Area Forecast Discussion
Issued by NWS Wilmington, OH

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830 FXUS61 KILN 060756 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 356 AM EDT FRI MAY 6 2016 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A CLOSED UPPER LOW HAS BEEN IN THE VICINITY FOR THE PAST FEW DAYS...BUT ITS INFLUENCE OVER THE OHIO VALLEY IS BEGINNING TO WANE. THE CIRCULATION ASSOCIATED WITH THE LOW IS OBVIOUS ON WATER VAPOR SATELLITE IMAGERY...MOVING ONLY VERY SLOWLY NNE OVER THE MID-ATLANTIC REGION. THOUGH THE LOW WILL NOT BE MOVING MUCH FURTHER AWAY FROM THE ILN FORECAST AREA TODAY...500MB HEIGHTS ARE EXPECTED TO RISE SLIGHTLY...AND SKIES (ESPECIALLY IN THE WESTERN HALF OF THE CWA) SHOULD REMAIN MORE CLEAR THAN CLOUDY. WITH 925MB/850MB TEMPS EXPECTED TO RISE SEVERAL DEGREES CELSIUS BY AFTERNOON...TEMPERATURES AT THE SURFACE SHOULD BE ABLE TO GET CLOSE TO NORMAL (WITH FORECAST HIGHS IN THE UPPER 60S). MODELS ARE INDICATING THAT A WEAK SURFACE TROUGH MOVING SOUTHWARD THROUGH WEST VIRGINIA (AND ATTACHED TO THE LOW PRESSURE FURTHER EAST) COULD ALLOW FOR THE DEVELOPMENT OF A FEW SHOWERS. ALL INDICATIONS ARE THAT THIS WILL REMAIN EAST OF THE ILN FORECAST AREA...THOUGH AN INCREASE IN CLOUDS DURING THE AFTERNOON HAS BEEN INDICATED...MAINLY EAST OF US-23.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
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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.
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&& .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
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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.
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&& .AVIATION /07Z FRIDAY THROUGH TUESDAY/... SKIES HAVE BECOME VFR AS A RIDGE OF HIGH PRESSURE BEGINS TO BUILD IN TO THE OH VLY FROM THE NW. EXPECT VFR CONDITIONS TO CONTINUE THROUGH THE TAF PERIOD FOR ALL SITES WHILE RIDGE MOVES ACROSS REGION. WITH LIGHT WINDS... IF ENOUGH CLEARING OCCURS... THERE MAY BE SOME PATCHY BR AT KLUK THROUGH 14Z TODAY. CLOUD COVER WILL BE ON A DECREASING TREND THROUGH MOST OF THE TAF PERIOD. EXPECT THAT ERN SITES OF KCMH/KLCK WILL HAVE TOUGHEST TIME SCATTERING OUT THROUGH 00Z SATURDAY DUE TO OCCLUDED LOW OVER MID ATLANTIC REGION CONTINUING TO PROVIDE SOME MIDLEVEL MOISTURE ACROSS ERN PORTIONS OF THE REGION. WINDS WILL GENERALLY BE NORTH/NORTHWESTERLY THROUGH 00Z SATURDAY FOR ALL SITES. EXPECT THAT WINDS OF AROUND 10 KTS AFTER 12Z TODAY WILL BEGIN TO DECREASE TOWARD 00Z AS PRESSURE GRADIENT RELAXES. EXPECT THAT LOW LEVEL MOISTURE WILL AGAIN BE ON THE INCREASE TOWARD 12Z SATURDAY ACROSS THE REGION AS A WARM FRONT MOVES THROUGH. OUTLOOK...MVFR CIGS AND VSBYS POSSIBLE SATURDAY INTO SATURDAY NIGHT...THEN AGAIN MONDAY THROUGH TUESDAY. THUNDERSTORMS ARE POSSIBLE SATURDAY AND AGAIN MONDAY AND TUESDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM...HATZOS LONG TERM...NOVAK AVIATION...KC

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