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000
FXUS63 KIWX 102328
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
628 PM EST TUE DEC 10 2013

.SYNOPSIS...
ISSUED AT 355 PM EST TUE DEC 10 2013

AN AREA OF LOW PRESSURE WILL APPROACH THE AREA TONIGHT AND MOVE
ACROSS NORTHERN INDIANA WEDNESDAY MORNING. SNOW IS EXPECTED TO
DEVELOP AHEAD AND NORTH OF THIS LOW WITH ACCUMULATIONS OF 1 TO 4
INCHES POSSIBLE...MAINLY NORTH OF THE HIGHWAY 30 CORRIDOR. THE
HEAVIEST AMOUNTS ARE EXPECTED NORTH OF THE TOLL ROAD ACROSS
EXTREME NORTHERN INDIANA AND SOUTHWEST LOWER MICHIGAN.
TEMPERATURES WILL REMAIN COLD WITH LOWS TONIGHT IN THE TEENS AND
SINGLE DIGITS. HIGHS ON WEDNESDAY WILL ONLY REACH THE LOWER TO
MIDDLE 20S.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 351 PM EST TUE DEC 10 2013

A COUPLE ISSUES TO SORT OUT IN THIS SHORT TERM PERIOD BEGINNING
WITH ONGOING LAKE EFFECT SNOW FOLLOWED BY NEXT SHORT WAVE LATE
TONIGHT AND WEDNESDAY.

SFC-850MB DELTA T VALUES IN MID TEENS COUPLED WITH RELATIVELY DEEP
MOIST LAYER UP TO 10KFT OFF LAKE MICHIGAN WAS CREATING LAKE EFFECT
SNOW SHOWERS ACROSS MAINLY NORTHERN BERRIEN AND CASS COUNTY THIS
AFTERNOON. CONDITIONS FAVORABLE DESPITE SHORT SOUTHWESTERLY FETCH
WITH ACCUMS UP TO AN INCH OR TWO EXPECTED. EXPECT INTENSITY TO
DIMINISH LATE THIS AFTERNOON AS INVERSION HEIGHTS AND
MOISTURE DEPTH LOWER BLO 5KFT DESPITE WEAK SURFACE TROUGH PASSAGE
AND BACKING WINDS. LIGHTER SNOW SHOWERS OR FLURRIES MAY PERSIST
THROUGH THE EVENING SO WILL KEEP A LOW POP IN LAKE FAVORED AREAS
THIS EVENING.

BREAK IN PCPN WILL BE SHORT LIVED ACROSS MICHIGAN AS NEXT SHORT WAVE
CURRENTLY DROPPING THROUGH THE NORTHERN PLAINS RACES EAST. WEAK WARM
AIR ADVECTION AND ISENTROPIC LIFT INCREASE ACROSS NORTHWEST AFTER
06Z BUT EXPECT DRY LOWER LEVELS TO TAKE SOME TIME TO SATURATE.
MODELS SHOWING A PERIOD FROM JUST BEFORE 12Z TO 18Z WITH GOOD
FRONTOGENETIC FORCING NORTH OF WEAK SFC LOW TRACK NEAR AND NORTH OF
IN/MI STATE LINE. THIS ALONG TIGHTENING BAROCLINIC ZONE WHICH
SUPPORTS A BRIEF PERIOD OF LIGHT TO MODERATE SNOW. MODELS TEND TO
BE OVERDONE WITH SYNOPTIC QPF FROM THESE FAST MOVING
CLIPPERS. FAVOR THE HIRES LOCAL WRF AND ARW EAST BLENDED WITH HPC
QPF WHICH IS LOWER THAN NAM12 ALONG WITH 20 TO 1 RATIO FOR
AMOUNTS. TRAJECTORIES WITH THIS SYSTEM FAVORS SOME LAKE
ENHANCEMENT TO PCPN OVER BERRIEN AND INTO CASS COUNTIES WITH DELTA
T VALUES REMAINING IN THE MID TEENS BEFORE RISING TO AROUND 20 IN
THE AFTERNOON. HIRES GUIDANCE SEEMS TO TAKE THIS INTO ACCOUNT AND
LIKE PLACEMENT OF HEAVIER QPF ACROSS MI COUNTIES WITH AMOUNTS
TAPERING FURTHER SOUTH AND ESPECIALLY SOUTH OF EXPECTED SURFACE
LOW TRACK WHICH CONSENSUS SHOWS NEAR THE HIGHWAY 30 CORRIDOR.

