Area Forecast Discussion
Issued by NWS Northern Indiana

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000 FXUS63 KIWX 230005 AFDIWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 705 PM EST MON DEC 22 2014 .SYNOPSIS... ISSUED AT 1127 AM EST MON DEC 22 2014 TWO LOW PRESSURE SYSTEMS WILL MOVE THROUGH THE AREA THIS WEEK...BRINGING RAIN AND SNOW TO THE REGION. EXPECT RAIN AND DRIZZLE OVERNIGHT TONIGHT AND TUESDAY. ON WEDNESDAY...EXPECT RAIN TO CONTINUE BEFORE CHANGING OVER TO SNOW LATE IN THE AFTERNOON. SNOW IS EXPECTED WEDNESDAY NIGHT. HIGHS WILL BE IN THE 40S. && .SHORT TERM...
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(THIS EVENING THROUGH TUESDAY) ISSUED AT 408 PM EST MON DEC 22 2014 AREA OF RAIN ASSOCIATED WITH LOW LEVEL THETA-E ADVECTION/ISENT LIFT/MOISTURE CONVERGENCE AHEAD OF DEEPENING CENTRAL PLAINS LOW SHOULD CONT TO OVERSPREAD OUR CWA FROM WEST-EAST LATE THIS AFTN/EVE. ANOTHER BATCH OF WIDESPREAD RAIN EXPECTED OVERNIGHT AS VORT MAX ROTATING AROUND THE UPR LOW LIFTS NE THROUGH NRN IL AND OCCLUDING SFC FRONT APPROACHES FROM THE WEST. RAINFALL SHOULD BE LIFTING NE OUT OF OUR CWA TUE MORNING AS DRY SLOT WRAPPING AROUND THE LOW SPREADS NE INTO OUR AREA. LOW LEVELS WILL LIKELY REMAIN SATURATED WITH SOME WK LIFT CONTG UNTIL OCCLUDED FRONT PASSES... SO EXPECT SOME LIGHT RAIN OR DRIZZLE WILL PERSIST UNTIL MIDDAY...ESPECIALLY ACROSS NRN/ERN PORTIONS OF CWA. WITH WARM FRONT MOVG THROUGH THE AREA THIS PERIOD... TEMPS SHOULD CONT ON A SLOW CLIMB OVERNIGHT AND TUE... REACHING HIGHS IN THE M-U40S TUE AFTN.
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&& .LONG TERM...
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(TUESDAY NIGHT THROUGH MONDAY) ISSUED AT 408 PM EST MON DEC 22 2014 ...MAIN FOCUS OF THE LONG TERM IS THE STORM SYSTEM EXPECTED CHRISTMAS EVE... UNFORTUNATELY NEW MODEL RUNS CONTINUE TO DISAGREE ON THE SECONDARY SFC LOW TRACK FOR CHRISTMAS EVE/CHRISTMAS DAY. THE 12Z GFS/GEM HAVE A STRONGER SYSTEM MOVING FROM KY AT 12Z WED...TO NE IN/NW OH BY 18Z WED...AND THE THUMB REGION/LAKE HURON BY 00Z THU. THE 00Z ECMWF/12Z NAM HAVE A WEAKER SURFACE LOW ALONG THE GULF 12Z WED WITH A TROUGH ACROSS THE OHIO VALLEY...THEN DEVELOP THE SURFACE LOW AND LIFT IT INTO KY BY 18Z WED...WITH THE ECMWF A BIT STRONGER WITH THE LOW. AT 00Z THU BOTH MODELS HAVE THE SURFACE LOW SITUATED OVER WESTERN OHIO...WITH THE NAM A BIT FURTHER NORTH. ALL OF THE MODELS HAVE A CLOSED/CUT OFF LOW AND NEGATIVELY TILTED TROUGH IN THE MID LEVELS...THOUGH THE NAM IS THE OUTLIER KEEPING THE CUT OFF LOW OVER SOUTHERN ILLINOIS VERSUS THE GEM/GFS/ECMWF HAVE IT OVER SW LOWER MI. AS MENTIONED IN PREVIOUS DISCUSSIONS...WITH THE DEEPENING LOW AND THE NEGATIVELY TILTED TROUGH WANT TO LEAN TOWARDS THE SLIGHTLY WESTWARD SOLUTIONS OF THE GEM/GFS. OVERALL WENT WITH A GEM/GFS/ECMWF COMPROMISE GIVEN THESE SIGNIFICANT DIFFERENCES. TUESDAY NIGHT AS THE FIRST SYSTEM MOVES OUT CUT POPS FOR THE FIRST SIX HOURS AS DRY SLOT MOVES OVER THE AREA. AFTER 6Z HAVE INCREASING TRENDS AGAIN AS SECONDARY LOW APPROACHES THE AREA. EXPECT RAIN THROUGH THE LATE AFTERNOON ACROSS A MAJORITY OF THE CWA BEFORE THE CHANGE OVER TO SNOW OCCURS...STARTING IN THE NORTHWEST NEAR LAKE MI. EXPECT A MAJORITY OF THE SNOW ACCUMULATION TO BE IN THE 00Z TO 6Z TIME FRAME AS TEMPERATURES FALL AND THE DEFORMATION ZONE OF THE DEEPENING LOW SWINGS OVERHEAD. GENERALLY THINK THE GOING FORECAST OF 1 TO 3 INCHES IS STILL ON TRACK...MAINLY IN THE WEST AND CENTRAL CWA GIVEN MIXED PRECIP/WARM GROUND CONCERNS WHEN THE FORCING IS STRONGEST. AGAIN THOUGH...UNCERTAINTY REMAINS AS TO WHERE THE STRONGEST FORCING WILL BE. TAKING A QUICK PEEK AT THE 12Z ECMWF...IT HAS COME IN LINE CLOSER TO THE GEM/GFS SOLUTIONS...WHICH MAY FORCE THE AXIS OF HEAVIER PRECIP FURTHER TO THE NORTHWEST. THOSE TRAVELING ON CHRISTMAS EVE SHOULD CONTINUE TO MONITOR THE LATEST FORECASTS.
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&& .AVIATION...
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(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING) ISSUED AT 659 PM EST MON DEC 22 2014 LARGE AREA OF RAIN ALG NOSE OF STG ISENTROPIC LIFT/LL MSTR SURGE WAS OVERSPREADING CWA THIS EVENING W/SWWD EXPANSION NOTED IN REGIONAL COMPOSITE IMAGERY. MVFR CONDS TO START WILL DETERIORATE GOING FWD OVERNIGHT W/AT LEAST IFR CONDS REALIZED AFT MIDNIGHT AND FURTHER REDUCTION TO LIFR LIKELY TWD DAYBREAK GIVEN UPSTREAM OBSERVATIONAL TRENDS OVR SE MO/WRN IL.
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&& .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...MCD SHORT TERM...JT LONG TERM...MCD AVIATION...T VISIT US AT WWW.WEATHER.GOV/IWX (ALL LOWER CASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSNORTHERNINDIANA WWW.TWITTER.COM/NWSIWX WWW.YOUTUBE.COM/NWSNORTHERNINDIANA

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