Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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782 FXUS63 KIND 092331 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 731 PM EDT Thu May 9 2024 .KEY MESSAGES... - Light showers possible Tonight - Decreasing clouds and cooler on Friday - Passing showers Saturday...before several rounds of showers/few non-severe t-storms, next Monday and onward - Slightly below normal to seasonable temperatures Thursday through Saturday...to slightly above readings next week && .SHORT TERM (This evening through Friday)... Issued at 259 PM EDT Thu May 9 2024 Synopsis: Surface analysis early this afternoon shows low pressure just west of Indianapolis. The broad low was providing cyclonic circulation across the region. A warm front extended east from the low, to southern OH and WV. This low also had a cold front associated with it, stretching west across Central Illinois to southern IA. Aloft, an active pattern remained in place. A large, broad, upper trough was in place from Quebec across the upper Midwest and continued to another upper low near UT and NV. Ahead of this trough across Indiana, a quick flowing westerly flow was in place. Water vapor showed moisture in place over MI and northern IN, ahead of the upper trough, while subsidence was in place over IL and central and southern Indiana. Radar this afternoon shows some scattered light showers across Central Indiana, beneath the stratocu deck. A few showers and thunderstorms were found across northern Indiana and Michiana. These showers were ahead of the mid and upper trough. Abundant cloud cover was still found across Central Indiana, but some clearing and heating was found over Knox county, pushing northeast. Plenty of moisture remained available as dew points remained in the lower 60s across our area. Tonight... The surface low over Central Indiana is expected to quickly push to Ohio this evening and then reach the middle Atlantic states overnight. This will allow for the development of a northerly surface flow of cooler air overnight. Meanwhile aloft, the previously mentioned surface trough will be sagging across Central Indiana trough the evening. Ongoing heating, combined with the cyclonic flow and approaching upper trough is expected to continue to develop scattered light rain showers across Central Indiana late this afternoon and early evening. SW central Indiana will need to be watched for possible thunderstorm activity. Clearing arriving in Knox county is allowing for additional heating that could trigger additional afternoon and early evening thunderstorms. HRRR suggests that as this cloud shield continues to lift northeast thunderstorms develop in combination with the arrival of the surface cool front. Will try to keep the Thunder mention at those southern locations, however a stray rumble of embedded within a shower will also be possible. Overnight, the upper trough will exit to the south and any associated forcing will be lost. Cold air advection will be in play as falling thicknesses are noted. This results in the formation of a stratus deck overnight, with a trapping inversion found aloft as seen within the forecast soundings. Thus overall, scattered late afternoon and evening showers are expected to continue with light rain amounts. Best thunder chances will be across far southern Central Indiana in association with any clearing and extra heating that occurs. Then expect cloudy and cooler conditions overnight as cold air advection is in play. Expect lows in the upper 40s and lower 50s. Friday... Models suggest the previous upper trough will quickly depart on Friday, allowing northwest flow along with moderate ridging to build across Indiana through the day. Surface high pressure over the plains is suggested to build a ridge axis across Indiana through the day, originating from the southern plains. Forecast soundings start the day with saturation within the lower levels due to the passed system, cold air advection and the trapped lower level moisture. However as the ridging builds, the lower levels are shown to mix out as the inversion aloft rises. This will allow for decreasing cloudiness in the morning followed by some high CU development during the afternoon. Cool northerly winds but with some afternoon sunshine will allow highs in the upper 60s to be reached. && .LONG TERM (Friday night through Thursday)... Issued at 259 PM EDT Thu May 9 2024 Friday night through Sunday... Northwesterly flow aloft will promote at least weak ridging this weekend...on either side of a passing northern-stream, plunging short wave in the late Friday night-Saturday timeframe. This quickly-passing feature should shake out some widely scattered rain showers from pre-dawn to afternoon hours on Saturday...with perhaps a rumble of late day thunder and moderate rainfall rates in isolated convection over eastern zones. Ample sun should otherwise prevail through the weekend. Seasonably low humidity will be the backdrop to slightly below normal maximum temperatures Saturday in mainly the 65-70F range, under the passing lower heights and west-northwest gusts as high as 20-30 mph...to more seasonably mild conditions Sunday in the 70s as lighter breezes return from the west-southwest. Monday through Thursday... A rather typical late spring pattern will prevail over much of the next workweek...as lower heights retracted to Canada allow a small yet progressive short wave to cross the central US to the Ohio Valley. Solid ribbon of Atlantic and eastern Gulf of Mexico moisture is expected to boost precipitable water values to 1.25-1.50 inches over much of the Midwest. The overall disturbed pattern should promote a few rounds of showers and thunderstorms...which so far appear will be best organized in the late Monday to Tuesday night timeframe. Total rainfall would likely be under an inch for most areas, with perhaps heavier amounts across southern counties...although ultimately this would be determined by wherever corresponding surface low pressure and associated boundaries would focus any heavier rains. Severe weather is so far not expected with primarily overcast skies likely limiting instability despite above normal dewpoints...and vertical wind shear likely low per the overall weak nature of the passing wave. Temperatures trending from near to slightly above normal...will be led by overnight lows in mainly the mid to upper 50s...courtesy of noticeable humidity amid the often southerly breezes. The normal max/min at Indianapolis for the long term is 73/53. && .AVIATION (00Z TAF Issuance)... Issued at 731 PM EDT Thu May 9 2024 Impacts: - MVFR conditions much of the night into Friday morning. Discussion: A large upper trough and secondary cold front are passing through the area this evening, bringing a few lingering showers primarily to northern portions of the area, and continuing to keep low stratus trapped across much of the region. Some sites have briefly returned to VFR this afternoon, but expect all to deteriorate again to low end MVFR if they have not already over the next couple of hours. LAMP guidance is fairly optimistic in MVFR ending overnight, but this is not well supported by forecast soundings, and the presence of a second vort lobe and climatological progression of overnight low ceilings suggests restrictions will continue into Friday morning before returning to broken VFR ceilings midday onward. Will depict some slow improvement later tonight. Winds will begin the period somewhere between 310-030 degrees depending upon the site, with all quickly becoming primarily northerly in the first few hours. A few gusts to near 20KT may persist at a couple of sites over the first hour or two, but these will quickly subside, with sustained winds largely 5-10KT overnight into tomorrow. Winds will back a bit during the day to a more northwesterly heading by late in the period. There is potential for some light fog at LAF, but most areas should see unrestricted visibility. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Puma LONG TERM...AGM AVIATION...Nield