Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 302333 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 733 PM EDT THU APR 30 2015 .SYNOPSIS... A COMPACT AND POTENT WEATHER SYSTEM WILL SHIFT FROM INDIANA THROUGH OHIO AND OFF THE EAST COAST OVER THE NEXT 36 HOURS. SHOWERS AND A FEW THUNDERSTORMS THIS AFTERNOON ATTENDANT TO THIS SYSTEM WILL DIMINISH MARKEDLY AFTER SUNSET THIS EVENING...AND THEN FOCUS EAST OF THE OHIO VALLEY ON FRIDAY. A DRY AND MILD WEEKEND IS IN STORE FOR THE OHIO VALLEY WITH HIGHS IN THE 70S. EARLY NEXT WEEK...A FRONTAL SYSTEM WILL STALL ACROSS THE LOWER GREAT LAKES...MEANING CONTINUED WARMTH SOUTH OF THIS FRONT FOR MUCH OF THE OHIO VALLEY...BUT WITH THAT WILL COME AN INCREASING THREAT FOR SHOWERS AND THUNDERSTORMS AS THE WEEK WEARS ON. && .NEAR TERM /THROUGH FRIDAY/... GOES WATER VAPOR LOOPS AND OBJECTIVE 18Z ANALYSIS INDICATES DEEP/CLOSED UPPER LOW OVER OHIO/INDIANA...WITH THE 250MB CLOSED CYCLONE OVER CENTRAL OHIO AND THE 700/500MB SYSTEMS DISPLACED WEST OVER CENTRAL INDIANA HEADING TOWARD CINCINNATI. MUCH OF THE SURFACE RESPONSE/REFLECTION TO THESE MID/UPPER LEVEL SYSTEMS WAS MUTED AND OFF TO THE SOUTHEAST OF THE AREA OVER THE CAROLINAS. THE 30.12Z KILN SOUNDING SAMPLED A VERY COLD TROPOSPHERE ALOFT WITH -26C AT 500MB AND A STEEP LAPSE RATE. OBJECTIVE ANALYSIS INDICATES THE MID-LEVEL POOL IS MAXIMIZING NOW THROUGH ABOUT 00Z AS THE CORE OF THE 700-500MB TROUGH PIVOTS ACROSS SW OHIO/SERN INDIANA AND ACROSS NRN KY. AS TYPICAL IN THIS MAINLY INSTABILITY-DRIVEN EVENTS...CUMULUS/SHRA ERUPTED QUICKLY WITH DIABATIC WARMING EARLY THIS AFTN AND NOW MUCH OF THE BOUNDARY LAYER INSTBY HAS TURNED OVER/BEEN USED. THUS...UPDRAFTS OVER THE LAST 60 MIN HAVE BEEN WEAK AND REPORTS OF THUNDER/PEA HAIL WHICH WERE COMMON BETWEEN 1230 PM AND 230 PM HAVE WANED CONSIDERABLY. THIS ACTIVITY HAS FOCUSED ON THE CYCLONIC SHEAR SIDE OF THE MID/UPPER LEVEL JETS NEAR THE EXIT REGION OF THE UPPER LEVEL JET /90-100KTS/ DIGGING DOWN THROUGH WRN IND/ERN ILL. STILL A FEW STRONGER UPDRAFTS THAT COULD LEAD TO SOME 0.50" SIZE HAIL WHERE INSTBY HAS BEEN UNDISTURBED IN NRN KY/SCNTL OH THOUGH THROUGH PEAK HEATING. HAVE CARRIED LIKELY RAIN CHANCES THROUGH THE SWRN/SRN CWA THROUGH LAT AFTN AND THEN SLOWLY BACKING DOWN AS SUNSET APPROACHES. THERE ARE HINTS IN THE DATA THAT LATER ON THIS EVENING SOME DYING ACTIVITY FROM PA/WV MAY TRY TO WRAP WEST/SOUTHWEST AROUND THE NRN PERIPHERY OF THE TRANSIENT CLOSED LOW BACK INTO CNTL OH SO HAVE HELD ONTO RAIN CHANCES IN THIS AREA TIL ABOUT 4 AM. