Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 010015 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 715 PM EST SAT FEB 28 2015 .SYNOPSIS... A WARM FRONT WILL MOVE THROUGH THE OHIO VALLEY ON SUNDAY...WITH SNOW AND RAIN EXPECTED ACROSS THE REGION. A STRONGER WEATHER SYSTEM WILL MOVE THROUGH THE AREA ON TUESDAY AND WEDNESDAY...BRINGING A SIGNIFICANT AMOUNT OF RAINFALL. HIGH PRESSURE WILL BRING DRY CONDITIONS FOR THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... A SIGNIFICANT AMOUNT OF WARM ADVECTION ALOFT IS ALREADY ONGOING OVER THE OHIO VALLEY...ESPECIALLY AT 850MB AND ABOVE. HIGH AND MID LEVEL CLOUDS ARE ALSO STREAMING INTO THE REGION. OVERALL...THE SURFACE PRESSURE PATTERN IS QUITE WEAK...AND THIS WILL REMAIN THE CASE THROUGHOUT THE NEXT COUPLE DAYS OF THE FORECAST. LATER THIS EVENING...A LOW-LEVEL JET IN THE 925MB-850MB WILL INCREASE IN INTENSITY...BEGINNING A MORE SIGNIFICANT TRANSPORT OF MOISTURE INTO THE REGION. IN AN AREA OF WEAK CONVERGENCE ALONG AND NORTH OF A SURFACE WARM FRONT...PRECIPITATION WILL OVERSPREAD THE REGION DURING THE OVERNIGHT HOURS...BECOMING WIDESPREAD ACROSS THE ILN FORECAST AREA BY SUNDAY MORNING. THE IMPACTS FROM THIS PRECIPITATION WILL BE DISCUSSED IN THE SHORT TERM FORECAST DISCUSSION. ALTHOUGH TEMPERATURES MAY FALL AFTER SUNRISE TONIGHT...THE INCREASING WARM ADVECTION IN THE LOW LEVELS WILL LEAD TO A REBOUND AFTER 06Z. THUS...MIN TEMPS SHOULD OCCUR NEAR OR JUST AFTER MIDNIGHT...AND MAY NOT BE MUCH LOWER THAN TEMPS CURRENTLY OBSERVED THIS AFTERNOON. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/... A WARM FRONT IS EXPECTED TO MOVE NORTH THROUGH THE ILN FORECAST AREA ON SUNDAY MORNING. AS THIS OCCURS...THETA-E ADVECTION WILL BE STEADY ACROSS THE AREA...WITH THE ENVIRONMENT BECOMING FAIRLY MOIST. ON SUNDAY MORNING AND EARLY AFTERNOON...MODEL SOUNDINGS INDICATE SATURATION OR NEAR-SATURATION FROM THE SURFACE ALL THE WAY THROUGH 10KFT. PRECIPITABLE WATER VALUES WILL RANGE FROM 0.5 TO 0.8 INCHES ACROSS THE FORECAST AREA...AND YET IT IS SNOW THAT REMAINS THE BIGGEST CONCERN FOR THE SHORT TERM OF THE FORECAST. THOUGH THE MOISTURE CONTENT WILL BE HIGH...OVERALL THE FORCING INVOLVED WITH THIS WEATHER SYSTEM WILL BE FAIRLY WEAK AND UNFOCUSED. IT IS CLEAR THAT THE GREATEST PRECIPITATION AMOUNTS WILL SET UP THROUGH (OR JUST NORTH OF) THE MIDDLE OF THE ILN FORECAST AREA...AND THAT THE EVENTUAL NORTHERNMOST EXTENT OF THE RAIN-TO-SNOW TRANSITION WILL ALSO EXIST SOMEWHERE IN THIS VICINITY. THE MODEL SPREAD IN THIS AREA OF TEMPERATURE TRANSITION IS ACTUALLY NOT ALL THAT LARGE...AND THE NORTHERNMOST EXTREMES AMONG THE SOLUTIONS ARE NOT AS FAR NORTH AS MIGHT BE EXPECTED WHEN CONSIDERING OTHER WEATHER EVENTS OF THIS NATURE. THUS...THERE IS CONFIDENCE THAT MIXED RAIN AND SNOW WILL BE ABLE TO MAKE IT NO