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000
FXUS61 KILN 112358
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
758 PM EDT TUE MAR 11 2014

.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL CROSS THE REGION TONIGHT THROUGH
WEDNESDAY. THIS WILL BRING RAIN TO THE AREA TONIGHT...WHICH WILL
CHANGE TO SNOW ON WEDNESDAY. MUCH COOLER CONDITIONS ARE EXPECTED
BY WEDNESDAY NIGHT. HIGH PRESSURE WILL MOVE INTO THE REGION
THURSDAY...WITH A SLIGHT WARMING EXPECTED ON FRIDAY.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
WITH VERY WARM CONDITIONS OVER THE OHIO VALLEY THIS
AFTERNOON...THE PRIMARY FORECAST CONCERN GOING INTO TONIGHT WILL
BE THE POTENTIAL FOR ELEVATED CONVECTION. SURFACE LOW PRESSURE IS
CURRENTLY LOCATED SOUTHWEST OF KANSAS CITY...AND WILL MOVE EAST
INTO THE OHIO VALLEY TONIGHT AND INTO EARLY WEDNESDAY MORNING.
AHEAD OF THIS LOW...A FAIRLY WIDESPREAD AREA OF SHOWERS WILL
DEVELOP...IN AN AREA OF FAVORABLE UPPER-LEVEL DIVERGENCE...WITH
PLENTIFUL WARM ADVECTION JUST OFF THE SURFACE. ALTHOUGH A STABLE
LAYER IS EXPECTED NEAR THE GROUND...ELEVATED INSTABILITY WILL
DEVELOP...LEADING TO CONFIDENCE THAT EMBEDDED THUNDERSTORMS WILL
BE POSSIBLE (MAINLY FOR THE SOUTHERN HALF OF THE ILN CWA). THERE IS
NOT MUCH TO INDICATE A SUBSTANTIAL THREAT FOR STRONGER
STORMS...THOUGH THE STRENGTHENING SURFACE LOW WILL LEAD TO SOME
INCREASE IN THE WIND FIELDS...AND SOME SMALL HAIL OR GUSTY WINDS
MAY BE POSSIBLE. THE MOIST ENVIRONMENT MAY ALSO SUPPORT BRIEF
HEAVY RAIN. HIGH-RES MODELS (SUCH AS THE ARW AND NMM) VERY MUCH
INDICATE A CELLULAR NATURE TO THE ACTIVITY...WITH SIGNS EVEN OF A
CONVECTIVE LINE MOVING ACROSS KENTUCKY (GENERALLY SOUTH OF THE ILN
FORECAST AREA).

THE SURFACE FRONT IS CURRENTLY NORTH OF THE CWA BOUNDARIES...BUT
IT WILL BEGIN MOVING SOUTH AS THE LOW CENTER MOVES
CLOSER...ALLOWING FOR A TIGHT TEMPERATURE GRADIENT TO FORM ACROSS
THE CWA BY WEDNESDAY MORNING.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
THOUGH HIGHER-RESOLUTION MODELS SUCH AS THE NAM12 / CMC REGIONAL /
ARW / NMM DEPICT A SLIGHTLY STRONGER AND SLOWER SURFACE
LOW...OVERALL CONFIDENCE IN TRACK AND TIMING IS IN PRETTY GOOD
SHAPE. THERE WILL BE A STRONG LOW-LEVEL FRONTOGENETIC RESPONSE
ACROSS THE ENTIRE ILN CWA BETWEEN 06Z AND 18Z...WITH ADDITIONAL
DEFORMATION SUPPORT IN THE NORTHERN THIRD OF THE CWA. IT ALSO
APPEARS THAT THE SHORTWAVE DRIVING THE SYSTEM WILL BE SHARPENING
AS IT CROSSES THE OHIO VALLEY. ALL IN ALL...QPF AMOUNTS ARE COMING
IN A FEW TENTHS ON EITHER SIDE OF AN INCH...WITH THE HIGHER VALUES
STRETCHING FROM THE WHITEWATER VALLEY THROUGH CENTRAL OHIO.

NOT ALL OF THE QPF IS EXPECTED TO FALL AS SNOW...AS STEADY RAIN IS
EXPECTED TO EXTEND ALL THE WAY BEYOND THE NORTHERN CWA BORDER
BEFORE 12Z WEDNESDAY MORNING. FROM THERE...AS THE FRONT PROGRESSES
SOUTHWARD...THERE WILL BE A FAIRLY TIGHT CHANGEOVER ZONE AS RAIN
TURNS TO SNOW. THANKFULLY...THE PRECIPITATION TYPE FORECAST WAS
NOT ESPECIALLY COMPLICATED. THE BIGGEST CONCERN WILL BE THE EXACT
TIMING OF THE CHANGE FROM RAIN TO SNOW...AS THE TIGHT TEMPERATURE
GRADIENT WILL MEAN THAT IT WOULD BE EASY TO MISS THE TRANSITION AT
A GIVEN LOCATION BY A COUPLE HOURS. THERE ARE ALSO SIGNS OF A
SMALL WARM (ABOVE FREEZING) LAYER NEAR 800MB...WHICH BUFKIT
SOUNDINGS (NAM/GFS) INDICATE WILL ONLY LAST FOR A SHORT PERIOD OF
TIME BEFORE THE ENTIRE SOUNDING GOES BELOW FREEZING. BECAUSE OF
THIS...THIS FORECAST WILL INDICATE THAT SOME SLEET MAY MIX IN NEAR
THE TRANSITION FROM RAIN TO SNOW. THIS IT NOT EXPECTED TO
REPRESENT VERY MUCH OF THE PRECIPITATION ENVELOPE FROM THIS
SYSTEM...AND IT SHOULD BE BRIEF IF IT OCCURS.

