Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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236 FXUS63 KIND 311028 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 628 AM EDT Fri May 31 2024 .KEY MESSAGES... - Showers and a few storms expected much of the day Saturday - Warming trend going into next week with periodic storm chances - Long range 8-14 day outlook trending toward below normal temperatures && .SHORT TERM (Today and tonight)... Issued at 302 AM EDT Fri May 31 2024 Conditions remain calm early this morning across Central Indiana as high pressure is centered over Ohio. Latest satellite imagery shows mainly clear skies over the region; however high clouds from an approaching storm system in the plains are slowly creeping north and east into Illinois. Despite slowly increasing upper clouds today, conditions will remain dry through late tonight. High pressure shifts eastward today, but will still be the dominant weather influence despite the approaching system. Winds shift southeasterly in the lower levels today leading to weak warm air advection aloft. Strong solar heating of the boundary layer is still expected despite high cirrus increasing with highs reaching the mid to upper 70s. Latest IND ACARs soundings show a very dry layer above ~1.5km agl. Short term models do suggest mixing heights reaching into this dry layer later this afternoon likely resulting in dew points falling to near 40 by mid afternoon. Low RH values may dip into the 20-30% range as well during peak heating of the day; however with very light winds through the column and recent rainfall, fire weather concerns are very low. Tonight, clouds continue to thicken and begin to lower as upper level moisture increases ahead of an area of low pressure pushing NE into N AR and S MO. Will have to watch how much the boundary layer dries out today as this may slow the onset of precipitation in Western and SW Indiana. Latest guidance has rain approaching the IN/IL state line in the 06-09z timeframe; however if the low levels are drier than what guidance suggests, rainfall may not reach the ground until the 09z-12z. Confidence is higher in dry conditions tonight for the eastern 2/3 of Central Indiana. Cloud cover will also result in temperatures remaining slightly elevated overnight, especially further west with lows ranging from the mid 50s to low 60s. && .LONG TERM (Saturday through Thursday)... Issued at 302 AM EDT Fri May 31 2024 Saturday and Sunday... Wet weather moves in for the first half of the weekend as the aforementioned low pressure system tracks northeast through Central Indiana. Guidance continues to have a solid handle on both the timing and strength of the low pressure system which allows for higher than normal confidence on the forecast progression. Isentropic lift and an increasing 30-40 kt low to mid level ahead of the system pumping in ample moisture northward will result in widespread rain across the state. Instability looks minimal for the morning and early afternoon hours, so any thunder should be isolated. The first wave of rain will likely be lighter with a few pockets of moderate rain embedded in the rain shield. A weak dry slot arrives by the afternoon, however the dry window may be short as the cold front quickly pushes through behind the main round of precipitation with additional showers and storms as early as mid afternoon. If the dry break is long enough for surface temperatures to increase ahead of the cold front, the atmosphere may become unstable enough for thunderstorms during the afternoon and evening hours. Severe weather threat is low as instability looks too weak to support organized convection. The main threat Saturday is the possibility of heavy rain and localized flooding with the timing of the heaviest rain likely during the evening hours. Widespread rainfall totals around a half inch to an inch are likely across Central Indiana with totals as high as 1-1.5 inches in areas that see repeated thunderstorm and heavy rain activity. The area of low pressure slowly meanders into Ohio on Sunday; however weak high pressure moving in with little forcing or dry air may result in low stratus hanging around much of the day. Lowered highs to the NBM25th percentile keeping temperatures in the 60s to near 70 much of the day. Expect breaks in the clouds from west to east during the mid to late afternoon hours. Monday through Friday... The chance for showers and storms sticks around for much of the week, but confidence on timing and location of convection remains low due to model inconsistencies. Flow aloft becomes much more stagnant with the main jet energy near the Canadian border and the pattern becomes more driven by mesoscale factors that are very uncertain this far out. There does look to be at least occasional showers and thunderstorms which will generally be diurnally driven so will focus POPs highest in the 18Z to 00Z timeframe. Surface flow will generally remain southerly through the week which will keep temperatures just above normal into the 80s with much higher dewpoints of mid to upper 60s. More organized convection with higher chances for rain exist Wednesday as a deeper trough digs into the Great Lakes and a cold front moves through the region. While it is too soon to talk about severe weather threats, with a warm and moist atmosphere, a strong to severe storm cannot be ruled out. Will continue to watch the Wednesday timeframe as this seems to be the strongest storm system this week with highest chances for widespread rainfall and storms. Longer range guidance continues to indicate troughing setting up over the region late week into the following weekend with below normal temperatures expected. && .AVIATION (12Z TAF Issuance)... Issued at 628 AM EDT Fri May 31 2024 Impacts: - Rain and possibly MVFR cigs/vis arriving near the end of the TAF period Discussion: VFR conditions will prevail through tonight. Satellite imagery this morning shows VFR cigs across all of Central Indiana with just high cirrus pushing in from the west. High pressure becomes centered over the Mid Atlantic states by this evening while an area of low pressure approaches from the southwest. Expect winds out of the southeast (120-140 deg), but remaining under 10 kts despite afternoon mixing as winds through much of the column are very weak. High clouds will increase during the afternoon and evening hours today then thicken and lower late tonight. Sub-VFR cigs/vis are not expected until the around the end or after this TAF period around sunrise Saturday morning when widespread rain moves in from the south and west. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CM LONG TERM...CM AVIATION...CM