327 FXUS63 KIWX 040658 AFDIWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 158 AM EST MON MAR 4 2013 .AVIATION... 06Z TAFS...VFR CONDITIONS EXPECTED THROUGH MOST OF THE PERIOD AS LOW LEVEL RIDGE AXIS DEPARTS TO THE EAST. EASTERLY FLOW WILL SET UP FOR TODAY IN RESPONSE TO DEVELOPING LOW PRESSURE TO THE WEST. HIGH CIGS TO GRADUALLY LOWER TO THE 3-4K FT RANGE TOWARD THE END OF THIS PERIOD WITH -SN LIKELY OVERSPREADING NORTH CENTRAL INDIANA. CONDITIONS WILL FURTHER DETERIORATE LATE NIGHT INTO TUESDAY MORNING AS STRONG UPPER TROUGH BEGINS TO EJECT OUT OF THE NORTHERN ROCKIES. && PREV DISCUSSION... /ISSUED 422 PM EST SUN MAR 3 2013/ SHORT TERM... /TONIGHT THROUGH MONDAY NIGHT/ BENIGN WX CONCERNS THROUGH THE FCST PD. RIDGELINE INTO FAR ERN WI/IL/LOWR MS VLY TO CONT STRONG DRY AIR ADVECTION TO EFFECTIVELY OBLITERATE ANY LES RESPONSE/FLURRIES BY EVENING. CONTD BLO NORMAL TEMPS THROUGH THE PD. GRTST POTNL LONGWAVE LOSSES OVERNIGHT WITH LIGHT WINDS/SFC RDG FOR SHARP SFC BASED INVERSION TO DVLP AMONGST LIGHT RELATIVELY FRESH SNOWCOVER/SPCLY ACRS FAR NERN IN/SCNTL LWR MI. THEREAFTER...MODEST SHORT AMPLITUDE NRN STREAM RIDGING INADVOF MORE VIGORED ERN MT WAVE PROGRESSING ESEWD AND LATER ENCAPSULATING RAPIDLY ZONAL WAVE CRNTLY ACRS NV. MIDTROPOSPHERIC WAVE UNDERGOES SUBSTANTIAL DEEPENING/COALESCENCE ACRS ERN NE/WRN IA BY 12 UTC TUE PER 100-140M/12 HR HGHT FALLS THAT CONT TO BLOSSOM TO NEAR 200 M/12 HR INTO OHIO VLY DURING THE DAYTIME TUE. PRIMARILY ANTICIPATE LWRG OF LYRD MSTR WITH SUBCLOUD DRY WEDGE SLOW TO ACQUIESCE TO PRECIP ALOFT. ONLY SOME MINOR/LESSER CONCERN FOR SLEET/PARTIAL MELT SHOULD WARM LYR REACH NAM INDICATED PROPORTIONS...OTHERWISE PRIMARILY LIGHT SN EVENT UNTIL 12 UTC WITH MUCH WORK NEEDED AGAINST 100-200MB 925 COND PRES DEFICITS SPCLY ACRS NERN TWO THIRDS OF CWA AT F36/00 UTC TUE. LONG TERM... /TUESDAY THROUGH SUNDAY/ FOCUS OF FORECAST REMAINS ON WINTER PRECIP CHANCES/TYPE/AMOUNTS DURING THE FIRST 24 TO 36 HOURS OF THE PERIOD. ALL IN ALL MODELS NOT VERY DIFFERENT IN TERMS OF UPPER LOW LOCATION AT 12Z TUES WITH FEATURES SOMEWHERE VCNTY OF W IOWA WITH MODELS DIVERGING IN UPPER LEVEL FEATURES BY 6Z WEDS SOMEWHERE BETWEEN CENTRAL KENTUCKY AND NORTHERN TENNESSEE. SURGE OF WARM AIR IN LOW LEVELS AHEAD OF THE SYSTEM WILL RAISE HAVOC WITH PTYPE AT THE START OF THE PERIOD