FURTHER NORTH THAN A LINE FROM ABOUT FRANKLIN COUNTY IN TO LICKING COUNTY OH...AND THAT ANYWHERE NEAR THAT LINE WILL EXPERIENCE MAINLY SNOW. THUS...THE HIGHEST SNOWFALL ACCUMULATIONS ARE FORECAST JUST NORTH OF THAT LINE...ROUGHLY FROM RICHMOND IN TO DELAWARE OH...WITH A SOLID SWATH OF 5 INCHES IN THE GRIDS. ALTHOUGH MOISTURE IS PLENTIFUL...AND THUS QPF AMOUNTS ARE SOMEWHAT HEAVY GIVEN THE WEAK FORCING...SNOW RATIOS WILL BE TOWARD THE LOW END OF THE SCALE. IN FACT...GUIDANCE NUMBERS FROM WPC (12:1 TO 14:1) MAY WELL BE TOO HIGH. THERE WILL BE LITTLE CONTRIBUTION FROM THE DENDRITIC GROWTH ZONE...WHICH WILL BE RESIDING SOMEWHERE AROUND 15KFT AND ABOVE THE MAJORITY OF THE MOISTURE. WHAT THIS EVENT HAS GOING FOR IT IS DURATION...WITH SNOW EXPECTED TO FALL ACROSS A PERIOD OF AROUND 18 HOURS. IN ADDITION...THERE MAY BE SOME ISOTHERM COMPACTION OCCURRING ACROSS THE NORTHERN ILN CWA ON SUNDAY MORNING (ESPECIALLY IN THE 925MB-850MB LAYER)...WITH WEAK FRONTOGENETIC SIGNATURES ON A FEW OF THE MODELS. THUS...SOME 6 INCH AMOUNTS WILL BE POSSIBLE...BUT WITH A LONG ENOUGH DURATION THAT HAZARDS WORTHY OF A WARNING DO NOT SEEM LIKELY. THE TRANSITION BETWEEN SNOW AND RAIN WILL UNDOUBTEDLY LEAD TO A LITTLE LESS CERTAINTY IN THE FORECAST FURTHER TO THE SOUTH...WHERE SNOW FORECAST TOTALS RANGE FROM 4 INCHES TO 1 INCH ACROSS A STRETCH OF ONLY 30 MILES. OF ADDITIONAL CONCERN IS THE POTENTIAL FOR ICE DURING THE MORNING HOURS. THERE IS A CLEAR SIGNAL FOR A WARM LAYER NEAR 900MB PUSHING ABOVE THE COLDER AIR AT THE SURFACE...GENERALLY ACROSS THE SOUTHERN THIRD OF THE FORECAST AREA BETWEEN 07Z AND 13Z. HOWEVER...BUFKIT SOUNDINGS SHOW THIS LAYER TO BE OF A FAIRLY SMALL MAGNITUDE...AND UNSATURATED. THIS IS NOT TERRIBLY SUPPORTIVE OF A WHOLE LOT OF FULL HYDROMETEOR MELTING...FAVORING A MIX OF FREEZING RAIN AND SLEET. THIS SEEMS MOST LIKELY TO OCCUR IN THE SOUTHWESTERN PART OF THE CWA...WHERE A TIER OF COUNTIES WAS ADDED TO THE WINTER WEATHER ADVISORY. THIS ADDITION WAS BASED ON A COMBINATION OF SNOW AMOUNTS (AROUND AN INCH) AND ICE POTENTIAL (PERHAPS UP TO FIVE HUNDREDTHS).5 TEMPERATURES SHOULD PEAK OUT IN THE 18Z-21Z TIME FRAME...MATCHING THE NORTHERNMOST EXTENT OF THE RAIN-SNOW LINE. AFTER THIS...WINDS WILL SHIFT TO THE WNW AND ALLOW COLD ADVECTION TO TAKE OVER...QUICKLY CHANGING THE PRECIPITATION TYPE TO SNOW ACROSS THE ENTIRE CWA. ADDITIONAL ACCUMULATIONS OF A FEW TENTHS (WITH PERHAPS ANOTHER INCH IN CENTRAL OHIO) WILL BE POSSIBLE BEFORE SNOW COMES TO AN END ON SUNDAY EVENING. TEMPERATURES ON SUNDAY NIGHT WILL COOL FROM NW TO SE...AS SKIES ALSO BEGIN TO CLEAR OUT. IGNORING THE RAW GFS NUMBERS...SHOULD RANGE FROM THE UPPER TEENS TO UPPER 20S. ON MONDAY...DRY HIGH PRESSURE WILL BUILD INTO THE REGION...WITH LIGHT WINDS AND MOSTLY SUNNY CONDITIONS. