECTED TO BE AS BIG OF AN ISSUE TUESDAY MORNING. WILL LIKELY SEE SOME REDUCTION IN VISIBILITIES AS WINDS DIE DOWN LATE TONIGHT...BUT DENSE FOG IS NOT ANTICIPATED. ATTENTION THEN TURNS TO PRECIP CHANCES TONIGHT AND BEYOND. MID LEVEL FLOW PATTERN IS FORECAST TO BECOME MORE AMPLIFIED THROUGH THE WEEK AS TROUGH DEEPENS ALONG THE WEST COAST AND NORTHERN ROCKIES AND RIDGE EXPANDS NORTH AND EAST INTO THE PLAINS. THIS PATTERN NORMALLY POINTS TO WARM TEMPERATURES AND MINIMAL RAIN CHANCES FOR OUR PART OF THE WORLD...AND THIS TIME IS NO DIFFERENT. SURFACE LOW PRESSURE WILL REMAIN WELL WEST OF OUR AREA IN THE HIGH PLAINS WHILE SOUTHERLY FLOW CONTINUES HERE. THUS SURFACE DEW POINTS IN THE 60S OR LOWER 70S LOOK TO PERSIST. MID LEVEL TEMPERATURES WILL HOLD STEADY THROUGH WEDNESDAY BEFORE WARMING ON THURSDAY...EFFECTIVELY CAPPING CONVECTION AT THAT TIME. HOWEVER UNTIL THEN...A COUPLE OF WEAK IMPULSES RIDING THROUGH THE PLAINS MAY SPARK AN ISOLATED STORM AS LOW LEVEL JET KICKS UP OVERNIGHT. PRECIPITATION THIS AFTERNOON WAS LINING UP ALONG MID LEVEL MOISTURE PLUME AND SHEARED VORTICITY TIED TO IMPULSE TRACKING THROUGH SOUTHERN CANADA. THAT IMPULSE WILL CONTINUE TO THE EAST TONIGHT...WITH SHEARED VORTICITY DISSIPATING AS IT MOVES OVER OUR AREA. THUS FORCING WILL BE MINIMAL BY THE TIME IT REACHES EASTERN NEBRASKA AS SHOWN BY RELATIVELY NON-EXISTENT LOW LEVEL JET PROGS ON MODEL OUTPUT. THUS WILL REMOVE ANY MENTION OF PRECIPITATION TONIGHT. TUESDAY NIGHT AND WEDNESDAY NIGHT WILL OFFER BETTER CHANCES WHEN WEAK WAVES LEAD TO STRONGER LOW LEVEL JET AND THUS STRONGER THETA-E ADVECTION. GFS/NAM/ECMWF ALL POINT TO ISOLATED TO SCATTERED SHOWERS DEVELOPING TUESDAY NIGHT...BUT BEGIN TO DIVERGE WEDNESDAY NIGHT AS WARMER MID LEVEL TEMPERATURES BEGIN TO SPREAD OVERHEAD. WHILE COVERAGE OF ANY THUNDERSTORMS LOOKS TO BE MINIMAL BOTH NIGHTS...WILL CONTINUE WITH SMALL CHANCES AS PER PREVIOUS FORECAST. WILL TWEAK AREAS A BIT BASED ON LATEST SYNOPTIC SCALE FEATURE PLACEMENT...AND WILL KEEP CHANCES CONFINED MAINLY TO THE OVERNIGHT HOURS WHEN LOW LEVEL JET IS STRONGEST. TEMPERATURES CLOSE TO 90 LOOK LIKELY AT ALL SITES TUESDAY AND WEDNESDAY...WITH THURSDAY LIKELY A LITTLE WARMER WHEN RIDGE AXIS IS OVERHEAD. OVERNIGHT LOWS WELL INTO THE 60S AND LOWER 70S SHOULD PREVAIL EACH NIGHT GIVEN HIGH DEW POINTS. .LONG TERM...(THURSDAY NIGHT THROUGH MONDAY) ISSUED AT 311 PM CDT MON AUG 31 2015 THE LONGER TERM PERIOD WILL BEGIN RELATIVELY WARM AND DRY WITH UPPER RIDGE OVERHEAD. HOWEVER A TRANSITION TOWARD COOLER AND WETTER CONDITIONS IS EXPECTED AS WE HEAD THROUGH THE WEEKEND. UPPER TROUGH ALONG THE WEST COAST IS FORECAST TO BEGIN A SLOW DRIFT TO THE EAST AND NORTHEAST WHILE RIDGE IN THE PLAINS IS SUPPRESSED TO THE SOUTH AND EAST. THUS FASTER SOUTHWEST FLOW ALOFT WILL EVENTUALLY OVERSPREAD OUR PART OF THE WORLD...BRINGING STORM TRACK CLOSER WITH TIME. GENERALLY IN THESE LONGWAVE PATTERNS THIS TRANSITION HAPPENS SLOWER THAN MODELS INITIALLY INDICATE...AND GFS IS SLOWER TODAY THAN YESTERDAY. ECMWF IS SLOWER THAN THE GFS AS WELL. SO WHILE THERE MAY BE ISOLATED STORM CHANCES FRIDAY INTO SATURDAY...BETTER CHANCES WILL COME DURING THE LATTER HALF OF THE WEEKEND INTO MONDAY. WILL TREND FORECAST IN THAT DIRECTION. AND WITH SLOWER PROGRESSION...EXPECT WARM TEMPERATURES TO CONTINUE INTO SATURDAY BEFORE A BIT OF COOLING IS REALIZED SUNDAY AND MORE DRAMATIC COOLING MONDAY. LOOK FOR HIGHS NEAR 90 AGAIN FRIDAY AND SATURDAY...80S SUNDAY...AND PROBABLY 70S ON MONDAY. && .AVIATION...(18Z TAFS FOR KOFK...KLNK AND KOMA.) ISSUED AT 1234 PM CDT MON AUG 31 2015 VFR CONDITIONS HAVE RETURNED...AFTER A FOGGY MORNING START. MAY SEE A FEW HOURS OF WIND GUSTS AROUND 20KT AT KOFK...BUT OTHERWISE...VFR CONDITIONS WITH SOUTH WINDS OF 10-12KT ARE EXPECTED THROUGH TODAY. LATE TONIGHT/CLOSE TO DAYBREAK...MAY SEE A RETURN OF MVFR VIS AT KOMA/KLNK FOR A FEW HOURS...WITH LINGERING LOW- LEVEL MOISTURE AND LIGHTER OVERNIGHT WINDS...AND FELT CONFIDENT ENOUGH TO ADD A GROUP FOR THOSE VIS CONDITIONS. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ SHORT TERM...DERGAN LONG TERM...DERGAN AVIATION...MAYES

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