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Displaying AFOS PIL: AFDIWX Received: 2018-09-20 10:15 UTC
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377 FXUS63 KIWX 201015 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 615 AM EDT Thu Sep 20 2018 .SYNOPSIS... Issued at 424 AM EDT Thu Sep 20 2018 One more hot day will be in store for many areas as highs reach the upper 80s to lower 90s. A chance for a shower or storm will exist mainly along and north of the Toll Road into this afternoon. There will be a chance of showers and thunderstorms Friday afternoon. Cooler temperatures will filter in behind a cold front with highs only into the 60s on Saturday, then mainly in the 70s next week. && .SHORT TERM...(Today and Tonight) Issued at 424 AM EDT Thu Sep 20 2018 Low confidence forecast regarding impacts of upstream convection and precip chances into this afternoon as well as temperatures. Elevated frontal boundary has been active for several hours now from NE Nebraska into southern Wisconsin. Recently developed showers and storms were also being seen across portions of west central lower Michigan. Activity should remain north of the area until possibly closer to the 12Z as outflow boundary pushes south and allows for at least a chance for a few showers or storms. Have attempted to capture this as best as possible with pops expanding southward for a period this afternoon as warm sector becomes rather unstable with MLCAPE 1000-2000 J/KG. Best shear will reside well north of the area resulting in more pulsy storms that are able to develop with SPC marginal risk being pushed north of the forecast area. Cloud cover today will be key in determining final afternoon highs with potential for locations in the southwest to get quite warm once again. Higher dewpoints may limit overall potential for mid 90s but can't fully rule out. Kept with previous forecast with coolest readings north and east where clouds may linger longer. Dry forecast this evening and most, if not all of tonight as line of showers and thunderstorms advertised to develop west of us along the cold front and move east. Most models weaken this convection as it outruns best forcing but left some low pops in W/NW areas towards morning. Winds will increase as low level jet ramps up to over 50 kts and at least some mixing of stronger winds occurs. && .LONG TERM...(Friday through Wednesday) Issued at 424 AM EDT Thu Sep 20 2018 Outflow boundary/pre frontal trough from overnight convection will be the main focus for best convection chances. Hi res models generally split on either this boundary re-firing in far SE areas or possibly remaining somewhat active with showers during the morning that eventually intensify. Instability and increasing shear warrant a marginal risk of severe for at least SE third if not a bit further NW. SPC Day 2 outlook expanded marginal NW into SE 2/3rd or so of the area. May be somewhat overdone but with some models hinting at storms further NW due to possible slower movement of front can't argue. Precip should be clear of the area by Friday night with much cooler air funneling in. Highs in the 60s will dominate Saturday with only some moderation back towards normal temps into mid week as stronger trough digs into the Plains and works east with increasing chances for showers and possibly some storms starting as early as Monday afternoon but especially Tues afternoon and evening when timing of energy and peak heating all combine. Colder air will return again behind the front. && .AVIATION...(For the 12Z TAFS through 12Z Friday Morning) Issued at 559 AM EDT Thu Sep 20 2018 Low level warm front is beginning to lift northward early this morning, with some warm advection induced showers and a few embedded storms having developed across southern Lower Michigan. Cyclogenesis across north central US and diurnal northward mixing of this warm front will continue to take better warm frontal forcing north of terminals this morning. For today, will have to watch evolution of weak outflow boundary across northern Illinois for potential redevelopment later today, although some question as to how far southeast this boundary will be able to progress given background synoptic flow. Some indications noted in HRRR/ARW model guidance of isolated-scattered showers/storms redeveloping this afternoon across far northern Indiana. Some support for this idea could be very weak vort max lifting through upstream portion of upper ridge from STL vicinity, possible contribution of lingering shallow weak outflow, and some weak differential heating forcing given mid/high cloud shield working across the southern Great Lakes. Still not quite enough confidence for any precip mention at terminals with 12Z TAFs given overall lack of substantial mid/upper forcing, but this will be monitored. Northward retreat of warm front will allow for moderate south- southwest winds in the 10-15G20KT knot range this afternoon. Did include mention of LLWS after 05Z tonight as northern Indiana is locked in warm sector with some decoupling and presence of strong low level inversion. VFR conditions should hold through this period outside of any low prob shower/storm chances both this afternoon, and then again toward very end of the period as pre- frontal trough approaches. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...Small Craft Advisory from 8 PM this evening to 11 AM EDT Saturday for LMZ043-046. && $$ SYNOPSIS...Murphy SHORT TERM...Fisher LONG TERM...Fisher AVIATION...Marsili Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana