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000
FXUS63 KIWX 290600
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
100 AM EST THU JAN 29 2015

.SYNOPSIS...
ISSUED AT 401 AM EST WED JAN 28 2015

CLOUDS WILL INCREASE THIS EVENING AS A RIDGE OF HIGH PRESSURE
SHIFTS OFF TO THE EAST. AN UPPER LEVEL DISTURBANCE ACROSS THE
ROCKIES WILL TRACK INTO THE GREAT LAKES AND OHIO VALLEY REGIONS
TONIGHT BRINGING A WINTRY MIX LATE TONIGHT INTO THURSDAY. SOME
MINOR ICE AND SNOW ACCUMULATIONS ARE POSSIBLE...PARTICULARLY
ACROSS FAR NORTHERN INDIANA...MUCH OF LOWER MICHIGAN...AND
NORTHWEST OHIO.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 359 PM EST WED JAN 28 2015

QUIET/DRY WEATHER CONTINUES INTO THIS EVENING WITH ATTENTION
TURNING TO LIGHT WINTRY MIX LATER TONIGHT/TOMORROW...

MID LEVEL TROP UNDULATION JUST ENTERING WESTERN NE/NORTHEAST CO WILL
TRANSLATE EAST WITH 120-140 METER HEIGHT FALL TRACK AT 500 MB
INTO THE NORTHERN OH VALLEY BY THURSDAY MORNING...WHILE A SEPARATE
NORTHERN STREAM WAVE DROPS OUT OF SOUTH-CENTRAL CANADA INTO THE
WESTERN LAKES BY THURSDAY AFTERNOON. PCPN TIED TO STRONG
ISENTROPIC LIFT/MOISTURE CONVERGENCE WITHIN DOWNSTREAM LLJ/THETA-E
RIDGE (AMPLE MOISTURE AS PWATS SURGE TO 0.80 INCHES AND 1000-850
MB MIXING RATIOS TO 4-5 G/KG WITHIN MOISTURE CHANNEL) SHOULD BREAK
OUT SHORTLY AFTER MIDNIGHT IN NW IN/SW LOWER MI...AND THEN SPREAD
ESE INTO THE REST OF THE FA THROUGH MID MORNING IN ADVANCE OF AN
ELONGATED SFC TROUGH. PCPN MAY BE MORE SPOTTY/SHOWERY DURING THIS
TIME GIVEN OVERSPREAD OF STEEP MID LVL LAPSE RATES AND SLIGHT LAG
OF DEEPER MOISTURE/MID-UPPER LVL ASCENT. SHOULD SEE LIGHT PCPN
FILL IN ALONG AND BEHIND THE SFC TROUGH LATE MORNING THROUGH MID
AFTN ACROSS MAINLY NORTHERN/EASTERN PORTIONS OF THE FORECAST AREA
AS WEAK DEFORMATION FORCING SHIFTS THROUGH. THIS FORCING/DEEPER
MOISTURE THEN EXITS EAST BY LATE AFTERNOON..ALTHOUGH SHOULD SEE
SOME DRIZZLE/LIGHT SNOW SHOWERS LINGER GIVEN SOME LAKE
ENHANCEMENT.

PTYPE INITIALLY STILL EXPECTED TO BE A SLEET/FREEZING RAIN MIX
LATER TONIGHT/EARLY THURSDAY MORNING AS SATURATION/WET BULBING
OCCURS AND WARM LAYER CENTERED AROUND 800 MB OVERSPREADS. SUB
FREEZING SFC AMBIENT TEMPS IN THE NORTH AND EAST LIKELY WITH LIGHT
ICING EXPECTED TOWARD DAYBREAK/MORNING COMMUTE HINTS AT THE
POTENTIAL FOR DIFFICULT TRAVEL FROM LIGHT ICE ACCRETIONS. PER
COLLABORATION AND POOR TIMING WILL ISSUE A HEADLINE FOR THESE
AREAS...WITH CONFIDENCE IN DURATION/MEASURABLE PCPN TOO LOW ACROSS
SOUTHWEST ZONES FOR A HEADLINE ATTM. SFC TEMPS AND ANY ICING
CONCERNS SHOULD ABATE BY LATE MORNING AS WARM/MOIST ADVECTION IN
SOUTHERLY FLOW ALLOWS SFC WET BULB TEMPS TO WARM ABOVE FREEZING.
PTYPE CONTINUES TO BE MESSY INTO THE AFTERNOON...MORE LIGHT
SNOW/SLEET THAN RAIN IN SOUTHERN LOWER MI AND RAIN CHANGING TO
LIGHT SNOW SOUTHERN HALF. DEEP LAYER OF TEMPS WARMER THAN -10C AND
MARGINAL BOUNDARY LAYER TEMPS WILL SIGNIFICANTLY REDUCE SNOW
RATIOS WITH LITTLE TO NO SNOW/SLEET ACCUMULATION EXPECTED.

