Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 020134 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 934 PM EDT WED APR 1 2015 .SYNOPSIS... HIGH PRESSURE AND DRY AIRMASS WILL MOVE OFF TO THE EAST TONIGHT. A FRONTAL ZONE WILL DEVELOP ON THURSDAY AND REMAIN IN THE AREA THROUGH FRIDAY. SEVERAL WAVES OF LOW PRESSURE TRAVELING ALONG THE FRONT WILL PROVIDE MULTIPLE ROUNDS OF RAINFALL. HIGH PRESSURE AND DRY AIR WILL MOVE BACK IN FOR SATURDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... HAVE BEEN TWEAKING VARIOUS PARTS OF THE FORECAST THIS EVENING. FOR THE REST OF TONIGHT...THIN CIRRUS WILL CONTINUE TO OVERSPREAD THE AREA AS SURFACE HIGH DRIFTS OFF THE ATLANTIC COAST. KILN VWP HAS ALREADY RESPONDED ABOVE THE DECOUPLED BOUNDARY LAYER SHOWING 30KTS JUST OFF THE DECK IN RETURN FLOW. AT THE SURFACE THOUGH WINDS WILL REMAIN LIGHT/SOUTHEAST THROUGH THE NIGHT AND SLOWLY VEER TO SOUTHERLY AND INCREASE. VERY DRY AIR AT THE SURFACE BEING HANDLED HORRIBLY BY ALL NWP /A TYPICAL APRIL PROBLEM/ AND THE NEW 02.00Z KILN SOUNDING SHOWS THAT DETERMINISTIC GUIDANCE IS WAY WAY OFF BELOW 850 MB IN TERMS OF MOISTURE. EVEN NASHVILLE/SPRINGFIELD ILL HAVE SIMILAR MODEL MOIST BIAS IN COMPARED TO REAL LIFE. THIS IS A VERY DRY AIRMASS OVER THE AREA SO HAVE DROPPED TEMPS A COUPLE OF DEGREES EVEN WITH WARM ADVECTION/INCREASING WINDS AS IT WILL TAKE A LONG TIME FOR BOUNDARY LAYER DWPTS TO COME UP. LATER IN THE NIGHT /AFTER 09Z/ THERE IS STRONG AGREEMENT THAT LOW LEVEL JET WILL INDUCE ACCAS AND MID CLOUD ABOVE THE VERY DRY BOUNDARY LAYER...AND LIFTING A PARCEL AT THE NOSE OF THE LOW LEVEL JET INDICATES THAT IF SATURATION CAN OCCUR...LAPSE RATES ARE STEEP AND INSTABILITY WILL LIKELY YIELD HIGH BASED/ELEVATED SHOWERS/STORMS MOVING QUICKLY FROM SW->NE ACROSS THE AREA EARLY THURS MORNING. ACTUALLY QUITE IMPRESSED WITH THE INSTBY - BUT HAVE RESERVATIONS ON THE LARGE QPF COVERAGE GIVEN MOISTURE ERRORS AS MENTIONED ABOVE. THINK THERE WILL BE ENOUGH ACCAS/ELEVATED INSTBY TO DRIVE SOME SHOWERS/STORMS QUICKLY THROUGH THE AREA SO INCREASED RAIN CHANCES IN THE MORNING FOR A QUICK HITTING/BUT LIGHT AMOUNT BAND OF THERMODYNAMICALLY DRIVEN ACTIVITY ROOTED WAY ABOVE THE BOUNDARY LAYER. MAY ACTUALLY BE QUITE A BIT OF RADAR ECHO BUT NOT MUCH MAKING IT TO THE GROUND VIA VERY DRY SUB-CLOUD LAYERS /VIRGA/ THURS MORNING. TWEAKED THURSDAYS HIGHS DOWN JUST A BIT WITH EVAPORATIVE COOLING OF SUBSTANTIAL DRY LAYER PERHAPS BEING A LITTLE SLOWER TO WARM WITH AMPLE CLOUD ON THURSDAY. HAVE ALSO TRIED TO INDICATE A LULL IN RAIN CHANCES BETWEEN MORNING ACTIVITY AND AFTN/EVENING FRONTAL ACTIVITY. REMAINDER OF THURSDAY DISCUSSION FOLLOWS BELOW. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... SLOW MOVING COLD FRONT TO APPROACH FROM THE WEST THURSDAY AND MOVE INTO OHIO THURSDAY NIGHT. NRN STREAM ENERGY TO PASS NORTH OF THE GREAT LAKES WITH SRN STREAM TROF HOLDING BACK OVER THE SRN PLAINS. THIS KEEPS ILN/S FA IN A MOIST SWRLY FLOW. 50-60 KT LOW LEVEL JET WITH ENHANCED LOW LEVEL CONVERGENCE DEVELOPING THURSDAY EVENING. FAVORABLE MOISTURE TRANSPORT FOR A PROLONGED PERIOD. PRECIPITABLE WATER VALUES INCREASE TO CLOSE TO AROUND 250 PERCENT OF NORMAL OR 2 TO 3 STD DEVIATIONS ABOVE NORMAL THURSDAY NIGHT. WILL CONTINUE LKLY POPS ACRS THE WEST THURSDAY AFTN AND CATEGORICAL THURSDAY NIGHT. MARGINAL INSTBY DEVELOPS THU AFTN/THU EVE. WITH THE FRONT STILL TO OUR WEST...STORMS WILL HAVE TO BE COLD POOL DRIVEN. EXPECT MARGINAL INSTBY WITH BOUNDARY LAYER CAPES LESS THAN 1000 J/KG. ALTHOUGH WIND FLOW WILL BE FAVORABLE THE INSTBY WILL BE LIMITING FACTOR AND EXPECT ONGOING STORMS TO WEAKEN AS THEY TRACK NE AWAY FROM MORE FAVORABLE INSTBY AXIS. WILL CONTINUE TO MENTION THIS MARGINAL POTENTIAL IN THE HWO PRODUCT. IN STRONG WAA PATTERN TEMPERATURES TO BE 20-25 DEGREES ABOVE NORMAL THURSDAY WITH HIGHS FROM THE UPPER 60S NORTHWEST TO THE LOWER/MID 70S SOUTHEAST. EMBEDDED MID LEVEL S/W IN THE SOUTHWESTERLY FLOW WILL INDUCE A SFC WAVE ON THE FRONTAL BOUNDARY. THIS WAVE TO RIPPLE NE THRU THE OHIO VALLEY LATE THURSDAY NIGHT/EARLY FRIDAY. THIS WAVE WILL PROVIDE AN ENHANCED CHANCE OF PCPN WITH FAVORABLE LOW LEVEL FORCING. LOWS THURSDAY NIGHT FROM THE UPPER 40S NORTHWEST TO THE UPPER 50S SOUTHEAST. WITH SFC WAVE/FRONT BISECTING THE AREA...THERE WILL BE A LARGE GRADIENT IN TEMPERATURES ON FRIDAY. FRIDAYS HIGHS ARE EXPECTED TO RANGE FROM THE MID 50S NW TO UPPER 60S SE. FLOWS MERGE WITH MEAN TROF OVER THE GREAT LAKES BY SAT MORNING. NUMERICAL MODEL SOLNS DIFFER SOME ON PLACEMENT BUT ALL HAVE A FINAL SFC WAVE PASSING THRU THE OHIO VALLEY FRIDAY NIGHT. DUE TO THE PROLONGED PERIOD OF PRECIPITATION AND THE MOIST ENVIRONMENT THE POTENTIAL FOR HEAVY RAIN WILL EXIST. NUMERICAL MODEL SOLNS SUGGEST 1 TO 3+ INCHES OF RAIN BUT DIFFER ON AMOUNTS AND PLACEMENT. AT THIS TIME WILL CONTINUE TO HIGHLIGHT HEAVY RAIN AND THE POTENTIAL FOR FLOODING IN THE HWO PRODUCT. IN CAA ON BACKSIDE OF DEPARTING LOW PRESSURE TEMPERATURES DROP TO LOWS FROM NEAR 30 NW TO THE UPPER 30S SE BY SATURDAY MORNING. A BRIEF PERIOD OF SNOW IS POSSIBLE PRIOR TO ENDING LATE FRIDAY NIGHT BUT DEEP MOISTURE AND BEST LIFT EXITS QUICKLY SO DO NOT EXPECT SIGNIFICANT SNOW. AT THIS TIME ONLY HAVE ONE TO TWO TENTHS IN THE N-NE. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... PRECIPITATION WILL BE EXITING THE EASTERN CWA EARLY SATURDAY MORNING AS SURFACE HIGH PRESSURE AND MUCH DRIER AIR BUILDS IN FROM THE WEST. DESPITE MOSTLY SUNNY SKIES...A BROAD UPPER TROUGH AND 850 TEMPS AROUND MINUS 5 C WILL MAKE FOR A CHILLY DAY WITH HIGHS RANGING FROM THE MID 40S NORTH TO LOWER 50S SOUTH. LOWS SATURDAY NIGHT WILL AGAIN DROP INTO THE 30S ACROSS THE AREA...BEFORE WAA KICKS IN ON SUNDAY ALLOWING TEMPS TO RETURN BACK TO NEAR NORMAL. A FRONTAL BOUNDARY STALLED NORTH OF OHIO WILL KEEP CHANCES FOR SHOWERS NORTH OF THE CWA ON SUNDAY. CLOUD COVER WILL CONSEQUENTLY BE MORE PREVALENT ACROSS THE NORTHERN HALF OF THE CWA. DETERMINISTIC MODELS AND ENSEMBLE GUIDANCE THEN DIVERGE SIGNIFICANTLY FOR THE REMAINDER