Winter Storm Watch 4, NWS Northern Indiana

Allen County, IN, Cass County, IN, DeKalb County, IN, Elkhart County, IN, Fulton County, IN, Grant County, IN, Huntington County, IN, LaGrange County, IN, Marshall County, IN, Miami County, IN, Noble County, IN, Pulaski County, IN, Starke County, IN, Steuben County, IN, Wabash County, IN, White County, IN, Whitley County, IN, Branch County, MI, Cass County, MI, Hillsdale County, MI, Saint Joseph County, MI, Williams County, OH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
730 PM EST MON NOV 28 2011

.AVIATION...
MAIN CONCERNS FOR PERIOD INCLUDE DETERIORATING CIGS AND VIS AS LIGHT
TO MODERATE RAINFALL APPROACHES BOTH TERMINALS FROM THE SOUTH AS
SIGNIFICANT LOW PRESSURE CENTER ACROSS KENTUCKY SLOWLY EDGES NORTH
NORTHEASTWARD. DRIER NORTHEAST FLOW HAS KEPT CIGS MVFR AT KFWA AND
KSBN THROUGH THE EARLY EVENING BUT IFR CIGS ACROSS CENTRAL INDIANA
AND OHIO WILL SLOWLY EDGE NORTHWARD AS THE COLUMN SATURATES. IFR
CEILINGS IN AT KFWA STARTING AT 00Z DUE TO EXPECTED CIG REDUCTION
SHORTLY. IFR CEILINGS WILL NOT REACH KSBN UNTIL CLOSER TO 06Z. AS
THE LOW PRESSURE CENTER MOVES ACROSS LAKE ERIE TUESDAY AFTERNOON
DYNAMIC COOLING WITHIN THE TROWAL REGION COUPLED WITH COLD AIR
ADVECTION WILL BEGIN TO MIX SOME SNOWFLAKES IN PER NAM/GFS BUFKIT
SOUNDINGS. WINDS WILL STAY OUT OF THE NORTHEAST AT BOTH TERMINALS
THROUGH THE OVERNIGHT HOURS AND MOST OF THE DAY TUESDAY. WINDS
WILL SHIFT TO NORTHWEST IN THE LATE AFTERNOON HOURS NEAR THE TIME
OF THE CHANGEOVER FROM RAIN TO SNOW. WINDS WILL BE STRONGER AT
KSBN DUE TO A STRONGER PRESSURE GRADIENT FURTHER AWAY FROM THE LOW
PRESSURE CENTER.

&&

.PREV DISCUSSION... /ISSUED 311 PM EST MON NOV 28 2011/

SHORT TERM.../TONIGHT THROUGH TUESDAY NIGHT/

..HEAVY RAIN EXPECTED ACROSS PORTIONS OF THE AREA FOLLOWED BY
ACCUMULATING SNOWFALL...

DIFFICULT FORECAST IN STORE NEXT 24 TO 36 HOURS AS DEEP UPPER LOW
CURRENTLY CUTTING OFF OVER THE GULF STATES THROWS MSTR NORTH INTO
THE AREA INTO TONIGHT AND THEN BEGINS ITS TREK NNE TOWARDS THE
REGION.

