Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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878 FXUS63 KIND 122344 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 744 PM EDT Sun May 12 2024 .KEY MESSAGES... - Showers and a few thunderstorms expected Monday and Tuesday - Up to around one inch of rain expected - Rain chances return Thursday into Friday && .SHORT TERM (This evening through Monday)... Issued at 216 PM EDT Sun May 12 2024 Rest of This Afternoon... Plentiful sunshine will continue through much of the afternoon with upper ridging across central Indiana. Some high clouds will arrive later, and a few mid clouds will accompany them. Tonight... The upper ridge will slide across the area tonight. An upper level system will move into the Plains by late tonight. Clouds will increase during the night from the system to the west. A few showers may try to sneak into the far western forecast area very late tonight ahead of the system, but lingering dry air along with subsidence from the upper ridge should keep central Indiana dry. Southwest winds and the increasing cloud cover will keep temperatures warmer than Saturday night, with lows in the middle 50s common. Monday... The upper system will continue its approach from the west, but the best forcing and moisture will remain west of the area. Even the limited moisture will take a while to arrive. Still, there will be some isentropic lift moving in, mainly during the afternoon hours. This will be enough to go with mainly chance PoPs, especially late in the day. Moisture might be deep enough for some likely category PoPs in the southwest near the end of the period (after 22Z or so). Rainfall amounts will be light. Temperatures could get near 80 degrees if thicker clouds hold off for long enough. && .LONG TERM (Monday night through Sunday)... Issued at 216 PM EDT Sun May 12 2024 The subtropical jet is modeled to amplify over our region Monday night into Tuesday preceding and eastward-moving shortwave trough. IVT and PWAT anomalies show broad but modest northward moisture surge with this system. Timing of initial richer moisture and warm advection ascent peaking will be Monday early-mid evening. This will be followed by a period of ascent with the main trough/vorticity maxima that will be positioned and paced in such a way that it should force additional precipitation through Tuesday and into Tuesday night. Multi-model ensemble model data has around 0.75-1.00 inch storm total QPF with few members at or above 1.5 and some under 0.50. The upper end seems to be conditional on convective elements which will more than likely be limited given weak midlevel lapse rates. If the dry conveyor belt is optimally positioned over the area and/or the deformation precipitation band under-achieves as it departs, the lower end (i.e., 10-25th percentile) precipitation amounts may be more favored. There may be opportunities in subsequent forecast updates to add more precision for possible dry periods early Tuesday after the initial warm advection precipitation band. On Wednesday, there should be enough of a push of drier continental air to decrease clouds and hold temperatures near mid-May climo. Ridge position and increased warm advection preceding the next system should push us to around +5 temperature anomalies Thursday, with increasing clouds. Thursday through the weekend, the synoptic pattern still features split progressive flow. These are notoriously lower predictability patterns and spaghetti plots do show increasing chaos. Models seem to vary with magnitude of lead wave and initial precipitation Thursday night, and how quickly precipitation departs Saturday. At this time, models indicate a CAPE/shear parameter space that isn`t favorable for organized severe, and a precipitation duration/magnitude signal that isn`t supportive of flooding. This isn`t a pattern that`s effective at dislodging higher latitude continental/colder air, so near or just above climo temperatures are anticipated this weekend. A low amplitude northern stream wave is shown in models with some timing variance possibly bringing some precipitation late Sunday or early Monday. Day 8-14: The subtropical jet is shown to be weaker in medium range model guidance during this period, with more phased and stronger mid- latitude westerlies. There could be one or more organized synoptic- scale systems during this period with attendant precipitation and convective severe potnetial, but details are fuzzy. The pattern indicates perhaps some opportunities for greater day-to-day temperature variances than will be seen this week given the more phased flow, though still probably averaging near or above normal during the period. && .AVIATION (00Z TAF Issuance)... Issued at 744 PM EDT Sun May 12 2024 Impacts: - Showers and a few thunderstorms expected late tomorrow afternoon Discussion: VFR conditions and southerly winds under 10kts persist the rest of the evening and into the overnight hours. Satellite imagery and observations do show an area of low pressure over Kansas which will slowly moves eastward towards the region tomorrow and Tuesday. Expect an increase in high clouds late tonight into tomorrow morning as the system approaches. Showers and a few thunderstorms will develop ahead of the system in Illinois late tomorrow afternoon and then push into Indiana after around 20-22z. Mainly VFR conditions expected even into most of the day tomorrow. After the TAF periods ends, expect an increase in showers and thunderstorms Monday night and through the day on Tuesday. MVFR to IFR cigs and vis likely at times due to convective activity. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...50 LONG TERM...BRB AVIATION...CM