Expires:No;;873676 FXUS63 KIND 061745 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 145 PM EDT Sun Apr 6 2025 .KEY MESSAGES... - Rivers are expected have already reached or are expected to reach moderate to major flood stage in Central and South Central Indiana - Widespread, significant river flooding continuing through next few weeks - Frost and freeze conditions likely Monday night and Tuesday night && .FORECAST UPDATE... Issued at 1008 AM EDT Sun Apr 6 2025 While the threat for heavy rain has ended, widespread flooding threat continues across Central and South Central Indiana as water will be slow to recede. For this reason, have extended the areal Flood Warnings along and south of the I-70 corridor through at least the rest of the day. Latest satellite and radar imagery show additional light rain showers pushing into Western and Southwest Indiana this morning as yet another weak wave rides along a boundary stretched out over Kentucky. Best forcing for ascent and moisture advection are well south of the Ohio River, so not expecting the heavy rainfall rates and amounts as seen the last several days. Most locations will end up with less than a tenth of an inch of additional rain today, with an exception for far southern portions of the state where up to a quarter inch is possible. Expect a drying trend tonight as the threat for rain pushes south and east. && .SHORT TERM (Today and tonight)... Issued at 310 AM EDT Sun Apr 6 2025 The surface cold front is now well south of central Indiana with modest N/NE flow across the region. This will keep conditions cool, but there will still be precipitation chances despite increasing low level subsidence as WAA continue to occur in the 800-700mb layer. This will create a strong temperature inversion aloft leading to widespread cloud cover and scattered showers. Deep layer moisture will not be present with this round of showers, leading to much lower QPF values than the days prior. Temperatures are expected to remain fairly stagnant today with highs in the mid 40s, however it will feel even colder within an 8-12mph NE wind with "feels-like" temps in the 30s. A few models are trying to show some mixed precipitation within showers this afternoon, but with the strong temperature inversion near freezing and temperatures in the 40s as precipitation onset, wetbulbing likely wouldn't be enough for snow to remain frozen prior to reaching the surface. For now, all rain will be the forecast for central Indiana. The Flood Watch and Flood Warnings continue across most of Central Indiana early this morning. Currently do not plan on extending the flood watch as rainfall rates have diminished significantly and rainfall today is expected to be less than 0.5". Major stem rivers will remain elevated above flood stage for the next week or two and will issue river flood products accordingly. && .LONG TERM (Monday through Saturday)... Issued at 310 AM EDT Sun Apr 6 2025 A large-scale pattern change will occur in the long term as a quick moving short wave will organized a push of much colder air into the Ohio Valley late Monday. The slow-moving trough that has been bringing us round after round of rainfall finally slides eastward Sunday night. Still the mid level baroclinic zone and corresponding jet streaks will aid in the creation of a modest shortwave. This wave would not be impactful typically, but the cold air behind the system and associated cold front that moves through late Monday will be rather sharp. High-res models are showing temperatures dropping 20+ degrees Monday evening, with further diurnal cooling Monday night pushing temperatures likely below freezing. Due to the abnormal warmth and moisture throughout late March and early April, growing seasons have already begun. For that reason a Freeze Watch has been issued for Monday night. Behind the cold front on Monday, much drier air is anticipated to push into central Indiana. However, there could be a brief period of time where moisture decrease lags behind temperature decreases with scattered light snow showers. If this does occur, accumulation is not expected, but something to note nonetheless. Winds may be gusty behind the front as well, perhaps up to 30-35mph. Surface high pressure quickly builds in Monday evening, with diminishing winds and clearing skies. The center of the high doesn't arrive until Tuesday, however, and there may be enough cyclonic flow regionally to promote lingering stratocumulus through the night and into Tuesday morning. Models tends to be a bit too optimistic with stratocu in these scenarios by clearing things up too quickly. We will retain some cloud cover in the forecast, especially northeast of Indianapolis, for now. Questions regarding cloud cover translate into questions regarding low temperatures, since lows will partly depend on the radiative component in addition to the advective. Should skies end up clearer, then we can expect values as low as the low 20s. Conversely, cloud cover may keep lows closer to 30. Regardless, sub-freezing temperatures are expected with widespread frost and hard freeze conditions. Sub-freezing lows are possible again Tuesday night, but by 00z that evening the core of the upper trough will be exiting to the east. Modest warm air advection begins and continues into the night as winds turn westerly. Lows in the 20s are possible, especially east of I-65. There remains some differences within guidance with how fast the surface high departs. Slower departure favors colder temps as ideal radiative cooling conditions linger into the night. Our next chance of precipitation arrive on Wednesday evening or early Thursday as a moisture-starved system zips by to our north. Guidance shows some weak convective instability, which combined with frontal forcing could lead to scattered showers and perhaps a thunderstorm. Additionally, some breezy southwesterly winds are possible immediately ahead of the system and its attendant cold front Wednesday afternoon. Cold advection returns after Thursday as northwesterly flow aloft and east coast troughing take hold. Additional overnights with frost potential are possible towards the end of the week and into next weekend. && .AVIATION (18Z TAF Issuance)... Issued at 145 PM EDT Sun Apr 6 2025 Impacts: - Sporadic Showers through the evening - Gusts to 20-25KT Monday mid morning through evening, SW winds becoming N Discussion: Mainly VFR conditions expected through the period. Latest satellite imagery shows widespread mid and high level clouds over the region with sporadic showers around, mainly near KBMG. ACARs soundings show enough dry air near the surface to keep cigs VFR today; however brief periods of MVFR cigs and vis are possible under a passing shower, mainly at KBMG. Winds should remain out of the NE throughout the day around 9-12 kts. Isolated gusts to 15-19 kts possible through this evening; however with the mixing layer very shallow under a low inversion, not expecting these gusts to be widespread. SW winds increase after sunrise tomorrow ahead of a strong cold front dropping down from the north. Sustained winds increase to 10- 15 kts with gusts 20-25 kts after 14z. The front will push south during the afternoon hours with winds quickly becoming NNW behind it. Added details to timing of the wind shift for the end of the TAF period tomorrow. Steep low level lapse rates and cold air advection aloft may result in elevated winds and a few gusts into Monday night. Will watch this closely and add it to future forecast issuances as confidence increases. && .IND WATCHES/WARNINGS/ADVISORIES... Freeze Watch from late Monday night through Tuesday morning for INZ021-028>031-035>049-051>057-060>065-067>072. Flash Flood Watch through Tuesday morning for INZ064. && $$ UPDATE...CM SHORT TERM...Updike LONG TERM...Updike/Eckhoff AVIATION...CM