AREA OF LIGHT RAIN RAPIDLY EXPANDING ACROSS PORTIONS OF CENTRAL
INDIANA INTO WESTERN OHIO. SUSPECT BY MID EVENING SE THIRD TO HALF
OF CWA WILL BE SEEING AT LEAST LIGHT RAIN/DRIZZLE OCCURRING WITH NW
AREAS LIKELY STILL DRY. THIS WILL CHANGE BY LATER TONIGHT AS UPPER
LOW BEGINS TO WORK NORTH AND LARGE TROWAL SETS UP ACROSS THE
FORECAST AREA. COMPUTER MODELS CONTINUE TO CRANK OUT 2 TO MORE THAN
3 INCHES OF RAINFALL IN SPOTS...GENERALLY IN NE TO SW ORIENTATION
ACROSS CENTRAL PORTIONS OF THE FORECAST AREA. EVEN IF ONE TO LOCALLY
2 INCHES FALLS...THIS WILL EXACERBATE FLOODING CONCERNS ACROSS
NORTHWESTERN OHIO AND NE INDIANA. IN ADDITION...RISING RIVER LEVELS
IN THE WESTERN BASINS AND POTENTIAL FOR HEAVIEST RAINS TO SET UP AND
PERSIST THE LONGEST IN THESE AREAS CAUSES ISSUES. AFTER MUCH
COORDINATION...HAVE OPTED TO ISSUE AREAL FLOOD WATCH FOR THE ENTIRE
AREA THROUGH TUES EVE. HEAVIEST RAIN WILL OCCUR BETWEEN 6Z TUE AND
00Z WEDS WITH POSSIBILITY OF DRY SLOT WORKING INTO SE AREAS FOR A
WHILE TUES AFTERNOON. QPF COULD BE LOWER AS A RESULT IN THESE AREA
BUT STILL MORE THAN SUFFICIENT FOR CONTINUED FLOODING CONCERNS ON
LOCAL RIVERS...STREAMS AND LOW AREAS. TEMPERATURES WILL NOT DROP
MUCH TONIGHT ACROSS THE AREA AND MAY ACTUALLY RISE SOMEWHAT IN SE
THIRD OR SO AS UPPER LOW DRAWS CLOSER AND WARM AIR TRIES TO MOVE IN.

NEXT CHALLENGE WILL BE ARRIVAL OF COLD AIR AND SWITCHOVER TO SNOW
ACROSS THE AREA AND RESULTANT ACCUMS. 12Z NAM/9Z SREF KEEP COLDEST
AIR ARRIVING FROM WEST TO EAST MORE AFTER 00Z WEDS VS
GFS/ECMWF/LOCAL WRF WITH TRANSITION DURING LATE AFTERNOON. WHILE
LEANING TOWARDS A COMPROMISE AT THIS POINT...DO FEEL THERE IS MERIT
TO FASTER SWITCH OVER IN WESTERN AREAS NEAR OR JUST PRIOR TO
SUNRISE. THAT BEING SAID...HAVE ONLY MADE FEW CHANGES TO PREV GRIDS
IN TERMS OF SNOWFALL MAINLY TO INCREASE SNOWFALL BY A FEW TENTHS ON
OUTER FRINGES OF THE AREA WHERE THERE SHOULD BE AT LEAST A DUSTING
AT SOME POINT TUES NGT. HPC GRAPHICS HAVE BACKED OFF ON 6 TO 8 INCH
AMOUNTS INTO OUR AREA...LEANING TOWARDS 4 TO 6 IN FAR NORTHEAST AND
LOWER AS YOU WORK SOUTH. GRIDS LIKELY TO CHANGE TONIGHT INTO
TOMORROW AS TRACK OF MID/UPPER LEVEL FEATURES BECOMES BETTER DEFINED
AND TIMING OF COLD AIR HOPEFULLY BECOMES CLEARER. HAVE HELD OFF ON
ANY SORT OF HEADLINES AND WILL REISSUE SPS WITH UPDATED AMOUNTS.

LONG TERM.../WEDNESDAY THROUGH MONDAY/
DEEP LOW OVER THE LWR GRTLKS WED MORNING WILL LIFT NE UP THE ST.
LAWRENCE RIVER VALLEY AND SHEAR OUT WED/THU. WRAP AROUND MOISTURE
MAY RESULT IN SOME PRECIP LINGERING OVER ERN PORTION OF CWA WED
MORNING...THOUGH WITH STRONGEST FORCING MOVG WELL NE OF THE CWA BY
THAT TIME AND SATURATION PSBLY LOWERING BLO DGZ...ANY ADDITIONAL
ACCUM SHOULD BE MINOR.

RIDGING WILL FOLLOW THIS SYSTEM ACROSS THE GRTLKS WED PM-THU
PROVIDING FAIR WX. SOME CONCERN THAT LINGERING MOIST LOW LEVELS AND
WK LOW LEVEL FLOW MAY RESULT IN SOME STRATUS/FOG WED NGT WHICH COULD
LINGER INTO THU...THUS STUCK WITH PREV FCST HIGHS WED NEAR 40 WHICH
IS GENERALLY BLO LATEST MOS GUIDANCE. WED NGT MINS SUPPORTED BY
LATEST MOS GUIDANCE AND EVEN IF STRATUS DVLPS COULD BE REACHED GIVEN
POTENTIAL FOR SOME LINGERING SNOW COVERED AREAS IN THE CWA.