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... HIGH PRESSURE WILL QUICKLY MOVE OFF TO THE EAST MONDAY NIGHT AS RETURN FLOW DEVELOPS ON THE BACK SIDE. WARM...MOIST ASCENT WILL INCREASE TO OUR WEST DURING THE EVENING AND WILL SHIFT EAST/NORTHEAST INTO THE REGION LATE MONDAY NIGHT INTO TUESDAY MORNING. COLD AIR WILL BE IN PLACE AT THE SURFACE. THUS...AS PCPN INITIALLY BEGINS AND BEFORE SATURATION...SNOW/SLEET/FREEZING RAIN WILL OCCUR. AS SATURATION INCREASES...AND MAX TEMPS ALOFT INCREASE...MORE AND MORE OF THE REGION WILL TRANSITION OVER TO A PERIOD OF FREEZING RAIN. TEMPERATURES WILL CONTINUE TO WARM ALOFT AND IN THE LOW LEVELS THROUGH TUESDAY MORNING WHICH SHOULD CHANGE THE WINTRY PCPN TO RAIN FROM SOUTH TO NORTH. PRELIMINARY AMOUNTS LOOK LIKE A TENTH OF AN INCH OR LESS OF ICING AND LESS THAN AN INCH OF SNOW/SLEET. MODELS CONTINUE TO INDICATE THAT A MID LEVEL S/WV WILL EJECT NE FROM THE CENTRAL PLAINS TO THE WESTERN GREAT LAKES MONDAY AFTERNOON INTO MONDAY EVENING. AS THIS OCCURS...A FAIRLY STRONG LLJ OF 60 TO 70 KNOTS ALONG WITH A DEEPENING SFC LOW WILL PUMP ANOMALOUSLY HIGH PWATS INTO THE LOWER GREAT LAKES AND THE OHIO VALLEY. THESE VALUES ARE FORECAST TO BE BETWEEN 1.20 TO 1.40 INCHES...WHICH IS ABOUT 300 PERCENT ABOVE NORMAL FOR EARLY MARCH. THIS SCENARIO WILL BRING RAIN TO THE REGION...MODERATE TO LOCALLY HEAVY. THERE WILL BE A CONCERN FOR FLOODING GIVEN MOIST CONDITIONS AND SNOW PACK/STORED SNOW WATER EQUIVALENT FROM SUNDAYS SYSTEM. ALTHOUGH MOST STREAMS/RIVERS ARE RUNNING LOW ATTM...SNOW MELT AND MODERATE/HEAVY RAIN WILL RESULT IN RAPID RISES. IN ADDITION...THE PROLONGED COLD HAS ALLOWED ICE TO FORM ON MANY RIVERS...CREEKS AND STREAMS...SOME THICK IN SPOTS. WATER FLOWING INTO FAIRLY ICE COVERED BASINS WILL HAVE A HARD TIME DRAINING WHICH MAY LEAD TO FLOODING AND/OR ICE JAMS. ANOTHER CONCERN...BUT WITH LOW CONFIDENCE ATTM...WILL BE WHETHER A LOW TOPPED QLCS (MAYBE A LINE OF FOCUSED SHOWERS WITH LITTLE TO NO THUNDER) GETS GOING ALONG THE FRONT IN A REGIME OF HIGH SHEAR/LOW CAPE ALONG WITH STRONG LOW LEVEL FRONTAL CONVERGENCE. TO ADD TO THE COMPLEXITY...WHERE SNOW COVER CAN HOLD ON...IT MAY ADD A SHALLOW STABLE LAYER TO ANY QLCS DEVELOPMENT. ATTM...THE BEST CHANCE FOR A POTENTIAL QLCS TO HAVE AN AFFECT SEEMS MORE POSSIBLE ALONG AND SOUTH OF THE OHIO RIVER. THE WARMEST TEMPERATURES OF THE WEEK WILL OCCUR TUESDAY NIGHT AHEAD OF FRONT AS TEMPERATURES WARM INTO THE 40S AND 50S. A FEW LOWER 60S MAY OCCUR IN OUR FAR SE COUNTIES. WILL CONTINUE TO MENTION THE WINTRY AND FLOOD THREATS IN THE HWO. WILL HOLD OFF ON THE MENTION OF THE QLCS POTENTIAL ATTM. WOULD LIKE TO SEE A FEW MORE RUNS AND SOME HIGH RESOLUTION MODELS. A COLD FRONT IN ASSOCIATION WITH THE MID LEVEL ENERGY/SFC LOW WILL PUSH SOUTHEAST THROUGH THE REGION LATE TUESDAY NIGHT INTO WEDNESDAY MORNING. THIS