Area Forecast Discussion
Issued by NWS Northern Indiana

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000 FXUS63 KIWX 310552 AFDIWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 152 AM EDT TUE MAR 31 2015 .SYNOPSIS... ISSUED AT 145 AM EDT TUE MAR 31 2015 DRY WEATHER WILL RETURN TODAY AS THE CLIPPER SYSTEM...THAT BROUGHT SOME LIGHT RAIN TO THE REGION MONDAY NIGHT INTO EARLY THIS MORNING...MOVES TO THE MID ATLANTIC REGION. TEMPERATURES WILL BE A BIT COOLER THAN YESTERDAY...BUT SHOULD STILL MAINLY REACH INTO THE 50S. LOWS TONIGHT WILL DIP BACK INTO THE 30S. && .UPDATE... ISSUED AT 942 PM EDT MON MAR 30 2015 EVENING UPDATE SENT MAINLY TO ACCOUNT FOR POP TRENDS. LEAD ISENTROPIC LIFT(FGEN)/LOW LEVEL THETAE SURGE HAS BEEN SUFFICIENT FOR LIGHT RAIN ACROSS FAR NORTHERN INDIANA THIS EVENING DESPITE FAIRLY DRY LOWEST 4K FT. NAM ISENTROPIC PROGS SUGGEST RISING CPDS AFTER MIDNIGHT IN THE WAKE OF THIS LEADING ISENTROPIC LIFT/FGEN FORCING...AND HAVE GENERALLY FOLLOWED PREVIOUS FORECAST IDEA OF DECREASING POPS FROM SOUTHWEST TO NORTHEAST. ONLY OTHER TWEAK WAS TO MODIFY WINDS FOR A SLIGHTLY SOUTHWARD ADJUSTED LOW TRACK BASED ON CURRENT TRENDS...BUT OTHERWISE NO SIGNIFICANT CHANGES TO FORECAST ELEMENTS. && .SHORT TERM...(THIS EVENING THROUGH TUESDAY) ISSUED AT 340 PM EDT MON MAR 30 2015 UPPER LEVEL JET STREAK WILL TRANSITION INTO THE GREAT LAKES TONIGHT AND SEND A STRENGTHENING MIDLEVEL VORT MAX THROUGH THE REGION. TIGHT BAROCLINIC ZONE IS ALREADY IN PLACE OVER THE GREAT LAKES AND THIS WAVE WILL INCITE A GOOD 850MB FRONTOGENETIC RESPONSE...ESPECIALLY GIVEN REDUCED STABILITY ABOVE THIS LAYER. TRACK IS NOT FAVORABLE FOR MOST OF OUR CWA THOUGH. ACTIVE FRONTAL ZONE WILL BE DRAPED ACROSS CENTRAL MICHIGAN AND ONLY CLIPS OUR FAR NORTHEAST COUNTIES. STILL SOME DISAGREEMENT AMONG LATEST NWP WITH RESPECT TO EXACT TRACK AND THIS WILL HAVE A LARGE EFFECT ON HOW MUCH OF OUR CWA SEES PRECIP GIVEN VERY SHARP CUTOFF TO FORCED ASCENT. KEPT OVERALL SPIRIT OF PREVIOUS FORECAST BUT DID INCREASE POPS OVER OUR NORTHEAST HALF BASED ON LATEST HI-RES GUIDANCE. AREAS SOUTH OF US-30 MAY REMAIN COMPLETELY DRY. FORECAST SOUNDINGS SHOW LOWEST 2 KFT IS WARM ENOUGH TO SUPPORT AN ENTIRELY RAIN EVENT IN AREAS THAT DO SEE PRECIP. NOT IMPOSSIBLE THAT OUR FAR NORTHEAST COULD SEE A BRIEF MIX DUE TO WET BULB EFFECTS BUT CHANCES AND IMPACTS ARE TOO LOW FOR INCLUSION IN THE FORECAST. RAIN SHOULD EXIT BY TOMORROW MORNING WITH DRIER AIR RETURNING TO THE REGION. LOWS TONIGHT WILL PROBABLY STAY ON THE WARM SIDE GIVEN INCREASING SOUTHWEST GRADIENT WITH PASSING SURFACE LOW. NUDGED INHERITED FORECAST UP JUST A BIT. HIGHS TOMORROW WILL BE SLIGHTLY COOLER THAN TODAY GIVEN BRIEF RETURN TO NNW FLOW/CAA. DECENT MIXING DEPTHS UNDER INCREASING SUN WILL AT LEAST PARTIALLY OFFSET CAA THOUGH AND HIGHS IN OUR SOUTHWEST COULD STILL REACH THE UPPER 50S. && .LONG TERM...(TUESDAY NIGHT THROUGH MONDAY) ISSUED AT 340 PM EDT MON MAR 30 2015 TRANSITION TO A MORE BONA-FIDE SPRING PATTN XPCD THIS PD W/LONGER TERM SUGGESTIONS OF GENERAL WKNG OF NEG HGT ANOMALIES UP ACRS ERN CANADA AND MORE TROUGHING ACRS THE WRN US BOTH OF WHICH HAVE BEEN LAGGING FOR SVRL MONTHS. BEGINNING OF PD LOOKS STELLAR W/SIG LL THERMAL MODERATION AHD OF POTENT NRN STREAM SW SWEEPING THROUGH SRN CANADA. SWWD TRAILING FNTL BNDRY ASSOCD/W THIS SYS LOOKS ACTIVE THU AFTN TIMED W/NWD REACH OF LL GOMEX MSTR RTN AND PERHAPS SOME RISK FOR THUNDER. HWVR WILL AWAIT LTR GUIDANCE AS FNTL TIMING MAY BE POOR W/LIMITED SFC BASED DESTABILIZATION AND EXTENT OF NWD MOISTENING. TAIL END OF UPR LVL DISTURBANCE EJECTS EWD FRI W/SFC WAVE XPCD TO DVLP INVOF THE OH RVR VALLEY. NWD REACH OF POTENTIAL OVERRUNNING PCPN SHIELD ASSOCD/W THIS SYS STILL QUITE UNCERTAIN AND KEPT W/SUBDUED N-S POP GRADIENT. UNSETTLED PATTN LOOKS TO INCREASE THROUGH NXT WEEK W/TEMPS MODERATING TO AOA NORMAL. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 153 AM EDT TUE MAR 31 2015 VEERING LOW LEVEL JET NOW TRAVERSING NRN IN. GAVE SOME GREATER DETAIL WITH RESPECT TO SHIFTING 2KFT FLOW NEXT FEW HOURS. STILL SOME CONCERN WITH WINDOW OF HIGH END MVFR CIGS...SPCLY AT KSBN WITH ONSET OF CU FIELD GENERATION LATER THIS AM. HOWEVER...GIVEN QUITE LOW POTNL FOR SIGNIFICANCE/BLO 2KFT CIG HGHTS...WILL DEFER TO LATER HIER RES GUID FOR 12 UTC ISSUANCE. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ UPDATE...MARSILI SYNOPSIS...AGD SHORT TERM...AGD LONG TERM...T AVIATION...MURPHY 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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