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... INFLUENCE OF COLD POOL RELAXES AS CORE OF MID/UPPER LEVEL TROUGH SHIFTS RAPIDLY OUT TO SEA. DESPITE THIS...TROPOSPHERIC LAPSE RATE REMAINS STEEP ON FRIDAY AFTERNOON SO CUMULUS SHOULD DEVELOP AGAIN BY LATE MORNING. FORECAST SOUNDINGS VIA 30.12Z NAM/GFS SHOW A STEEP LOW LEVEL LAPSE RATE BUT A WEAK SUBSIDENCE INVERSION ABOUT 8-10KFT AGL WHICH WEAKENS THE LAPSE RATE ABOVE THE BOUNDARY LAYER - THIS SHOULD ACT TO LIMIT VERTICAL GROWTH OF CUMULUS AND THUS AM RUNNING A DRY FORECAST. CAN/T RULE OUT A ROGUE SHOWER ESPECIALLY OUR FAR SOUTH/EAST CLOSEST TO THE REMNANT COLD POOL - BUT BETTING AGAINST IT. OTHERWISE...MIX OF CLOUDS AND SUN ON FRIDAY AND MIXING 925MB TEMPS TO SFC AND STATISTICAL MOS YIELDS A GOOD AGREEMENT ON HIGHS IN THE UPPER 60S. TRADITIONAL WARM SPOTS MAY PUSH 70 BUT THIS WILL BE MORE LIMITED. ON SATURDAY...THERE/S A LITTLE DISAGREEMENT ON INTENSITY OF A SHORTWAVE TROUGH ON SATURDAY CROSSING THE AREA. THE 30.12Z NAM WAS MUCH STRONGER WITH A BETTER VERTICAL MOTION COMPONENT DURING THE AFTERNOON...GFS MUCH WEAKER. EVEN A NAM PERSPECTIVE YIELDS MOSTLY MID-LEVEL MOISTURE ATOP WHAT IS STILL A RATHER STEEP LAPSE RATE /MARGINAL INSTBY/. RIGHT NOW EVEN A WORSE CASE SCENARIO LOOKS LIKE SCT SPRINKLES OR A VERY LIGHT SHOWER...BUT FOR RIGHT NOW WILL KEEP A 40-60% CLOUD COVER THROUGH SAT AFTERNOON AND GO DRY GIVEN GFS SOUNDINGS MUCH DRIER AND WEAKER /LITTLE/ VERTICAL MOTION AS THIS WAVE PASSES. A FEW DEGREES WARMER SO EXPECTING WIDESPREAD LOWER 70S MOST AREAS. && .LONG TERM /SUNDAY THROUGH THURSDAY/... TROUGHING WILL BE MOVING OFF THE EAST COAST ON SUNDAY MORNING...WITH HEIGHTS RISING STEADILY OVER THE OHIO VALLEY THROUGH THE NEXT TWO DAYS. AS THIS OCCURS...SURFACE HIGH PRESSURE OVER THE SOUTHEASTERN STATE WILL STRENGTHEN...LEADING TO SOUTHERLY (AND EVENTUALLY SOUTHWESTERLY) FLOW OVER THE OHIO VALLEY. A SURFACE BOUNDARY IS FORECAST TO SET UP WEST-TO-EAST ACROSS THE GREAT LAKES...LEAVING THE VAST MAJORITY OF THE ILN FORECAST AREA WITH INCREASINGLY WARM AND GENERALLY DRY CONDITIONS. WITH WARM ADVECTION CONTINUING FOR SEVERAL DAYS...TEMPERATURES WILL EASILY RISE ABOVE NORMALS...PEAKING OUT IN THE UPPER 70S IN THE SOUTHERN HALF OF THE FORECAST AREA (AND THE FIRST 80-DEGREE TEMPERATURE AT CVG WILL CERTAINLY BE POSSIBLE). MIN TEMPS WILL RESPOND SIMILARLY...INCREASING SLIGHTLY EACH