Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 061311 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 911 AM EDT FRI MAY 6 2016 .SYNOPSIS... DRIER CONDITIONS ARE EXPECTED TODAY...WITH TEMPERATURES RISING TO VALUES NEAR NORMAL. SHOWERS AND THUNDERSTORMS ARE EXPECTED ON SATURDAY...AS A COLD FRONT MOVES INTO THE AREA FROM THE NORTH. THIS FRONT WILL REMAIN IN PLACE ACROSS THE OHIO VALLEY THROUGH THE FOLLOWING SEVERAL DAYS...WITH CONTINUED CHANCES FOR OCCASIONAL RAIN THROUGH AT LEAST THE MIDDLE OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A WEAK AXIS OF SURFACE HIGH PRESSURE WILL SAG SLOWLY SOUTHEAST INTO THE AREA THROUGH THIS AFTERNOON. AHEAD OF THIS...WEAK NORTHERLY LOW LEVEL FLOW MAY ALLOW FOR SOME CU DEVELOPMENT...ESPECIALLY ACROSS EASTERN PORTIONS OF THE AREA. WITH A FAIR AMOUNT OF SUNSHINE THOUGH...EXPECT TEMPERATURES TO PUSH INTO THE MID TO UPPER 60S THIS AFTERNOON.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... A NARROW 500MB RIDGE...WITH ITS AXIS ORIENTED IN A SOUTHWEST-TO-NORTHEAST DIRECTION...WILL BRIEFLY MOVE INTO THE MIDDLE OHIO VALLEY TONIGHT. A DEEP TROUGH MOVING SOUTH FROM NORTHERN ONTARIO WILL THEN MOVE CLOSER TO THE OHIO VALLEY...HELPING TO KICK THE CLOSED UPPER LOW OUT OF THE COASTAL STATES...AND ALSO HELPING TO DRIVE A COLD FRONT THROUGH THE UPPER MIDWEST AND INTO THE GREAT LAKES / OHIO VALLEY REGION. AN INTERESTING NOTE REGARDING THE WEATHER SYSTEM FORECAST TO AFFECT THE REGION THROUGH THE WEEKEND IS THE SOMEWHAT UNUSUAL ORIENTATION OF THE KEY FEATURES...THANKS TO THE OVERALL NORTHWEST FLOW PATTERN THAT THE SYSTEM EXISTS WITHIN. THE WARM FRONT THAT WILL MOVE THROUGH THE REGION EARLY SATURDAY WILL DO SO BY MOVING EASTWARD...WITH THE FRONT ALONG A NEARLY DUE NORTH-TO-SOUTH AXIS. THE COLD FRONT...COMING IN LATER IN THE DAY ON SATURDAY...IS FORECAST TO BE MOVING NEARLY DUE SOUTH. IN TERMS OF TEMPERATURES...THIS SHOULD ALLOW A PERIOD OF RELATIVELY STRONG WARMING IN THE WARM SECTOR FOR THE SOUTHERN HALF OF THE FORECAST AREA ON SATURDAY. TEMPERATURES NEAR 80 ARE NOW IN THE FORECAST...WITH MID TO UPPER 70S FURTHER NORTH. AS WARM FRONTAL PROCESSES BEGIN EARLY SATURDAY MORNING...MID- LEVEL CLOUDS WILL BEGIN TO INCREASE...AND SOME VERY LIGHT PRECIPITATION WILL BE POSSIBLE. THOUGH MORE LIKELY TO BE VIRGA...SOME SPRINKLES MAY REACH THE GROUND...AND THIS HAS BEEN ADDED TO THE FORECAST (MAINLY FROM 09Z TO 15Z). WITH THE TRIPLE POINT WELL NORTH OF THE ILN FORECAST AREA...THERE SHOULD