Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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951 FXUS63 KIND 281854 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 254 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 && .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 (18Z TAF Issuance)... Issued at 1238 PM EDT Tue May 28 2024 Impacts: - Low probability showers and thundershowers between 22Z and 04Z. - Gusty winds and temporary MVFR conditions possible in showers/storms. - WNW wind gusts to 20-25kt possible today and tomorrow. - Period of MVFR ceilings possible early Wed morning. Discussion: VFR conditions should persist through this afternoon. A weak storm system diving down from the northwest may induce a few showers or thundershowers towards the evening. These look to arrive somewhere between 22Z and 04Z. Showers/storms will be fast-moving and will not persist in any one location for a prolonged period of time. Brief MVFR conditions along with gusty winds are possible with these. Ambient surface winds will be out of the west-northwest between 10- 15kt with gusts 20-25kt. Winds decrease a bit overnight as the boundary layer stabilizes but should pick up again Wednesday afternoon. A brief period of MVFR ceilings are possible Wed morning as the center of the weak storm system swings by. These clouds should diminish as the day progresses, due to boundary layer mixing and the system itself departing eastward. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Eckhoff LONG TERM...Updike AVIATION...Eckhoff