OF THE EXTENDED PERIOD. GENERALLY USED AN EQUAL BLEND OF WPC GUIDANCE...GFS AND ECMWF FOR MONDAY THROUGH WEDNESDAY. GFS IS QUICKER THAN ECMWF TO BRING THE NEXT SYSTEM INTO THE GREAT LAKES REGION LATE MONDAY INTO TUESDAY. THE ILN CWA WILL BE IN THE WARM SECTOR BOTH DAYS WITH PERSISTENT WAA ALLOWING TEMPS TO WARM INTO THE UPPER 50S TO MID 60S ON MONDAY AND INTO THE MID 60S TO NEAR 70 ON TUESDAY. ISENTROPIC LIFT WILL PROVIDE A CHANCE OF SHOWERS DURING THE DAY ON MONDAY. A DEVELOPING LLJ MONDAY NIGHT WILL THEN TRANSPORT AMPLE GULF MOISTURE INTO THE OHIO VALLEY WITH PWATS AROUND 1 TO 1.5 INCHES (OVER 200 PERCENT OF NORMAL) ON TUESDAY. PRECIP CHANCES WILL BE HIGHEST MONDAY NIGHT INTO TUESDAY AND HAVE INCLUDED THUNDER IN THE GRIDS ON TUESDAY AS FAVORABLE INSTABILITY DEVELOPS THANKS TO THE INCREASING WARMTH AND LOW LEVEL MOISTURE. CHANCES FOR SHOWERS AND ISOLATED THUNDER WILL CONTINUE INTO WEDNESDAY AS A COLD FRONT DROPS SOUTHEAST ACROSS THE AREA. LOW CONFIDENCE IN TIMING OF FROPA HOWEVER AS GFS IS QUICK TO PUSH IT THROUGH TUESDAY NIGHT AND ECMWF DOES NOT PUSH IT THROUGH UNTIL LATER WEDNESDAY. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... CHANGING WEATHER ACROSS THE TERMINALS IN THIS CYCLE AS HIGH PRESSURE OVER THE AREA THIS EVENING QUICKLY DEPARTS. FIRST 12 HOURS OF THE TAFS ARE QUIET WITH VFR CONDITIONS AND WEAK SOUTHEASTERLY FLOW ON THE BACKSIDE OF THE HIGH. TOWARD 12Z...STRONG LOW LEVEL JET AND WARM ADVECTION WILL DRIVE ELEVATED SHOWERS AND PROBABLY A FEW THUNDERSTORMS ACROSS THE TERMINALS IN SCATTERED FASHION. THINK ALL AIRPORTS WILL RECEIVE AT LEAST A LITTLE RAIN...DESPITE AN /INITIALLY/ VERY DRY SUB-CLOUD LAYER. INSTABILITY ABOVE THE CLOUD BASE WILL BE APPRECIABLE...AND WHILE TAFS DO NOT MENTION THUNDER RIGHT NOW IN THE 12Z-16Z TIME PERIOD...IT MAY NEED TO BE ADDED LATER THIS EVENING OR OVERNIGHT. THINK ANY AVIATION IMPACTS WITH THESE SHRA/ISOLD STORMS WOULD BE MVFR CIGS/VSBY. STRONG SSWLY WINDS WILL PICK UP LATER THURS MORNING AND INCREASE THROUGH THE AFTERNOON. HAVE PRETTY MUCH 20G30KT WINDS AT ALL AIRPORTS DURING PEAK MIXING OF LATE MORNING/AFTERNOON...WOULD NOT BE SURPRISED TO SEE A FEW GUSTS TOWARD 37 OR 38 KTS IF SUNSHINE/MIXING BECOMES MORE THAN FORECAST. WILL KEEP VFR CIGS ACROSS THE TAF SITES THROUGH AFTN AND INCREASE COVERAGE/IMPACT OF SHRA/TSRA ON THURS AFTN INTO EVENING. AM SURE VSBY/CIGS WILL NEED TO BE LOWERED ONCE STORMS PRESENT ON RADAR BUT RIGHT NOW JUST PROVIDING A BROAD WINDOW OF HIGHER COVERAGE /MVFR/ SHOWERS AND STORMS LATER THURS AFTN/EVE. AS RAIN CONTINUES INTO THURS NIGHT EXPECT CIGS TO DROP WELL INTO MVFR CATEGORIES...AND MAY APPROACH IFR DURING THE NIGHT. OUTLOOK...MVFR AND POSSIBLY IFR CEILINGS AND VISIBILITIES ARE POSSIBLE THURSDAY NIGHT INTO FRIDAY NIGHT...ESPECIALLY IN PERIODS OF HIGHER INTENSITY SHOWERS/STORMS. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...AR NEAR TERM...BINAU SHORT TERM...BINAU/AR LONG TERM...KURZ AVIATION...BINAU

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