FXUS63 KIWX 162036 AFDIWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 336 PM EST FRI JAN 16 2009 .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT MAIN FOCUS IN THE SHORT TERM IS TEMPS/WIND CHILLS TONIGHT AND SN/FZDZ CHANCES SAT INTO SAT NIGHT. WINDS DROPPING TO NEAR 5 KNOTS AND MAINLY CLEAR SKIES EARLY THIS EVENING WILL PROBABLY ALLOW TEMPS TO PLUMMET BACK TOWARDS -10F THIS EVENING. EXPECT SOME WARMING AFTER MIDNIGHT AS SOUTHWESTERLY LL FLOW DEVELOPS ON BACKSIDE OF 1040MB ARCTIC HIGH WHICH WILL SHIFT EASTWARD INTO THE CENTRAL APPS/MIDDLE ATLANTIC. THEREFORE...HAVE NON DIURNAL TEMPS TONIGHT WITH VALUES HOPEFULLY WARMING INTO THE SINGLE DIGITS ABV ZERO BY 12Z SAT. COLD TEMPS COMBINED WITH LIGHT SSW SFC WINDS WILL KEEP APPARENT TEMPS IN THE -15 TO -25F RANGE...SO WENT WITH A WIND CHILL ADVISORY FOR THE ENTIRE CWA THROUGH 09Z SATURDAY. SHORTWAVE CURRENTLY OVER NRN FRINGE OF HIGHLY AMPLIFIED EASTERN PAC/WESTERN NOAM RIDGE WILL RAPIDLY SLIDE SEWD INTO THE UPPER MIDWEST LATE TONIGHT...AND THE GREAT LAKES SATURDAY INTO SATURDAY NIGHT. FAVOR FARTHER NORTH AND DRIER NAM/SREF/ECMWF SOLUTIONS OVER THE GFS IN TRACKING ASSOCIATED SFC REFLECTION INTO CENTRAL LOWER MICHIGAN BY SATURDAY EVENING...AS THE NAM HAS PERFORMED BETTER FOR THE LAST SEVERAL CLIPPER EVENTS WHEN COMPARED TO THE GFS. WAA/ISENTROPIC UPGLIDE WITH 40-50KT CROSS ISOBARIC FLOW AND 2-3 G/KG MOISTURE SURGE OVER ARCTIC DOME DOES SUPPORT A BAND OF LIGHT/MODERATE SNOW PIVOTING EAST THROUGH AT LEAST FAR NORTHERN AREAS ON SATURDAY. BETTER CHANCES FOR DECENT SNOW ACCUMULATIONS IN THE 1-3 INCH RANGE APPEAR POSSIBLE IN THE COLDWATER/HILLSDALE AREAS CLOSER TO THE DEEPER MOISTURE AND BETTER DYNAMICS. MAYBE A COATING TO AN INCH IN CENTRAL AREAS WITH LITTLE IF ANY ACCUMULATION IN THE SOUTHWEST. ADDED FREEZING DRIZZLE MENTION TO WESTERN/SOUTHERN AREAS SAT AFTN/EVE AS NAM FCST SOUNDINGS CONSISTENT IN SHOWING LACK OF MOISTURE IN THE ICE PRODUCTION ZONE WITH LL MOISTURE TRAPPED UNDER A LOWERING INVERSION. SLICK SPOTS ON AREA ROADS WILL BE POSSIBLE IF THIS MATERIALIZES. OTHERWISE... IT WILL FEEL BALMY OUT BY TOMORROW AFTERNOON WITH HIGHS RECOVERING ALL THE WAY BACK INTO THE 20S. LARGE SCALE LIFT PER 5-3H Q-VECTOR CONVERGENCE AND DIFF PVA AHEAD OF H5 TROUGH AXIS SHIFTS EAST BY 00Z SUN WITH JUST LINGERING LIGHT SNOW SHOWERS/FLURRIES/PATCHY FZDZ SAT EVE. CAA BEHIND SYSTEM WILL ALLOW FOR LAKE EFFECT SNOW SHOWERS TO DEVELOP ACROSS THE FAR NW LATE SATURDAY NIGHT. CONTINUED WITH LIKELY POPS IN THESE AREAS 06-12Z SUN. DELTA T/S OF 15-18 AND SATURATION WITHIN THE DGZ INDICATE POTENTIAL FOR SOME SNOW ACCUMULATION WITH LAKE EFFECT. HOWEVER...INVERSION NEAR 5KFT AND UNFAVORABLE 280/290 DEGREE FETCH DO NOT FAVOR ACCUMS ABOVE 2 INCHES. && .LONG TERM... SUNDAY THROUGH FRIDAY... LONG TERM WILL SEE CHANGES TO LARGE SCALE UPPER AIR PATTERN OVER THE CONUS AS WESTERN RIDGE BEGINS TO BREAK DOWN AS STRONG PACIFIC ENERGY UNDERCUTS IT. TROUGHINESS OVER