ANY OF THE HEAVIER PRECIPITATION WILL ALREADY BE ENDING ACROSS
THE ILN CWA BY 18Z...WHILE THE RAIN-TO-SNOW TRANSITION WILL NOT
HAVE EVEN CLEARED THE OHIO RIVER. BECAUSE OF THIS...IT IS EXPECTED
THAT THE SOUTHERN HALF OF THE CWA WILL PICK UP A GENERAL LIGHT
AMOUNT OF SNOW...WITH UP TO AN INCH IN THE FAR SOUTH AND ONE OR
TWO INCHES ACROSS THE BETWEEN-INTERSTATES-70-AND-71 CORRIDOR.
HOWEVER...THE SNOWFALL GRADIENT WILL BECOME MUCH MORE SIGNIFICANT
NEAR AND NORTH OF INTERSTATE 70...ESPECIALLY IN THE MIAMI VALLEY.
A THREE-SEGMENT ADVISORY WAS REQUIRED NORTH OF HERE...WITH AROUND
THREE INCHES EXPECTED FROM WAYNE COUNTY INDIANA TO DELAWARE COUNTY
OHIO...FOUR INCHES NORTH OF THAT...AND FIVE INCHES IN THE FAR
NORTHERN TIER OF THREE COUNTIES (MERCER THROUGH HARDIN). THE
SNOWFALL ACCUMULATION GRIDS ACTUALLY PRODUCED VALUES JUST SHY OF 6
INCHES IN THE FAR NORTHERN PARTS OF THESE COUNTIES...BUT THE
ADVISORY CRITERIA IS EXPECTED TO COVER A MAJORITY OF REPORTS GIVEN
THESE FORECAST NUMBERS. IF THERE IS A TRACK SHIFT JUST SLIGHTLY
SOUTH...OR A QUICKER CHANGEOVER TO SNOW EXPECTED...A WARNING COULD
BECOME NECESSARY FOR THESE THREE COUNTIES. HIGH-RESOLUTION MODELS
DEPICT THE HEAVIEST SIMULATED RADAR ECHOES IN THIS AREA BETWEEN
12Z AND 18Z.

WITH STRONG NORTHERLY FLOW ON THE BACK SIDE OF THE FRONT...WIND
GUSTS OF 30-40 MPH ARE EXPECTED. A FEW GUSTS NEAR 45 MPH ARE NOT
OUT OF THE QUESTION. WITH ADVISORY CRITERIA REQUIRING GUSTS OF 46
MPH OR GREATER...AND NO EXPECTATION THAT THIS WILL OCCUR ON A
WIDESPREAD BASIS...A WIND ADVISORY IS NOT NECESSARY. WHAT THIS
WIND MAY DO IS LEAD TO SOME BLOWING SNOW IN THE NORTHWESTERN
CWA...AND THIS HAS ALSO BEEN INCLUDED IN THE GRIDS. FINALLY...AS
TEMPERATURES FALL AND THE GUSTY WINDS CONTINUE INTO THE
EVENING...THERE WILL BE SOME RISK OF THE WET ROADS FREEZING.
CONFIDENCE IS NOT HIGH IN THIS SCENARIO...BECAUSE ROAD
TEMPERATURES ARE CURRENTLY QUITE WARM...AND WILL BE ESPECIALLY SO
AFTER A DAY OF TEMPERATURES IN THE 60S TO 70S. IF ANYTHING...THE
WARM INITIAL CONDITIONS MAY HELP KEEP THE SNOW-RELATED IMPACTS
SLIGHTLY LOWER THAN AVERAGE (AT LEAST DURING THE DAY) WHEN COMPARED
TO OTHER SIMILAR ACCUMULATION AMOUNTS.

LIGHT SNOW MAY CONTINUE ON THE BACK SIDE OF THE SYSTEM...AS RATIOS
INCREASE RAPIDLY IN THE COOLING AIR. HOWEVER...FORCING WILL BE
DEPARTING THE OHIO VALLEY...AND ANY ADDITIONAL ACCUMULATIONS AFTER
21Z WILL BE LIGHT. THE STRONG COLD ADVECTION WILL LEAD TO BIG
DROPS IN TEMPERATURES. COMPARED TO CURRENTLY OBSERVED VALUES AT
20Z ON TUESDAY AFTERNOON...MIN TEMPS FOR THURSDAY MORNING ARE
EXPECTED TO BE 50-60 DEGREES COLDER. WIND CHILLS ARE EXPECTED TO
DROP BELOW ZERO FOR THE NORTHERN HALF-TO-TWO-THIRDS OF THE
FORECAST AREA.

A WEAK AREA OF ISENTROPIC LIFT WILL PASS NORTH OF THE ILN CWA LATE
THURSDAY INTO THURSDAY NIGHT...AS WARM ADVECTION BEGINS ALOFT. THE
CURRENT FORECAST WILL REMAIN DRY...BUT SOME VERY LIGHT
PRECIPITATION IN THE NORTHERN CWA IS POSSIBLE. THE WARM ADVECTION
WILL BEGIN AT THE SURFACE DURING THE OVERNIGHT HOURS...FORCING
NON-DIURNAL TEMPERATURES GOING INTO FRIDAY MORNING.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
DRY CONDITIONS WILL START OUT THE LONG TERM PERIOD.  WARMER AIR WILL
WORK UP INTO THE AREA WITH SOUTHERLY WINDS ON FRIDAY.  WINDS WILL
GUST TO 30 TO 35 MILES PER HOUR AT TIMES FRIDAY AFTERNOON.

PRECIPITATION WILL BEGIN TO MOVE INTO THE FA DURING THE FRIDAY
EVENING HOURS IN ADVANCE OF A COLD FRONT.  THE COLD FRONT WILL MOVE
THROUGH THE AREA FRIDAY NIGHT INTO SATURDAY.  TEMPERATURES ARE WARM
ENOUGH THAT SOUTHERN PORTIONS OF THE FA WILL RECEIVE RAIN WITH THIS
SYSTEM.  A MIX OF RAIN AND SNOW IS EXPECTED ACROSS NORTHERN PORTIONS
OF THE AREA.  PRECIPITATION WILL TAPER OFF SATURDAY MORNING.

BY SUNDAY HIGH TEMPERATURES ARE ONLY EXPECTED TO BE IN THE 30S TO
MIDDLE 40S.  MODELS ARE IN DISAGREEMENT ON WHETHER A SYSTEM SOUTH OF
THE FA WILL WORK NORTHWARD INTO THE AREA ON SUNDAY.  WENT CLOSER TO
THE GFS AND HAVE A DRY FORECAST FOR SUNDAY.  KEPT DRY CONDITIONS
ACROSS THE FA THROUGH MOST OF THE DAY ON TUESDAY.  ANOTHER SYSTEM
WILL BEGIN TO APPROACH THE AREA TUESDAY EVENING BRINGING A RETURN OF
PRECIPITATION TO THE AREA.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
SHOWERS WILL LIFT ACROSS THE REGION AFTER 05Z. COULD BE SOME
EMBEDDED THUNDER PARTICULARLY IN THE CINCINNATI AREA. WITH OR
WITHOUT THUNDER THERE WILL BE SOME POCKETS OF MODERATE TO HEAVY
RAIN THAT MAY TEMPORARILY REDUCE THE VISIBILITY TO IFR. AFTER
INITIAL SURGE OF SHOWERS THERE WILL STILL LIKELY BE SCATTERED
ACTIVITY BUT MORE IMPORTANT IS THAT THE CEILINGS WILL DROP TO MVFR
AND PERHAPS IFR.

LOW PRESSURE WILL TRACK ACROSS THE AREA BETWEEN 10Z AND 15Z. ONCE
THE LOW PASSES THEN WINDS WILL INCREASE SUBSTANTIALLY FROM THE
NORTH NORTHWEST AND GUST. THESE STRONGER WINDS WILL PERSIST
THROUGH THE REMAINDER OF THE FORECAST PERIOD. A SECOND BAND OF
PRECIPITATION WILL FOLLOW ON THE BACK SIDE OF THE LOW. RAIN WILL
CHANGE TO SNOW. CONDITIONS WILL BE IFR OR EVEN LIFR FOR A PERIOD
OF TIME WHEN MORE CONCENTRATED SNOW MAY OCCUR. HOWEVER THE SYSTEM
IS FAST MOVING...SO CEILINGS AND VISIBILITIES WILL LIFT TO MVFR
AND SNOW MAY EVEN END BEFORE 00Z.

OUTLOOK...MVFR CEILINGS EXPECTED LINGER INTO WEDNESDAY NIGHT. MVFR
CEILINGS AND VISIBILITIES POSSIBLE FRIDAY NIGHT AND SATURDAY.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...WINTER WEATHER ADVISORY FROM 8 AM TO 8 PM EDT WEDNESDAY FOR
     OHZ026-034-035-042>046-051-052.
KY...NONE.
IN...WINTER WEATHER ADVISORY FROM 8 AM TO 8 PM EDT WEDNESDAY FOR
     INZ050.

&&

$$
SYNOPSIS...HATZOS
NEAR TERM...HATZOS
SHORT TERM...HATZOS
LONG TERM...NOVAK
AVIATION...