WITH SOUNDINGS INDICATING POTENTIAL FOR SLEET OR POSSIBLY FREEZING RAIN THROUGH LATE MORNING BEFORE COLDER AIR ARRIVES AND PRECIP SWITCHES TO ALL SNOW. DID INCREASE POPS TO CATEGORICAL SW TUES MORNING AND ALL AREAS BY TUES AFTERNOON WITH ALL SIGNS CONTINUING TO POINT TOWARDS EVERYONE SEEING AT LEAST A PERIOD OF MEASURABLE PRECIP. FOR THE TIME BEING HAVE INTRODUCED SLEET INTO SOUTHERN AREAS TUES MORNING. BY FAR THE BEST FORCING AND AT LEAST A PORTION OF DGZ INTERACTION TAKES PLACE TUES AFTERNOON INTO TUESDAY EVENING ACROSS THE AREA. BY THIS POINT ALL PRECIP SHOULD BE SNOW AND COULD BE FALLING AT A DECENT CLIP. SFC TEMPS MAY STILL BE AROUND FREEZING DURING THE AFTERNOON WHICH MAY LIMIT IMPACTS INITIALLY BUT EVENTUALLY SNOW COVERED ROADS AND REDUCED VSBYS WILL SETTLE IN. ECMWF REMAINS MOST SOUTHERLY SOLUTION COMPARES TO GEFS/GFS/NAM/SREF WITH THESE ALL LINGERING PRECIP WELL INTO TUES NGT AND EVEN FIRST PART OF WEDS. PREV FORECAST AMOUNTS STILL GENERALLY ON TRACK WITH A GENERAL 3 TO 6 INCHES ACROSS THE AREA FROM LATE MONDAY NIGHT THROUGH TUESDAY NIGHT. HEAVIEST AMOUNTS ARE PRESENTLY IN SW AREAS WHERE FORCING WILL BE MAXIMIZED THE LONGEST. HOWEVER THESE SAME AREAS COULD SEE REDUCED SNOW ACCUMS...BEING REPLACED BY SLEET OR EVEN FREEZING RAIN. AFTER IN HOUSE AND SURROUNDING OFFICE COORDINATION...HAVE DECIDED TO HOLD OFF ON A WATCH AND WILL ISSUE SPS TO HIGHLIGHT MULTIPLE CONCERNS AND UNCERTAINTY OF FORECAST. LITTLE IN THE WAY OF DETAIL OR CHANGES BEYOND WEDS GIVEN FOCUS ON MAIN SYSTEM. WARMER WEATHER WILL BUILD IN INTO THE WEEKEND. EXACTLY HOW FAST THE WARM AIR CAN BE REALIZED WILL DEPEND ON AMOUNT OF SNOW COVER AND EVENTUAL SUNSHINE. HYDRO CONCERNS COULD POTENTIALLY UNFOLD WITH RUNOFF OF NEW PRECIP/MELTING SNOWPACK WEDS INTO FRIDAY. CONSIDERING NO ADDITIONAL PRECIP IS EXPECTED THROUGH AT LEAST FRIDAY NIGHT AND RIVERS ARE ALL WELL BELOW ANY SORT OF ACTIONABLE LEVELS WILL SIMPLY MAKE MENTION IN HWO. COLD FRONT WILL BE MOVING TOWARDS THE AREA OVER THE WEEKEND. MODELS ARE BECOMING A BIT MORE AGGRESSIVE ON MSTR RETURN AHEAD OF THE FRONT...BUT GENERALLY KEEP BEST CHANCES FOR LARGER SYSTEM INTO NEXT WEEK. WILL RUN WITH SLGT CHC/CHC POPS INHERITED FOR SAT/SAT NGT BUT KEEP SUN DRY FOR NOW. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...MURPHY LONG TERM...FISHER AVIATION...MARSILI