THE EASTERN CONUS EXPECTED TO PERSIST AS NORTHERN BRANCH OF UPPER JET REMAINS DOMINANT AND CONTINUES TO DIVE INTO THE GREAT LAKES. ECMWF AND GFS HAVE SIGNIFICANTLY DIFFERENT SOLUTIONS IN HOW THIS PATTERN WILL EVOLVE AND THEREFORE A LARGE DEGREE OF UNCERTAINTY IN THE LATTER PART OF THE LONG TERM GRIDS. BEGINNING OF PERIOD WILL SEE CLIPPER SYSTEM CROSSING AND EXITING THE AREA WITH CHANCES FOR LIGHT SNOW SUNDAY. LAKE EFFECT POTENTIAL CONTINUES BEHIND CLIPPER SUNDAY AFTERNOON AND SUNDAY NIGHT...INTO MONDAY MORNING. THIS IS AN INTERESTING SETUP AND HAS POTENTIAL FOR A DECENT SNOW EVENT ASSUMING MOISTURE REMAINS IN PLACE. LIMITING FACTOR WILL BE TRANSITORY NATURE OF BAND AND DEPTH OF MOISTURE. DUE TO LIMITING FACTORS AND QUESTIONS ON BAND PLACEMENT HAVE CONTINUED WITH HIGH CHANCE POPS RATHER THAN LIKELY OR CATEGORICAL. LATEST NAM INDICATING EVOLUTION INTO SINGLE BAND INTO FAR WESTERN COUNTIES BY MONDAY MORNING. NAM HAS ALSO STRUGGLED WITH RECENT LAKE EVENTS IN THESE PERIODS SO STILL SOME DOUBT. STAYED CLOSE TO A BLEND OF PREVIOUS GRIDS AND HPC FOR MIDDLE TO LATE PART OF LONG TERM GIVEN MODEL DIFFERENCES. ECMWF HAS BEEN MODEL OF CHOICE MOST OF WINTER AND IT IS NOT AS AGGRESSIVE WITH MID WEEK WARM UP AS GFS...WHICH SHOWS 850MB TEMPS WELL ABOVE CLIMO FOR MID JANUARY. HAVE DOUBTS AT THIS TIME ON SUCH A PRONOUNCED WARM UP GIVEN STRONG ARCTIC AIR MASS IN PLACE AND DEEP SNOW PACK THAT EXISTS. PREFER COOLER ECMWF. GRIDS AND HPC IN THE MIDDLE AND PREFER TO KEEP IT THAT WAY UNTIL CLEAR PATTERN EVOLVES. ECMWF SHOWING ANOTHER COLD ARCTIC FRONT LATE IN THE PERIOD. GFS DEVELOPING A RATHER STRONG CYCLONE BY DAY 7. AGAIN WILL STAY IN MIDDLE GROUND AND SIDE WITH HPC FOR COLLABORATION GIVEN WIDE VARIETY OF POSSIBLE SOLUTIONS. && .AVIATION...18Z TAFS VFR CONDITIONS ARE EXPECTED AT THE TAF SITES THIS AFTERNOON INTO TONIGHT AS STRONG SFC HIGH SLIDES SEWD FROM THE OH VALLEY TO THE CENTRAL APPALACHIANS. THIS WILL ALLOW WINDS TO CONTINUE TO BACK MORE TO THE SSW WITH TIME...WHICH WILL KEEP LAKE EFFECT MVFR SC DECK NORTH OF SBN. WINDS WILL LIKELY PICK UP INTO THE 14-20KT RANGE BY MID MORNING ON SATURDAY...DUE TO INCREASING SFC PRESSURE GRADIENT AHEAD OF A POTENT SHORTWAVE/CLIPPER THAT WILL BE APPROACHING THE GREAT LAKES. SOME CONCERN FOR A BRIEF BURST OF LIGHT SNOW WITH MVFR/IFR CONDITIONS AFTER 12Z SATURDAY IN ASSOCIATED STRONG WARM AIR/THETA-E ADV REGIME. DEEPER MOISTURE AND BETTER FORCING LOOKS TO STAY JUST NORTH OF TAF SITES SATURDAY MORNING...SO WILL CARRY AN OPTIMISTIC VFR FORECAST SATURDAY MORNING WITH LOWERING CIGS. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WIND CHILL ADVISORY UNTIL 4 AM EST /3 AM CST/ SATURDAY FOR INZ003>009-012>018-020-022>027-032>034. MI...WIND CHILL ADVISORY UNTIL 4 AM EST SATURDAY FOR MIZ077>081. OH...WIND CHILL ADVISORY UNTIL 4 AM EST SATURDAY FOR OHZ001-002-004- 005-015-016-024-025. LM...NONE. && $$ SHORT TERM...STEINWEDEL LONG TERM...LASHLEY AVIATION...STEINWEDEL