SHRTWV SOUTH OF GULF OF ALASKA TODAY EXPECTED TO SPLIT WITH NRN
STREAM OPEN WAVE MOVG ACROSS THE NRN PLAINS THU AND GRTLKS FRI WHILE
LOW CUTS OFF OVER THE SWRN U.S.. CDFNT ASSOCIATED WITH NRN STREAM
SYSTEM SHOULD PASS THE CWA THU NGT...PSBLY ACCOMPANIED BY SOME SNOW
SHOWERS BUT MOISTURE LIMITED AND FORCING WK SO ACCUMULATION LOOKS
UNLIKELY ATTM. SOME LAKE EFFECT POTENTIAL IN WAKE OF FRONT FRIDAY AS
DELTA T'S INCREASE INTO THE MID TEENS...BUT INVERSION HEIGHT RATHER
LOW AND SUBSIDENCE/DRYING ALOFT DURING THE DAY WILL AGAIN LIKELY
RESULT IN LITTLE OR NO ACCUM.

MEDIUM RANGE MODELS CONT TO INDICATE PHASING OF SWRN CUTOFF LOW
WITH NEXT NRN STREAM TROF MOVG INTO THE PLAINS OVER THE WEEKEND. 12Z
GFS/ENSEMBLES COMING INTO BETTER AGREEMENT WITH 00Z ECMWF ON
EVOLUTION OF THIS EVENT...THOUGH ECMWF STILL A LITTLE LESS
AGGRESSIVE WITH CAA SUNDAY NIGHT/MON. NO SGFNT CHANGE TO CENTRAL
REGION HEADQUARTERS PRESCRIBED MODEL BLEND IN THE MEDIUM RANGE
TIMEFRAME WITH HIGH CHC POPS FOR RAIN SUNDAY...TRANSITIONING TO CHC
SNOW SHOWERS...MAINLY NEAR LM BY MON EVE WITH TEMPS FALLING WELL BLO
NORMAL BY MONDAY NIGHT.

AVIATION...
DETERIORATING CONDITIONS EXPECTED AT BOTH TAF SITES OVER THE NEXT
12 TO 24 HOURS...KFWA BEING FIRST AS INCREASING LOWER CIGS BEGIN
TO ARRIVE WITH NORTHWARD PUSH OF RAIN SHIELD INTO THE AREA BY
TONIGHT. AT KSBN...LOWER STRATUS DECK HAS BEEN TAKING SHAPE THIS
MORNING WITH MVFR CIGS ALREADY EXPANDING. NO SIGNS OF THIS ENDING
WITH EVENTUAL LOWERING OF CIGS LATER TONIGHT AS RAIN ARRIVES IN
THE AREA. RAINFALL WILL PERSIST THROUGH TUESDAY ACROSS BOTH SITES
WITH LIKELIHOOD OF IFR CIGS AND POCKETS OF REDUCED VSBYS. COLD AIR
WILL ARRIVE AROUND OR AFTER 00Z WEDS...BUT STILL SOME CONCERNS ON
EXACT LOW TRACK AND HOW FAST THE COLD AIR ARRIVES. THIS WILL BE
LOOKED AT FURTHER WITH 00Z ISSUANCE.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FLOOD WATCH THROUGH TUESDAY EVENING FOR INZ003>009-012>018-020-
     022>027-032>034.

MI...FLOOD WATCH THROUGH TUESDAY EVENING FOR MIZ077>081.

OH...FLOOD WATCH THROUGH TUESDAY EVENING FOR OHZ001-002-004-005-015-
     016-024-025.

LM...SMALL CRAFT ADVISORY UNTIL 4 AM EST TUESDAY FOR LMZ043-046.

     GALE WARNING FROM 4 AM TUESDAY TO 10 AM EST WEDNESDAY FOR LMZ043-
     046.

&&

SHORT TERM...FISHER
LONG TERM...JT
AVIATION...BENTLEY