BE A SHORT BREAK BETWEEN THE PRIMARY FORCING MECHANISMS...BEFORE A MORE ACTIVE PERIOD BEGINS ON SATURDAY AFTERNOON ALONG AND AHEAD OF THE COLD FRONT. BASED ON FAIRLY STRONG MODEL TIMING AGREEMENT...LIKELY POPS HAVE BEEN USED...PASSING SOUTHWARD ACROSS THE CWA FROM 20Z- 02Z. THE AFOREMENTIONED NORTHWESTERLY FLOW PATTERN IS ONE THAT WILL PROVIDE A FAIR AMOUNT OF WIND SHEAR FOR THE COLD FRONT TO INTERACT WITH. IT IS INTERESTING TO NOTE THAT SREF WIND SHEAR PROBABILITIES ACTUALLY INDICATE A LOCAL MINIMUM OF DEEP-LAYER SHEAR OVER THE ILN FORECAST AREA ON SATURDAY AFTERNOON...PERHAPS SUGGESTING THAT THE STRONGER SHEAR WILL BE SLIGHTLY OUT OF PHASE WITH THE EXPECTED DIURNAL HEATING AND EVENTUAL COLD FRONTAL TIMING. NONETHELESS...COMBINED WITH THE STRONG FRONTAL FORCING...THERE SHOULD BE ENOUGH SHEAR TO SUPPORT A DEGREE OF THUNDERSTORM ORGANIZATION. THE DIRECTIONAL SHEAR IS NOT OVERLY STRONG EITHER...BUT THROUGH THE 0-3KM LAYER...WINDS SHOULD SHIFT FROM ABOUT 260 DEGREES AT THE SURFACE TO AROUND 300 DEGREES AT 3KM. INSTABILITY IS ANOTHER FACTOR THAT APPEARS SUFFICIENT THOUGH NOT OVERLY IMPRESSIVE...WITH MLCAPE VALUES OF AROUND 1000-1200 J/KG AS A FAIR MODEL CONSENSUS. THE WARM ADVECTION PATTERN THROUGH THE BOUNDARY LAYER IS ESSENTIALLY DUE WESTERLY...NOT A FAVORABLE PATTERN AT ALL FOR SIGNIFICANT MOISTURE FLOW INTO THE OHIO VALLEY. THIS WILL LIMIT INSTABILITY FROM BECOMING STRONGER...AND WILL ALSO KEEP CLOUD BASES AT AROUND 4000-5000 FEET. THE END RESULT IS THAT THE CHANCE OF SEVERE WEATHER CERTAINLY EXISTS...WITH THE POTENTIAL FOR SOME ORGANIZED SEGMENTS AND POSSIBLY SUPERCELLS...WITH A CHANCE OF PRODUCING LARGE HAIL AND DAMAGING WINDS. HOWEVER...CONFIDENCE IN A MORE SIGNIFICANT SEVERE EVENT IS LIMITED BY THE QUESTIONS ABOUT THE SHEAR TIMING AND QUALITY (WIDENESS) OF THE INSTABILITY PROFILE. FURTHERMORE...THE TORNADO THREAT APPEARS VERY LOW...WITH UNFAVORABLE NEAR-SURFACE THERMODYNAMICS AND MARGINAL 0-1KM SHEAR. THE COLD FRONT IS NOT EXPECTED TO GET TOO FAR BEYOND THE SOUTHERN ILN FORECAST AREA ON SATURDAY NIGHT...STALLING OUT SOMEWHERE IN THE VICINITY...AND POSSIBLY CONTINUING TO ACT AS A FOCUS FOR SOME SHOWERS GOING INTO SUNDAY. THOUGH THERE APPEARS TO BE A BREAK IN THE FORCING ON SUNDAY AFTERNOON...WHEN THE FRONT STARTS A NORTHWARD MOTION AS A WARM FRONT AGAIN SUNDAY NIGHT...PRECIPITATION CHANCES WILL INCREASE FROM THE SOUTH AND WEST. THOUGH BOUNDARY LAYER CONDITIONS WILL BE SOMEWHAT STABLE...SOME ELEVATED CONVECTION