WILL BE FOLLOWED EVENTUALLY BY AN ARCTIC FRONT. MODELS ARE NOW HEDGING ON WHETHER OR NOT ADDITIONAL ENERGY MOVING THROUGH THE SOUTHWEST FLOW ALOFT WILL ALLOW FOR A SECONDARY SURGE OF PRECIPITATION NORTH INTO OUR REGION LATER ON WEDNESDAY. HAVE KEPT SOME CONTINUITY WITH THE PREVIOUS FORECAST TO ALLOW FOR A HIGHER CHANCE FOR PCPN FOR POINTS ALONG AND SOUTH OF THE OHIO RIVER. PCPN IN THE CAA WILL TRANSITION FROM RAIN TO SNOW. GIVEN LOW CONFIDENCE ON SECONDARY SURGE...PINPOINTING POTENTIAL SNOW AMOUNTS ATTM WOULD NOT BE PRUDENT. THE ENTIRE SYSTEM FINALLY GETS SHUNTED FAR ENOUGH EAST FOR PRECIPITATION TO END WEDNESDAY NIGHT. HIGH PRESSURE WILL BUILD IN THURSDAY AND FRIDAY BRINGING DRY CONDITIONS BUT A RETURN TO BELOW NORMAL TEMPERATURES. A WEAK FRONT IS FORECAST TO DROP THROUGH THE REGION ON SATURDAY. THIS FRONT APPEARS MOISTURE STARVED. TEMPERATURES WILL MODERATE SOME AHEAD OF THE FRONT ON SATURDAY BUT WILL STILL AVERAGE BELOW NORMAL. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... LATEST RUNS OF THE HIRES MODELS ARE INDICATING THAT THE INITIAL SHOT OF SNOW THAT IS WORKING UP THE OHIO VALLEY WILL ONLY GRAZE CVG/LUK...SO ADJUSTED THE FORECAST FOR SOME MVFR CIGS AND VSBYS FROM 04-06Z DUE TO THE SNOW. ADDITIONAL LIFT COMES IN TOWARDS 12Z CAUSING PCPN TO REDEVELOP. SOUNDINGS ARE INDICATING THAT PCPN MIGHT FALL AS FZRA/PL BY THAT TIME...BEFORE TRANSITIONING TO RAIN AFTER SUNRISE. FARTHER N INTO ILN...THE SNOW SHOULD LAST LONGER BEFORE THE WARMER AIR BEGINS TO MIX IN AFTER 12Z. KEPT A RA/SN MIX FOR MUCH OF THE DAYLIGHT HOURS AFTER 14Z AS THE RAIN/SNOW JUST SEEMS TO HANG OVER ILN. KDAY SHOULD REMAIN ALL SNOW THROUGH THE EVENT...WITH THE HEAVIEST SNOW 10-14Z. A COUPLE OF THE MODELS ARE SUGGESTING A BRIEF BREAK/DECREASE IN INTENSITY IN THE PCPN AROUND 18Z...SO TRIED TO SHOW THAT IN THE TAFS. COLDER AIR BEGIN TO WORK BACK IN LATE SUNDAY AFTERNOON GRADUALLY CHANGING THE PCPN BACK TO SNOW FOR ALL LOCATIONS. OUTLOOK...MVFR/IFR CEILINGS LIKELY INTO SUNDAY NIGHT. MVFR/IFR CEILINGS AND VISIBILITIES ARE POSSIBLE TUESDAY INTO WEDNESDAY WITH RAIN AND SNOW. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...WINTER WEATHER ADVISORY UNTIL 10 PM EST SUNDAY FOR OHZ026-034- 035-042>046-051>056-060>062. WINTER WEATHER ADVISORY UNTIL 3 PM EST SUNDAY FOR OHZ063>065- 070>072-077. WINTER WEATHER ADVISORY UNTIL 10 AM EST SUNDAY FOR OHZ078. KY...WINTER WEATHER ADVISORY UNTIL 10 AM EST SUNDAY FOR KYZ089>093. IN...WINTER WEATHER ADVISORY UNTIL 10 PM EST SUNDAY FOR INZ050-058- 059. WINTER WEATHER ADVISORY UNTIL 3 PM EST SUNDAY FOR INZ066-073- 074. WINTER WEATHER ADVISORY UNTIL 10 AM EST SUNDAY FOR INZ075-080. && $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM...HATZOS LONG TERM...HICKMAN AVIATION...SITES

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