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Area Forecast Discussion
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000
FXUS61 KILN 282119
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
419 PM EST SAT FEB 28 2015

.SYNOPSIS...
HIGH PRESSURE WILL MOVE EAST OF THE REGION TONIGHT. 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 /20Z SATURDAY THROUGH THURSDAY/...
SYSTEM COMING IN FROM THE SOUTHWEST TONIGHT WILL SEE HIGH CLOUDS
THICKEN AND LOWER OVERNIGHT WITH SNOW DEVELOPING LATE THIS
EVENING. ENOUGH WARM AIR WILL BE PULLED INTO THE SOUTHEASTERN
CWA...GENERALLY SOUTHEAST OF I-71 CORRIDOR...TO MIX WITH AND
CHANGE OVER TO SLEET AND THEN RAIN DURING THE MORNING ON SUNDAY.
40KT H8 JET WILL HELP STREAM MOISTURE INTO THE REGION AND FLOW
ABOVE THE SURFACE IS FAIRLY UNIFORM FROM THE WEST-SOUTHWEST. THIS
PUTS THE LINE OF MIXED RAIN/SNOW/SLEET IN A HIGHER STATE OF
UNCERTAINTY BUT MODELS ARE GENERALLY KEEPING SIMILAR LOW LEVEL
1000-850 THICKNESSES. THIS SUGGESTS ALL SNOW AT KDAY AND A
DAYBREAK MIXING CHANGING TO RAIN FOR KCVG/KLUK. KCMH/LCK MAY GET
ENOUGH INSOLATION DURING THE DAY TO MIX AT TIMES DURING DAYLIGHT
HOURS BUT MODELS ARE INDICATING LITTLE TO NO CHANGEOVER AND
KEEPING THE PRECIP HERE ALL SNOW. 

CIGS IN THE SNOW TONIGHT WILL QUICKLY DROP TO MVFR AND THEN HOVER
IN THE IFR RANGE BELOW 1KFT. VSBYS WILL BOUNCE FROM LIFR IN THE
HEAVIER SNOW TO IFR IN MOST LOCATIONS.

WITH THIS SYSTEM...IT WILL PRECIPITATE MORE OFTEN THAN NOT BUT
SOME BREAKS ALONG WITH BRIEFLY IMPROVED CIGS/VSBYS SHOULD BE
EXPECTED.

OUTLOOK...MVFR/IFR CEILINGS AND VISIBILITIES ARE LIKELY WITH
PRECIPITATION 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 FROM 7 PM THIS EVENING TO 10 PM EST 
     SUNDAY FOR OHZ026-034-035-042>046-051>056-060>062.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 3 PM EST 
     SUNDAY FOR OHZ063>065-070>072-077.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST 
     SUNDAY FOR OHZ078.
KY...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST 
     SUNDAY FOR KYZ089>093.
IN...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 PM EST 
     SUNDAY FOR INZ050-058-059.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 3 PM EST 
     SUNDAY FOR INZ066-073-074.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST 
     SUNDAY FOR INZ075-080.

&&

$$
SYNOPSIS...HATZOS
NEAR TERM...HATZOS
SHORT TERM...HATZOS
LONG TERM...HICKMAN
AVIATION...FRANKS






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