HEADLINES FOR THIS EVENT HAVE BECOME A BIT PROBLEMATIC GIVEN WE HAVE
BECOME SANDWICHED BETWEEN ADVISORIES TO OUR WEST AND NORTH FOR
DIFFERENT ISSUES. ADVISORY TO WEST HAS TO DO MORE WITH IMPACTS
DESPITE LOWER SNOW AMOUNTS WITH RUSH HOUR TRAFFIC ACROSS THE
CHICAGOLAND AREA. ADVISORY TO OUR NORTH DEALING WITH HIGHER AMOUNTS
FROM LAKE ENHANCED SNOW AND IMPACTS. OUR CURRENT FORECAST PLACES A
SWATH OF 1 TO 3 INCHES ALONG/NEAR THE TOLL ROAD ACROSS EXTREME NORTHERN
LAPORTE COUNTY INTO BERRIEN...THEN EAST THROUGH CASS AND ST.JOSEPH
COUNTIES IN MICHIGAN. A FEW HIGHER 4 INCH AMOUNTS COMING UP FROM
BERRIEN TO CASS WITH LAKE ENHANCEMENT WEDNESDAY. NOT REALLY
WORTHY OF OLD FASHIONED CRITERIA BASED ADVISORY BUT GIVEN TIMING
OF BEGINNING DURING MORNING COMMUTE FOR THE SOUTH BEND METRO AREA
AND FALLING BETWEEN ADVISORIES ALREADY IN PLACE HAVE OPTED TO
INCLUDE THESE COUNTIES IN A WINTER WEATHER ADVISORY FOR IMPACT
RELATED EVENT AND A SEAMLESS PICTURE. EXPECT A SHARP GRADIENT TO
THE SOUTH AND TRIED TO INCORPORATE THIS INTO LATEST FORECAST WITH
AMOUNTS SOUTH OF 30 LESS THAN INCH.


&&

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 351 PM EST TUE DEC 10 2013

SYSTEM WILL BE EXITING THE REGION AROUND 00Z THURSDAY...AS PV
ANOMALY TRACKS EAST ACROSS THE GREAT LAKES. LOW LEVEL THERMAL TROF
WILL SLIDE ACROSS THE REGION INTO THURSDAY MORNING. LAKE EFFECT
RESPONSE ANTICIPATED THROUGH THE 12Z PERIOD AS 850 MB TEMPS NEAR
-20C WITH LAKE SFC TO 850 MB DELTA T VALUES EXCEEDING 15C.
HOWEVER...WITH INITIAL NW FLOW QUICKLY BACKING WESTERLY THROUGH
12Z...AND VERY SHALLOW SATURATED LAYER/LIFT SHOULD LIMIT ANY
APPRECIABLE ACCUMULATION ONCE SYNOPTIC MOISTURE PULLS EAST OF THE
REGION. KEPT WITH MINOR ACCUMULATIONS LESS THAN A HALF INCH...MAINLY
ACROSS BERRIEN AND CASS COUNTIES. VERY COLD LOW
TEMPERATURES/NEGATIVE WIND CHILL VALUES EXPECTED...HOWEVER DEGREE OF
RADIATIVE COOLING EFFECTS WILL BE HIGHLY DEPENDENT ON LAKE EFFECT
CLOUD COVER AND AREA OF FRESH SNOWPACK. KEPT LOWS CLOSE TO PREVIOUS
FORECAST.

SUBTLE LOW LEVEL TROF WILL SLIDE EAST ACROSS LK MI THROUGH SRN LWR
MI THURSDAY MORNING INTO AFTERNOON. THIS MAY HELP TO REINVIGORATE
LAKE EFFECT SNOW SHOWERS GIVEN ENHANCED BOUNDARY LAYER
MOISTURE....HOWEVER FEEL THAT MOST OF THE SNOWFALL POTENTIAL WILL
REMAIN NORTH OF THE FORECAST AREA. KEPT A FLURRY MENTION DOWNWIND OF
THE LAKE. ANY SNOWFALL POTENTIAL/FLURRIES WILL QUICKLY DIMINISH
THURSDAY AFTERNOON AS HIGH PRESSURE BUILDS INTO THE REGION...WITH
THERMAL RIDGING/WAA AND BACKING SOUTHWEST LOW LVL FLOW.

