Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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677 FXUS63 KIND 282246 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 646 PM EDT Tue May 28 2024 .KEY MESSAGES... - Scattered showers and at least a few storms are possible late in the day and early tonight. Strong wind gusts are the primary hazard. - Dry and Seasonable Wednesday through Friday, Rain chances Saturday into Sunday && .MESOSCALE UPDATE... Issued at 522 PM EDT Tue May 28 2024 Scattered convection continues to pulse up and down in intensity across the northwest parts of the forecast area late this afternoon. Storms have sporadically produced CG lightning strikes along with pea size hail...the most recent confirmed near Lafayette just prior to 21Z. The current KIND ACARS sounding continues to show a narrow layer of CAPE with MLCAPE values generally at 500 j/kg or less. Steep lapse rates up through about 700mb are present with a noticeable dry layer in the mid levels. With the freezing level hovering around 9kft...stronger cells will continue to carry a threat for small hail into the evening. The greater threat from any stronger storms will be gusty winds as the combination of the subsidence aloft with the dry adiabatic thermodynamics through the boundary layer should support easy transport of briefly stronger winds to the surface with elevated cores. Convective coverage will increase slightly after 23Z in response to the upper wave over northern Illinois pivoting E/SE through the evening. Greatest threat for rain and storms will remain near and north of I-74...shifting east of the forecast area by late evening. Additional mesoscale AFD updates may be issued through the evening. && .SHORT TERM (This evening through Wednesday)... Issued at 252 PM EDT Tue May 28 2024 Generally northwesterly flow exists through the depth of the atmosphere today as a trough axis resides to our east. A short wave embedded within the broader flow is currently diving to the southeast out of central Canada. This feature should pass just to our north this evening and overnight. Given the cooler air aloft, associated with the trough, lapse rates are fairly steep today. RAP soundings show 7-8 C/Km with super adiabatic values (up near 10C/km) very near the ground. ACARS soundings out of IND do not show this super-adiabatic near-surface lapse rates, however. Despite the steep lapse rates, instability is modest with values generally between 500- 1000 J/Kg. This is in part due to a lack of moisture within the boundary layer. Enough lift is present within and ahead of the vort max that showers and thundershowers are shown by most guidance. Observations tend to agree with this, as weak radar echoes are beginning to develop in northern Illinois and even into northern Indiana. Continued growth is expected through the afternoon with greater concentration nearer to the vort max. Given the steep lapse rates and relatively dry column, strong downbursts/wind gusts are the primary hazard with any shower or storm. Activity should diminish after 00z as diurnal heating wanes and the boundary layer stabilizes. Overnight, expect quiet weather with diminishing winds. Low-clouds cover may develop towards morning from the north as the vort max swings by. Wouldn`t rule out a few light rain showers within the area of low clouds either. These low clouds may persist into the morning hours but should dissipate as daytime mixing resumes and the vort max pulls away. Surface winds should pick up again as well once the boundary layer begins to mix. Gusts upwards of 20kt are possible at times tomorrow afternoon. Temperatures look to be a bit below the climatological average for this time of year due to the broad troughing aloft. Typical values at IND are 77/57. && .LONG TERM (Wednesday night through Tuesday)... Issued at 252 PM EDT Tue May 28 2024 The long term will begin with our first consistent reprieve from wet conditions as high pressure moves in from the north. Troughing over the Mid-Atlantic region has brought a succession of waves through the region, but as of Wednesday, confluence in the upper jet stream and broad AVA will aid in raising heights through the mid to upper atmosphere. Eventually, the amplifying ridge axis will lead to surface high pressure over the Ohio Valley. Initially, some semblance of surface moisture will stick around on Wednesday (DP in the low 50s). However, by Thursday, adiabatically warmed subsidence should drop surface dew points in the mid to low 40s. The combination of subsidence, and drying air will lead to quiet conditions Wednesday night through Friday. Highs will begin to slightly increase on Thursday and Friday (Mid to upper 70s) within well mixed PBLs. Even with deep PBLs, the lack of a LLJ should keep winds rather calm; expect winds to top out around 10-12kts Thursday and Friday afternoons. The next wave of moisture/lift looks to arrive late Friday through Saturday. Although the upper wave may arrive Friday night, the dry low to mid levels from prior day subsidence should keep any precipitation from reaching the ground until sometime on Saturday. Overall this system looks to be mostly showery due to poor mid level lapse rates, but its still too far out to have high confidence in the details. The forecast beyond Saturday becomes much more murky due to the relatively elevated surface moisture and remnant boundaries and weak surface level waves in the remnants of the Saturday upper level system. && .AVIATION (00Z TAF Issuance)... Issued at 646 PM EDT Tue May 28 2024 Impacts: - Scattered convection possibly impacting KIND and KLAF early evening - Gusty winds and temporary MVFR conditions possible in showers/storms - W/NW wind gusts to 20kt Wednesday - MVFR ceilings expected Wednesday morning Discussion: Isolated to scattered convection continued across northern portions of Illinois and Indiana early this evening in tandem with an upper level wave. As this feature pivots southeast through the evening... scattered convection will persist and may briefly impact KIND and KLAF prior to 02Z. Clouds will scatter and wind gusts will diminish into the overnight. By predawn Wednesday...the upper wave will track into western Ohio with lower clouds swinging back down across northern Indiana and eventually encompassing the terminals Wednesday morning. Model soundings support MVFR stratus with saturation through much of the boundary layer. Cannot rule out a stray shower at both KIND and KLAF as well in the morning but coverage too low to include at this time. Ceilings will gradually lift into a broken VFR cu/stratocu field for the afternoon before clouds diminish Wednesday evening. N/NW winds may periodically gust to around 20kts on Wednesday. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ MESOSCALE...Ryan SHORT TERM...Eckhoff LONG TERM...Updike AVIATION...Ryan