Area Forecast Discussion
Issued by NWS Northern Indiana

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000 FXUS63 KIWX 070446 AFDIWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1246 AM EDT TUE JUL 7 2015 .SYNOPSIS... ISSUED AT 703 PM EDT MON JUL 6 2015 A COLD FRONT OVER THE UPPER MIDWEST AND PLAINS WILL MOVE EAST ACROSS OUR AREA OVERNIGHT INTO TUESDAY. SHOWERS AND A FEW THUNDERSTORMS ARE EXPECTED TO ACCOMPANY THE FRONT AS IT MOVES THROUGH THE AREA. LOWS TONIGHT WILL BE IN THE UPPER 60S AND LOWER 70S WITH HIGHS TOMORROW REMAINING IN THE 70S BEHIND THE FRONT. && .SHORT TERM...(THIS EVENING THROUGH TUESDAY) ISSUED AT 344 PM EDT MON JUL 6 2015 CONSOLIDATING POSITIVELY-TILTED LONGWAVE TROUGH EXTENDING FROM HUDSON BAY CLOSED LOW CONTINUES TO SLOWLY PUSH EAST AND THE ASSOCIATED COLD FRONT IS THE MAIN FEATURE OF NOTE FOR THIS SHORT TERM FORECAST. BEST CVA FORCING PASSES WELL TO OUR NORTH BUT MODELS STILL INDICATE DECENT MIDLEVEL HEIGHT FALLS GENERATING A HEALTHY (BY JULY STANDARDS ANYWAY) STRIPE OF LOW LEVEL (925-850MB) CONVERGENCE AND FRONTOGENESIS...AIDED TO SOME DEGREE BY NORTHERN LAKES UPPER JET STREAK. THIS COMBINED WITH A STRONG...ALBEIT NARROW...SURGE OF DEEP TROPOSPHERIC MOISTURE JUST AHEAD OF THE FRONT WILL SET THE STAGE FOR NUMEROUS SHOWERS AND THUNDERSTORMS LATE TONIGHT INTO TOMORROW. LATEST REGIONAL SURFACE OBS SHOW ACTUAL SURFACE BOUNDARY STILL WELL UPSTREAM ACROSS CENTRAL IOWA AND WISCONSIN. THERE IS HOWEVER A LINE OF CONVECTION MOVING THROUGH THE CHICAGO AREA ASSOCIATED WITH PREFRONTAL COLD POOL/OUTFLOW FROM OLD REMNANT MCS THAT HI- RES/CONVECTION-ALLOWING MODELS HAVE STRUGGLED ALL DAY TO CAPTURE. THIS ACTIVITY WILL MAKE A RUN FOR OUR WESTERN COUNTIES THIS EVENING BUT SHOULD CONTINUE TO SLOWLY FIZZLE OUT AS IT SHIFTS EAST. CONVECTIVE LINE IS ALREADY LOOKING OUTFLOW DOMINANT AND VERY RAGGED PER LATEST KLOT RADAR IMAGERY AND CONTINUES TO MOVE WELL OUT AHEAD OF MAIN SYNOPTIC SUPPORT. 12Z KILX AND KDTX UPPER AIR SOUNDINGS ALSO SHOWED A VERY DRY AND CAPPED ENVIRONMENT THAT HAS BEEN SLOW TO DISLODGE DUE TO WESTWARD DISPLACEMENT OF BETTER LLJ AND MOISTURE FLUX CONVERGENCE. SPC/RAP MESOANALYSIS CONFIRM THIS WITH MUCH DRIER AND MORE STABLE CONDITIONS OVER LOWER MICHIGAN AND NORTHERN INDIANA. A FEW DECAYING SHOWERS/STORMS MAY SNEAK INTO OUR WESTERN ZONES THIS EVENING BUT STILL EXPECT MUCH BETTER CHANCES FOR RAIN TO HOLD OFF UNTIL AROUND MIDNIGHT TONIGHT. ONLY REAL CHANGE TO GOING FORECAST WAS TO BUMP UP TIMING A BIT BASED ON LATEST GUIDANCE AND UPSTREAM OBS. STILL THINK JUST LIKELY POPS APPROPRIATE FOR OUR CWA...GIVEN FRONTAL PASSAGE DURING DIURNAL INSTABILITY MINIMUM. SEVERAL HI-RES MODELS HAVE LITTLE MORE THAN SCT SHOWERS AND WITH A LACK OF SUBSTANTIAL FORCING ALOFT...NOT COMFORTABLE GOING CATEGORICAL. SEVERE WEATHER RISK IS VERY LOW BOTH TONIGHT AND TOMORROW. POOR DIURNAL TIMING AND PALTRY MIDLEVEL LAPSE RATES LIMIT AVAILABLE INSTABILITY AND DEEP LAYER SHEAR IS 15 KTS OR LESS AHEAD OF THE FRONT. SLIGHT CHANCE FOR AN ISOLATED STRONG STORM SOUTH OF US-24 TOMORROW GIVEN SLIGHTLY LATER FRONTAL PASSAGE BUT EVEN THEN...BETTER SBCAPE VALUES REMAIN CONFINED SOUTHEAST OF OUR CWA BORDER. BRIEF HEAVY RAIN POSSIBLE GIVEN PW VALUES AOA 2 INCHES IMMEDIATELY ALONG FRONT BUT LACK OF GOOD INSTABILITY AND STRONG FORCING SUGGEST ANY HEAVIER RAINFALL RATES/AMOUNTS WILL BE ISOLATED. NOT EXPECTING MANY FLOODING ISSUES THANKS TO RECENT STRETCH OF DRY WEATHER. && .LONG TERM...