Area Forecast Discussion
Issued by NWS Northern Indiana

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS63 KIWX 231814 AFDIWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 114 PM EST SUN NOV 23 2014 .SYNOPSIS... ISSUED AT 410 AM EST SUN NOV 23 2014 A STORM SYSTEM WILL ORGANIZE ACROSS THE CENTRAL UNITED STATES TODAY AND WILL BRING A WIDESPREAD RAINFALL TO THE REGION FROM LATE THIS AFTERNOON THROUGH MONDAY MORNING. RAIN SHOWERS WILL CHANGE TO SNOW SHOWERS MONDAY AFTERNOON AS COLDER AIR RUSHES INTO THE AREA BEHIND THIS SYSTEM. SOME LIGHT SNOW ACCUMULATIONS WILL BE POSSIBLE FROM MONDAY AFTERNOON INTO TUESDAY MORNING...MAINLY ACROSS PORTIONS OF NORTHWEST AND NORTH CENTRAL INDIANA...ALONG WITH SOUTHERN LOWER MICHIGAN. HIGH TEMPERATURES TODAY WILL REACH MAINLY INTO THE MID 50S. TEMPERATURES WILL NOT DROP MUCH TONIGHT...WITH LOWS FROM THE UPPER 40S TO LOWER 50S. && .SHORT TERM...(TODAY AND TONIGHT) ISSUED AT 410 AM EST SUN NOV 23 2014 FORECAST ITEMS TO ADDRESS FOR THE SHORT TERM WILL BE EVOLUTION OF ONGOING RAIN THIS MORNING...AND THEN A MORE WIDESPREAD RAINFALL EVENT FOR LATE THIS AFTERNOON AND TONIGHT. A RELATIVELY NARROW ZONE OF 900-750 HPA MOISTURE CONVERGENCE HAS SUPPORTED AN AREA OF RAIN THAT HAS AFFECTED PRIMARILY SOUTHEAST HALF OF THE AREA DURING MOST OF THE OVERNIGHT HOURS. SHORT TERM NAM/RAP PROGS SUGGEST THAT MAGNITUDE OF THIS MOISTURE CONVERGENCE SHOULD GRADUALLY WANE OVER NEXT FEW HOURS AND LIFT TO THE NORTHEAST. THIS IDEA IS SUPPORTED WELL IN HIGHER RES ARW/NMM OUTPUT THIS MORNING. THUS WILL CARRY CATEGORICAL POPS OVER THE NEXT FEW HOURS ACROSS THE SOUTHEAST...WITH A FAIRLY STEADY DOWNWARD TREND IN POPS TOWARD DAYBREAK. DAYBREAK SHOULD ALSO MARK THE APPROXIMATE TIME WEAK VORT MAX EVIDENT IN WATER VAPOR IMAGERY ACROSS SOUTHWEST LOWER MICHIGAN DEPARTS TO THE EAST. THUS...STILL EXPECTING A SIZABLE LULL IN GREATER PRECIP COVERAGE FROM EARLY THIS MORNING THROUGH AT LEAST EARLY AFTERNOON WITH RELATIVELY WEAK FORCING. BY MID TO LATE AFTERNOON...LOW LEVEL MOISTURE TRANSPORT SHOULD STRENGTHEN ONCE AGAIN AS VIGOROUS UPPER LEVEL SHORT WAVE ACROSS THE LOWER MS VALLEY BEGINS TO LIFT NORTH-NORTHEASTWARD. INITIAL HIGHER POPS LATER THIS AFTERNOON MAY BE CONFINED TO A RELATIVELY NARROW ZONE AND DEPEND ON EXACT POSITIONING OF STRONGEST LOW LEVEL MOISTURE TRANSPORT. HOWEVER...TOWARD EVENING...GUIDANCE IS STILL IN GOOD AGREEMENT IN DEPICTING SYNOPTIC SUPPORT INCREASING AS SMALLER SCALE UPPER VORT MAX TRACKS INTO OHIO VALLEY...AND LARGER SCALE UPPER TROUGH WORKS ACROSS CENTRAL CONUS. COUPLED UPPER JET STRUCTURE ALSO SHOULD TEND TO AID IN EXPANDING RAIN SHOWER COVERAGE BY EARLY THIS EVENING. NO CHANGE TO CATEGORICAL POPS FROM LATE AFTERNOON THROUGH THE EVENING WITH SOME RESPECTABLE RAINFALL AMOUNTS OF AROUND AN INCH POSSIBLE BY DAYBREAK MONDAY. MOST OF THIS RAIN SHOULD OCCUR IN THE 22Z-06Z TIMEFRAME AS STRONGER UVM SHIFTS NORTHEAST OF THE AREA OVERNIGHT WITH PASSAGE OF INITIAL SHORT WAVE. POCKET OF SLIGHTLY DRIER LOW/MID LEVEL AIR BEHIND THIS FEATURE WILL BE SHORT LIVED AS LARGER SCALE TROUGH APPROACHES FROM THE WEST WITH MORE WIDESPREAD RAIN SPREADING BACK INTO THE AREA TOWARD DAYBREAK MONDAY. GIVEN STRONG LLJ/UPPER DYNAMICS/MOISTURE TRANSPORT...REALLY CANNOT RULE OUT ISOLD THUNDER ANY TIME FROM LATE THIS AFTERNOON THROUGH TONIGHT BUT PROBABILITIES STILL APPEAR TO BE VERY LOW FOR ANY GIVEN LOCATION AND WILL NOT ADD ANY MENTION AT THIS TIME. PERHAPS THE BEST CHANCE OF ISOLD THUNDER WILL BE VERY LATE TONIGHT ACROSS THE WEST WHERE DIFFERENTIAL TEMP ADVECTION SHOULD SETUP POCKET OF WEAK INSTABILITY FROM NORTHERN ILLINOIS INTO NORTHWEST INDIANA. IN TERMS OF TEMPERATURES....HIGHS TODAY SHOULD REACH INTO THE LOWER TO MID 50S...WITH NEARLY STEADY TEMPERATURES TONIGHT DUE TO CONTINUED WAA/LLJ/CLOUD COVER. && .LONG TERM...