DAY AND EVENTUALLY ENDING UP IN THE UPPER 50S TO NEAR 60 BY TUESDAY MORNING. THE AFOREMENTIONED GREAT LAKES FRONT WILL MOVE VERY LITTLE IN A LATITUDINAL SENSE...WITH FLOW ON TUESDAY AND WEDNESDAY REMAINING CLOSE TO ZONAL ACROSS THE NORTHEASTERN QUADRANT OF THE CONUS. A CONSENSUS OF THE 12Z GFS/CMC/ECMWF MODEL RUNS DOES ALLOW FOR THIS CONVERGENT ZONE TO MOVE A LITTLE FURTHER SOUTH DURING THE FIRST HALF OF THE WEEK (COMPARED TO THE MODEL RUNS YESTERDAY)...SO POPS WERE INCREASED SLIGHTLY. ALTHOUGH THERE ARE NO OTHER SIGNIFICANT SIGNS OF FORCING OVER THE ILN CWA...THE INCREASING HEAT AND MOISTURE WILL MEAN THAT A COMPLETELY DRY FORECAST MAY NOT END UP AS THE BEST OPTION ANYWAY...ESPECIALLY CLOSER TO THE BOUNDARY IN THE NORTHERN PORTIONS OF THE FORECAST AREA. BY THE SECOND HALF OF THE WEEK...UPPER-LEVEL FLOW WILL BECOME MORE AMPLIFIED...WITH TROUGHING IN THE WESTERN CONUS AND A BUILDING RIDGE IN THE TENNESSEE/OHIO VALLEY REGIONS (EXTENDING NORTH INTO THE WESTERN GREAT LAKES). TO NO SURPRISE...THIS PATTERN WILL SUPPORT CONTINUED WARMTH THROUGH THE OHIO VALLEY...WITH STABILITY IN THE RIDGING SOLUTION SHOWN IN GFSE SPREADS AND TEMPERATURE ANOMALY PROJECTIONS. PRECIPITATION CHANCES MAY BEGIN TO INCREASE BY THE END OF THE WEEK...BUT WEST-TO-EAST PROGRESSION OF ANY SIGNIFICANT FORCING APPEARS VERY SLOW. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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CLOSE PROXIMITY OF THE UPPER LOW DOES NOT ALLOW ME TO REMOVE SHOWERS FROM CVG/LUK IN THE NEXT FEW HOURS BUT THIS WILL BE THE PROGRESSION OF THE OVERNIGHT. CENTER OF THE LOW IS EXITING THE AREA WHICH MEANS H8 WAA AND A GENERAL LESSENING OF THE CLOUD COVER. CURRENT SHOWERS WILL NOT BE ABLE TO MAINTAIN THEMSELVES IN A WARMING ENVIRONMENT. WANING CLOUD COVER WILL OCCUR OVERNIGHT AS WELL AND NORTH WINDS WILL GENERALLY BE 10-12KT THROUGH THE OVERNIGHT AND INTO TOMORROW. A FEW HIGHER GUSTS TO 18KT OR SO MAY OCCUR WHERE FULL SUN PEEKS THROUGH DURING THE DAY. FAIR WX CU WILL SOMETIMES CONSTITUTE A BKN DECK LATER IN THE DAY BUT THIS WILL BE ABOVE THE MVFR THRESHOLD OF 3KFT. SURFACE HIGH BUILDS WEST OF THE AREA OVERNIGHT AND WINDS GO LIGHT AND VARIABLE AT THE TAIL END OF THE FORECAST. OUTLOOK...NO SIGNIFICANT WEATHER EXPECTED.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...BINAU NEAR TERM...BINAU SHORT TERM...BINAU LONG TERM...HATZOS AVIATION...FRANKS

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