(TUESDAY NIGHT THROUGH MONDAY) ISSUED AT 344 PM EDT MON JUL 6 2015 COLD FRONT SHOULD EITHER BE THROUGH THE FORECAST AREA OR CONFINED TO FAR S/SE SECTIONS AT THE START OF THE PERIOD. MAY BE A FEW LINGERING SHOWERS OR STORMS IN ITS WAKE BUT MAJORITY OF TUESDAY NIGHT INTO FIRST PART OF WEDNESDAY SHOULD BE DRY. WHILE 12Z GFS/ECMWF ARE SIMILAR IN DEPICTION OF SERIES OF UPPER LEVEL DISTURBANCES...SURFACE FEATURES VARY SOMEWHAT WITH ECMWF/09Z SREF/12Z NAM12 ALL SHOWING FURTHER NORTH TRACK WITH VARYING AMOUNTS OF QPF WEDS NGT INTO THURS AND ECMWF AGAIN THURS NGT INTO FRIDAY. WITH GROUND STILL VERY WET TO SATURATED HYDRO CONCERNS COULD QUICKLY MATERALIZE. SINCE ANY OF THE SOLUTIONS ARE PLAUSIBLE AND CONFIDENCE IN ANY ONE LOW (CONSIDERING HOW MODELS ARE HANDLING TODAY`S CONVECTION) NOT COMFORTABLE MAKING ANY MAJOR CHANGES. MESOSCALE INFLUENCES ARE LIKELY TO WRECK HAVOC ON THE FRONTAL POSITION AND POTENTIAL TRACKS OF ANY COMPLEXES...RESULTING IN LOW TO MODERATE CONFIDENCE OF ADDITIONAL RAINFALL BUT LOW CONFIDENCE ON WHERE IT OCCURS. HAVE BLENDED HALF PREVIOUS FORECAST AND HALF SUPERBLEND OF MODELS WHICH COMES UP WITH A COMPROMISE. TEMPERATURES SHOULD HOLD BELOW NORMAL INTO FRIDAY BUT LOW LEVEL FLOW WILL INCREASE AND ALLOW HIGHS TO CLIMB BACK NEAR OR SLIGHTLY ABOVE NORMAL LEVELS. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 1235 AM EDT TUE JUL 7 2015 CDFNT OVER NWRN IL WILL MOVE EAST ACROSS NRN INDIANA TODAY. ALTHOUGH CONVECTION IN THE FRONTAL ZONE TO OUR WEST HAS BEEN WKNG EARLY THIS MORNING... EXPECT INCREASE IN COVERAGE OF SHRA/TS DURING THE DAY TUE WITH GREATEST IMPACT AT FWA WHERE FROPA LIKELY WILL HOLD OFF UNTIL AFTN. CONTD WITH JUST VCTS MENTION IN THE FWA TAF AS CLOUD COVER SHOULD LIMIT DESTABILIZATION ACROSS NRN INDIANA. IFR/MVFR CONDITIONS IN THE FRONTAL ZONE UPSTREAM ATTM AND EXPECTED TO MOVE THROUGH NRN INDIANA DURING THE DAY. CONDITIONS SHOULD IMPROVE LATE TUE AFTN/EVE AS HIGH PRESSURE BUILDS INTO THE UPR GRTLKS. IMPROVEMENT WILL BE SLOWER AT FWA HWVR AS FRONT TAKES ON A MORE E-W ORIENTATION TONIGHT. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...BEACH HAZARDS STATEMENT FROM 7 AM CDT TUESDAY THROUGH TUESDAY EVENING FOR INZ003. MI...BEACH HAZARDS STATEMENT FROM 8 AM EDT THIS MORNING THROUGH THIS EVENING FOR MIZ077. OH...NONE. LM...SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO MIDNIGHT EDT TONIGHT FOR LMZ043-046. && $$ SYNOPSIS...LASHLEY SHORT TERM...AGD LONG TERM...FISHER AVIATION...JT 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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