(MONDAY THROUGH SATURDAY) ISSUED AT 410 AM EST SUN NOV 23 2014 MAIN FOCUS REMAINS ON PTYPE/STRONG WINDS/FALLING TEMPS WITH DYNAMIC PHASED LOW LIFTING THROUGH THE GREAT LAKES REGION MONDAY-MONDAY EVENING. UNSEASONABLY CHILLY/DRIER THEREAFTER... 00Z GUIDANCE OVERALL PICKING UP ON STRONGER SHEARED SHORTWAVE ENERGY NOW INTO THE FOUR CORNERS IN LEFT EXIT REGION OF A 140 KT UPPER JET. THE RESULT HAS BEEN A TREND TOWARD A MORE ROBUST DEFORMATION/FGEN AXIS LIFTING NE THROUGH THE MID MS VALLEY/WESTERN LAKES MON-MON EVE AS THIS JET COUPLING/SHORTWAVE ENERGY ROUNDS THE BASE OF AN AMPLIFYING CENTRAL CONUS LONGWAVE TROUGH. STRONG COLD ADVECTION FOLLOWING THE PASSAGE OF THE SYSTEM COLD FRONT SHOULD ALLOW RAIN TO CHANGE OVER TO SNOW WITHIN THIS BURGEONING DEFORMATION AXIS MON AFTN. FAVORED ECMWF/GFS GUIDANCE SUGGEST THAT THIS FEATURE WILL PIVOT INTO OUR NORTHWESTERN ZONES DURING THIS TIME WITH LIGHT ACCUMULATIONS POSSIBLE...ESPECIALLY SW LOWER MI THANKS TO LAKE ENHANCEMENT. MID LEVEL DRY SLOT SHOULD IMPINGE ON SOUTHEASTERN ZONES SUPPORTING A DOWNTREND IN RAIN SHOWER COVERAGE DURING THE DAY...WITH LATER CHANGEOVER TO LIGHT SNOW SHOWERS/FLURRIES (LITTLE TO NO ACCUM) DELAYED TO LATE MON EVE HERE AS PRIMARY HEIGHT FALL AXIS SETTLES IN. HEADLINE WORTHY WIND GUSTS (>45 MPH) ALSO REMAINS A POSSIBILITY FOR THE ENTIRE CWA BY LATER MON MORNING-AFTN. STILL CONSIDERABLE DIFFERENCES NOTED IN GUIDANCE ON JUST HOW DEEP SFC REFLECTION WILL BE ONCE REACHING THE NRN LAKES...RESULTING IN SOME UNCERTAINTY. IMPRESSIVE PRESSURE RISES AND SLIGHT DEEPENING OF MIXED LAYER IN RESPONSE TO THE COLD ADVECTION PROCESS MAY BE ENOUGH TO TAP INTO 40-50 KT 900 MB JET CORE (LOW CONFIDENCE). COLD/MOIST CYCLONIC FLOW WITHIN DEEP LAYERED EASTERN CONUS TROUGH AXIS WILL KEEP CLOUDS AND SPORADIC SNOW SHOWERS/FLURRIES AROUND LATER MONDAY NIGHT INTO TUESDAY...ESPECIALLY NORTHWEST ZONES AS 850 MB DELTA T`S DROP INTO THE MID TEENS. A GRADUAL TRANSITION TO LOWER AMPLITUDE WNW FLOW IS EXPECTED WED THRU SAT...BUT EXPECT THE LOCAL AREA TO MAINLY REMAIN ON COLD SIDE OF A PLAINS TO MID MS VALLEY BAROCLINIC ZONE...RESULTING IN AN EXTENDED PERIOD OF BELOW NORMAL TEMPS. SEVERAL MOISTURE STARVED SHORTWAVES WILL RIPPLE THROUGH IN THIS FLOW...ONE LATER WED-THU AM AND ANOTHER POSSIBLE TOWARD END OF PERIOD...BRINGING A COUPLE CHANCES FOR LIGHT SYSTEM SNOW AND RENEWED LAKE RESPONSES. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON) ISSUED AT 1253 PM EST SUN NOV 23 2014 AN INTENSE UPPER LEVEL TROF WILL LIFT NORTH ACROSS THE AREA TONIGHT AND BECOME NEGATIVELY TILTED. THE EXIT REGION OF A VERY STRONG UPPER LEVEL JET AND A 65 KT LOW LEVEL JET WILL HELP AID IN THE DEVELOPMENT OF PRECIPITATION AS MOISTURE FLUX INCREASES IN THE LOW LEVELS. ADDED TEMPO HEAVY RAIN AT BOTH SBN AND FWA IN THIS REGARD. ALSO...WINDY CONDITIONS ARE EXPECTED AFTER 12Z AS A VERY TIGHT SURFACE GRADIENT MOVES OVER THE AREA. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...GALE WATCH FROM MONDAY MORNING THROUGH LATE MONDAY NIGHT FOR LMZ043-046. SMALL CRAFT ADVISORY UNTIL 9 AM EST MONDAY FOR LMZ043-046. && $$ SYNOPSIS...MARSILI SHORT TERM...MARSILI LONG TERM...STEINWEDEL AVIATION...SKIPPER 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

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.