COULD OCCUR GOING INTO MONDAY MORNING. AGAIN IN THE WARM SECTOR (AND WITH A BRIEF PERIOD OF MID-LEVEL RIDGING MOVING IN)...CHANCES FOR PRECIPITATION WILL BE MARGINAL FOR MONDAY AFTERNOON...BUT APPEAR LIKELY TO INCREASE SIGNIFICANTLY GOING INTO MONDAY NIGHT AND TUESDAY. TEMPERATURES ON SUNDAY ARE EXPECTED TO BE COOL...WITH THE ILN CWA FIRMLY ON THE NORTHERN SIDE OF THE FRONTAL BOUNDARY. THIS WILL CHANGE WITH THE FRONT MOVING NORTH ON MONDAY...ALLOWING FOR ANOTHER WARMING TREND TO BEGIN. IN EITHER CASE...THE SWING SHOULD REMAIN GENERALLY WITHIN AROUND 5 DEGREES OF CLIMATOLOGICAL NORMS. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... SEVERAL DISTURBANCES WILL WORK THROUGH THE REGION FROM MONDAY THROUGH THURSDAY KEEPING PRECIPITATION CHANCES IN THE FORECAST FOR MOST OF THIS TIME. WENT WITH A MODEL BLEND DURING THIS TIME. MODELS ARE IN GENERAL AGREEMENT ON THE MAIN FEATURES THROUGH WEDNESDAY ALTHOUGH THERE ARE SOME DIFFERENCES IN TIMING AND STRENGTH OF EACH SYSTEM. MODELS START TO DIVERGE FOR THURSDAY WITH THE ECMWF KEEPING PRECIPITATION ACROSS THE REGION WHILE THE GFS IS DRIER. AT THIS POINT TRENDED TOWARDS THE ECMWF WITH A CHANCE OF PRECIPITATION FOR THURSDAY. HIGH TEMPERATURES THROUGH THE LONG TERM WILL GENERALLY BE IN THE 60S AND 70S WITH LOWS IN THE 40S AND 50S. WENT CLOSE TO THE MODEL BLEND FOR TEMPERATURES DURING THIS TIME. && .AVIATION /13Z FRIDAY THROUGH TUESDAY/... SKIES HAVE BECOME MOSTLY CLEAR THIS MORNING...AND VFR CONDITIONS ARE EXPECTED THROUGH THE REST OF THE FORECAST PERIOD. THE ONLY EXCEPTION WILL BE DURING THE NEXT HOUR OR TWO AT KLUK...WHERE SOME FOG HAS FINALLY DEVELOPED EARLY THIS MORNING. SOME VFR CUMULUS MAY DEVELOP TODAY...WITH NORTHWESTERLY WINDS OF AROUND 10 KNOTS. GOING INTO TONIGHT...WINDS WILL SHIFT TO THE SOUTHWEST...AND MAY BECOME LIGHT AND VARIABLE FOR A FEW HOURS IN THE EVENING AND EARLY OVERNIGHT HOURS. WINDS WILL BEGIN TO INCREASE AGAIN BEFORE SUNRISE...WHICH SHOULD LIMIT THE THREAT OF FOG. WITH INCREASING MID AND HIGH CLOUDS TOMORROW MORNING...THERE IS A SLIGHT CHANCE OF A SPRINKLE AT THE AIRPORTS...BUT NOTHING WORTH MENTIONING IN THE TAFS. OUTLOOK...THUNDERSTORMS ARE POSSIBLE ON SATURDAY AFTERNOON AND EVENING...WITH A CHANCE OF MVFR/IFR CONDITIONS. THUNDERSTORMS ARE AGAIN POSSIBLE ON MONDAY AND TUESDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...JGL SHORT TERM...HATZOS LONG TERM...NOVAK AVIATION...HATZOS

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