Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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747 FXUS63 KIND 051629 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1229 PM EDT Fri Jul 5 2024 .KEY MESSAGES... - Chances for showers and thunderstorms this afternoon. - Becoming partly cloudy this afternoon and mostly clear tonight. - Rain chances return late Monday into Tuesday. && .FORECAST UPDATE... Radar was showing a dying MCS moving ENE across central Indiana. Only weak surface based instability was in place over far south central Indiana which has been keeping the convection sub-severe and should continue to do so before it moves out Midday. Meanwhile, more convection was lifting northeast across the upper Wabash Valley, just ahead of a cold front, that extended from near a Chicago to southeastern Missouri line. The cold front is expected to move to extreme eastern sections of central Indiana by 18z this afternoon. This should result in convection for the most part ending, although CAMs suggest a few storms could still pop up ahead of the upper trough. Regardless, drying soundings and upstream visible satellite both support increasing sunshine which should allow temperatures to recover to the lower and middle 80s. Confidence in severe storms is non-zero but very low as the dying MCS is getting closer to moving into northern Kentucky and Ohio. Confidence in flooding is also low based on MRMS radar estimate trends. && .MESOSCALE UPDATE... Issued at 1229 PM EDT Fri Jul 5 2024 Radar and lightning data was indicating the MCS remnants were well east into southwestern Ohio midday. Otherwise, scattered convection has developed over the Wabash Valley just ahead of an approaching cold front. No lightning has been detected with these showers and lightningcast procedure was not keying in on any imminent lightning strikes. That said, RGB day convection satellite imagery hinted that glaciation may be nearing and SPC mesoanalysis page was showing weak instability was moving into this area from the west. Thus, expect a few storms to fire up as we move into the afternoon. 30 to 35 knot sfc-3km bulk shear and 40 to 50 knot 0-6km bulk shear along with increasing instability suggests a few of these storms could produce damaging winds this afternoon, mainly east of US-31 per the DAY1 SPC Severe Weather Outlook Marginal Risk. The cold front was running a little slow compared to previous progs. It may now not exit east of the forecast area until after 4 PM. That said, pops still look on target, so will not make any changes. Breaks in the overcast may still allow temperatures to reach the 80s but if these so not occur or last long, it may not quite reach the forecasted highs. && .SHORT TERM (Today and tonight)... Issued at 240 AM EDT Fri Jul 5 2024 Surface analysis early this morning shows low pressure in place over the upper Mississippi River Valley with a cold front extending south across eastern IA, western IL to SE MO. A convective complex was found over SE MO, ahead of the front and was showing signs of warming tops. Flow across Central Indiana was weak and disorganized. Dew point depressions across the area were less than 2F and some areas of fog were developing. Today... Upper pattern today shows a broad upper trough in place across the northern CONUS with a trough axis over western MN and western IA. This trough axis is expected to push east to the Great Lakes and toward Central Indiana today. The accompanying surface low will also reach Michigan and drag a cool front across Central Indiana by late afternoon. HRRR suggests best forcing will be the result of the decaying convective complex over MO as is reaches Central Indiana this morning and passes by this afternoon. This system will be passing across Indiana during the diurnal minimum, thus showers/storms will look to be more scattered in nature. Hence only chance pops will be used. By this afternoon the lower level flow becomes more westerly in the wake of the front as forecast soundings start a trend of drying out. Thus will try and contain pops to hours before 18Z. Highs in the lower and middle 80s are expected. Tonight... Broad troughing aloft looks to remain in place over the CONUS tonight. However little to no forcing appears to push across Central Indiana. Meanwhile within the lower levels high pressure over the plains is expected to build eastward into the Ohio Valley. This should lead to mostly clear skies and light winds overnight. Forecast soundings support this with a dry column through the night. Lows overnight in the lower to middle 60s will be expected. && .LONG TERM (Saturday through Thursday)... Issued at 240 AM EDT Fri Jul 5 2024 Saturday Through Tuesday. A quiet and cool start to the weekend is expected with zonal flow aloft and light westerly winds expected for Saturday. Slightly drier air will move into central Indiana after the rain comes to an end on Friday with afternoon dewpoints around 60 with highs near 80. Dry and quiet conditions will continue into Sunday with a gradually warming trend going into early next week as the surface flow becomes more southerly. Skies will remain mostly clear through Sunday night before the pattern shifts going into Monday. A broad trough will slowly exit the Central Plains late Monday into Monday night with a broad area of light precipitation expected to push into Indiana during the daytime hours on Tuesday. Models are suggesting a localized area of convergence where higher precipitation amounts are likely, but there remains quite a bit of model spread as to where exactly that settles. There is some model clustering across the upper Wabash Valley for this axis, but it may be as far north as the Chicago area or as far south as south central Indiana. Instability will be the limiting factor keeping the severe potential to near zero. Wednesday and Thursday. Forecast confidence then falls off Wednesday into Thursday in the aftermath of the rain on Tuesday. There is some signs that there could be some residual precipitation along the stalled frontal boundary but where that stalls remains very uncertain. Weak northwesterly flow aloft will help to keep temperatures mild, especially if cloud cover sticks around longer than models currently suggest. && .AVIATION (12Z TAF Issuance)... Issued at 540 AM EDT Fri Jul 5 2024 Impacts: - Brief MVFR possible 12Z-16Z with possible showers and decaying thunderstorms. - Mainly VFR conditions this TAF period after 051600Z Discussion: Thunderstorm complex over southern Illinois is expected to push across southern Central Indiana this morning, decaying in the process as GOES16 shows warming cloud tops. As this system arrives, morning fog will quickly dissipate as some mixing occurs. Have used tempo groups for the best chances for thunder through 15Z-16Z. Brief MVFR conditions will be possible with any TSRA that strikes a TAF site. After this morning round of possible showers passes, forecast soundings show a dry column with afternoon CU development as convective temperatures are reached. A mid level inversion will prevent deep convective growth. This should mainly be VFR CIGS. High pressure over the plains states will build across Indiana tonight and VFR conditions will continue under mostly clear skies and light winds. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ MESOSCALE...MK UPDATE...MK SHORT TERM...Puma LONG TERM...White AVIATION...Puma