&&

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 359 PM EST WED JAN 28 2015

STEADY COURSE THIS FORECAST CYCLE. ASSURED THOUGH MODEST/SHALLOW LES
CONVECTION CULMINATING LATE THU NIGHT...WITH LAKE INDUCED CAPE AOB
300 J/KG AND EQL BLO 6KFT. DRY AIR ENTRAINMENT/BACKING STEERING FLOW
AND INCREASED TURBIDITY WITHIN CBL TO SHARPLY DEGRADE RESPONSE BY
MIDDAY FRIDAY. MOST FOCUS ON POSSIBLE SAT NIGHT/SUNDAY SNOW EVENT.
INCREASED MODEL SPREAD LENDING TO LOW CONFIDENCE FOR ANY SIG EVENT.
LATEST ECMWF QUELLS MOISTURE FARTHER SWD THAN PRIOR AND EVEN PRIOR
ALL IN GEM HAS BACKED OFF CONSIDERABLY BUT STILL SLOW/STRONG WITH
GFS WEAK AND DECISIVELY FAST. BEST COURSE OF ACTION ATTM TO
CONT/THOUGH SLIGHTLY LOWER MSRBL POPS FOR LIGHT SNOW EVENT SUN AS
UPSTREAM ATTEMPT TO CONGEAL NOTABLE SHORTWAVE ENERGIES CURRENTLY
LOCATED ACRS NRN CANADA/GULF OF AK/SIBERIAN STRAITS. AT LEAST
80-100M/12 HR HEIGHT FALL CENTROID PER LATEST MIDDLE OF ROAD
ECMWF...ON ORDER OF 50M/12 HR WEAKER THAN PRIOR ITERATION... DROPS
ESEWD FROM NRN PLAINS INTO MID OHIO SHOULD ILLICIT SUFFICIENT DEEP
LAYER ASCENT FOR AT LEAST A LIGHT EVENT. LATER FORECASTS ALLOWED TO
FINE TUNE AS POTENTIAL OUTCOMES HOPEFULLY HONE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1253 AM EST THU JAN 29 2015

PRIMARY FORECAST CONCERNS FOR THE 06Z TAFS WILL CONTINUE TO BE
POTENTIAL OF A BRIEF PERIOD OF FREEZING RAIN EARLY THIS MORNING
ALONG WITH DETERIORATION TO IFR CONDITIONS EXPECTED AFTER DAYBREAK.
ZONE OF LOW/MID LEVEL MOISTURE CONVERGENCE HAS REACHED NORTHWEST
INDIANA WITH A NARROW SWATH OF LIGHT PRECIP. LOW LEVEL WARM
ADVECTION APPEARS TO BE BALANCING EVAPORATIVE COOLING EFFECTS TO
KEEP SFC TEMPS RIGHT NEAR THE FREEZING MARK OR SLIGHTLY ABOVE. A
VERY BRIEF PERIOD OF -FZRA APPEARS TO BE POSSIBLE AT BOTH
TERMINALS THROUGH 10Z...BUT CURRENT EXPECTATION IS THAT PRECIP
SHOULD CHANGE OVER TO MAINLY RAIN. PRECIP AMOUNTS ARE EXPECTED TO
REMAIN QUITE LIGHT...GENERALLY A FEW HUNDREDTHS OF AN INCH OR
LESS. SFC REFLECTION TO TRACK ACROSS NORTHERN INDIANA THURSDAY
MORNING WITH IFR OR LOWER END MVFR CIGS OVERSPREADING THE AREA FOR
MOST OF THURSDAY. WEAK DEFORMATION ZONE ON BACKSIDE OF THIS SYSTEM
SHOULD ALLOW FOR OCCASIONAL RAIN AND SNOW SHOWERS THROUGH MOST OF
THE DAY BUT LITTLE OR NO SNOW ACCUMULATION IS EXPECTED. WEST
NORTHWEST WINDS WILL BECOME GUSTY IN ASSOCIATION WITH POST COLD
FRONTAL ADVECTION...WITH GUSTS TO AROUND 25 KNOTS EXPECTED FOR THE
AFTERNOON HOURS.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FREEZING RAIN ADVISORY FROM 4 AM TO 10 AM EST THIS MORNING FOR
     INZ007-009-018-026-027.

     FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR
     INZ004>006-008-016-017.

MI...FREEZING RAIN ADVISORY FROM 4 AM TO 10 AM EST THIS MORNING FOR
     MIZ080-081.

     FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR
     MIZ077>079.

OH...FREEZING RAIN ADVISORY FROM 4 AM TO 10 AM EST THIS MORNING FOR
     OHZ001-002-004-005-015-016-024-025.

LM...NONE.
&&

$$

SYNOPSIS...MARSILI
SHORT TERM...STEINWEDEL
LONG TERM...MURPHY
AVIATION...MARSILI


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