HIGH PRESSURE WILL PROVIDE DRY CONDITIONS AND SLOWLY MODERATING
TEMPERATURES ON FRIDAY. AFTER HIGHS IN THE TEENS/LOW 20S ON
THURSDAY...TEMPERATURES SHOULD REBOUND NICELY ON FRIDAY...WITH HIGHS
IN THE UPPER 20S TO LOWER 30S. MAIN CHALLENGE FOR FRIDAY`S HIGH
TEMPERATURE FORECAST IS THE DEGREE OF LOW LEVEL WAA OVER A POTENTIAL
FRESH SNOWPACK ACROSS THE NORTHERN PART OF THE AREA. TEMPS MAY NEED
TO BE ADJUSTED IN THESE AREAS TWO IN SUBSEQUENT FORECASTS.

FOCUS TURNS TO SNOWFALL POTENTIAL FRIDAY NIGHT THROUGH SATURDAY. SFC
CYCLONE DEVELOPMENT EXPECTED NEAR TEXAS PANHANDLE FRIDAY
AFTERNOON...AS SOUTHERN STREAM 500 MB S/W TRACKS ACROSS THE MID
MISSISSIPPI VALLEY INTO THE OHIO VALLEY BY SATURDAY. NORTHERN STREAM
S/W ENERGY WILL SLIDE SOUTHEAST INTO THE OHIO VALLEY AND PHASE WITH
LEAD WAVE...AS A STRONG 500 MB TROF/CUTOFF LOW DROPS SOUTHEAST INTO
THE GREAT LAKES. 12Z MODELS SIMILAR TO PREVIOUS RUNS...WITH THE MOST
NOTABLE CHANGE BEING THE SPLITTING OF THE SFC CYCLONE INTO TWO
LOWS...ONE TRACKING SOMEWHERE INTO THE GREAT LAKES...AND THE OTHER
QUICKLY DEEPENING INTO A NOREASTER OFF THE ATLANTIC COAST.

THE EVOLUTION OF THE UPPER LEVEL PHASING AND SUBSEQUENT SFC CYCLONE
DEVELOPMENT WILL DICTATE HOW THE EVENT UNFOLDS ACROSS THE
AREA...HOWEVER AT THE MOMENT...LOOKS LIKE MOST OF THE AREA WILL SEE
SOME SORT OF SNOWFALL ON SATURDAY. HAVE BUMPED UP TO LIKELY POPS
EVERYWHERE ON SATURDAY...AND DELAYED THE ARRIVAL OF POPS UNTIL AFTER
00Z SATURDAY. ACCUMULATIONS WILL DEPEND ON THE TRACK OF THE
MID/UPPER LEVEL WAVES AND SFC CYCLONE...ALONG WITH ANY POTENTIAL
MESOSCALE BANDING. COLDER AIR INTRUDES BACK INTO THE REGION BEHIND
THIS SYSTEM INTO EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 616 PM EST TUE DEC 10 2013

LOW CLOUDS ALONG CDFNT WHICH MOVED THROUGH THE AREA THIS AFTN HAVE
MOVED TO THE EAST AS RIDGE APPROACHES FROM THE WEST. EXPECT VFR
CONDITIONS WILL CONT ACROSS NRN INDIANA THROUGH MOST OF THE NIGHT
AS LAKE EFFECT CLOUDS STAY JUST NORTH OF SBN AND RIDGE MOVES
ACROSS THE AREA. ANOTHER CDFNT OVER MN/SD WILL MOVE ACROSS THE
AREA WED. A LITTLE BETTER MOISTURE/FORCING ASSOCIATED WITH THIS
SYSTEM THAN TODAYS... ESPECIALLY NEAR THE MI LINE... SO EXPECT A
PERIOD OF SNOW WITH IFR CONDITIONS WED MORNING AT SBN FOLLOWED BY
MVFR CONDITIONS WITH LAKE EFFECT SNOW SHOWERS IN THE AFTN AS WINDS
VEER NW. FWA COULD GET IN ON SRN EXTENT OF SNOW SHIELD ASSOCIATED
WITH THIS SHRTWV SO MENTIONED A PROB30 FOR SNOW MIDDAY THERE...
WITH POST FRONTAL LAKE EFFECT SNOW SHOWERS CAUSING MVFR CONDITIONS
IN THE AFTN.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY FROM 3 AM EST /2 AM CST/ TO 1 PM EST
     /NOON CST/ WEDNESDAY FOR INZ003-004.

MI...WINTER WEATHER ADVISORY FROM 3 AM TO 1 PM EST WEDNESDAY FOR
     MIZ077>079.

OH...NONE.
LM...GALE WARNING UNTIL 10 PM EST THIS EVENING FOR LMZ043-046.

&&

$$

SYNOPSIS...LASHLEY
SHORT TERM...LASHLEY
LONG TERM...NG
AVIATION...JT


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